Master Plan for the Agusan River Basin

Technical Assistance Consultants Report

Project Number: 36540-01May 2008

Philippines: Master Plan for the Agusan River Basin

Prepared by CTI Engineering International Co. Ltd; Halcrow; and Woodfiled Consultants, Inc.

Philippines

For Department of Environment and Natural Resources National Water Resources Board

This consultants report does not necessarily reflect the views of ADB or the Government concerned, and ADB and the Government cannot be held liable for its contents. (For project preparatory technical assistance: All the views expressed herein may not be incorporated into the proposed projects design.

TABLE OF CONTENTS

MASTER PLAN FOR THE AGUSAN RIVER BASIN PROJECT FINAL REPORTTABLE OF CONTENTS

iLIST OF TABLESvLIST OF FIGURESviiiACRONYMS and ABBREVIATIONSix1.0INTRODUCTION1-1BACKGROUND1-1STUDY AREA1-1GOAL AND OBJECTIVES1-1APPROACH AND METHODOLOGY1-2KEY ACTIVITIES1-22.0PHYSICAL AND ENVIRONMENTAL CONDITION2-1GEOGRAPHIC SETTING2-1CLIMATE2-3RAINFALL2-5STREAMFLOW2-7GROUNDWATER2-9ENVIRONMENTAL SETTING2-9Natural Physical Environment2-10Biological Environment2-133.0SOCIO-ECONOMIC CONDITION3-1ECONOMIC SETTING3-1Economic Profile3-1THE SOCIAL SETTING3-10Stakeholders of the Basin3-11Demographic and Socio-economic Profile3-154.0REVIEW AND ASSESSMENT OF RELEVANT POLICIES AND PLANS4-1INTERNATIONAL ORGANIZATIONS INITIATIVES ON WATER MANAGEMENT4-1WATER POLICIES AND MULTI-LATERAL AGENCIES4-2NATIONAL POLICY OBJECTIVES4-2SECTOR POLICIES4-3REGULATORY FRAMEWORK4-4REGIONAL AND PROVINCIAL POLICY OBJECTIVES AND TARGETS.4-9Caraga Region4-9Davao Region.4-12AGUSAN RIVER BASIN WATER POLICY4-14Assessment of Policy Context4-14Harmonization of the Basin Policy4-15GENDER AND DEVELOPMENT4-18Gender, Age and Household Distribution4-18Gender Analysis4-18Policies and Institutions on Gender4-245.0INSTITUTIONAL FRAMEWORK5-1Institutional Participation5-1Existing Institutional Set-up in National Water Resources Management5-1Institutional Stakeholders in the ARB5-1MAJOR INSTITUTIONAL IMPEDIMENTS5-2National Level5-2ARB Level5-3FORMATION OF THE AGUSAN RIVER BASIN ORGANIZATION5-6Tapping the Potentials of Existing Basin Organizations5-7Existing Working Models5-7Imperatives for RBO Formation5-12FUNDING THE AGUSAN RIVER BASIN ORGANIZATIONAND ITS DEVELOPMENT ACTIVITIES5-15Identified Funding Sources of Selected IRBM Organizations .. 5-15 5.4.2Funding the Agusan RBO5-17RBO FORMATION AND DEVELOPMENT5-21Basin Governance Options5-21The Proposed RBO5-22The Proposed Structure5-256.0PARTICIPATORY APPROACHES AND DEVELOPMENT STRATEGIES6-1KEY ENVIRONMENTAL ISSUES AND STAKEHOLDER PRIORITIES.6-1BASIN REALITIES AND KEYS TO INTEGRATION6-5Key Basin Realities6-7Keys to Integration6-8ARBMP DEVELOPMENT VISION,GOALS AND OBJECTIVES6-11Development Vision6-11Development Goal6-12Development Objectives6-12VGO and the ARB Policy6-13ARB DEVELOPMENT STRATEGY6-15General6-15Why a Governance Initiative and RBO Formation Strategy6-15Why an Intervention Initiative and WRM Intervention Strategy..6-16Why a Knowledge Development Initiative and GIS Development Data Banking Strategy6-17UNITY OF THE DEVELOPMENT STRATEGY6-17FROM POLICY TO STRATEGY TO PRINCIPLES6-19FROM POLICY TO STRATEGY TO PROJECTS6-207.0BASIN PROGRAMS AND PROJECTS7-1ASSESSMENT OF BASIN WATER CONTROL STRUCTURE7-2Irrigation Development7-2Water Supply Systems7-8Flood Control7-12Roads and Bridges7-13River Transport7-13Hydropower7-14PROGRAMS/PROJECTS BY KEY THEME7-14Water Quality Management Program7-14Flood Management Program7-15Water Resources Development Program7-17Watershed Management Program7-18Agusan Marsh and Wildlife Sanctuary (AMWS) Management Program7-23Indigenous Peoples Development Program7-24River Basin Organization Development Program7-278.0IMPACT ASSESSMENT8-1STRATEGIC ENVIRONMENTAL ASSESSMENT8-1Objectives8-1Methodology8-1Categories of Projects8-3Key Environmental Issues8-3Potential Environmental Impacts8-3Cumulative Impacts and Mitigating Measures8-8Potential Benefits8-15Institutional Requirements and Environmental Monitoring8-20

ivLIST OF TABLES

Table 2-1List of TributariesTable 2-2List of Rainfall StationsTable 2-3List of Streamflow Gauging StationsTable 2.4Surface Water Potential of Sub-Basins, ARB, 20000 Table 3-1Gross Value Added by Industry, Caraga Region( in million at constant 1985 prices )Table 3-2Gross Value Added by Industry, Davao Region (in million pesos at constant 1985 prices )Table 3-3Caraga Region: Projected Gross Regional Domestic ProductTable 3-4Davao Region Fross Regional Domestic Products Actual and Targets Table 3-5Palay Production by Province, Caraga Region, 2002-2003Table 3-6Corn Production by Province, Caraga Region, 2002-2003 Table 3-7Area and Production of Major Crops, 1998 Compostela ValleyTable 3-8Employed Persons by Industry Group, Caraga Region, 1997-2002 Table 3-9Employed Persons by Industry Group, Davao Region, 2003Table 3-10Family Income and Expenditure by Region, Philippines, 2001-2003 Table 3-11Annual Per Capita Poverty Threshold and Poverty Incidence, 1997-2000 Table 3-12Distribution of Municipalities and Cities in ARB Provinces, 2005Table 3-13Formal Users of Forestry, Mineral and Fisheries Within the ARB, 2005 Table 3-14Population Size by Municipality and Growth Rates, ARB, 1960-2000 Table 3-15Gender and Age Distribution of the Population in the ARB, 1980-1990 Table 3-16Crude Birth Rate and Death Rate (Per 1000 population) ARB, 2004 Table 3-16Mother Tongue in the ARB, 1980-2000Table 3-17Population by Ethnicity in the ARB, 2000Table 3-18Ethnics Groups in Barangays Covered by the Field Study, ARB, 2005 Table 3-19Land Ownership among Households in the ARB, 2000Table 3-20Estimated Percentage of Households With Titled Land in Study Barangays, ARB, 2005Table 3-21Land Use and Distribution, ARB, 2005Table 3-22Main Sources of Household Income, Gibong River Watershed, 2002 Table 3-23Sources of Drinking Water among Households, ARB, 1980-1990 Table 3-24Consensus on Sufficiency of Drinking Water ARB, October 2005(N= 19 Barangays)Table 3-25Consensus on Drinking Water Characteristics ARB, October 2005 (N= 19 Barangays )Table 3-26Irrigated Ricelands in the ARB, 2004Table 3-27Consensus on Sufficiency of Irrigation Water ARB, October 2005 (N= 19 Barangays)Table 3-28Reasons for Insufficiency of Irrigation Water ARB, October 2005 (N= 19 Barangays)Table 3-29Morbidity (Per 100,000 Population), ARB, 2004Table 3-30Five-Year Mortality (Per 100,000 Population) ARB, 1999-2004

Table 3-31Rate of Toilet Use of Households by Type of Toilet ARB, 1980-2000 Table 3-32Cooking Fuel of Households, ARB, 1980-2000Table 3-33Walling Materials Used by Households, ARB, 2000Table 3-34Wellness Rating of Families by Wellness Indicators, ARB, 2002 Table 3-35Percentage of Households by Type of Conveniences Owned, ARB,1980-2000Table 3-35Positive Changes Noted in the Past 20 Years in Studied Barangays, ARB, 2005Table 3-36Cooperative Efforts in Barangays, ARB, 2005Table 4-1Observations on Policy Environment on Water in the Philippines Table 4-2ARB Water Policy and GOP Water Policy, 2006Table 4-3ARBMP Water Policy, 2006Table 4-4Gender and Age Distribution of the Population in the ARB, 1980-1990 Table 4-5Gender Analysis Framework, ARB, 2005Table 4-6Literacy Level (10 Years Old and Over), ARB, 1980-2000Table 4-7Average Number of Tasks Done by Men and Women, ARB, 2005 Table 4-8Number of Barangays by Type of Changes in Work DistributionBetween Men and Women (last 20 Years Ago), ARB, 2005Table 4-9Average Number of Decision Situations Handled by Men and Women, ARB, 2005Table 4-10Average Number of Assets Owned by Men and Women, ARB, 2005 Table 4-11Holders of Forest Product User and Distributor Permits by Gender, ARB,2005Table 4-12Key Issues and Objectives of Caraga Gender Development Directional Plan, 2006-2010Table 5-1Sources of Funds for River Basin OrganizationsTable 5-2Summary of Aggregate Statement of Income and Expenses For the Years Ended December 31, 2004For Agusan del Norte, Butuan City, Agusan del Sur and Compostela Valley (In thousand pesos)Table 5-3Summary of Aggregate Statement of Income and Expenses,Local Government Units in the Agusan River Basin For the Years December 31, 2003 and 2004,All Funds (In thousand pesos)Table 5-4Approved Water Permits by the NWRB, 2004Table 6-1Primary Environmental Issues (Needs Assessment) ARB, 2005 Table 6-2Priority Concerns on the Agusan Watershed, 2005Table 6-3IRBM Attributes and Preconditions and ARB Gaps/ Problems ARB, 2005-2006Table 6-3Priority Issues/ Special Case Themes in the ARB, 2005-2006Table 6-4Vision Statements from Stakeholder Groups December 2005 Workshop, Butuan CityTable 6-5ARB VGO and Water Policy, 2005Table 6-6ARB Policy Areas and Development Objectives, 2005Table 6-7Key Themes, Intervention Initiative, ARB Master Plan, 2005-2006

Table 6-8Vertical and Horizontal Integration, ARB Development Strategy 2005-2006Table 6-9Policy Initiatives to Development Programs/ Projects ARB Master Plan, 2006Table 7-1The 17 Sub-River Basins of the ARB, 2005-2006 Table 7-2NWRB Water Permits, Selected Uses, ARB, 2005 Table 7-3Communal Irrigation Systems, ARB, 2004Table 7-4National Irrigation Systems, ARB, 2004 Table 7-5Proposed Dam Sites, ARBTable 7-6Water Permits and Discharges, Buenavista WD ARB, 2005 Table 7-7Water Permits and Discharges, Bayugan WD ARB, 2005 Table 7-8Water Permits and Discharges, Prosperidad WD ARB, 2005 Table 7-9Water Permits and Discharges, San Francisco WD ARB, 2005 Table 7-10Water Sources of Level III- Served Municipalities ARB, 1999 Table 7-11Water Permits and Discharges, Nabunturan WD ARB, 2005 Table 7-12Water Rates, Selected Water DistrictsTable 7-13Forecasted Municipal Water Demand ARB, 2000-2020 (unit: 1,000 cu.m) Table 7-14Forecasted Industrial water Demand ARB, 2000-2020 (unit: 1,000 cu.m) Table 7-15Water Balance (Municipal & Industrial Demand) ARB, 2005-2020Table 7-16Flood Control Structures, ARB, 2005 Table 7-17Proposed Hydropower Projects, ARBTable 7-18Estimated Cost of Projects in Water Quality Management Program ARB Master Plan, 2005-2006Table 7-19List of Proposed Flood Management Projects ARB Master Plan, 2005-2006Table 7-20List of Water Resources Development Projects ARB Master Plan, 2005-2006Table 7-21List of Watershed Management Projects ARB Master Plan, 2005-2006 Table 7-22List of Agusan Marsh and Wildlife Sanctuary Management Projects ARBMaster Plan, 2005-2006Table 7-24List of Indigenous Peoples Development Projects, ARB Master Plan, 2005-2006Table 7-25List of Agusan River Basin Organization Development Projects ARB Plan,2005-2006Table 8-1Checklist for Screening of Potential Environmental Impacts ARB Master PlanTable 8-2Simplified Screening Matrix of Environmental Impacts SEA, ARB Master PlanTable 8-3Summary of Significant Adverse Impacts & Mitigation Measures SEA, ARB Master PlanTable 8-4Simplified Screening Matrix of Cumulative Impacts SEA, ARB Master Plan

viiLIST OF FIGURES

Figure 1Location of Project Area, ARB, 2005-2006 Figure 2-1Administrative and Basin Boundaries Figure 2-2Climatological MapFigure 2-3Location of the Rainfall StationsFigure 2-4Location of Streamflow Gauging StationsFigure 3-12005 Gross National Regional Domestic Product Figure 3-22005 per capita GRDPFigure 3-3Thousand Persons Employed, CARAGA 2001-2005 Figure 3-4Comparative Distribution of Municipalities, ARB, 2005Figure 3-5Percentage Distribution of the ARB Population by Province, 2000 Figure 5-1Proposed Structure for the Agusan River Basin Organization Figure 6-1Conceptual Framework of IRBM for Agusan River BasinFigure 6-2Development Approach to IRBM for Agusan River Basin Figure 6-3IRBM Strategy for the Agusan River BasinFigure 7-1Location of Projects for Water Quality Management Program, ARB Master Plan, 2005-2006Figure 7-3Location of Projects for Flood Management Program, ARB Master Plan, 2005-2006Figure 7-4Location of Projects for Water Resources Development Program, ARB Master Plan, 2005-2006Figure 7-5Location of Projects for Watershed Management Program ARB Master Plan, 2005-2006Figure 7-6Location of AMWS Management Program Projects, ARB Master Plan, 2005-2006Figure 7-7Location of Projects for Indigenous Peoples Development Program, ARB Master Plan, 2005-2006

viiiLIST OF ANNEXES

ANNEX 2A: RAINFALL INTENSITY DURATION FREQUENCY (RIDF) ANNEX 2B: STREAMFLOW AVAILABILITYANNEX 2C: WATER BALANCE ANALYSIS ANNEX 2D: FLOOD SIMULATIONANNEX 2E: VULNERABILITY OF ARB TO HAZARDS

ANNEX 2F: ASSESSMENT OF MERCURY CONTAMINATION OF AGUSAN RIVER SYSTEM

ANNEX 2G: BIO-PHYSICAL FEATURES OF THE AGUSAN RIVER BASIN ANNEX 2H: BIO-PHYSICAL FEATURES OF ARB SUB-BASINSANNEX 2I: LAND USE AND LAND COVER

ANNEX 2J: MANAGEMENT OF AGUSAN MARSH AND WILDLIFE SANCTUARY ANNEX 4A: GENDER ACTION PLANANNEX 5A: SECRETARIAT ROLL-OUT STRATEGY

ANNEX 6A: INTER-RELATED CONCERNS

ACRONYMS AND ABBREVIATIONS

AAGRAnnual Average Growth RateADBAsian Development BankAFFAgriculture, Fishery and ForestryAFMAAgriculture and Fisheries Modernization ActAMWSAgusan Marsh and Wildlife SanctuaryARBAgusan River BasinARBAAgusan River Basin AuthorityARBMPAgusan River Basin Master PlanARBOAgusan River Basin OrganizationARMMAutonomous Region of Muslim MindanaoBODBiological Oxygen DemandBOTBuild-Operate TransferBPOBusiness Process OutsourcingBSWMBureau of Soils and Water ManagementCACommission on AuditCARCordillera Administrative RegionCARPComprehensive Agrarian Reform ProgramCBFMACommunity-Based Forest Management AgreementsCEPACommunication, Education and Public AwarenessCIPCarbon-in-pulpCISCommunal Irrigation SystemsCLTCertificate of Land TransferCLUPComprehensive Land Use PlanCNcyanideCOSTMACo-o, Sinug-ang, Tinagoand Masabong CPPAPComprehensive Priority Protected Areas Project CSCCertificate of Stewardship ContractDADepartment of AgricultureDA-BFARDA- Bureau of Fisheries and Aquatic ResourcesDAODENR Administrative OrderDENRDepartment of Environment and Natural ResourcesDepEdDepartment of EducationDIDPDavao Integrated Development ProgramDODissolved OxygenDOEDepartment of EnergyDOHDepartment of HealthDOTDepartment of TourismDPWHDepartment of Public Works and HighwaysEHSEnvironmental Health and SanitationEIAEnvironmental Impact AssessmentEMBEnvironmental Management BureauEMPEnvironmental Management PlanEUEuropean UnionEVATExpanded Value Added TaxFAMEFishery, Agri-Forestry, Mineral and EcotourismFAOFood and Agriculture OfficeGADGender and Development

GDPGross Domestic ProductGISGeographic Information SystemGMAGinintuang Masaganing AniGOCCGovernment-owned and Controlled CorporationGOPGovernment of the PhilippinesGRDPGross Regional Domestic ProductGWPGlobal Water PartnershipHgmercuryICCsIndigenous Cultural CommunitiesIPMIntegrated Pest ManagementsIPsIndigenous peoplesIRAInternal Revenue AllotmentIRBMIntegrated River Basin ManagementITInformation TechnologyIUCNInternational Union for the Conservation of NatureIWRMIntegrated Water Resources ManagementJBICJapan Bank for International CooperationJICAJapan International Cooperation AgencyLADALower Agusan Development AllianceLADPLower Agusan Development ProjectLAMPLand Administration and Management ProjectLCEsLocal Chief ExecutivesLGAsLocal Government AgenciesLGUsLocal Government UnitsLFPRLabor Force Participation RateLLDALaguna Lake Development AuthorityLMDALake Mainit Development AllianceLWUALocal Water Utilities AdministrationMAPMinerals Action PlanMDBMurray-Darling BasinMDGMillennium Development GoalsMISManagement Information SystemMMTMultipartite Monitoring TeamsMOAMemorandum of AgreementMOOEMiscellaneous and Other Operating ExpensesMSU- NaawanMindanao State University NaawanMTMetric tonsMTPDPMedium-Term Philippine Development PlanMWSSMetropolitan Waterworks and Sewerage SystemNNitrogenNCRFWNational Commission of the Role of Filipino WomenNCRNational Capital RegionNEDANational Economic and Development AuthorityNGOsNon Governmental OrganizationsNIANational Irrigation AdministrationNIPASNational Integrated Protected AreasNIPASNational Integrated Protected Areas SystemNRMPNatural Resources Management Program

NSCBNational Statistical Coordination BoardNSONational Statistics OfficeNTFPNon-timber Forests ProductsNWRBNational Water Resources BoardNWRBNational Water Resources BoardNWRCNational Water Resources CouncilODAOfficial Development AssistanceODAOfficial Development AssistanceOPAOffice of the Provincial AgricultureOPVOffice of the Provincial VeterinarianPPhosphorousPAGASAPhilippine Atmospheric, Geophysical and Astronomical Services AdministrationPAPPublic Awareness PanPBCPPPhilippine Biodiversity Conservation Priority-setting Program PCEEMPeople Collaborating for Environmental and Economic Management PDPresidential DecreePENROProvincial Environment and Natural Resources OfficePHOProvincial Health officePIAPhilippine Information AgencyPIAPhilippine Information AgencyPIPsPump Irrigation ProjectsPPAPhilippine Port AuthorityPPDCsProvincial Planning and Development CoordinatorsPPFPsProvincial Physical Frameworks PlansPPGDPhilippine Plan for Gender-Responsive DevelopmentPPPPsPolicies, Plans, Programs and ProjectsPSIWRMPhilippine Strategy for Improved Watershed Resources ManagementPTFWRDMPresidential Task Force on Water Resources Development and ManagementRARepublic ActRBCORiver Basin Control OfficeRCResource CapitalRDCRegional Development CouncilRIARCRegional Integrated Agricultural Research CenterRIPsRiver Irrigation ProjectsRISRiver irrigation SystemRPFPRegional Physical Framework PlanRSALUPRegional Sustainable Agriculture Land Use PlanRTDsRegional Technical DirectorsRWDCRural Waterworks Development CorporationSAFDZsStartegic Agricultural and Fisheries Development ZonesSEAStrategic Environmental AssessmentSECSecurities and Exchange CommissionSIDASwedish International Development AgencySMEsSmall and Medium EnterprisesSOCCSKSARGENSouth Cotabato, Cotabato City, Sultan Kudarat, Sarangani and General Santos CityTATechnical Assistance

xiiTGTheme GroupsTLWTalomo-Lipadas WatershedTSSTotal Suspended SolidsTWGTheme Working GroupsULEGUnified Local Environmental GovernanceUNUnited NationUNCEDUN Conference on Environment and DevelopmentUNDPUnited Nations Development ProgramUNIDOUnited Nations International Development OrganizationVGOVision, Goals and ObjectivesWBWorld BankWCEDWorld Council on Environment and DevelopmentWDsWater DistrictsWQMAWater Quality ManagementWRMPPWater Resources Policy PaperWWCWorld Water CouncilWWFWorld Water Forums

xiii

INTRODUCTION

1.0 INTRODUCTION

1.1 BACKGROUND

The Agusan River Basin (ARB) Master Plan (ARBMP) Project is a Technical Assistance (TA) provided by the Asian Development Bank (ADB) to the Government of the Philippines (GOP) here represented by the Department of Environmental and Natural Resources (DENR) and the National Water Resources Board (NWRB) as co-Project implementers.

The TA Study is commissioned to the Consultants consisting of CTI Engineering International Inc. (CTII, Japan), Halcrow (UK), and Woodfields Consultants Inc. (Philippines).

The TA is designed into two (2) phases. Phase I involves the formulation of the Water Policy and Development Strategy; and Phase II, the Master Plan. Total Project duration is 12 months, from August 2005 to July 2006.

1.2 STUDY AREA

The Agusan River Basin is the third largest river basin of the Philippines with drainage area of 10,921 km. It is located in the northeastern part of Mindanao as shown in Figure 1-1. The Agusan River passes mainly through three (3) provinces in Region XI and Caraga. The River originates from the slopes of Davao Oriental, traverses northward through Compostela Valley, Agusan Marsh in Agusan del Sur, and Agusan del Norte, before draining into Butuan Bay.

Figure 1-1 Location of Project Area, ARB, 2005-2006

1-11.3 GOAL AND OBJECTIVES

The goal of the Master Plan is to map out a development strategy that, once implemented, will promote optimal development of resources and reduce poverty in the Agusan River Basin. With reference to the TOR, the specific objectives of the TA are as follows:

Conduct of extensive consultations with stakeholders in the Agusan River Basin;

Formulation of a plan to strengthen IRBM capability in relevant government organizations as well as people in communities; and

Identification of appropriate institutional arrangements for managing the Basin

1.4 APPROACH AND METHODOLOGY

The TA provided by ADB will assist DENR-NWRB in preparing a Master Plan for the Agusan River Basin in Mindanao with the Integrated River Basin Management (IRBM) approach as its development framework. The process shall involve participation of all stakeholders, including civil society, the private sector, local government units (LGUs), and the National Government. IRBM denotes the implementation of Integrated Water Resources Management (IWRM), while IWRM as define by GWP is a process which promotes the coordinated development and management of water, land, and related resources in order to maximize the resultant economic and social welfare in an equitable manner without compromising the sustainability of ecosystems.

Implementing an IWRM process is particularly a question of getting the three pillars right on i) Moving towards an enabling environment of appropriate policies and strategies for sustainable development and management; ii) Putting in place the institutional framework through which the policies and strategies may be implemented; and iii) Setting up the instruments required by these institutions for appropriate action. The diagram showing the linkages of the pillars to the master plan in order to attain the vision, goal and objectives is shown in Figure 1-2.

VISIONVISION

GOAL

OBJECTIVES

APPRO POLICI LEGISLPRIATES and ATIONSINSTRSUMENT ETINSTITUTIONALEFRAMEWORK INPLACE

Master Plan for the Agusan River Basin

Strategies/Activities/Sub-Activities

Programs/Projects

Figure 1-2 Three Pillars Linkages Diagram

1-21.5 KEY ACTIVITIES

The TOR for the Consulting Services, as designed by ADB, consists of task activities grouped into two (2) phases as follows.

Phase 1: Review of Water Policy and Strategy for Basin Development

Phase 1 involves an elaboration of a Development Strategy for the Basin, while the highlights of major activities are:

(i) Collection of relevant statistical data relating to climatic, hydrologic, geographic, hydro geological, environmental and socioeconomic conditions in the Basin; and review of existing policies and strategies in water-related sectors. It includes a review of the role and sustainability of river basin organizations, resource transfer mechanisms between downstream residents and poor people in the upstream living in watershed areas, and participatory approaches for stakeholder involvement in drawing up the Master Plan.

(ii) Conduct of intensive consultation meetings with stakeholders in the downstream, midstream and upstream areas to identify needs and resolve conflict of interests, and determine approaches for future development of the Basin while protecting environmental sensitive areas.

(iii) Assessment of the role of existing basin organizations, such as Laguna Lake Development Authority and Agno River Basin Commission, with analysis of the issues on sustainability of inactive organizations, such as the Cagayan River Basin Commission and Bicol River Basin Commission.

(iv) Firming up of the development strategy for the Agusan River Basin, taking into consideration the outcome of stakeholder consultations. The Consultants to hold a workshop at the end of Phase 1 with representatives from the DENR, NWRB, Department of Agriculture (DA), NIA, Department of Public Works and Highways (DPWH), four (4) provincial governments of Northeastern Mindanao, Butuan City government, non-government organizations (NGOs), and other stakeholders. The workshop shall be the venue for discussing the Basin Development Strategy as well as the results to be presented in the Interim Report. The development strategy will be discussed at the Tripartite Meeting among representatives from the Government, the Consultants, and ADB.

Phase 2: Formulation of a Master Plan

The key activity involves the formulation of a Master Plan for the Agusan River Basin based on the Development Strategy agreed upon at the end of Phase 1. The Master Plan will identify measures for strengthening capability for IRBM, and assess the necessity for the Agusan River Basin Commission. Likewise, it will include the prioritized list of potential projects in irrigation, watershed restoration and management, environmental protection, hydropower, domestic and industrial water supply and other sectors, with preliminary cost estimates of each project. This will be presented and discussed in a Final Workshop, and will serve as baseline by the Government and ADB and other development partners for future development activities in the Basin.

PHYSICAL AND ENVIRONMENTAL CONDTION

2.0 PHYSICAL AND ENVIRONMENTAL CONDITION

2.1 GEOGRAPHIC SETTING

An understanding of the physical system and its interaction with the environment is a prerequisite for an effective planning and management of water resources.

The Agusan River Basin is a strategic water resource forming three (3) sub-basins in the northeastern portion of Mindanao, popularly referred to as the Lower, Middle, and Upper Agusan River basins.

Lower Agusan River Basin (Downstream Watershed), which is the area downstream of the Agusan wetland along the downstream reach from Talocogon in Agusan del Sur Province; Middle Agusan River Basin (Midstream Watershed), which is the area along the reach between Talocogon and Sta. Josefa in Agusan del Sur Province including the Agusan wetland; and, Upper Agusan River Basin (Upstream Watershed), which is the area along the upstream reach from Sta. Josefa in Compostela Valley Province

Figure 2-1 Administrative and Basin BoundariesThe Agusan River flows through three (3) provinces of Agusan del Norte, Agusan del Sur and Compostela Valley in Mindanao as shown in Figure 2-1. It is the third largest river in the Philippines with a total catchment area of about 10,920 km. Fed by eleven (11) principal tributaries, the 350-km river originates from the slopes of Mounts Mayo and Tagopo in Compostela Valley, traverses northward through Compostela Valley, Agusan Marsh in Agusan del Sur, and Agusan del Norte, before draining into Butuan Bay. The Basin is comprised of 11 principal river systems as listed in Table 2-1.

Figure 2-1 Administrative and Basin Boundaries

2-1Table 2-1 List of Tributaries

NWRBCodeRiver BasinDrainage AreaEstimated Annual

(sq. kms.)Run-off (MCM)

10315Agusan10,92127,880

10316Ojot76519,523

10317Wawa7952,030

10419Andanan380970

10318Libang228582

10319Maosam4181,067

10320Kasilan284725

10321Gibong8242,104

10322Adgaoan9652,464

10323Simulao9442,410

10324Kayonan8022,048

10325Haoan6641,695

The Agusan River Basin is an elongated half-graben structure closely related to the Philippine Fault Zone which transverses through the centre from north to south. The major physiographic features of the basin are the Pacific Cordillera on the east and south, the Central Cordillera on the west and the Davao-Agusan trough in the central part. The Pacific Cordillera forms the eastern and southern boundaries of the region and separates it from the Pacific Ocean. Peak elevations range from 1,700 m along the eastern boundary and 2,500 m in the southern mass. A low section with elevations of a couple hundred meters exists adjacent to the central portion of the basin. The Central Cordillera is a discontinuous mountain range and volcanic chain having peak elevations over 1,700 m.

The southern portion of the basin, approximately 65 km in length, is narrow and mountainous with an average width of only 25 km. The remaining basin averages 50 70 km in width. Within the wider portion of the basin, an alluvial plain occupies the central part. This central flood plain slopes gently downwards to the north and is generally less than 50 m above sea level and the average width is approximately 30 km. Foothills occupy the area between the central alluvial plain and the mountains.

An essential feature of the Basin is the wetland located in the middle reach of the river (Middle Agusan), known as Agusan Marsh, which serves a flood retention basin that cuts peak discharge of flash floods to downstream areas. The wetland also acts as a sediment trap during flood season.

The wetland harbors unique and pristine habitats like sago, peat swamp forests and snails carrying schistosomiasis parasites. It is also the habitat of rare and endangered fauna. Physically, the Agusan Marsh is about 19,200ha, 14,836ha of which was proclaimed a Wildlife Sanctuary in 1996 and is registered under the Ramsar Convention, being the most important freshwater wetland in the country. The Marsh is also a designated protected area under the National Integrated Protected Areas System (NIPAS).

2.2 CLIMATE

The Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA) utilizes three climatic classification systems, namely: Corona, Hernandez, and Koppen. The Corona classification gives emphasis on season type, the Hernandez on the number of wet and dry months, and the Koppen on the temperature range and the amount of rainfall in the driest month.

Based on Corona Climatological Classification, the climate of the Agusan River Basin is generally classified as Type 2, which is characterized by the absence of a dry season and a very pronounce maximum rainfall occurring from November to January. However, the southern portion of the

basin, which covers the area of Compostela Valley exhibits the characteristic of Type 4. The climate of the basin is described as no dry season with a very pronounced maximum rainfall during the months of November to January.

Similarly, under the Hernandez classification, the basin belongs to Type A or rainy throughout the year and under Koppen, Type A for tropical wet climate.

A map of the basin with the areas classified under the different types of climatic conditions is shown in Figure 2-2.

Figure 2-2 Climatological Map

2.3 RAINFALL

Within the Agusan River Basin, the Philippine Atmospheric, Geophysical, and Astronomical Services Administration (PAGASA) maintains only one rainfall recording station, which is located at Bancasi Airport, Butuan City. Other nearby PAGASA stations include: Surigao City; Hinatuan, Surigao del Sur; Cagayan de Oro, Misamis Oriental; Davao City; and Malaybalay, Bukidnon. The data from these stations is almost continuous over the last 20 years.

Within the basin, daily rainfall information was made available from NIA irrigation system offices. Generally this data is collected at the office compound and at the site of the irrigation diversion structure, but the record length is not as long as that from the PAGASA stations. However, this information is better distributed throughout the basin. Additional historic information, usually in the form of monthly averages, has been extracted from previous reports. A summary of the recording stations is given in Table 2-2.

Table 2-2 List of Rainfall Stations

LocationsProvinceLatitude LongitudeYear of RecordMaintaine d byElevationAbove msl (m)

1. Butuan CityAgusan del Norte8o 57'125o 33'1960 - 2001PAGASA18.00

2. La Suerte, Prosperidad Pilot Demo Farm, GRISAgusan del Sur8o 27'125o 54'1981 - 2001NIA48.00

3. Sta. Irene, Bayugan ARISAgusan del Sur8o 44'125o 57'1981 - 2001NIA100.00

4. Gagbas, BayuganAndanan RIS CompoundAgusan del Sur8o 47'125o1991 - 2000NIA38.00

5. Patin-ay Agromet StationProsperidadAgusan del Sur8o 36'125o 53'1970 - 1999DA45.00

6. NIA - PIORosarioAgusan del Sur8o 27'125o 53'1989 - 1998NIA92.00

7. Simulao RISTrentoAgusan del Sur8o 03'126o 04'1983 - 2001NIA60.00

8. Tagum Agromet Station *Twin RiverDavao del Norte7o 25'125o 48'1972 - 2000PAGASA18.00

9. Malaybalay*Bukidnon8o 09'125o 05'1949 - 2000PAGASA627.00

10. Hinatuan*Surigao del Sur8o 22'126o 20'1971 - 2000PAGASA3.00

11. Davao City*Davao del Sur7o 07'125o 39'1902 - 2000PAGASA18.00

12. Sagbayan, San Miguel *Tago RISSurigao del Sur8o 56'126o 02'1990 - 2000NIA15.00

13. CompostelaBatutu RISCompostela Valley7o 35'126o 6'1970 - 2000NIA140.00

14. CMU, Musuan*Bukidnon7o 53'125o 02'1978 - 1999PAGASA350.00

15. Cagayan de Oro City *Misamis Oriental8o 29'124o 38'1908 - 1999PAGASA6.00

16. Surigao City*Surigao del Norte9o 48'125o 30'1902 - 2000PAGASA39.00

17. Lumbia Airport*Cagayan de OroMisamis Oriental8o 26'124o 37'1977 - 2000PAGASA182.00

Note:* Rainfall Station located outside the Watershed

In total, rainfall information was available for 17 sites within the Agusan River Basin. Apart from the PAGASA stations outside of the basin, the network is exclusively located on the east side of the valley and the highest elevation of a station being 627 meters. The locations of the rainfall recording stations are indicated in Figure 2-3.

Figure 2-3 Rainfall Stations and Isohyetal Map

An isohyetal map of average annual rainfall in the basin is also delineated in Figure 2-3. As shown in this map, the average annual rainfall is not uniform throughout the basin. It varies from 2,000 mm to over 4,000 mm. The lowest accumulations occur in the area between Talacogon and Butuan, and upstream of Sta. Josefa into the central portion of Compostela Valley. The highest rainfall occurs in the mountains that bound the basin on the east and west. The rainfall in the central portion of the basin varies between 3,300 and 3,600 mm. Of interest, Rosario, Agusan del Sur has the highest recorded average annual rainfall of 3,633 mm although its elevation is only about 60 m. As compared to Butuan City, the higher average depth in the central region is a result of a greater number of days of rain and higher intensities.

Although outside the basin, the PAGASA station at Hinatuan has been selected as the index station for the central and southern portions of the basin, Butuan has been used as the index station for the northern region downstream of Talacogon

In the northern and southern portions of the basin, the average annual rainfall is about 2,000 mm. The minimum and maximum annual rainfall for these areas is 1,000mm and 3,000 mm respectively. In the central portion of the watershed, the long-term average annual is 3,600 mm with the minimum annual rainfall being 2,200 mm and the maximum annual rainfall reaching 5,000 mm.

These values indicate that there is a very large variation in rainfall, not only between different locations, but from year to year.

The rainfall intensity duration frequency (RIDF) is explained in Annex 2A.

2.4 STREAMFLOW

Discharge data is available from two primary sources: NIA and BRS (NWRB). The NIA data consists of daily means and is collected at their diversion weirs for the larger irrigation systems. The officially released BRS data consists of daily mean and in some instances daily maximum values up to 1992. A 2004 publication is available from BRS but there are no river systems included within the basin. The discharge values are determined through gauge readings conducted three times a day and in the case of high flows, at a smaller interval.

A total of 18 NWRB or BRS gauging stations have been installed and operated in the basin at one time or another. Presently, data is only being collected for 6 stations. Table 2-3 contains a summary of the available data and other information about these stations, while their approximate point locations are shown in Figure 2-4.

Table 2-3 List of Streamflow Gauging Stations

No.

Station ID

River Name

Station Name

Drainage area (km2)

Year of Record

OperationalZero Gage Elev.(m)

Latitude LongitudeMax. Q Min. Q (cms)

Gage Height (m)

110SW085252 PW005Agusan RiverMagsaysay Bridge, baan, Butuan City11,5101957-1991Yes-8O57"-

4.95125O32"-

210SW084254 BRS032Wawa RiverWawa, Bayugan, Agusan del Sur3961981-1990No98.528O49"2,296.53

5.49125O42"0.60

310SW082454 BRS033Andanan RiverSta. Irene, Bayugan, Agusan del Sur2011983-1987Yes-8O45"209.22

1.84125O45"3.52

410SW084254 BRS031Wawa RiverWawa, Esperanza, Aguasn del Sur1,0311957-1984No0.427 (AMSL)8O47"841.00

41.98125O41"0.020

510SW083253 PW009Busilao RiverMilagros, Esperanza, Agusan del Sur3161967-1970No8O38"-

125O34"-

610SW083255 PW013Gibong RiverBah-bah, Prosperidad, Agusan del Sur4271964-1975No5.968O36"582.00

5.20125O54"0.30

710SW083254 PW010Agusan RiverSan Isidro, Talacogon, Agusan del Sur7,390No98.028O32"-

7.76125O46"-

810SW082254 PW012Kasilayan RiverBaylo, Talacogon, Agusan2091968-1969No-8O27"-

-125O42"-

910SW081254 PW014Kayawan RiverLangasian, La Paz, Agusan del Sur3481967-1980No47.158O14"530.66

3.80125O42"0.90

1010SW081254 PW015Adgaoan RiverHalapitan, La Paz, Agusan del Sur8201967-1970No-8O14"-

-125O45"-

1110SW080255 PW017Ihaoan RiverNueva Gracia, Loreto, Agusan6671967-1968No-8O06"-

-125O52"-

1210SW080255 BRS030Simulao RiverSan Teodoro, Bunawan, Agusan del Sur1,0301981-1990Yes92.4148O09"810.60

6.98125O59"1.85

1310SW080255 BRS029Agusan RiverSta. Josefa, Bunawan, Agusan del Sur1,5991982-1991Yes-7O59"1,857.84

8.00126O02"2.04

1410SW080260 BRS028Simulao RiverSan Ignacio, Trento, Agusan del Sur2861984-1991Yes-8O01"196.20

3.70126O08"0.064

1510SW074260 BRS027Agusan RiverMagas, Mamonga, Monkayo, ComVal1,5221981-1986No-7O48"544.20

6.88126O03"0.35

1610SW073260 BRS026Agusan RiverCamanlangen, New Bataan, ComVal3431967-1985No92.967O31"212.00

3.12126O07"0.63

1710SW075260 BRS028Agusan RiverKalaw Bridge, Monkayo, ComVal1,3551959-1995Yes-7O50"2,114.00

-126O03"-

18-Agusan RiverBatutu River Irrigation System290Yes-7O35"-

-126O06"-

Figure 2-4 Location of Streamflow Gauging Stations

Dependability Analysis. To ensure adequate water supply during dry or drought conditions, a low flow analysis has been conducted to establish available discharges on tributaries during these periods. Flow duration curves for 15 tributaries at their confluence with the Agusan River have been developed. Flow duration curves provide the percentage of time a certain flow is equaled or exceeded. Dependable stream flow can be derived from these curves by reading off values for a particular percentage of time, say 80%. Eighty percent (80%) dependability is the limit adopted by NWRB in granting water rights.

For an exceedance probability of 80%, the surface water potential for each sub-basin has been estimated as shown in Table 2-4. The streamflow availability analysis is presented in Annex 2B, while the water balance analysis is shown in Annex 2C.

Table 2-4 Surface Water Potential of Sub-Basins, ARB, 2000Sub-Basin No.Name of RiverPotential Surface Water (MCM)

Area (km2)

1Wawa1,026851.47

2Gibong1,269473.04

3Simulao997441.51

4Upper Agusan454.12

5Manat196138.76

6Boabo14144.15

7Logum15150.46

8Ihaoan656220.75

9Umayam782315.36

10Adgaoan983378.43

11Kasilayan300378.43

12Maasam400441.5

13Libang280283.82

14Ojot805756.86

15Bugabus184145.06

Source: Study on Watershed Management and FWS of the Agusan River Basin(DPWH, 2003)

2.5 GROUNDWATER

Recently the NWRB endeavored to consolidate all water resources developments and corresponding data throughout the country. Well drillers and well owners have been required to submit well-log data from their wells prior to their application of water permits. However, despite rigorous campaign by the NWRB, the registration of water users still needs further enhancement.

Groundwater mining in the Agusan Basin shows total groundwater storage at an estimated 2,690 MCM with an inflow to the groundwater reservoir system of about 940 MCM/year (NWRC, 1983). The recommended safe yield level is set at 940 MCM/year. Barring any major change, 994 MCM/year would be available for a 50-year mining withdrawal.

Groundwater availability is reportedly restricted by the occurrence of natural gas in the middle and lower reaches of the river system (DPWH, 2003). Groundwater cannot be abstracted easily both as a source of potable water and of irrigation water, due to its high iron content, a constraint for use in some crop types in irrigation. There is also evidence of fecal pollution in groundwater, particularly near large settlements, and of salinity in younger aquifers found near coastal areas.

2.6 ENVIRONMENTAL SETTING

Situational analysis of the environmental setting of the ARB covers four (4) essential aspects; namely the: (i) natural physical environment, distinguished from the previous discussion by providing corresponding environmental perspectives on several physical features of the Basin; (ii) biological environment, as encompassed by forest-watershed resources/terrestrial, freshwater, and marine habitats; (iii) environmental issues and social dimensions, taking into account of major issues arising from interaction of social and environmental elements in the Basin, particularly of human practices and decisions related to and impacting resource use and sustainability; and, (iv) key environmental issues and stakeholder priorities, which is 2-tiered in dealing with local views and positions on the environment as a whole, and on the status of watershed management in particular.

2.6.1 Natural Physical Environment

(i) Atmosphere

The main consideration of air pollution in the ARB from the perspective of water resources management is that pollutive air particles may land on the ground and find their way into surface and groundwater systems. The potential sources of atmospheric pollution are isolated industrial processing plants particularly in Butuan City, where there is a concentration of wood processing. In Agusan del Sur, palm oil mills are potential air polluters, although these tend to use generated organic waste as fuel rather than non- renewable hydrocarbons. However, there is presently no baseline air quality monitoring data by which to understand the extent of air pollution from such sources.

(ii) Climatic Conditions

From an environmental planning perspective, the daily distribution of rainfall is crucial to the hydrology of the Basin. Intense localized monsoon rains of 3-5 days duration are causes of significant flooding affecting even coastal areas from October to February each year.

(iii) Flooding

Flood studies previously conducted on the Basin have indicated the flood-retarding capacity of the Agusan Marsh. Flood analysis carried out in a 2003 DPWH Study1 showed that while behaving in Butuan City at 2,600m3/s for a 2-year return period and nearly 5,000m3/s for a 30-year return period, peak discharges immediately downstream of the Marsh tends to be slower at 1,000m3/s for a 2-year return period and 2,100m3/s for a30-year return period.

The same flood analysis indicated that most peak flood events downstream of the Agusan Marsh are due to flood conditions on its tributaries downstream. However, the total discharge volume and duration of such flooding will still be influenced by flows coming from the Marsh.

In the Upper Agusan River Basin, comprising of the municipalities of Monkayo, Montevista, Compostela, New Bataan, Nabunturan and Maragusan, flooding is caused by the overflowing of heavily silted rivers. Moreover, the meandering narrow gorge downstream of Kalaw Bridge causes backwater to extend upstream of it, inundating large agricultural lands.

The flood simulation discussion is presented in Annex 2D, while the vulnerability of the basin to hazards is discussed in Annex 2E.

(iv) Surface Water

(a) Water Quantity

Shortages in surface water would be critical in the future at several sub-basins in the ARB, due primarily to increases in population and expansion of irrigation developments. To reiterate, eight (8) sub-basins would experience water deficit before year-2030.

(b) Water Quality

Major surface water quality issues in the Basin are due to pollution from: 1) industry including mining, palm and coco oil processing and wood-based industries, 2) domestic waste water and solid waste, and (iii) agri-chemical use.

1 DPWH, 2003, Study on Watershed Management and FWS of the Agusan River Basin

1) Industry

Pollution from Mining. Two (2) gold mining areas exist in the Basin. One is within the upper catchment in the Diwalwal gold rush area in Compostela Valley. In this area, small and medium-scale illegal mining operations have been going on unregulated for the last 20 years, until State control was imposed in late 2002. The other is within the middle catchment in the Co-o, Sinug-ang, Tinago and Masabong (COSTMA) area between Rosario and Bunawan in Agusan del Sur. Here, a modern, closed-cycle system of carbon-in-pulp (CIP) milling and treatment facilities is available but operates at only 6% of its design capacity, alongside informal small-scale operations.

A serious environmental concern in both areas is the use of mercury (Hg) and cyanide (CN) in the process of amalgamation and cyanidation to extract gold from ore. The DENR-Environmental Management Bureau (EMB) XI started monitoring mercury and cyanide levels in surface water only in 1995 but ceased after early 2003. Meanwhile, no regular data collection on these surface water environments in being undertaken by DENR-EMB XIII.

Available surface water data show the alarming levels of toxic elements in several river systems within or contiguous to the ARB especially those located close to mining areas. The data likewise indicates the spread of mining pollutants into agricultural and marine ecosystems.

DENR-EMB XI monitoring results until 2002 reveal that in Naboc River, about 5km downstream of the Diwalwal mine site, Hg levels in water were often more than 10 times the national standard of 0.002 mg/L. In Agusan River, about 30km from the confluence with Naboc River, Hg levels in water were as high as 4 times the allowed limit. Hg levels in water were below standard only in 2002, during the imposition of the state moratorium on mining in Diwalwal. After mining was resumed in 2003, Hg levels in water once more soared to as high as 750 to 900 times the acceptable level.

A special UNIDO2-funded study carried out in Diwalwal by the British Geological Survey (UNIDO, 2000) showed that Hg levels in polluted sediments from Naboc River that found their way into irrigated rice paddies in nearby fields were as high as 66mg/kg. Levels of Hg in bottom sediments in Agusan River downstream of the confluence with Naboc River were as high a 55 times the Canadian standard of 1 ppm or 0.001 mg/L. An assessment by DENR-MGB in 2002 confirms that Hg levels in sediments were indeed as high as 13 times the Canadian standard in the Diwalwal area and were at alarming levels (17.6 mg/L) in the Sinug-ang mine area.

A marine resource assessment study conducted by the Mindanao State University at Naawan (MSU-Naawan) for the DA-Bureau of Fisheries and Aquatic Resources (DA-BFAR) in 2002 also confirmed that Hg concentrations in coastal waters, sediments and fish samples were also a cause for alarm, as polluted river sediments move into the marine system.

Pollution from Palm/Coconut Oil Processing. The concern on vegetable oil processing is its production of waste with relatively high levels of organic matter that could result to low levels of biological oxygen demand (BOD) in water and, in extreme cases, render surface water pollution. Specific industrial pollutants generated can also be major contributors of phosphorus (P) and nitrogen (N) that may cause eutrophication of water bodies.

In the Basin, extensive palm oil plantations are found in its middle catchment, notably in Rosario, San Francisco, Trento and Veruela in Agusan del Sur. A palm

2 United Nations International Development Organization (UNIDO)

2-10oil processing plant is located in Rosario while a coconut oil processing plant is operating in the coastal municipality of Magallanes in Agusan del Norte. These industries were perceived by communities to have been responsible in the incidence of fish kills in the Basin.

Regular DENR-EMB XIII monitoring show that dissolved oxygen (DO) and BOD were consistently within acceptable levels. However, there is no regular point source monitoring of effluents from these industries.

Pollution from Wood-based Industries. Match and plywood factories concentrated near the mouth of Agusan River in Magallanes pose potential problems to surface water quality of Agusan River as well as Butuan Bay due to high level of organic wastes and chemical effluents disposed into these river systems. Aside than this, manufacturing plants also produce noxious gases from smokestacks. Meanwhile, most sawmills located in the banks of Agusan River in Butuan also discharge waste directly into the river and burn these in the open, the practice causing ash and other particulates to pollute both air and water. Other non-operational saw mills, meanwhile, have abandoned waste stockpiles that become washed out during flood events. Similar to processing plants, there is no regular point source monitoring of effluents from these wood industries.

2) Pollution from Domestic Waste Water

The provision of sanitation facilities in the Basin is very inadequate. While it is reported that sanitation has generally improved (with more than 90% of households having sanitary toilets throughout the Basin), there are no closed domestic wastewater collection systems or treatment facilities in the study areas, not even in Butuan City, a settlement of more than 200,000 people. In areas without sanitation facilities such as the marshland/wetland area, households directly dispose human waste into the river system while also relying on this as a direct source of domestic water supply during the dry months.

There is very limited DENR-EMB monitoring data on fecal coliform for the Davao portion of the Basin and none for Caraga. However, the MSU study found that the bacterial pour plate counts, total coliform bacteria, and fecal coliform levels were high near major coastal settlements where human population is concentrated, especially in Butuan City.

3) Potential Pollution from Agricultural Chemicals

The potential pollution from agriculture is associated with the use of agri- chemicals in rice producing and palm oil areas. The practice is also suspect in areas planted to banana and high-value vegetables in the uplands. It is, however, difficult to assess the degree to which ecological health, especially of the Agusan marshland/wetland and particularly fisheries habitats, have been compromised in the absence of pertinent water quality monitoring data available on N and P as well as pesticide and herbicide levels in these areas.

Indicative, however, is the MSU study of Butuan Bay that detected levels of ammonia, nitrites, nitrates and phosphates in marine waters in 2000 and 2001 at levels relatively high and at times way over national standards. The highest levels tended to be at specific locations where smaller local catchments flow into the Bay. Pesticide levels (specifically organochlorines and organophosphates) were found to be low, but these are indicators of only a few of the wide range of agro- chemicals available to farmers in the area. High levels of cadmium were identified in the marine system, the source partly attributed to nitrate and phosphate fertilizer.

Aquaculture may also be a potential source of pollution. Cadmium is considered particularly problematic in its capacity to bio-accumulate like mercury.

In order to determine the status of mercury contamination an assessment was conducted and discussed in Annex 2F.

(v) Erosion and Sedimentation

The assumption that sedimentation in the Basin is being caused primarily by upland erosion due to the removal of primary forest cover in its upper catchment appears to be unfounded. Field observations confirm that subsequent vegetation re-growth and grassland succession have been strong and rapid enough to arrest erosion. In areas where vegetation cover has been stripped for limited upland cultivation, the land has not scarred or gullied.

Channel erosion and bed load (rocks and coarse gravels) deposition is a problem though in the upstream catchment and has rendered parts of the Batutu irrigation facility in Compostela Valley practically useless. In Monkayo and Nabunturan, the Upland Development Project of the DA reports of severe erosion due to upland cultivation in areas with steep slopes. Upland erosion is also a problem in mining areas particularly in Diwalwal.

In midstream and downstream reaches, field observations confirm that the main contributor of suspended sediment is riverbank erosion in specific locations, particularly along river bends. The river picks up significant material upon leaving upland areas andhits soft red/brown deposits in the floodplain, as earlier confirmed in a 1976 UNDP/FAO3 study. The same study found out that going downstream, levels of total suspended solids(TSS) increased from 140-180ppm in New Bataan to 233ppm in Compostela and 268ppm in Monkayo.

Interestingly, the study also determined that sediment level at the point where Agusan River leaves the Marsh in Talacagon was only 140ppm, about half the level of the inflow water in Sta Josefa. However, within 30km downstream from Talacogon, the sediment level almost doubled again to 270ppm, confirming the role of the Marsh as a natural sediment catch basin. Interviews with marshland/wetland communities confirm that Agusan River deposits as much as 30-50cm of sand, silt and organic materials with each flood event. Moreover, field observations confirm that bank erosion is also actively going on in inland tributaries downstream of the Marsh, for example, where Ojot and Wawa Rivers meet the main Agusan River.

The MSU study earlier cited, meanwhile, found that Agusan River is by far the most significant contributor of sediment deposition in Butuan Bay.

2.6.2 Biological Environment

(i) Forest-Watershed Resources/Terrestrial Habitats

(a) Development Trends

The ARB comprises an estimated 1,382,622ha of forest lands as of 2003, distributed over Agusan del Sur (49%), Agusan del Norte (14%) and Davao del Norte (37%), the latter considered representative of Compostela Valley. Correspondingly, its total A&D lands are about 585,932ha and respectively distributed as follows: Agusan del Sur (38%), Agusan del Norte (11%), and Davao del Norte (51%).

A land use dynamic is the trade off between A&D lands and forest lands, which in the study areas is expected to follow the same trend as that observed for the Philippines as a whole. The Philippines, from 1978 to 2003, has been experiencing a decline in forest land at 6.38% alongside an increase in A&D lands of 8.22%. Forest lands covering 16,929,114ha in 1978 was down to 15,85,922ha in 2003. Correspondingly, A&D lands expanded from 13,070,888ha to 14,145,078ha. Such trend could be assumed similar to

3 UNDP = United Nations Development Program; FAO = Food and Agriculture Office

the ARB based on the results of ocular field survey and the reported rapid cutting of natural rain forest in the area as early as the 1960s. Remaining virgin forests in the whole country may be estimated at less than 1 million ha at present; a state indicative of the need to pursue protection and restoration strategies preservation and/or restoration of productive and protective values of its forest lands including those within the ARB.

The ARB hosts several wood and forest-based industries generating income to the national economy including forest management arrangements for the sustainable development of forest resources. The reference shall be Caraga region, which represents the majority of study areas.

Caraga happens to be fifth among all other regions as to total vegetative cover, the four dominant of which are second growth forest (484,807ha), brush land (184,040 ha), plantation forest (188,500ha) and old growth dipterocarp forests (78,619 ha). The region hosts seven (7) watershed forest reserves (5th in all) although despite these forest assets,Caraga has no declared national parks/national marine parks/national marine reserves, or game refuge and bird sanctuaries.

Although possessing only the fifth largest forest lands, the region is the top producer of major forest-based products (i.e., logs, lumber, veneer, plywood) in the entire country. Total log production in Caraga from three (3) major sources (i.e., A&D lands, IFMA/TPLA and TLAs), totaled 471,574.57 cu. m. as of December 2003. In 2001, the region then generated about 480,777 cu. m. or 75% of log requirements in the country. Other than this, the region particularly Butuan City hosts several wood processing plants that support wood-based industries in the Philippines. The total annual log requirement of these wood-processing plants was 964,124.71 cu. m. as of June 21, 2002. Wood-processing plants are complemented by the presence of several TLAs in the area, the total number of which has declined from six in 1994 to only two in 2003.

Substantial CBFM areas are also found within the ARB. In the Caraga Region alone in 2003, about 500,000ha are the sites of up to 517 CBFM areas benefiting about 51,514 households with 133 POs.

Further discussion on the bio-physical features of Agusan River Basin is in Annex 2G, while the sub-basin is in Annex 2H.

(b) Environmental Conditions

There has been rapid removal of natural forest cover within the ARB during the logging boom that may have started in the 1960s. By 1997, there remained a total of 867,321ha of forest lands in the Caraga Region (ADN and ADS alone) broken down as follows: unclassified forest lands (1,125ha) and classified forest lands (866,196ha). Classified forest lands are further categorized into established forest reservations (212,389ha), established timberland (647,601ha), and civil reservations (6,206ha). Total forestland in this case constituted 75.05% of the total land area of Agusan del Norte and Agusan del Sur.

When left alone, secondary re-growth (i.e., grasses, bushy/brushy and eventually, secondary growth forest) tended to be rapid. On logged-over areas, 153,768ha have been planted with fast-growing timber species, mostly falcata, gmelina and bagras. Such trend was encouraged under the old reforestation paradigm of the DENR through its various tenurial instruments (e.g., IFMA, TLA, ISF, SIFMA). These programs tended to be counter-productive though in improving bio-diversity. Nonetheless, this situation may be reversed with the paradigm shift to watershed rehabilitation using agro-forestry.

The degradation of forests in the ARB still continues though, as observed in several agricultural and land use conversion practices. In some sloping lands, at present, cleared forest areas have given way to unsustainable farming practices, including kaingin (slash-and-burn) farming systems and conversion to plantations. In the Davao region, some upland areas of Nabunturan, Compostela Valley have been devoted to large-scale

banana plantations operated by multi-national corporations. In the middle catchment notably in Roasario, San Francisco, Trento and Veruela, more lands are being converted to palm oil plantations.

In coastal areas within the Basin, much of saltwater mangrove forests have been removed, partly to clear land for brackish water shrimp and saltwater fish aquaculture. The removal of such vegetation has increased the risk of coastal erosion, considering that mangrove vegetation is extremely effective at dissipating wave energy.

Cultivated areas, on the other hand, are concentrated in floodplains found in the middle reaches of the Basin. The lowlands, notably Bayugan, Prosperidad, Rosario, Bunawan, Esperanza and Sta. Josefa are primarily devoted to rice and, to a lesser degree, corn production. The trend is towards expanding rice cultivation where possible and intensifying this to two (2) crops a year with irrigation.

The discussion on Land use and land cover are further discussed in Annex 2I.

(ii) Freshwater Habitat

The Agusan Marsh Wildlife Sanctuary is the most ecologically sensitive area in the Basin and requires utmost attention. It is included in the Philippine NIPAS and, owing to its endemism and biological diversity, is among integrated priority conservation areas in Mindanao, recognized under the Philippine Biodiversity Conservation Priority-setting Program (PBCPP). To reiterate, the marsh is of international significance, having been listed under the Ramsar Convention on Wetlands as the most important freshwater habitat in the Philippines.

The designated protected area of the Marsh consists of 19,196ha, with 14,836ha defined as the core by virtue of Presidential Proclamation 913 in 1996. There is a wider management area of 111,540ha, presently considered as the buffer zone, which has already been significantly encroached by human activity. A new bill filed in Congress proposes to expand its marshland/wetland management areas to more than 40,000 ha.

During the dry months, the marshland/wetland is a series of isolated ponds or interconnected lakes. However, during the rainy season, the perennially and seasonally flooded water bodies merge into one lake system. The marshland/wetland area has seven (7) major habitat types with three (3) very unique types of flood-tolerant vegetation communities. It also contains a mossy forest with relic vegetation communities while a large seasonal water body near Talacogon has unique grassland cover. A special feature of the Marsh is its peat forest, which is beginning to draw worldwide conservation interests.

A full species inventory of the Agusan Marsh was prepared in 2001 under the WB-funded Comprehensive Priority Protected Areas Project (CPPAP). The inventory identified more than a hundred species of terrestrial plants and freshwater flora that are adapted to its flooding pattern. It also included hundreds of species of fauna including mammals, herptiles, birds and fish species. Several of its species of freshwater crocodiles, flying foxes, and soft-shelled freshwater turtles are on the International Union for the Conservation of Nature (IUCN) Red List of threatened, endangered and critically endangered species. Some of its reptiles, bats, frogs, geckos, skinks and snakes are endemic, including the Reticulated Python and Philippine Cobra. The Marsh also hosts rare species of butterflies, crocodiles, lizards, frogs and snakes.

On an international scale, the Agusan Marsh is recognized as a crucial link in the migratory routing of birds between Siberia and Australia; the prime reason for which the Marsh received recognition under the Ramsar Convention. With this function, several migratory species including the purple heron and some ducks are already to habitate the marshland/wetland.

The most productive fish habitats in the Marsh are its perennial water bodies. Fish species disperse to breed and grow in seasonally flooded areas, retreating to perennial water bodies as water levels fall. Its 2001 inventory includes both indigenous and introduced fish species, two (2) species of which (i.e., mullet and tarpan) are migratory and move seasonally between the marine system and the marshland/wetland area.

The management of Agusan Marsh and wildlife sanctuary is discussed in detailed inAnnex 2J.

(iii) Marine Habitats

Although the ARB covers only 10km of the coastline of Butuan Bay, complex interactions and interface of habitats between these fluvial and marine systems need careful consideration. These two (2) river systems therefore should not be studied in isolation of each other.

To illustrate, the 2002 MSU study found that mangrove, coral reef, fish, seagrass and seaweed, and soft bottom communities of Butuan Bay have been severely affected by pollution from various natural and human sources. In particular, the potential of Hg contamination from continuous sediment transport from Agusan River into the Bay is a cause for concern.

2.7 CONCLUSIONS AND RECOMMENDATIONS

A primary concern in the water resources study is the coverage and quality of existing hydrological and meteorological data. An upgrading of hydrological and meteorological data collection networks may have to be implemented to develop a comprehensive knowledge base of the ARB. A lead agency should be responsible for ensuring a quality data is collected and reviewed. Such entity may also have to be equipped of facilities for proper data dissemination. Specifically, the following recommendations may be considered: (a) installation of additional or new monitoring stations for rainfall and stream flow, particularly new rainfall stations in high elevations on the west side of the Basin; (b) establishment of new stream flow or water level gauging sites on the Agusan River near Maragusan, between Kalaw Bridge and Sta Josefa, within Agusan Marsh, and at the marsh outlet; (c) establishment of a sediment-monitoring program; and (d) establishment of a system for groundwater data collection.

Available water in the Basin demonstrated in water balance studies are sufficient enough to meet domestic demand, but the concern is on the present quality of waters that could be abstracted from principal river sources considering the incidence of pollution, sedimentation and agricultural run-off. Related to this is whether existing and potential groundwater sources are dependable considering that in some areas, deep wells are generating water of high chemical content. The continued assessment of the environment in the Basin should be conducted.

RAINFALL INTENSITY DURATION FREQUENCY (RIDF)

Final Report

ANNEX 2A: RAINFALL INTENSITY DURATION FREQUENCY (RIDF)

1.1 RAINFALL INTENSITY DURATION FREQUENCY (RIDF)

The first step in the derivation of the rainfall-intensity-duration frequency curves is frequency analysis and selection of the fitted distribution. The synoptic rainfall stations operated by PAGASA with applicable information for the above methodology are Cagayan de Oro, Hinatuan, Malaybalay, Surigao City and Davao City.

1.2 Frequency Analysis

This involves the fitting of theoretical frequency distributions to the annual maximum rainfall data. Four (4) types of theoretical distributions are used in this study, namely Extreme Value Distribution (Gumbel), Log Pearson Type III Distribution, Log Normal Distribution, and 2- Parameter Gamma Distribution.

(a) Extreme Value Distribution (Gumbel)

This distribution utilizes the Fisher-Tippet extreme value function which relates magnitude linearly with the logarithm of the reciprocal of the exceedance probability. Working equations are the following:

Annex 2A-1 /6RTr

K Tr

= R + K Tr S

(YTr - Yn )=Sn

YTr

= -(0.83405

+ 2.3025

log log

Tr)

Tr - 1

Where,

RTr

= Probable rainfall at return period Tr

R = Mean of the annual maximum rainfall series

K Tr

= Frequency factor at return period Tr

S = Standard deviation of annual maximum rainfall series

YTr

= reduced variate at return period Tr

Yn , Sn = reduced mean and reduced standard deviation n = number years of record

Final Report

Table 2A-1 Reduced Mean and Standard Duration

nY nS nnY nS nnY nS n

00.4952 20.94963 21 0.52 519 1.06 938 3 10.53714 1 .11588

10 0.4952 20.94963 22 0.52 673 1.07 547 3 20.53803 1 .11927

11 0.4996 90.96753 23 0.52 819 1.08 115 3 30.53889 1 .12245

12 0.5034 80.98327 24 0.52 959 1.08 648 3 40.53959 1 .12557

13 0.5069 90.99712 25 0.53 084 1.09 143 3 50.54026 1 .12849

14 0.5100 01.00951 26 0.53 202 1.09 615 3 60.54107 1 .13127

15 0.5128 51.02055 27 0.53 326 1.10 048 3 70.54177 1 .13391

16 0.5154 21.03058 28 0.53 419 1.10 471 3 80.54243 1 .13649

17 0.5177 01.03972 29 0.53 533 1.10 860 3 90.54294 1 .13900

18 0.5197 81.04806 30 0.53 616 1.11 238 4 00.54363 1 .14130

19 0.5217 71.05575

20 0.5235 21.06282

(b) Log Pearson Type III Distribution

This distribution belongs to the family of distribution suggested by Pearson with log transformation of rainfall data. The parameters used are the mean, standard deviation and skewness coefficient. The working equations are the following:

RTr

= R + K Tr S

K Tr =

2 {[( K n - G ) G

+ 1]3 - 1}

G66

Where

RTr

= Log of probable rainfall at return period Tr

R = Mean of the log of rainfall series

K Tr

= Frequency factor at return period Tr

S = Standard deviation of the log of rainfall series

K n = Normal frequency factor (see table) G = Skewness coefficient of the seriesP = Probability

Final Report

Table 2A-2 Norman Frequency Factor

K n PT rK n PT r

- 3 . 7 1 9 0 2 0 . 9 9 9 9 01 . 0 0 0 0 . 0 0 0 0 00 . 5 0 0 0 0 2 . 0 0 0

- 3 . 2 9 0 5 3 0 . 9 9 9 5 01 . 0 0 1 0 . 1 7 7 3 30 . 4 2 9 6 0 2 . 3 2 8

- 3 . 0 9 0 2 3 0 . 9 9 9 0 01 . 0 0 1 0 . 2 5 3 3 50 . 4 0 0 0 0 2 . 5 0 0

- 2 . 8 7 8 1 6 0 . 9 9 8 0 01 . 0 0 2 0 . 5 2 4 4 00 . 3 0 0 0 0 3 . 3 3 3

- 2 . 5 7 5 8 3 0 . 9 9 5 0 01 . 0 0 5 0 . 8 4 1 6 20 . 2 0 0 0 0 5

- 2 . 3 2 6 3 5 0 . 9 9 0 0 01 . 0 1 0 1 . 2 8 1 5 50 . 1 0 0 0 0 1 0

- 2 . 0 5 3 7 5 0 . 9 8 0 0 01 . 0 2 0 1 . 6 4 4 8 50 . 0 5 0 0 0 2 0

- 1 . 9 5 9 9 6 0 . 9 7 5 0 01 . 0 2 6 1 . 7 5 0 6 90 . 0 4 0 0 0 2 5

- 1 . 7 5 0 6 9 0 . 9 6 0 0 01 . 0 4 2 1 . 9 5 9 9 60 . 0 2 5 0 0 4 0

- 1 . 6 4 4 8 5 0 . 9 5 0 0 01 . 0 5 3 2 . 0 5 3 7 50 . 0 2 0 0 0 5 0

- 1 . 2 8 1 5 5 0 . 9 0 0 0 01 . 1 1 1 2 . 3 2 6 3 50 . 0 1 0 0 0 1 0 0

- 0 . 8 4 1 6 2 0 . 8 0 0 0 01 . 2 5 0 2 . 5 7 5 8 30 . 0 0 5 0 0 2 0 0

- 0 . 5 2 4 4 0 0 . 7 0 0 0 01 . 4 2 9 2 . 8 7 8 1 60 . 0 0 2 0 0 5 0 0

- 0 . 2 5 3 3 5 0 . 6 0 0 0 01 . 6 6 7 3 . 0 9 0 2 30 . 0 0 1 0 0 1 0 0 0

- 0 . 1 7 7 3 3 0 . 5 7 0 4 01 . 7 5 3 3 . 2 9 0 5 30 . 0 0 0 5 0 2 0 0 0

0 . 0 0 0 0 00 . 5 0 0 0 0 2 . 0 0 03 . 7 1 9 0 2 0 . 0 0 0 1 01 0 0 0 0

(c) Log Normal Distribution

This method uses a 2-parameter function identical to the Log Pearson III distribution except that the skew coefficient is neither computed nor used. Values of frequency factor K which are related to the probability of exceedance p and return period Tr are computed by the use of transformed normal distribution function available in MS Excel.

(d) 2-Parameter Gamma Distribution

The method is identical to Gamma 3 except that the location parameter is set to zero, hence only the shape and scale parameters are used in the computation. Values of frequency factor K which are related to the probability of exceedance p and return period Tr are computed by the use of the Gamma Distribution function available in MS Excel. Input parameters to the Gamma function in MS Excel are the alpha a and beta 1 variables which are computed using the following working equations:

a = 1 +

1 + 4 (ln R -3

1 ln R )n

- ti a

4 (ln R -

1 ln R )n

f3 = a

1n R

Where

R = Annual maximum rainfall

R = Mean of the rainfall series

n = number of years of records

Figure 4.1Rainfall Intensity Duration Frequency (Cagayan de Oro City)Final Report

1.3 Selection of the Fitted Distribution Curve

From the above results on probable maximum rainfall of short duration, RIDF curves are produced by converting the probable rainfall magnitudes into rainfall intensities and fitting them to an exponential equation. Two types of exponential equation are tried to fit the rainfall intensity duration. These RIDF equations are expressed as follows:

Type 1:R = A / (C + Tb) Type 2:R = A / (C + T)b

where:R=Rainfall intensity (mm/hr);

T=Duration (min); and

A, b, C=Constants obtained from curve fitting.

RIDF equations, both for short (10 min to 1-hr) and long (1-hr to 1-day) duration, derived for all return periods, the 2-yr, 5-yr, 10-yr, 25-yr, 50-yr and 100-yr for the five (5) synoptic stations are shown in Figures 2A-1 to 2A-5. Selection of the fitted equations is based on both the residual of the least square coefficients and visual fitting.

Figure 2A-1Rainfall Intensity Duration Frequency (Cagayan de Oro City)

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Figure 2A-2Rainfall Intensity Duration Frequency (Davao City)

Figure 2A-3Rainfall Intensity Duration Frequency (Hinatuan)

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Figure 2A-4Rainfall Intensity Duration Frequency (Malaybalay)

Figure 2A-5Rainfall Intensity Duration Frequency (Surigao City)

STREAMFLOW AVAILABILITY

Final Report

ANNEX 2B: STREAMFLOW AVAILABILITY

1.1 STREAMFLOW AVAILABILITY

A low flow analysis has been conducted to establish available discharges on tributaries during dry or drought conditions to ensure adequate water supply during these periods. Since only few of these tributaries have any discharge records, it was envisioned that the results for gauged streams would be transferred to the ungauged ones.

1.2 Streamflow Duration Curves

In order to produce the desired curves, the daily streamflow information from ten (10) stations are analyzed. Table 2B-1 listed the stations to be used for the analysis.

Table 2B-1Selected Streamflow Gauging Stations

RiverLatitudeLongitudeArea, kmQ, m/s

degminsecdegminsec

1 Agusan River, Kalaw Bridge, Monkayo750012630126.0501,355.0067.30

2 Agusan River, Camanlangan, New Bataan73033126618126.105343.0017.10

3 Agusan River, Sta. Josefa, Bunawan80381255810125.9691,599.0097.80

4 Agusan River, San Isidro, Talocogon83241254631125.7757,390.00698.00

5 Wawa River, Wawa, Esperanza84741254123125.690396.0017.48

6 Kawayan River, Langasian, La Paz814561254259125.716348.0037.50

7 Adgaoan River, Malapitan, La Paz81456125458125.752820.0069.80

8 Gibong River, Bahbah, Prosperidad836401255446125.913427.0019.40

9 Andanan River, Bayugan8440125430125.717201.006.70

10 Busilao River, Milagros, Ezperanza838491253415125.571316.0012.90

Again, the index stations identified in the runoff analysis plus the sub basin rainfall are used to develop flow duration curves for each of the sub-basins.. For each of the index sites, daily streamflow data are arranged from highest to lowest and plotted to form the flow duration curves. Figure 2B-1 shows the derived flow duration for each of the stations.

The shape of the flow duration curves shows a rapid decrease from 0% of the time followed by a long gently downward sloping portion which means there is not a large variation in the dependable low flows in a system. The rapid drop in the curve reflects how uniform the rainfall in the basin, wherein theres only a few extremely high rainfall events. For gauged rivers where the discharge record was long enough, a statistical low flow analysis was performed to estimate the 5 and 10 year return period low flows. The resulting discharges are slightly larger than those determined from the duration curves, corresponding approximately 90% and 80% dependable flows. Therefore, it is felt that the use of the curves for this study is applicable asconservative decisions would be made.

Annex 2B 1/2

Agusan River Basin Master Plan ProjectANNEX 2BFinal Report

10000

1000

Streamfkow, m/s100

10

1

0.1

0102030405060708090100

Time in Percent of exceedance

Figure 2B-1Flow Duration Curve

Annex 2B 1/2

WATER BALANCE ANALYSIS

Final Report

ANNEX 2C: WATER BALANCE ANALYSIS

1.1 WATER BALANCE ANALYSIS

1.2 Input Data

The following data are used in the analysis;

(a) Basin terrain model based on the SRTM (Shuttle Radar Topographic Mission) DEM (Digital Elevation Model) with grid size of 3 arc seconds, approximately 92 m by 92 m in metric scale.

(b) River system in the Basin.

(c) Sub basin flow duration curves, sub-basin monthly rainfall data and monthly evaporation data

(d) 2000 Population Data, Barangay Level

(e) Barangay Map

(f) Land Use Map

(g) Land Cover Map

(h) Existing and proposed water resources development

1.3 Methodology

The assessment of the availability and dependability of water resource for development is anchored on the extent of available information of the Basin under scrutiny. As discussed earlier, the information available is not enough to directly use the information at hand to forecast water balance analysis for planning purposes. Nevertheless, water balance analysis is required thus the methodology applied herein will require mathematical modeling of the basin focused on the low flow or dependable flow analysis.

The steps required in this endeavor are the following;

(a) Derivation of monthly sub-basin rainfall.

The available rainfall information is transformed into grid format (similar to isohyetal map) using Arcview GIS software. By overlaying the sub-basin boundaries on the gridded data, monthly rainfall data for each sub-basin will be computed through the use of the HEC- GeoHMS ArcView Extension Software.

(b) Rainfall- Runoff Analysis

On the annual basis, relationship between rainfall, evaporation/evapotranspiration and streamflow data by spatial correlation facilitated by HEC-GeoHMS ArcView Extension Software is derived. End output of this step is the estimated annual flows for each of the sub- basins.

(c) Flow Duration Curves for each of the Sub-basin

The output of step (c) can be converted into flow duration curves. This is undertaken using the converted duration curve of the daily flows of the index streamflow stations earlier discussed into dimensionless format and superimposing the derived annual flows based on rainfall-runoff model for each of the sub-basins.

(d) Dependable Flow for each of the Sub-basin.

As defined in the Water Code and being practiced by local water resource planner, the dependable flows are those amount available 80% of time of exceedance. Through the use of the flow duration curves, dependable flows for each of the sub-basins are computed. This step conclude the estimation of the water availability analysis

Annex 2C-1/7Final Report

(e) Water Demand

On the other side of the water balance analysis is the estimation of the water demand for relevant water resource development such as water supply and irrigation. It is consisted of domestic and municipal water demand, industrial water demand and agricultural water demand. Likewise, riprarian releases for environmental protection which is about one percent (1%) of the dependable is included in the computation of the water demand.

(f) Water Balance

By equating the water availability with water demand with respect to the targeted planning horizon, deficits on water availability can be estimated.

1.2.1 Sub-basin Rainfall

The monthly isohyetal maps developed from monthly rainfall data of various stations are transposed into grid format. By clipping the gridded data using sub-basins boundaries earlier presented, clipped rainfall grid data is converted into average values. This is done for the twelve maps representing for the 12 months for each of the sub-basins. The result of the analysis is shown in Table 2C-1.

Table 2C-1Estimated Sub-basin Monthly RainfallRainfall, mm

BasinJanFebMarAprMayJunJulAugSepOctNovDecAnnual

1 Adgaoan3142362041662142522552382422682222222,834

2 Bugabos2661921451081221731691381692141851852,066

3 Gibong5143833122261852012011531792453003003,199

4 Haoan3352602281962282502542342372522322322,939

5 Kasilan3472532131671982332342112252562262262,789

6 Kayonan-Umayam2762141901652272672702612582782152152,835

7 Libang2801921561261692142151912142451961962,394

8 Logom-Baobo4233132672182232332462132152332522523,089

9 Maasam2521781501281862372382212362601951952,478

10 Manat5873933302511871981951541631943073083,268

11 Minor4123042471851742012021651882332532532,817

12 Ojot232153121981391951911641992281681682,057

13 Simulao5884183492662182252281821912213183173,520

14 Sulibao5624143452532202142351832002483093093,491

15 Taguibo4994003142201401631651151502033263263,021

16 Wawa-Andanan4813752972111521781741291562183053052,982

Consistency test of the sum of the twelve months with the annual rainfall data is also undertaken with positive result.

1.2.2 Sub-basin Streamflow Duration Curves

A low flow (duration curve) analysis has been conducted to establish available discharges on tributaries during dry or drought conditions to ensure adequate water supply during these periods. As only a few of these tributaries have any discharge records, it was initially envisioned that the results for gauged streams would be transferred to the ungauged ones. In order to produce the desired curves, estimated rainfall has been used instead.

The link between rainfall and runoff values is established by correlation. Table 2C-2 shows the comparison.

Final Report

Table 2C-2Rainfall-Runoff Comparison

RiverLatitudeLongitudeArea, kmQ, m/sYieldRainfallRatio

degminsecdegminsecmmmm

1AgusanRiver, KalawBridge, Monkayo75007.83312630126.0501,355.0067.301,5663,2680.4793

2AgusanRiver, Camanlangan, NewBataan730337.509126618126.105343.0017.101,5723,2680.4811

3AgusanRiver, Sta. Josefa, Bunawan80388.0111255810125.9691,599.0097.801,9293,2680.5903

4AgusanRiver, SanIsidro, Talocogon83248.5341254631125.7757,390.00698.002,9793,1070.9586

5WawaRiver, Wawa, Esperanza84748.7841254123125.690396.0017.481,3922,9820.4669

6KawayanRiver, Langasian, LaPaz814568.2491254259125.716348.0037.503,3982,8341.1989

7AdgaoanRiver, Malapitan, LaPaz814568.249125458125.752820.0069.802,6842,8340.9471

8GibongRiver, Bahbah, Prosperidad836408.6111255446125.913427.0019.401,4333,1990.4478

9AndananRiver, Bayugan84408.733125430125.717201.006.701,0512,9820.3526

10BusilaoRiver, Milagros, Ezperanza838498.6471253415125.571316.0012.901,2872,0570.6260

It must be noted that the curves that have been produced are based on daily rainfall. In creating the duration curves, days where the effective rainfall (rainfall minus evaporation) is zero were removed from the records. The calculated discharges correspond only to rainfall events and loss to storage and base flows were not accounted for. As a result, the peak discharges again will most likely have been over estimated and the minimum flows under estimated.

The shape of the flow duration curves, a rapid decrease from 0% of the time followed by a long gently downward sloping portion, means there is not a large variation in the dependable low flows in a system. The rapid drop in the curve reflects how uniform the rainfall in the basin is with being a few extremely high rainfall events. For gauged rivers where the discharge record was long enough, a statistical low flow analysis was performed to estimate the 5 and 10 year return period low flows. The resulting discharges are slightly larger than those determined from the duration curves, corresponding approximately to the 90% and 80% dependable flows. Therefore, it is felt that the use of the curves for this study is applicable as conservative decisions would be made.

The index stations identified in the runoff analysis plus Simulao, Agusan del Sur is converted into dimensionless format and used for the target sub-basins. Attachment 3 contains the flow duration curves for the each of the sub-basins.

1.2.3 Water Demand

Basically the water users can be classified as those that consumed water and those that can be reuse. Domestic, municipal, industrial, and agricultural water demands are normally consumed whereas those for hydro power can be re-used.

Target level is set for each water usage as shown below:

1) Domestic and Municipal Water Demand

The unit water consumption Water demand per head that is commensurate with the income level is set. Not only the average income level but also its classification should be considered. Multiplying this value with the estimated future population gives the domestic and municipal water demand

Based on the Key Informant Interview of the different water districts, the unit water consumption per capita ranges from 97 to 136 liters per capita per day (lpcd). They are as follows: Butuan WD 121 lpcd, Bayugan WD 98 lpcd, Prosperidad WD 136 lpcd, Bunawan WD 136 lpcd, Nabunturan WD 97 lpcd. They are all within the set standard established under the NEDA Board Resolution.

Other Level III system has exhibited similar characterization on the unit water consumption. Crossing Gabi Rural waterworks System & Multipurpose Cooperative (Compostela) has water consumption of 93 lpcd, Compostela Waterworks System (Compostela) has 112 lpcd unit

Final Report

consumption,Maragusan Waterworks & sanitation Multipurpose Cooperative (Maragusan) has 92 lpcd consumption, Monkayo Waterworks System (Monkayo) has 149 lpcd water consumption, Montevista water System & Multipurpose service Coop. (Montevista) has 123 lpcd, New Visayas Rural Water & Sanitation association has 82 lcpd and Cabinuangan Rural waterworks & Sanitation Association (New Bataan), Inc. Has 98 lpcd.

With the above information, the unit water consumption for the planning horizon is projected and exhibited in Table 2C-3:

Table 2C-3Unit Water Consumption for Level I, II, III and Water Districts

Level I, Level II, & Level III(Unit : lpcd)

YearRegionLevel ILevel IILevel III

2005Region XI2162103

Region XIII2163106

2010Region XI2164106

Region XIII2368113

2020Region XI2266110

Region XIII2575125

Water Districts(Unit : lpcd)

YearCity/MunicipalityLowMediumHigh

2005Butuan City118120122

San Francisco127129132

Bunawan103105107

Prosperidad133136138

Bayugan100102104

Nabunturan100102104

2010Butuan City125130136

San Francisco134139147

Bunawan109115119

Prosperidad136138141

Bayugan103105108

Nabunturan103105108

2020Butuan City138130136

San Francisco148139147

Bunawan121115119

Prosperidad152138141

Bayugan115105108

Nabunturan115105108

2) Industrial Water Demand

The industrial water demand may be estimated from the water permits granted by NWRB. There are only 13 water permits within the river basin classified under industrial use. The water permit is limited in number and as the same time it is impossible to estimate the total volume of water consumption from the water rights granted for industrial use.

In this case, the estimated industrial water demand is assumed to be certain percentage of the domestic and municipal water demand. The industrial water demand is taken at 5, 8 and 10% of domestic and municipal water demand for 2005, 2010 and 2020, respectively. Table 2C-4 presents the domestic, municipal and industrial water consumption for 2005, 2010 and 2020.

Final Report

Table2C-4Domestic, Municipal and Industrial Water Demand (2005 2020)

Water Demand (x1000 m3)

Municipality200520102020

Bayugan98015573139

Buenavista5639211825

Bunawan4487081310

Butuan City4506733811090

Cabadbaran6198171214

Compostela54110772505

Esperanza5079181963

La Paz206281805

Laak57810272509

Las Nieves2984451060

Loreto3416611383

Mabini299413903

Maco6348021812

Magallanes422491665

Maragusan4345151289

Mawab299413903

Monkayo74514053132

Montevista3305421192

Nabunturan5579151911

Nasipit5639211825

New Bataan4526521346

Pantukan61010842385

Prosperidad90314033438

RT Romualdez191287534

Rosario6638711714

San Francisco130518843352

San Luis2785381149

Sibagat4837441358

Sta. Josefa2926141393

Talacogon4457131361

Trento4569102066

Veruela4128042146

3) Agricultural Water Demand

The main component for the agricultural water demand largely depends on the irrigation water demand for a particular crop. The values are based on detailed analysis of parameters involving soil type, crop factor, evaporation, evapo-transpiration, rainfall, seepage, and ir