Bega 2012-13 Hydro met Assesment

7/29/2019 Bega 2012-13 Hydro met Assesment

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Hydro meteorological Impactassessment for Bega 2012 overdifferent catchments.

February 1, 2013


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Background

Objectives

Major river catchments of Ethiopia

Methods

Results Summary


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Water supply interest are concernedwith the total amount of wateravailability.

Water demand management practice

Managing and Forecasting the inflowand discharge rates


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To assess the impact of Bega 2012 onwater resources in the differentcatchments of the country.

To assess the impact of Bega 2012weather on Reservoirs, Dams andirrigation schemes.


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Thornthwaite introduced the concept of theprecipitation effectiveness index , which iscomputed from the monthly values of rainfall andevaporation. The evaporation is computedempirically from mean monthly air temperature.

In assessing the effectiveness of rainfall, in

terms of water availability relationships betweenthe rainfall and air temperature has been workedout in terms of moisture indices.

Where, R = monthly rainfall in mm;

T = temperature in C


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Index Status Symbol

< than 16 Dry

1631 Semi-Dry

32 63 Sub-humid

64

128 Humid

> than 128 Wet

0

16

32

64

128


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Aridity status for Bega 2012 at different basins


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Distribution of Heavy fall days exceeding 30mmrainfall during Bega 2012 over main river basins.

STATION Heavyfall(mm)

ADET 37.1

ADWA 38.0

ARBA MINCH 30.5

ARJO 36.2

AYKEL 56.0

BLATE 37.0

BUI 32.0CHAGINI 39.1

DANGILA 38.6

DEBARK 38.1DEBRE TABOR 30.0DOLLO-MENA 77.1

GAMBELLA 44.8

GINNIR 30.0

JINKA(BAKO) 38.2

KIBREMENGIST 46.4

LARE 61.5

MOYALE 34.1

NEDJO 30.6NEKEMTE 44.4

TEPPI 79.0


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....

STATION HEAVYFALL(mm)

GOLOLCHA 34.7

TEPPI 32.1

GINNIR 30.0

CHIRA 30.0

STATION HEAVYFALL(mm)

JIJIGA 30.1

MAJI 39

METEHARA 31.6

SIRINKA 45.3


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98

100

102

104

106

108

110

112

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

WaterLevel(m)

Month

Koka

2005

20062007

2008

2009

2010

2011

20122013

Mean


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2502

2504

2506

2508

2510

2512

2514

2516

2518

2520

2522


Wat

erlevel(m)

Month

Melka Wakena

200520062007200820092010

201120122013Mean


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2212

2213

2214

2215

2216

2217

2218

2219


Wa

terLevel(m)

Month

Fincha

20062007200820092010

201120122013Mean


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1783

1784

1784

1785

1785

1786

1786

1787

1787

1788

1788


WaterLevel(m)

Month

Tana Beles

20052006200720082009

2010201120122013Mean


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1645

1650

1655

1660

1665

1670

1675


Waterlevel(m)

Month

GilGel Gibe 1

20052006200720082009

2010201120122013Mean


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1020

1040

1060

1080

1100

1120

1140

1160


Waterlevel(m)

Month

Tekeze

2008

2009

2010

2011

2012

2013

Mean


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Seasonal mean of Bega 2012


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In October and November over western half of Abay,Baro Akob, southern half of Omo Gibe and central Rift

Valley, upper and middle parts of Genale Dawa and pocketareas of lower Tekeze were experienced in wet condition. In the rest parts of eastern Abay, most parts of Tekeze,

middle Wabishebele and middle Omogibe and Rift valleycatchments were performed humid to semi humid

condition. Awash, eastern Abay, upper Omo Gibe and Rift Valley andsome parts of upper and lower Wabishebele the drycondition were observed in October and November.

In December and January the dry Bega condition weredominated over all basins except lower Omo Gibe andsouth eastern parts of Baro Akobo.


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During October some stations reported heavy falls thatexceed 30 mm for 1 to 4 heavy fall days over mostcatchments. The maximum heavy fall days was reportedover Genale Dawa basin at Kibremengist station.

In November many stations reported heavy falls for oneday except Awash and Wabishebele catchments, and inthe rest two Bega months some station also reportedheavy fall over Wabishebele, Awash, Baro Akobo, OmoGibe and Genale Dawa for one day for each basins.

In general during Bega 2012 except Genale dawa basin the

upper and middle parts of all catchments were dominatedunder dry and semi dry condition.


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Hydro meteorological outlook for Belg2013 Over different Basins

February 1 , 2013


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Outline of Presentation

Objectives Selected analogue Year

Methods Results Summary


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Objectives To indicate the impact of climate outlook

of Belg 2013 on water resources in thedifferent catchments of the country.

To indicate the impact of climate outlookof Belg 2013 on Reservoirs, Dams andirrigation schemes.


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For the coming season the selected analogueyear 1778, 2005, 2007,1980,1995 and 2003were compared based on probabilisticseasonal forecast for Belg 2013 and viewedout on catchments based map usinggeostatistical kriging method. Among whichthe year 2007, 2005 and1778 are the best

analogue year that can enlighten the Ariditystatus in the coming Belg season.

Selected analogue Year


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MethodsThornthwaite introduced the concept of the

precipitation effectiveness index , which iscomputed from the monthly values of rainfalland evaporation. The evaporation is computedempirically from mean monthly air temperature.

In assessing the effectiveness of rainfall, interms of water availability relationships betweenthe rainfall and air temperature has beenworked out in terms of moisture indices.

Where, R = monthly rainfall in mm;T = temperature in C

F b


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February

M h


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March


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April

M


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May


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Seasonal mean of Belg for each analogue year


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For the coming Belg season in the first month Februarywill be performed humid to semi humid condition oversome parts of the upper catchments of many basins.

In March wet condition will be observed over EasternBaro Akobo, upper Wabishebele, upper Genale Dawa,OmoGibe and some parts of upper Rift valley willexpected to be wet condition.

During April and May the wet condition will bedominated over wide areas of southern and westernbasins of the country respectively.

The coming Belg 2013 Omo Gibe and Wabishebele damswill have a better chance to get some amount of water.

However it should be noted that Belg rain has smallcontribution for surface runoff.

It is important those catchments which will be in wetcondition to compensate the loss of water due toevaporation over irrigation schemes, hydro-electric

dams and drinking water purposes.


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Thank you

Documents

Bega 2012-13 Hydro met Assesment