mo hinh toan

8/2/2019 mo hinh toan

1/14

AI HOC ONG A

So 04-201140

NG DNG M HNH TON NH GI

CHT LNG NC H LU SNG NG NAIN NM 2020

ThS. Phan Vit ChnhKhoa Xy dng-i hc ng

TM TT

Trong bi bo ny, m hnh ton dng chy h mt chiu MIKE11 c p dng m

phng nh gi cht lng nc h lu sng ng Nai on chy qua thnh ph Bin Ha

hin trng nm 2005 v m phng d bo cht lng nc nm 2011 v 2020 do tc ng

bi cc ngun x thi ca th Bin Ha theo qui hoch pht trin kinh t x hi n nm

2020 ca tnh ng Nai. Tc gi s dng s liu a hnh, s liu thy lc, thy vn nm

2003, s liu cht lng nc thc o nm 2003 v nm 2005 hiu chnh v kim tra

m hnh. S dng b thng s hiu chnh m phng d bo cht lng nc cho cc

phng n pht trin kinh t x hi ca thnh ph Bin Ha n nm 2020.

Kt qu m phng cht lng nc nm 2011 v 2020 c so snh nh gi vi qui chun

mi trng nc mt: QCVN08: 2008/BTNMT. Nhn chung, cht lng nc sng ng Nai

on chy qua thnh ph Bin Ha u khng m bo ngun cp nc loi A2 theo qui

chun; tuy nhin khi cc h thng x l nc thi sinh hot hon thnh v a vo s dng

vi hiu sut x l 100% th cht lng nc trn on sng ny c ci thin ng k.

ABSTRACT

In this paper, the modun MIKE 11, describing one-dimensional flow model was applied for

calculating water quality downstream of the Dong-Nai river system; the reach flows through

Bien-Hoa city status in 2005 and predicting water quality in 2011 and 2020 due to impact-

emissions by sources of urban planning of Bien-Hoa in economic and social development

until the year 2020. Subject use of terrain data, hydraulic and hydrological data in the year

2003; water quality data observed in the year 2003 and 2005 were used to calibrate and

verification model. And using these parameters to predict water quality of Dong-Nai river

which correspondents plans for economic and social development by the year 2020.


2/14

AI HOC ONG A

So 04-201141

1. t vn

Hin nay, vi s pht trin ca cng ngh thng tin cng nh khoa hc k thut nichung, cc m hnh ton ng dng ngy cng c pht trin nhanh. Cc m hnh ton vicc u im nh cho kt qu tnh ton nhanh, gi thnh r, d dng thay i cc kch bn biton, v.v... ang tr thnh mt cng c mnh, phc v c lc trong nhiu lnh vc, trong c lnh vc qun l ti nguyn v mi trng. La chn m hnh l khu u tin rt quantrng trong phng php m hnh ton, n ph thuc vo yu cu cng vic, iu kin v tiliu cng nh tim nng ti chnh v ngun nhn lc sn c. Trn th gii ni chung v VitNam ni ring, hin nay c rt nhiu m hnh ton ang c s dng. Trong nghin cuny, vi mc tiu m phng v tnh ton ch thy lc v cht lng nc cho sng ngNai on chy qua thnh ph Bin Ha, tc gi la chn p dng b phn mm MIKE11,bi n p ng c nhng tiu ch sau:

- on sng ny khng rng, cho php m t bi ton l mt chiu;- L b phn mm tch hp a tnh nng;

- L b phn mm c kim nghim thc t;

- Cho php tnh ton thy lc v cht lng nc vi chnh xc cao;

- Giao din thn thin, d s dng;

- C ng dng k thut GIS, l mt k thut mi vi tnh hiu qu cao.

2. Gii thiu m hnh ton MIKE 11M hnh MIKE11 l mt phn mm k thut chuyn dng do Vin Thu lc an Mch

(DHI) xy dng v pht trin, c ng dng m phng ch thy lc, cht lng nc

v vn chuyn bn ct vng ca sng, trong sng, h thng ti, knh dn v cc h thng

dn nc khc. MIKE11 l cng c lp m hnh ng lc mt chiu, thn thin vi ngi s

dng nhm phn tch chi tit, thit k, qun l v vn hnh cho sng v h thng knh dn

n gin v phc tp. Vi mi trng c bit thn thin vi ngi s dng, linh hot v tc

Calculating results of water quality of the years 2011 and 2020 were compared with

regular assessment of surface water environmental standards: QCVN08: 2008/BTNMT.

In general, Dong-Nai river water quality flowing through the city of Bien-Hoa city arenot guaranteed water supply in accordance with standard type A2. However, when the

wastewater treatment system activities completed and put into use with 100% efficiency

reason, the water quality in the river has improved significantly.


3/14

AI HOC ONG A

So 04-201142

, MIKE11 cung cp mt mi trng thit k hu hiu v k thut cng trnh, ti nguyn

nc, qun l cht lng nc v cc ng dng quy hoch. M un thu ng lc (HD) l

mt phn trung tm ca h thng lp m hnh MIKE11 v l c s cho hu ht cc m unkhc: d bo l, ti khuch tn, cht lng nc v cc m un vn chuyn bn ct.

Trong nghin cu ny, tc gi s dng cc m un HD, AD v Ecolab m phng

nh gi hin trng v d bo cht lng nc ca sng ng Nai, on chy qua thnh ph

Bin Ha.

2.1. C s l thuyt ca m hnh ton MIKE11

2.1.1. M un thy ng lc (HD) MIKE11

M un thy ng lc l phn quan trng nht trong b m hnh MIKE11, c xydng t h phng trnh Saint - Venant cho dng mt chiu, khng n nh.

- Phng trnh lin tc:

x

Q Aq

t

+ =

(1)

dx

Qdx

x

QQ

h(t+dt)

h t Thi im t

Thi im t + dt

Hnh 1: S m t phng trnh lin tc

Phng trnh ng lng2

2

| |0

x AR

Q Q z Q QgA g

t x A C

+ + + =

(2)

Trong : Q - Lu lng dng chy qua mt ct (m3s-1)

A - Din tch mt ct c (m2)

- H s iu chnh, 1


4/14

AI HOC ONG A

So 04-201143

g - Gia tc trng trng (ms-2)

R - Bn knh thy lc (m)

C - H s Chezy, C = Ry/nn - h s nhm.;

y - h s thy lc, theo Maninh y = 1/6

Z - Cao trnh mc nc thi im tnh ton (m)

q - Lu lng nhp lu trn mt n v chiu di dc sng (m2s-1)

t - Thi gian (s)

x - Khong cch gia cc mt ct (m)

X

Z

Q

A

B

H

Y

Hnh 2: S dng chy gia hai mt ct tnh ton

S dng s sai phn su im ca Abott, gii h phng trnh Saint - Venant.

u vo l s liu v c tnh h thng cng s liu ca ngun nc vo ra trn ton hthng. H phng trnh 4.1 v 4.2 l h phng trnh vi phn phi tuyn, c h s bin i.

Cc nghim cn tm l Q v Z l hm s ca cc bin c lp x, t. T h phng trnh Saint

- Venant (1) v (2), ta c th vit li theo bin Q v h:

Q hB q

x t

+ =

(3)

2

2

1 | |0

x AR

Q Q h Q QgA g

t B x h C

+ + + =

(4)

Gii h phng trnh vi phn trn s xc nh c gi tr lu lng, mc nc (dng

cc nhy), ti cc mt ct ngang trong mng sng mi thi im trong khong thi gian

nghin cu.

2.1.2. M un cht lng nc MIKE11

M un truyn ti khuych tn (AD) c chc nng tnh ton s lan truyn ca cc

cht huyn ph hoc ha tan (phn hy) di tc ng ca dng chy. Bi ton t ra trong


5/14

AI HOC ONG A

So 04-201144

nghin cu ny l bi ton c lin quan n cc chu trnh sinh ha din ra trong dng sng,

do tc gi khng nhng ch s dng m un truyn ti khuych tn m cn phi kt hp

vi m un sinh ha (Ecolab) gii quyt vn . Phng trnh c bn trong hai m unny l phng trnh truyn ti khuych tn.

a) M un truyn ti khuch tn

Trong MIKE11, qu trnh truyn ti khuych tn m t bng phng trnh:

2Dx x

AC QC CA AKC C Q

t x

+ = +

(5)

Trong : A - Din tch mt ct (m2

)C - Nng (kg/m3)

D - H s khuych tn

Q - Lu lng dng chy, m3/s

q - Lu lng dng gia nhp trn mt n v chiu di sng, m2/s

K - H s phn hu sinh hc, K ch c dng khi cc hin tng hay qu

trnh xem xt c lin quan n cc phn ng sinh ho.

Phng trnh ti khuych tn phn nh hai c ch vn chuyn:

1. Qu trnh vn chuyn cht do dng chy (advection)

2. Qu trnh khuch tn cc cht do dng chy ri (turbulent diffusion)

b) M un sinh thi (Ecolab)

M un sinh thi trong m hnh MIKE11 gii quyt kha cnh cht lng nc trong

sng ti nhng vng b nh hng bi cc hot ng dn sinh kinh t.v.v. M un ny phi

c i km vi m un ti - khuch tn, iu ny c ngha l m un cht lng nc gii

quyt cc qu trnh bin i sinh hc ca cc hp cht trong sng cn m un ti - khuch

tn c dng m phng qu trnh truyn ti khuch tn ca cc hp cht .

3. Phng php nghin cu

Phng php nghin cu s dng trong nghin cu ny bao gm phng php thu

thp, phn tch cc ti liu t cc ngun hin c, phng php kho st thc a, ly mu

phn tch thc trng cht lng nc ti cc v tr quan trc cht lng nc dc sng, nhm

nh gi hin trng mi trng ti khu vc nghin cu v thu thp cc ti liu cn thit cho

tnh ton. Tip , ng dng phng php m hnh ton tnh ton, m phng ch thy


6/14

AI HOC ONG A

So 04-201145

vn thy lc v din bin cht lng nc mng li sng ng Nai on chy qua thnh

ph Bin Ha.

4. Gii thiu v lu vc nghin cuLu vc sng ng Nai nm trong khong:

- Kinh ng t 105045 (Tn Bin - Ty Ninh) n 109012 (Ninh Hi - Ninh Thun)

- V Bc t 1001917 (mi Vng Tu) n 12020 (ak Mil - k lak)

Sng ng Nai on chy qua tnh ng Nai ng vai tr quan trng trong vic cung

cp ngun nc mt cho tnh ng Nai. Dng chnh sng ng Nai ti tuyn Ti L vi

din tch lu vc l 8.850km2. Dng chnh sng ng Nai ti Bin Ha c din tch lu vc

22.425km2.

Thnh ph Bin Ha nm pha ty tnh ng Nai, Bc gip huyn Vnh Cu, Nam

gip huyn Long Thnh, ng gip huyn Trng Bom, Ty gip th x D An, Tn Uyn tnh

Bnh Dng v Qun 9 - TP. H Ch Minh. Bin Ha hai pha ca sng ng Nai, cch

trung tm thnh ph H Ch Minh 30 km (theo Xa l H Ni v Quc l 1A), cch thnh

ph Vng Tu 90 Km (theo Quc l 51).

Tng din tch t nhin l 264,08 km2, vi mt dn s l 2.970 ngi/km2. Thnh

ph Bin Ha nm pha Ty Nam tnh ng Nai, l Trung tm kinh t, vn ha, chnh tr,x hi ca tnh ln ny.

Vic qun l thng nht v tng hp ngun nc trn lu vc sng ng Nai on

chy qua thnh ph Bin Ha khng th tch ri vic qun l m bo lu lng v cht

lng nc. c im kh hu v kh tng trn lu vc l nhng yu t nh hng ndng

chy b mt, ch thy vn v mi trng nc. V vy cc thng tin lin quan cn c

nghin cu, cp nht v lm c s cho vic nh gi nh hng ca chng n ngun nc.

5. Cc ti liu s dng

Vi mc tiu tnh ton cht lng nc, ti liu, s liu phc v cho m hnh trong

tnh ton cn rt nhiu, bao gm cc s liu v thu vn, thu lc v cht lng nc, c th

nh sau:

5.1. Ti liu mt ct

S tnh m hnh thy lc mng li sng ng Nai t Tr An - Sng B n Long

i c phn thnh 12 chi lu c to bi 7 nt sng (hnh 3), trong c 4 nt nhp lu

(nt 1, 3, 5, 7) v 3 nt phn lu (nt 2, 4, 6). S mt ct mi chi lu th hin trong bng 1.


7/14

AI HOC ONG A

So 04-201146

Bng 1: Thng k s lng mt ct tnh ton trong mng li sng

TT Nhnh sng S mt ct TT Nhnh sng S mt ct

1 NG NAI N1 8 7 NG NAI N7 6


3 NG NAI N3 3 9 SNG CI N9 8




Hnh 3: S mng li sng ng Nai trong MIKE 11

5.2. Ti liu kh tng thy vn

- S liu thu vn, thu lc ti cc bin Long i, Tr An ly theo mc nc triu ti

Long i v lu lng x ti Tr An do Vin Quy hoch Thu li Min Nam o c theo gi t

thng 3 n thng 4 nm 2003 c dng lm iu kin bin trn (Q~t), bin di (H~t).

- Ch x trung bnh trn bin Phc Ho vo thi im thng 3 n thng 4 nm

2003 dao ng t 100m3/s (thng 4) n 110m3/s (thng 3).

- S liu lu lng v mc nc trung bnh gi thc o vo thng 3 v thng 4 nm

2003 trm Bin Ha dng hiu chnh m hnh.


8/14

AI HOC ONG A

So 04-201147

5.3. Ti liu cht lng nc

- S liu quan trc nc mt:

c dng lm iu kin bin trn, bin di v hiu chnh m hnh cht lng nc.

Cc s liu cht lng nc quan trc (DO, BOD, nhit ) t thng 3 n thng 4 nm

2003 c dng lm iu kin bin trn v bin di.

Cc s liu cht lng nc quan trc (DO, BOD, nhit ) thng 4 nm 2005 c

dng hiu chnh m hnh.

- S liu ngun thi v ngun gy nhim

Trong qu trnh pht trin, cng nghip ha, hin i ha, cc a phng dc sngng Nai v ang tip tc i mt vi vn nhim ngun nc ngy mt gia tng,

c bit l khu vc h lu sng ng Nai on chy qua thnh ph Bin Ha. Cc ngun

thi gy nhim chnh bao gm: Ngun thi t cc khu th; Ngun thi t cc khu cng

nghip tp trung; Ngun thi t cc c s cng nghip phn tn; Ngun thi t hot ng

chn nui heo; Ngun thi t hot ng nui trng thy sn.

Cc s liu thu vn, thu lc trc tin c s dng din ton ch thu lc

trong mng li sng nghin cu, lm u vo cho bi ton cht lng nc, sau kt hp

vi cc s liu cht lng nc tnh ton m phng cht lng.

6. Kt qu ng dng m hnh MIKE11

6.1. Kt qu tnh ton hiu chnh m hnh thy lc

Mc tiu ca tnh ton thy lc xc nh b thng s thu lc ph hp nht i vi

lu vc nghin cu, phc v cho m hnh cht lng nc. Cn c vo nhim v tnh ton,

ti liu mt ct v cc ti liu c bn thu thp c, s tnh ton thy lc cho mng

sng ng Nai on chy qua thnh ph Bin Ha nh hnh 3.

Hnh 4: So snh mc nc m phng v thc o ti Bin Ha vo thng 3, 4/2003


9/14

AI HOC ONG A

So 04-201148

Vic hiu chnh thng s ca m hnh thy lc c thc hin ch yu qua vic thay

i h s nhm Manning, kt qu tnh ton v thc o mc nc nm 2003 ph hp vi

nhau. Sau khi hiu chnh thng s, m hnh m bo chnh xc cn thit vi bc thigian tnh ton lt = 5 pht, h s nhm dao ng trong khong 0.0167 - 0.03. Kt qu hiu

chnh m hnh HD ti trm Bin Ha th hin trn hnh 4.

Sai s gia s liu m phng v thc o mc nc ti trm Bin Ha c nh gi

theo ch s Nash-Sutcliffe, c th nh trong bng 2.

Bng 2: Phn tch hiu qu v sai s ca hiu chnh m hnh

TT Thi gian kim nh Mc hiu qu ca m hnh

1 Thng 3/2003 91,74%2 Thng 4/2003 95,21%

6.2. ng dng m hnh MIKE 11 tnh ton cht lng nc h lu sng ng Naion chy qua thnh ph Bin Ha

6.2.1. Mc tiu

Xc nh b thng s cht lng nc ph hp nht cho khu vc nghin cu. Do hn

ch v thi gian v ti liu cht lng nc nn trong nghin cu ny tc gi ch tp trung

vo hai ch tiu cht lng nc DO, BOD5, tng ng vi cc iu kin bin thy lc vcc ngun thi.

6.2.2. Thit lp bi ton

Da trn kt qu ca m hnh thy lc tnh ton phn trn. Bi ton cht lng

nc cho lu vc nghin cu c xy dng tip tc nh sau:

- Thit lp cc iu kin bin v cht lng nc v cc ngun thi vo sng: Cc

thng s cht lng nc ti cc bin trn (cc v tr quan trc), thng s cht lng nc ti

cc bin di, v tr v lu lng thi, nng cc ngun x thi;- Hiu chnh m hnh xc nh cc thng s ph hp;

- S dng m hnh vi cc thng s mi m phng tnh ton cc phng n n

nm 2020.

6.2.3. Hiu chnh m hnh

Kt qu m phng v hiu chnh m hnh cho DO v BOD5 vo thng 4/2005 th hin

trn Hnh 5, Hnh 6.


10/14

AI HOC ONG A

So 04-201149

Hnh 5: Biu kt qu hiu chnh m hnh i vi DOminv DOmax

Hnh 6: Biu kt qu hiu chnh m hnh i vi BOD5min v BOD5max

Kt qu sai s hiu chnh m hnh cho DO v BOD5 th hin trong bng 3.

Bng 3: Sai s hiu chnh m hnh cht lng nc

TT Ch tiu cht lng nc m phng Kt qu hiu chnh m hnh (%)

1 Nng DO 93

2 Nng BOD5 91

Theo kt qu tnh ton, sai s gia kt qu tnh ton vi kt qu thc o nh hn 10%,nh vy m hnh cht lng nc t c chnh xc yu cu v c s dng d bocht lng nc theo cc phng n qui hoch pht trin kinh t n nm 2020.

Sau khi hiu chnh cc m hnh HD v AD, tc gi s dng b thong s mi dbo cht lng nc cho sng ng Nai on chy qua thnh ph Bin Ha theo cc nhmphng n:

Nhm 1: Nhm phng n cc c s gy nhim di di, cha c trm x l ncthi sinh hot (TXLNTSH)

Nhm 2: Nhm phng n cc c s gy nhim c di di v xy dngTXLNTSH tp trung trong trng hp.

Trng hp TXLNTSH gp s c, hiu sut x l t 0%




11/14

AI HOC ONG A

So 04-201150

Kt qu tnh ton m phng cht lng nc cho sng ng Nai on chy qua thnh

ph Bin Ha theo cc phng n tnh ton c trnh by trn cc Hnh 7 n Hnh 10.

a) Sng ng Nai b) Sng Ci

c) Sng ng Nai d) Sng Ci

Hnh 7: Biu m phng DOmin v BODmax sng ng Nai v Sng Ci cho nhmphng n cc c s gy nhim di di, cha c TXLNTSH



Hnh 8: Biu m phng DOmin, BODmax sng ng Nai v sng Ci cho nhm phngn cc c s gy nhim di di, c TXLNTSH nhng b s c, x l 0%


12/14

AI HOC ONG A

So 04-201151



Hnh 9: Biu m phng DOmin, BODmax sng ng Nai v sng Ci cho nhmphng n cc c s gy nhim di di, c TXLNTSH nhng b s c, x l 50%



Hnh 10: Biu m phng DOmin, BODmax sng ng Nai v sng Ci cho nhm

phng n cc c s gy nhim di di, c TXLNTSH nhng b s c, x l 90%


13/14

AI HOC ONG A

So 04-201152

7. Kt lun

- Kt qu m phng hin trng cht lng nc sng ng Nai on chy qua thnh

ph Bin Ha cho thy: hin trng, khng m bo ngun cp nc loi B1 theo ch tiu DOv khng m bo ngun cp nc loi A1 theo ch tiu BOD5, thm ch, trn nhnh sng

Ci qua trung tm thnh ph, ch tiu BOD5 khng m bo ngun cp nc loi A2 theo

QCVN 08: 2008/BTNMT.

- Qua tnh ton cc phng n vi gi tr lu lng thng ngun khc nhau th xu

th chung nu dng chy thng ngun v nhiu hn th cht lng nc s tt hn tuy

khng nhiu.

- Kt qu d bo n nm 2020 cho thy, nu cha xy dng cc TXLNTSH hoc xy dng nhng b s c (XL0%) th cht lng nc gim i rt nhiu. Trn nhnh sng

Ci, ch tiu BOD5 vt qu qui chun loi B1 nu cha xy dng TXLNTSH s 3, v khng

m bo qui chun loi A2 nu TXLNTSH s 3 xy dng. Tuy nhin, nu cc TXLNTSH

hon thnh v hot ng vi hiu sut 90% th cht lng nc trn on sng ny c

ci thin ng k. Ch tiu BOD5 ti cc v tr u m bo ngun cp nc loi A2 theo

QCVN 08: 2008/BTNMT.

Tm li, cht lng nc sng ng Nai on chy qua TP Bin Ha c c ci thin

hn hay khng l ph thuc vo qu trnh lu lng v t thng ngun, vo s u t xy

dng cc TXLNTSH, vo cng ngh x l v hiu sut hot ng ca cc TXLNTSH

TI LIU THAM KHO

[1] Chuyn :M hnh cht lng nc,

http://www.ebook.edu.vn/?page=1.18&view=14893.

[2] GS. TS. Nguyn Tt c (2010),Nghin cu xy dng phn mm thy lc kt hpvi chuyn ti cht nhim trn cc h thng sng tch hp vi cng ngh GIS, NXB

Nng nghip, TP. H Ch Minh.

[3] GS. TS. Nguyn Tt c (2005), M hnh ton cho dng chy v cht lng nctrn h thng knh sng, NXB Nng nghip, TP. H Ch Minh.

[4] DHI (2000), Hng dn s dng Mike 11, http://www.tainguyennuoc.vn/forum/showthread.php?p=6579

[5] GS. TS. Nguyn Th Hng (2004), Phng php phn t hu hn trong cht lng,NXB Xy dng, H Ni.


14/14

AI HOC ONG A

So 04-201153

[6] GS. TS. Nguyn Th Hng (1996), Gio trnh phng php s, H Nng.

[7] GS. TS. Nguyn Th Hng (2004),Bi ging chuyn thy lc, H Nng.

[8] L Trnh, L Quc Hng (2004),Mi trng lu vc sng ng Nai-Si Gn, NXBkhoa hc k thut, H Ni.

[9] Phm Th Kiu Loan (2007), ng dng m hnh ton nh gi cht lng nc

ca sng ng Nai on chy qua thnh ph Bin Ha theo qui hoch pht trin

kinh t - x hi n nm 2020 ca tnh ng Nai, Lun vn thc s k thut, i hc

Nng.

[10] Hong Vn Qu(2005), C hc cht lng ng dng, NXB Xy dng, H Ni.

[11] Nguyn Thanh Sn (2005),nh gi ti nguyn nc Vit Nam, NXB i Hc qucgia, H Ni.

[12] TS. Trn Hng Thi v nhm nghin cu (2006), Bo co tng kt d n ngdng m hnh tnh ton d bo nhim mi trng nc cho cc lu vc sng: Cu,

Nhu - y, Si Gn ng Nai , Vin Khoa hc Kh tng thy vn v Mi trng,

H Ni.

[13] on Th Kim Phng (2009), Water quality modeling for the Huong river networksin central, Master of the text, Department of Civil Engineering, NCU Library.

[14] DHI software (2007),MIKE11 A modelling system for Rivers and Channels UserGuide, DHI Water & Environment.

[15] DHI software (2007),MIKE11 A modelling system for Rivers and Channels ReferenceManual, DHI Water & Environment.

[16] DHI software (2007), MIKE VIEW A Results Presentation Tool for MOUSE,MIKE SWMM, MIKE NET and MIKE11 User Guide and Tutorial, DHI Water &

Environment.

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