PHAN 1 - THUY LUC, SONG BIEN VA PHONG CHONG LUT BAO... 135
OANH GIA BI^N 0 6 l DONG CHAY VE KRATIE THEO CAC KICH BAN PHAT TRIEN O THUONG LU'U
NCS. ThS. To Quang Todn"' PGS. TS Nguyin Quang Kim'^' PGS. TS Tdng Dde Thdng"' Tom tit:
Ddng bang sdng Cdu Long cd dien tich ty nhien khoang 3,9 trieu ha, trong dd dien tich dat ndng nghiep vao khoang 2,4 trieu ha, dia hinh tuong doi bing phing va thip, vdi cao do binh quan khoang 1 m+MSL. Nd dugc xem la vya lua chinh cua ca nudc vdi sy ddng gdp khoang 40% san lygng luong thyc va 85% san lygng lua gao xuat khau.
DBSCL nim a cuoi nguon sdng Me Kdng, chiu tac dgng do phat trien a thugng luu, dac biet cac phat thin lam gia tang nhu cau nudc (nong nghiep, sinh hoat va cdng nghiep...) va lam thay doi chd do thuy van ddng chay tren luu vyc (thuy dien, chuyen nydc...), didu kien thuy van, thuy lyc va chat lugng nudc vd ddng bing, lam thay ddi dien bidn lu Iut va xam nhap man a DBSCL, de doa an toan va an ninh luong thyc. Nghien ciru nay danh gia bidn doi ddng chay v§ Kratie theo cac kich ban phat trien a cac nudc thudc luu vyc sdng Me Kdng. Day dugc xem nhy dy bao ddng chay ddn thugng luu ddng bing trong tuong lai de cd giai phap hgp ly trong quan li va khai thac ngudn nudc thich ung vdi cac kich ban phat triin thugng luu a OBSCL.
TO' khoa: DBSCL; Sdng Me Kdng, Md hinh toan; Thuy van luu vyc; Kich ban luu vyc.
Summary:
Assessment of variation of Mekong River flow at Kratie for different upstream development scenarios
Vietnamese Mekong Delta (VMD) has a total land area of about 3.9 million hectares, of which 2.4 million hectares are agricultural lands. The delta is flat and low with an averaged altitude of about 1 m+MSL. The delta is considered the granary of the country as it contributes 40% of the national rice product and 85% of the rice export. Located on the downstream of the Mekong River, the Delta water resources is affected by upstream developments, especially those increase the use of water from the Mekong River.
Upstream developments may result in changes in hydrological regime and reduction of downstream flow that in turn amplifies salt intrusion in the delta and threatens food safety and security of the whole country. This study evaluates the variation of flow at Kratie coresponding to different usptream development scenarios. This study consequently predicts future inflows that can be used for water balance calculation and appropriate water resources planning and management for the delta.
Key words: Mekong Delta, Mekong River, Modelling, Hydrology, Basin development scenarios.
' " Vien Khoa hpc Thuy lgi mien Nam '-' Trirang Dai hoc Thiiy Igi
I. Dat vin d§
Ddng bing song Ciru Long (DBSCL) cua Viet Nam nam d cudi ngudn luu vyc sdng Me Kdng (LVSMK), vdi tdng dien tich ty nhien vio khoing 3,9 trieu ha. Phia Bac giip Campuchia, phia Ddng giap Bien Ddng v i phia Tay giap vinh Thai Lan. Dja hinh kha bang phing, cao do binh quan li J-l m so vdi muc nudc bien. Bj inh hudng cua thuy trieu va xam nhap man hing nam vdi dien tich nhiem man len tdi 1,7 trieu ha, DBSCL cdn bj lu Iut hing nam, dien tich bj ngap lu len tdi Vi dien tich toan ddng bing, muc ngap lu tir 1 ^ 4 m v i thdi gian ngap tir 1 din 6 thing.
Lu va xam nhap man theo miia hing nim l i nhung van de khd trinh khdi, do dja hinh thap trung chi tren dudi 1 m so vdi mye nudc bien, trong khi dao dgng thuy trieu ldn, d Bien Ddng tu -2,1 din 1,7 m va Biln Tiy li 0,4 d i n 1 m bao trum ban 600 km dudng bien, liru lugng nudc ve miia kiet nhd khoing 2.000 mVs v i o thing 4 lim inh hudng ciia dao dgng thuy trieu vio sau trong luc dja, cd t h i thiy len tdi Phndm Penh, Campuchia, nai cich bien den ban 300 km. Luu lugng mua lu lai rit ldn, luu lugng IQ max len tdi 67.000 nrVs (nam 1939) tai Kratie gay ra ngap lyt d ha luu, dien tich ngap chiem khoang 5% cua dien tich toan luu vyc.
Dinh gii nhung thay ddi ve lugng nudc den ding bing do phit triin d phia thugng luu cung nhu nhung tic dgng lien quan khac cd vai trd rit quan trgng cho sy phat trien ben vung cua DBSCL cQng nhu sy I n djnh phit triin kinh t l cua Viet Nam.
Nghien cim nay nham danh gia tic dgng ciia cic kjch ban phat triin d thugng luu din thay doi che do thuy van vl thugng luu DBSCL - nhu l i cac yiu td lam anh huang din sy thay ddi tdi IQ v i xam nhap man d DBSCL.
II. S6 lieu va phifo-ng phap nghien ciru //./. Hien trgng thiiy vdn vi DBSCL
DBSCL cd 2 mat giap bien vdi tdng chiiu dii ban 600 km, phia Ddng giip Biln Dong, noi cd che do ban nhat trieu vdi bien do dao ddng 3.5 m/ngiy (tu -2,1 din +1.7 m). Phia Tay giip vinh Thii Lan, trilu cd bien do dao dgng nhd ban. khoang 1 m/ngiy (tir -0,4 m den +1.0 m). Ve miia khd, tir thing 1-4 luu lugng nudc tu thugng nguon dd ve giam dan. dat nhd nhat \'ao thing 4, khoang 2000 m^/s, nudc man vi thi cung vio sau, man cd ndng do 4g/l \ a o sau din 50^60 km, khu vyc mQi Ca Mau, bj nhilm"man 6-9 thing/nam. Tdng dien tich bj anh hudng man hang nam vdi ndng do hon 4 g/1 len tdi hon 1,7 trieu ha va hon 1 g/1 l i 2,1 trieu ha.
DBSCL bj inh hudng IQ Iut hing nim, tuy nhien lu d luu vyc sdng Me Kdng (LVSMK) thudng hiin hda, IQ thudng xuit hien vao thing 8, dat dinh v i o cudi thing 9 ho^c diu thing 10, lu len vdi cudng suit thip. thudng 2-3 cm/ngiy va lu rut chim din cuoi thing 11. Vio nam myc nudc IQ tai Tan Chau vugt qui 4,2 m dugc coi la nam lu Idn. dien tich ngap xap xi Vz dien tich DBSCL, lim anh hudng din sin xuit v i thiet hai ve CO so ha ling. Tuy nhien nudc lu thudng dem theo phii sa bdi d i p cho dong bing la
PHAN I - THUY Lire, SONG BIEN vA PHONG CHONG LUT BAO... 137
gia ting do phi nhieu cua dat. Nudc lu gdp phan rira trdi, em cic dgc td tren dit phen tao sy thuan lgi cho khai thic vimg dat khd tinh niy.
11.2. Hiin trgng phdt triin nam 2000 tren lwu virc
Theo cic tii lieu lien quan [3, 4, 5, 7], tinh den thdi diem nam 2000, dan sd ha LVSMK vao khoing 54,7 trieu dan, trong do ban 75% dan sd phu thugc vio canh tic nong nghiep. Dien tich canh tic ndng nghiep d ha LVSMK vao khoing 7.4 trieu ha, trong dd Thai Lan: 1,42 trieu ha, Lio: 0,33 trieu ha, Campuchia: 1,35 trieu ha v i Viet Nam khoang 4,1 trieu ha. Tdng dung tich eac hd chua eua Thii Lan vio khoing 7.4 ty m , ciia Lio khoing 5,5 ty m^, Viet Nam l i 0,78 ty m^. Phit trien ndng nghiep trong LVSMK thuge 2 nudc thugng luu Trung Qudc v i Myanma l i khong ding ke.
11.3. Xu hw&ng phdt triin trin lwu vwc
Dy bio d i n sd ha LVSMK se dat 74 trieu dan vao 2020 vdi tdc do gia ting binh quan luu vyc khoang l,5%i, trong do cao nhat d Lao: 2,6%, Campuchia: 2,3%, Viet Nam: 1,4 v i Thii Lan khoing 1%. LTu tien phit trien tren phan lanh thd cua cic quoc gia trong LVSMK chu yeu van li phit trien ndng nghiep v i thuy dien, dugc xem la CO tiem ning phit trien cao. Phit trien cdng nghiep tren luu vyc cdn d mirc do thip va chu yeu li cdng nghiep che bien phuc vu nong nghiep v i thiiy san tap trung d viing Dong Bae Thii Lan v i d DBSCL.
11.3.1. Ve phdt trien nong nghiep
Theo danh gii vl diiu kien dat thich nghi cho phat trien ndng nghiep tren LVSMK cho thiy, dien tich dit thich nghi cho phit trien nong nghiep tren luu vyc vao khoang 29,8 trieu ha, trong dd Thai Lan: 12,2 trieu ha, Lio: 2,7 trieu ha, Campuchia:
11,2 trieu ha v i Viet Nam li 3,7 trieu ha. Tuy nhien, khd khan Idn nhat doi vdi phat triin nong nghiep d cic nudc thugng km li dieu kien dja hinh doi niii doc khd khan cho phat triin cdng trinh thuy lgi - diu tu ldn, dieu kien dat dai - dat xim bac miu cd he s l thim ldn v i diiu kien nguIn nudc - die biet viing Dong Bac Thii Lan, mua it vi hien da dugc khai thic tuong ddi cao.
K I hoach phit triin ndng nghiep d cac quoc gia trong luii vyc cho thay, den 2020 dien tich ndng nghiep d Lao dy kiln ting gip 2 vao miia mua (500.000 ha) v i tang gap 1.5 lin vao mua khd (180.000 ha). Phit triin nong nghiep lua cd tudi d viing Ddng Bac Thii Lan vio khoang 1,2 + 1,4 trieu ha. chu yiu tap trung vao mua mua, miia kho chi dat hon 100.000 ha, cic no lyc phat triin tudi dy kiln dua dien tich dugc phuc vu tudi len khoang 1,6 trieu ha din 3,1 trieu ha. Tiim nang phit trien nong nghiep d Campuchia l i rit cao, dien tich canh tic lua dy kiln din 2020 len tdi 2.5 trieu ha, trong dd chil yiu canh tic mua mua.
11.3.2. Vi phdt triin thiiy dien
LVSMK cd tiim nang phat triin thuy dien tuong ddi cao, tdng cong suit udc tinh len tdi 53.000 MW, trong dd phin Trung Qudc li 23.000 MW, tiem nang thiiy dien
ddng chinh khoing 13.000 MW, cdn lai la tiim nang thuy dien ddng nhanh (Lao:
13.000 MW, Campuchia: 2.000 MW va Viet Nam li 2.000 MW). Tdng dung tich cic hd chiia len tdi hing tram ty m \ bao gdm c i cdng trinh ddng chinh va ddng nhinh.
Phan luu vyc thudc Thii Lan dugc xem nhu da khai thic het tiem nang thuy dien ty nhien, hien phia Thai Lan d i cd diu tu thiiy dien Lam-Ta-Kong vdi hd chua nhan tao, bam tich nudc v l dem va xa nudc phat dien ban ngiy. Tdng dung tich huu ich cic hd chira trong luu vyc da dang v i sip dugc xiy dyng len tdi xap xi 50 ty m .
11.4. Moi de dga din swphdt triin bin virng eda DBSCL
Cin cii vao ke hoach phit trien ciia cic qudc gia tren luu vyc, cQng nhu cin cir vio dieu kien dat dai thich hgp cho cic loai cay trdng v i k h i nang tiep can ngudn nudc, phit trien den nam 2020 tren luu vyc chu yeu l i gia tang phit trien ndng nghiep v i gia tang phit trien thuy dien. Phit trien ndng nghiep trong kjch b i n phit trien thap gia ting 1,5 lan v i 2 lan trong kjch ban ndng nghiep phit trien cao so vdi hien trang canh tic nim 2000 [3, 5, 7]. Tdng hgp cic bdi cinh phat trien luu vyc dugc dua ra d bang 1.
Bdng 1. Cdc boi cdnh phdt trien cita luu vuc theo dieu kien ndm 2000 vd tuang lai Thir
tu
1
2 3 4 5
B6i canh
Hien trang phat trien nam 2000 - BLOO Thiiy dien Trung Quoc ThCiy dien trong tuang lai gin
Nong nghiep phat trien thip
Nong nghiep phat tri4n cao
Ki hieu
BLOO
TDTQ TLG
Dien tich tuoi (1000 ha)
3.400
3.400 3.400 PTT 4.200 PTC 1 6.620
1
Dung tich h&u ich cac h6 chLi'a(10''m^) Ha luu vuc
13.680
13.680 26.230
Trung Qu6c -
22.700 22.700
Ghi chil T:12h6;L:5;
V:1
T:12h6; L:5;
V:1;TQ:6 T:12; L:14;
V:10;TQ:6
Tdng dung tich huu ich cic hd thuy dien tai Trung Qudc trong k l hoach len tdi 22,7 ty m\ bao gdm cic h i Xiaowan (9,8 ty m\ ke hoach d i n 2013), Manwan (0,29 ty m^), Dachaoshan (0,24 ty m^) va Nuozhadu (12,4 ty m\ k l hoach d i n 2017). Phia ha luu se cd viec gia ting cic hd chira d Lio: 10,25 ty m , Viet Nam: 2,3 ty m^. Nhu vay tdng dung tich huu ich cic hd chua thiiy dien da v i dang xay dung tren luu vyc chiim din hon 1 \% tong lugng ddng chiy sdng Me Kdng, ben canh dd gia ting g i p ddi dien tich ndng nghiep so vdi hien tai ban lam thay ddi ding ke luu lugng mua khd v i dien biln lu ha luu vi yay dugc xem l i nhung thich thire ddi vdi DBSCL.
PHAN I - THUY LIJC, SONG BIEN vA PHONG CHONG LUT BAO.. 139
II.5. Mo hinh todn mo phong thay dol dong ehdy lwu vwc song Me Kong
Nghien cim n i y urng dung bg cdng cy DSF (Cdng cu hd trg ra quyet djnh) dugc phat trien bdi doan ehuyen gia tu van Halcrow cua Anh Qudc, trong chuong trinh Sir dung nudc (WUP) ciia Uy hgi qudc te sdng Me Kdng (UHMK) v i dugc cic qudc gia thanh vien thdng nhat sir dung de phan tich danh gii cic tic dgng va hd trg ra quyet djnh.
Nghien cim da cap nhap nhirng ket qui img dung md hinh dugc cap nhat mdi nhit do nhdm md hinh cua UHMK lap, bao gdm nhung ket qua hieu chinh v i cai tien md hinh mdi nhat ciia md hinh SWAT v i IQQM. Cic ket qui b i o eio can chinh dugc dua ra trong cic b i o cao ciia Halcrow v i UHMK da dugc cic qudc gia chap thuan sir dyng.
Md hinh SWAT dugc sir dung d l md phdng, tii tao ddng chiy luu vye tir mua.
Cic ket qui d i dugc Halcrow cung cic cgng sy can chinh nam 2003, dugc nhdm md hinh cua UHMK tiip tue can chinh din 2008, pham vi iing dung cua SWAT nhu ehi ra d hinh 1. Nghien cim nay khai thac cac ket qui sin cd cua md hinh SWAT ve mo phdng dong chiy tu mua tren toin luu vyc theo chudi sd lieu khi tugng tir 1985 den 2000.
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Hinh 1. Sff hga irng dung cdc mo hinh trong mo phong tde dpng cdc kich bdn phdt triin xuong hg lwu
Md hinh IQQM (md hinh md phdng luu vyc), cd pham vi iing dung nhu hinh 1, dugc can chinh nam 2003, tiip tuc phit triin v i cap nhat cic bien luu lugng tii can chinh giai doan 2004-2007. Nghien cuai k l thira sa dd IQQM cua UHMK va thilt lap mdi cic kjch b i n phit triin luu vyc tren ca sd phan tich dinh g i i cic yeu td phit trien tren luu vyc cd thi lim thay dii chi do thuy van ddng chiy ve ha luu v i thay ddi nhu ciu nudc d thugng luu.
Nghien ciiu lya chgn diiu kien phat triin nim 2000 lim co sd de so sinh vi dinh gii sy thay ddi thiiy van ddng chiy do tic dgng cic kjch bin phit trien - phat trien thuy dien d din nam 2000 hiu nhu khdng ding kl, nhung nam sau nay cd thay ddi ldn hon vi vay viec dinh gii thay doi ddng chiy ty nhien khdng cdn dugc chinh xic nua. Cac kjch bin duge xay dyng dya tren 2 yiu t l chinh: diiu kien ty nhien v i tic dgng con ngudi nhu so hga d hinh 2 vi tdng hgp cac kich ban xiy dung vi md phdng duge the hien d bang 2.
Hinh 2: S c hpa cau true cau thanh kjch b an thuang luu
Hinh 2. Sff hga cdu triic cdu thdnh kich bdn thwffng lwu Bdng 2. Tong hgrp cdc kich bdn xdy dung vd mo phong ket qud
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BLOO TDTQ
TLG
TDTQ+PTT
TLG+PTC
BLOO+PTC
D i i n giai kich ban Di4u kien phat trien nam 2000: (Nong nghiep va thuy dien nhu d4n 2000) Thiiy dien Trung qudc (TDTQ): co them 6 cong trinh TDTQ
T u o n g lai g i n (TLG): Thuy dien TQ (6) va cac cong trinh thuy dien da, dang va s i p xay dung a phia thugng luu (18)
TDTQ CO them kjch ban Nong nghiep Phat trien a mirc t h i p (PTT)
TLG CO them kich ban nong nghiep phat trien a muc cao (PTC)
Hien trang cong trinh 2000 them NN phat then cao - 'cue doan'
Chu5i thuy van mo phong 1985-2000
1985-2000 1985-2000
1985-2000
1985-2000
1985-2000
Ghi chil Lam ccc s d so sanh - khong co cong trinh Tac (Jong dgc lap TDTQ
Tac dpng phat trien thiiy dien TLG
D u bao dong chay khi co TDTQ va gia tang NN- PTT
D u bao dong chay khi co TLG va gia tang NN- PTC
Canh bao kha nang anh h u d n g cua PTNN
PHAN I - THUY Lire, SONG BIEN VA PHONG CHONG LUT BAO.. 141
Trong sd cae kich bin tren, kjch bin 4 v i 5 dugc xem nhu l i cd khi ning xiy ra trong tuong lai, kich bin 6 dugc xem l i cyc doan vi hien tai cic cdng trinh thuy dien trong TLG da hoan thinh tuong ddi nhiiu.
III. Kit qua nghien ciru
III.l. Thay doi nhu cdu nw&c phia thwffng lwu theo cdc phwffng dn phdt triin Nhu cau nudc (NCN) phia thugng luu cua DBSCL dugc tdng hgp theo timg qudc gia v i theo cic kjch bin phit trien ndng nghiep dugc trinh b i y d hinh 3, bao gdm dieu kien phat trien nim 2000, phit trien ndng nghiep d miic thap v i phit trien ndng nghiep d mirc cao vdi gii thiet dan sd ting den 2020. Nhu ciu nudc dugc tdng hgp theo luu lugng binh quan thing cd xet den thay ddi nhu ciu nudc vdi cic dieu kien khi tugng thuy van tir 1986 din 2000.
T 4 N G VK'P MHU C A U N U U C THEO TRUWO aiNH THANG Ut*3 VOI CAC KICH BAN PHAT TRIEN V A T H A V V6\ D K KHi TUOMO THl>i' V A N I U 19e6-XCC
OBLCO DPIT DPIC
1 723 1.224 2.094
2 63S 1,062 1,885
3 509 e2S 1.167
t 376 432 722
5 330 476 603
6 52J S07 777
7 677 686 1.127
8 591 833 1.08S
9 748 949 1,333
,0 1,020 1,412 IfJbl
11 971 '.392 1.771
13 1,026 1.531 2,376
Hinh 3. Tdng hop Nhu cdu nw&c irng v&i cdc kich bdn phdt trien & thwffng lwu Tir kit qui md phdng cho thiy, nhu cau nudc binh quan irng vdi dieu kien phit triin nam 2000 d thugng luu la khdng ding kl, luu lugng dung binh quan c i nam li 670 m-'/s, nhu ciu nudc iing vdi kjch bin phat trien ndng nghiep d miic thip vio khoang 952 mVs v i nhu ciu nudc iing vdi kjch bin phit trien ndng nghiep d mure do cao vio khoing 1.411 m^/s. Kit qui cho thiy nhu ciu nudc cd the ting gip 3 lin vl miia khd trong kjch bin phat triin ndng nghiep cao, day la mdi ding lo ngai cho sy dn djnh phit trien ndng nghiep d DBSCL.
III.2. Thay ddi dong ehdy din Kratie theo cdc kich bdn phdt trien
Kit qui dinh gii thay ddi luu lugng ve Kratie theo cic kjch bin phit triin d thugng luu dugc dua ra d cae hinh 4.1-^4.6. Ket qui cho thay, trong hau het cic trudng hgp (hinh 4.1^ hinh 4.5) luu lugng trung binh cic thing mua kiet irng vdi ehi do thiiy van tir 1986 din 2000 diu gia ting ding ke so vdi luu lugng ve irng vdi diiu kien phit triin nam 2000 (H4.1) tir 300-H800 mVs. Ngoai tru kjch ban 'cyc doan'(BLOO-HPTC), 114.6, luu lugng binh quan cic thing mua kiet giam xap xi 600 mVs so vdi dieu kien hien trang phit trien nam 2000.
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//4.6. Lwu twffng TB, Max, Min thdng tgi Kratie, BLOO+PTC
Tuong ty, ngoai trir kjch bin 'eye doan', luu lugng binh quan thing kiet nhit trong dieu kien khi tugng thiiy van tir 1986 den 2000 van dat hon 2.200 mVs mac dii cd tac dgng cua cic kjch bin phit trien thiiy dien v i phit trien ndng nghiep. Luu lugng binh quan thing ldn nhit miia lii cd tic dgng inh hudng cic kjch ban phit trien li 44.038 m^/s, nhd hon so vdi luu lugng binh quan thing ldn nhit d hien trang phit trien nam 2000 (44.100 m^/s).
III.3. Ddnh gid thay doi lwu Iwffng din Kratie vd dnh hw&ng co thi xuong hg lwu Ket qui md phdng thay ddi luu lugng ve Kratie theo cic kjch ban phit trien d thugng luu cho thiy, trong hau het cic truong hgp luu lugng trung binh cic thing mua kiet irng cd xu hudng gia tang v i luu lugng trung binh miia lii cd xu hudng giim. De dinh gii tic dgng bit lgi do cic hd can nudc trudc khi lii ve den Kratie do gap nim khi tugng thuy van bat lgi, nghien cuu da tdng hgp Luu lugng binh quan thing (QtbT) ve Kratie giai doan 1986 den 2000, luu lugng thing ldn nhit v i thing nhd nhit vl Kratie sau khi cd tic ddng dieu tiet ciia cic hd vi sir dyng nudc d cic kjch bin phit trien dugc xem la da va cd the ban nhu: BLOO; TDTQ-PTT; v i TLG-PTC. Ket qui dugc dua ra d cic hinh 5.1 den 5.3.
Ket qua phin tich cho thiy, do tic dgng dieu tiet cua toin luu vyc, anh hudng cue bg cd the xiy ra d mgt sd hd thuy dien, tuy nhien khi ddng chiy ve den Kratie thi cic tic dgng deu dirong, luu lugng binh quan thing cua nam nhd nhat trong chuoi thuy vin tir 1986 den 2000 sau khi cd inh hudng thay ddi ddng chiy dieu kien phit triin ciia cac
kjch bin deu ldn han so vdi dieu kien hien trang phit trien n i m 2000. Tuong ty, luu lugng trung binh thing ldn nhat miia lii cung nhd hon so vdi dien bien lii d dieu kien phit trien nim 2000. Dieu dd cd the thiy ring vdi dieu kien thiiy van nhu liet 1986 din 2000, cac kjch bin md phdng vdi van hinh binh thudng cua cac cdng trinh thuy dien, chua thay cd tic ddng bat lgi nio den thay ddi ddng chay ve thugng luu ddng bang tai Kratie do tic dgng dieu tiet qua lai giiia cic nhanh trong luu vuc.
H5.1. QtbT giai doiin 1986-2000 theo cdc kich hdn co thi
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H5.3. QtbT nho nlidt giai dogn 1986-2000, kwh bdn cd tlii
P H A N I - THUY Lire, SONG BIEN vA PHONG CHONG LIJT BAO... 145
III.4. Ddnh gid thay doi nhu cau nw&c & thwang lwu vd dnh hw&ng co thi xuong hg lwu Ket qua md phdng thay ddi nhu cau nude d thugng luu trong cic kich bin phit trien cho thay NCN d thugng luu cd the tang gip 3 lin so vdi hien trang sir dung nudc nam 2000, tuy nhien do tic ddng dieu tiet ciia phit trien ciia thiiy dien trong luu vye, die biet d Lao va Trung Qudc lim nudc ve thugng luu ddng bing theo cic kjch bin deu gia ting tir 300-^800 m /s ve miia khd va cat giim ding ke luu lugng binh quin dinh lii die biet cic nim lii nhd. Ngoai trir phuang i n eye doan, ndng nghiep phit trien cao trong khi chua cd dieu tiet cua cic cdng trinh thiiy dien dy kien.
Theo mgt sd nghien ciiu, ngudng khai thic 30% dugc xem li pham vi an toin. So sinh NCN d thugng lim so vdi luu lugng ve thugng luu ddng bing d Kratie cho thay d dieu kien hien trang nhu nam 2000, sir dung nudc tren luu vye chi dao dgng nhd ban 20% luu lugng ddng chiy, dugc xem la van nam trong pham vi an toin - thye te sd lieu do dac ve chat lugng nudc tren ddng chinh ciing cho thay chua cd bieu hien inh hudng mdi trudng nio tren Iuu vyc. Trong phuang i n phit trien thip cung nam trong pham vi an toin niy. Tuy nhien, trong phuang in phit trien ndng nghiep cao, ngay c i khi cd cic cong trinh thiiy dien dieu tiet, nhu cau khai thic nudc d cic thing miia khd da xap xi bang hay vugt nguang an toan nay, die biet neu khdng co tic dgng thiiy dien thi khai thic nudc d thugng luu cd the dat ngudng ban 40%. Dieu dd ddng nghTa se co tic dgng ding ke den mdi trudng sinh thii tren luu vyc ciing nhu chat lugng nudc ve ha luu, mac dil xim nhap man cd the khdng gia ting so vdi hien trang trong dieu kien niy.
IV. Kit luan va thao luan
Tir kit qui tinh toin cic kjch bin phit trien d thugng luu, mdt sd ket luan dugc riit ra:
- Tic dgng cua cic kjch bin phit trien d phia thugng luu ndi chung v i die biet phit triin ndng nghiep v i chuyen nudc luu vyc ndi rieng qui l i ding quan tam, khi m i khdng cd thuy dien diiu tilt nudc d thugng luu, gia ting phit trien ndng nghiep phia thugng luu d mirc cao cd the lim giim luu lugng binh quan ve thugng luu ddng bing vio khoing 600 mVs, tire l i xip xi vdi nhu ciu nudc binh quan nam d ddng bang, nhu vay se cd tic ddng ding kl din hien trang canh tic ndng nghiep d DBSCL va dien bien xam nhap man.
- Tic dgng diiu tilt ciia cic cdng trinh thiiy dien Trung Qudc d dieu kien boat dgng binh thudng v i NCN nhu d BLOO thi cd the lim gia tang luu lugng ve miia khd vao khoing ban 600 m-'/s v i trilt giam luu lugng binh quan thing dinh Id khoang ban 1.000 mVs. Trong dieu kien tuong ty cd phit trien ndng nghiep d mirc thap, luu lugng vl miia khd van cd the gia ting khoing 500 m Is,.
- Tic ddng diiu tilt ciia cic cdng trinh thiiy dien trong tuong lai gin d dieu kien boat dgng binh thudng v i NCN nhu d BLOO thi cd the lam gia tang luu lugng ve miia khd vio khoing hon 800 mVs v i triet giim luu lugng binh quin thing dinh lu xap xi
2.000 mVs. Trong diiu kien tuong ty cd phit triin ndng nghiep d miic eao, luu lugng ve miia khd vin cd the gia ting khoing 500 m /s.
- Mac dil cd tic dgng diiu tilt nudc ciia cic cdng trinh thuy dien phia thugng luu lim gia tang ding kl luu lugng vl thugng luu DBSCL trong cac kich bin cd ca phit triin ndng nghiep, tuy nhien niu ndng nghiep phat trien d miic cao hay cao ban mure gii thilt trong nghien ciiu niy thi khai thic nudc d thugng luu se vugt qui 30% tiem ning nudc d cic thing miia khd, nhu vay cd thi cd cic anh hudng ve chat lugng nudc ddng chinh vl thugng luu ddng bing vi nhQng tic ddng do bien ddi sinh thii khac tren luu vyc.
Thao luan
- Cic cdng trinh thiiy dien dy kiln diu chua cd dugc qui trinh van hanh, vi vay viec van hinh cic hi chira nay dugc dieu chinh chu ddng triet giim de khdng hi xudng dudi mye nudc chit vio cudi miia khd vi tich nudc ngay khi cd the - chua xet den nhiem vu dieu tiet lii hay dieu tiet da muc tieu.
- Nghien ciru niy mdi xet den su lim viec binh thudng cua cic hd chiiti ma chua xet den cic td hgp bat lgi, chang ban hd tich nudc trong qui trinh thi cdng, hd ngirng phat dien trong mgt khoing thdi gian de sua chira, sy cd... thi tic ddng cui nd cd the li rit nguy hai, die biet ddi vdi cic hd chira ldn nhu Xiaowan va Nuozhadu. Tuong tu, viec van hinh cic cdng trinh thiiy dien phu dinh ngiy-dem ciing nhu van hinh qui mirc lam myc nude giam xudng dudi myc nudc chet trudc khi lii ve phii ngimg boat dgng ciia cae cdng trinh;
- Vi nhirng ban che nhu da neu d tren, ket qui trong nghien ciiu niy dugc xem nhu li nhirng mat lgi eua phit trien thiiy dien phia thugng luu trong diiu kien van hinh binh thudng (ly tudng), nhiing mat trii cua phit trien thuy dien d phia thugng luu se dugc xem xet trong mgt bii viet khic.
TAI LIEU THAM KHAO