Tác động BĐKH lên tài nguyên nước ĐBSCL.pdf

C QUAN PHT TRIN QUC T AN MCH

DANIDA

B TI NGUYN V MI TRNG

MONRE

TC NG CA BIN I KH HU

LN TI NGUYN NC

V CC BIN PHP THCH NG

NG BNG SNG CU LONG

H Ni, thng 11/2010

VIN KHOA HC KH TNG THY VN V MI TRNG

D N

TC NG CA BIN I KH HU LN TI NGUYN NC

V CC BIN PHP THCH NG

NG BNG SNG CU LONG

C quan thc hin: Vin Khoa h c Kh t n Thu v n v M i t n

C quan t i t : i s qun an Mch ti Vit Nam

H Ni, thn 11/2010

i

MC LC

M U .................................................................................................................................... 1

CHNG I. S LC LU VC SNG M CNG ....................................................... 2

CHNG II. S LC NG BNG SNG CU LONG ............................................. 8

2.1. iu kin t nhin ........................................................................................................... 8

2.1.1. Khi qut c im a l t nhin ......................................................................... 8

2.1.2. c im kh hu .................................................................................................... 9

2.1.3. Mng li sng ngi, knh rch ............................................................................ 11

2.2. c im thy vn ........................................................................................................ 13

2.2.1. Dng chy nm ..................................................................................................... 13

2.2.2. Ch dng chy .................................................................................................. 13

2.2.3. c im l lt ...................................................................................................... 14

2.2.4. Cht lng nc sng ........................................................................................... 17

2.3. c im ti nguyn nc ngm BSCL .................................................................... 19

2.4. c im thy triu BSCL ...................................................................................... 20

2.5. Tnh hnh kinh t v x hi ........................................................................................... 21

2.5.1. Tnh hnh dn sinh ................................................................................................. 21

2.5.2. Tnh hnh pht trin kinh t ................................................................................... 21

2.6. Thc trng h thng cng trnh, thy li ...................................................................... 25

2.6.1. Vng t sng Tin (TST) ...................................................................................... 25

2.6.2. Vng T gic Long Xuyn (TGLX) ..................................................................... 26

2.6.3. Hin trng thy li vng Bn o C Mau (BCM) ............................................ 27

CHNG III. NH GI TC NG CA BIN I KH HU LN TI

NGUYN NC CA BSCL ............................................................................................ 30

3.1. Cc m hnh c ng dng trong lu vc M Cng tnh ton tc ng ca bin i Kh hu ln ti nguyn nc .......................................................................................... 30

3.1.1. M hnh thy vn .................................................................................................. 31

3.1.2. M hnh cn bng nc lu vc ........................................................................... 31

3.1.3. M hnh thy ng lc .......................................................................................... 33

3.2. Cc kch bn bin i kh hu lu vc sng M Cng .............................................. 35

3.2.1. Kt qu ca Vin KTTV&MT tnh ton bng m hnh ng lc PRECIS. ......... 39

ii

3.2.2. Kch bn bin i kh hu xy dng bng phn mm MAGICC/SCENGEN kt hp vi hiu chnh thng k cho BSCL ................................................................. 45

3.2.3. Bc thot hi tim nng (ETo) .............................................................................. 52

3.2.4. Kch bn nc bin dng ...................................................................................... 54

3.3. Kch bn tnh ton nh gi tc ng bin i kh hu ln dng chy lu vc sng M Cng ca y hi M Cng ................................................................................... 55

3.4. nh hng ca BKH n dng chy Vit Nam ........................................................ 57

3.4.1. Tc ng chung ..................................................................................................... 57

3.4.2. Phn tch tc ng ln dng chy vo BSCL ..................................................... 60

CHNG IV. NH HNG CA BKH N NGP LT V XM NHP ............ 79

4.1. Tc ng ln ngp lt .................................................................................................... 79

4.2. Tc ng n xm nhp mn ........................................................................................ 92

CHNG V. TC NG CA BKH N NHU CU NC CHO TI

NG BNG SNG CU LONG..................................................................................... 101

XUT MT S BIN PHP NG PH ................................................................... 111

KT LUN ........................................................................................................................... 119

TI LIU THAM KHO .................................................................................................... 121

iii

Danh mc bng

Bng 1-1. Phn b dng chy trong lu vc sng M Cng ................................................. 7

Bng 2-1. Lng ma trung bnh thng, nm ti mt s v tr trong ng bng sng Cu Long ............................................................................................................. 10

Bng 2-2. Lu lng nh l Tn Chu, Chu c trong l ln ......................................... 17

Bng 2-3. Tnh hnh s dng t nm 2007- vng BSCL................................................. 22

Bng 3-1. Thay i nhit trung bnh nm, kch bn A2, B2 so vi thi k 1985- 2000, lu vc sng M Cng (Ngun MRC, 2010) ............................................ 35

Bng 3-2. Thay i lng ma nm, ma ma ma (V-X), ma kh (XI-IV), ng vi kch bn A2, B2 so vi thi k 1985- 2000, lu vc sng M Cng (Ngun MRC, 2010) ......................................................................................................... 37

Bng 3-3. Mc thay i nhit trung bnh nm ti mt s trm kh tng so vi thi k 1980 1999 theo cc kch bn BKH ........................................................... 45

Bng 3-4. T l thay i lng ma (%) so vi kch bn nn ca cc trm kh tng (kch bn A2) ....................................................................................................... 47

Bng 3-5. T l thay i lng ma (%) so vi kch bn nn ca cc trm kh tng (kch bn B2) ....................................................................................................... 48

Bng 3-6. T l thay i lng ma (%) so vi kch bn nn ca cc trm kh tng (kch bn B1) ....................................................................................................... 49

Bng 3-7. Lng bc thot hi tim nng nm (mm) ti mt s trm kh tng theo cc kch bn bin i kh hu .............................................................................. 52

Bng 3-8. Cc kch bn pht trin c la chn tnh ton nh gi tc ng bin i kh hu ln ch dng chy lu vc sng M Cng (MRCS 2009) .......... 56

Bng 3-9. Lu lng trung bnh nm, ma l, ma cn ti mt s trm thy vn (ngun MRCS 2010) ........................................................................................... 57

Bng 3-10. Tc ng bin i kh hu ln dng chy ............................................................ 58

Bng 3-11. Tc ng tng hp ca bin i kh hu v pht trin khai thc s dng nc trn lu vc ln dng chy (ngun MRCS 2010) ...................................... 59

Bng 3-12. Dng chy nm trung bnh cc thi k ............................................................... 62

Bng 3-13. Thay i dng chy nm trung bnh cc thi k so vi kch bn nn ................. 62

Bng 3-14. c trng dng chy ti trm Kratie ................................................................... 65

Bng 3-15. Dng chy trung bnh ma l ti mt s trm trn dng chnh sng M Cng .................................................................................................................... 66

iv

Bng 3-16. Thay i dng chy trung bnh ma l ti mt s trm trn dng chnh sng M Cng ..................................................................................................... 67

Bng 3-17. Dng chy trung bnh thng ln nht ti mt s trm trn dng chnh sng M Cng .............................................................................................................. 68

Bng 3-18. Thay i dng chy trung bnh thng ln nht ti mt s trm trn dng chnh sng M Cng ........................................................................................... 69

Bng 3-19. Tng lu lng qua trm Tn chu v Chu c trong cc thng ma cn ....... 71

Bng 3-20. Dng chy trung bnh ma cn ti mt s trm trn dng chnh sng M Cng .................................................................................................................... 72

Bng 3-21. Thay i dng chy trung bnh ma cn ti mt s trm trn dng chnh sng M Cng ..................................................................................................... 72

Bng 3-22. Dng chy trung bnh ba thng cn nht ti mt s trm trn dng chnh sng M Cng ..................................................................................................... 74

Bng 3-23. Thay i dng chy trung bnh ba thng cn nht ti mt s trm trn dng chnh sng M Cng ........................................................................................... 75

Bng 3-24. Dng chy trung bnh thng cn nht ti mt s trm trn dng chnh sng M Cng .............................................................................................................. 75

Bng 3-25. Thay i dng chy trung bnh thng cn nht ti mt s trm trn dng chnh sng M Cng ........................................................................................... 76

Bng 4-1. Din tch b ngp tng ng vi cc mc ngp khc nhau-l 2000, s dng t hin ti ........................................................................................................... 85

Bng 4-2. Din tch b ngp tng ng vi cc mc ngp khc nhau-l nm 2020, s dng t hin ti .................................................................................................. 85






Bng 4-8. Din tch b ngp tng ng vi cc mc ngp khc nhau l nm 2000, s dng t nm 2020 ......................................................................................... 87

v

Bng 4-9. Din tch b ngp tng ng vi cc mc ngp khc nhau - L nm 2020, s dng t nm 2020 ......................................................................................... 87






Bng 4-15. Din tch b ngp lt ng vi con l ln nht trong cc thi k khc nhau theo cc kch bn ................................................................................................. 90

Bng 4-16. Chiu di xm nhp mn ti mt s sng chnh trong cc thi k-kch bn A2 ........................................................................................................................ 93

Bng 4-17. Thay i chiu di xm nhp mn ti mt s sng chnh trong cc thi k-kch bn A2 ......................................................................................................... 93

Bng 4-18. Chiu di xm nhp mn ti mt s sng chnh trong cc thi k-kch bn B2 ........................................................................................................................ 94

Bng 4-19. Thay i chiu di xm nhp mn ti mt s sng chnh trong cc thi k-kch bn B2 .......................................................................................................... 94

Bng 4-20. Din tch t b nh hng bi danh gii mn 1 s dng t hin ti ................................................................................................................. 95

Bng 4-21. Din tch t b nh hng bi danh gii mn 4 s dng t hin ti ................................................................................................................. 95

Bng 4-22. Din tch t b nh hng bi danh gii mn 1 s dng t tng lai .......... 96

Bng 4-23. Din tch t b nh hng bi danh gii mn 4 s dng t tng lai .............................................................................................................. 96

Bng 5-1. Din tch cy la ca BSCL ........................................................................... 101

Bng 5-2. D kin c cu s dng t BSCL ................................................................. 101

Bng 5-3. Tng nhu cu nc ti theo cc thng ng bng sng Cu Long qua cc thi k- Kch bn A2 .................................................................................. 103

Bng 5-4. Tng nhu cu nc ti theo cc thng ng bng sng Cu Long qua cc thi k - Kch bn B2 .................................................................................. 104

vi

Bng 5-5. Tng nhu cu nc trung bnh nm cho nng nghip trn ng bng sng Cu Long ........................................................................................................... 104

Bng 5-6. S thay i tng nhu cu nc trung bnh nm cho nng nghip trn ng bng sng Cu Long ......................................................................................... 104

Bng 5-7. Nhu cu nc ti cc vng thuc BSCL trung bnh cc thi k 1991-2000 ................................................................................................................... 105

Bng 5-8. Nhu cu nc ti cc vng thuc BSCL trung bnh thi k 2010-2019 kch bn A2 ....................................................................................................... 106




Bng 5-12. Nhu cu nc ti cc vng thuc BSCL trung bnh thi k 2010-2019 kch bn B2 ........................................................................................................ 108




Bng 6-1. Quy hoch cc tuyn bin cc tnh thuc BSCL .................................... 117

Bng 6-2. Mt s cng ngn mn d kin ......................................................................... 118

vii

Danh mc hnh

Hnh 1-1. V tr a l lu vc sng M Cng ....................................................................... 3

Hnh 1-2. Phn b tng lng dng chy (t m3) trn sng M Cng .................................. 6

Hnh 1-3. T l ng gp (%) ca cc quc gia vo vo dng chy sng M Cng theo cc ma dng chy ........................................................................................ 7

Hnh 2-1. Bn a hnh ng bng sng Cu Long (ngun B TN&MT 2009) .................................................................................... 9

Hnh 2-2. Bn ng tr ma nm ng bng sng Cu Long ......................................... 11

Hnh 2-3. Phn phi dng chy trong nm ti trm Tn Chu v Chu c ...................... 14

Hnh 2-4. Qu trnh mc nc ti Kratie trong cc nm l ln v trung bnh nhiu nm ...................................................................................................................... 15

Hnh 2-5. Qu trnh mc nc ti Chu c trong cc nm l ln v trung bnh nhiu nm ...................................................................................................................... 15

Hnh 2-6. nh v tinh khu vc ngp trn l thng 9 nm 2000 ng bng sng Cu Long .................................................................................................... 16

Hnh 2-7. Bn tim nng tr lng nc ngm lu vc ng bng sng Cu Long. ................................................................................................... 20

Hnh 2-8. Bn hin trng s dng t sng ng bng sng Cu Long ......................... 23

Hnh 2-9. Bn quy hoch thy li ng bng sng Cu Long ....................................... 29

Hnh 3-1. Cc m hnh p dng tnh ton cho ng bng sng Cu Long ......................... 31

Hnh 3-2. S phn chia lu vc sng M Cng trong m hnh SWAT ......................... 32

Hnh 3-3. S m hnh IQQM cho vng thng lu Kratie ............................................ 32

Hnh 3-4. S m hnh IQQM cho vng Bin H v BSCL ......................................... 33

Hnh 3-5. S thy lc mng sng M Cng ................................................................... 34

Hnh 3-6. Thay i nhit trung bnh nm thi k 2010-2050 so vi thi k 1985-2000 (ngun MRCS, 2010) ................................................................................. 36

Hnh 3-7. Thay i lng ma nm thi k 2010-2050 so vi thi k 1985-2000 ............ 36

Hnh 3-8. S thay i nhit nm (C) trong cc thp nin 2050, 2070 v 2100 so vi thi k 1980-1999 theo kch bn trung bnh B2 ........................................... 39

Hnh 3-9. Mc thay i (%) ca lng ma nm trong cc thp nin 2020, 2030, 2050 v 2080 so vi thi k 1980-1999. Kch bn B2 ....................................... 41

viii

Hnh 3-10. Mc thay i (%) ca lng ma ma ma trong cc thp nin 2020, 2030 so vi thi k 1980-1999, Kch bn B2 ..................................................... 41

Hnh 3-11. Mc thay i (%) ca lng ma ma ma trong cc thp nin 2050, 2060, 2080 v 2090 so vi thi k 1980-1999, Kch bn B2 ............................. 42

Hnh 3-12. Mc thay i (%) ca lng ma ma kh trong cc thp nin 2060, 2070, 2080 v 2090 so vi thi k 1980-1999. Kch bn B2 ............................. 44

Hnh 3-13. Thay i nhit theo cc kch bn BKH ti mt s trm kh tng .............. 46

Hnh 3-14. Thay i lng ma nm ti mt s trm kh tng trn ng bng sng Cu Long ............................................................................................................. 51

Hnh 3-15. Thay i lng thng nm n nm 2050 ti mt s trm kh tng trn ng bng sng Cu Long .................................................................................. 51

Hnh 3-16. Thay i bc hi tim nng ETo (%) theo kch bn theo cc kch bn bin i kh hu ti mt s trm kh tng ................................................................. 53

Hnh 3-17. Qu trnh triu ti mt s v tr ng vi ng vi cc mc nc bin dng khc nhau ............................................................................................................. 54

Hnh 3-18. Qu trnh dng chy sng M Cng ti trm Kratie ........................................... 60

Hnh 3-19. Qu trnh dng chy sng M Cng ti trm Phnom Penh ................................. 61

Hnh 3-20. Qu trnh dng chy sng Tin ti Tn Chu ...................................................... 61

Hnh 3-21. Qu trnh dng chy sng Hu ti Chu c ...................................................... 61

Hnh 3-22. Qu trnh lu lng trung bnh nm ti Kratie cc kch bn ............................... 63

Hnh 3-23. Qu trnh lu lng trung bnh nm ti Phnom Penh cc kch bn .................... 63

Hnh 3-24. Qu trnh lu lng trung bnh nm ti Tn Chu cc kch bn. ........................ 64

Hnh 3-25. Qu trnh lu lng trung bnh nm ti Chu c cc kch bn ........................ 64

Hnh 3-26. c trng dng chy trm Kratie kch bn A2 ................................................ 65

Hnh 3-27. c trng dng chy trn sng M Cng ti trm Kratie, kch bn B2 .............. 65

Hnh 3-28. Dng chy l trung bnh trn sng M Cng ti trm Kratie .............................. 67

Hnh 3-29. Dng chy l trung bnh trn sng M Cng ti trm Phnom Pnh ................... 67

Hnh 3-30. Dng chy l trung bnh trn sng Hu ti trm Tn Chu ................................ 68

Hnh 3-31. Dng chy l trung bnh trn sng Tin ti trm Chu c ............................... 68

Hnh 3-32. Dng chy trung bnh thng ln nht trong ma l trm Kratie ......................... 69

ix

Hnh 3-33. Dng chy trung bnh thng ln nht trong ma l trm Phom Pnh ................. 69

Hnh 3-34. Dng chy trung bnh thng ln nht trong ma l trm Tn Chu ................... 70

Hnh 3-35. Dng chy trung bnh thng ln nht trong ma l trm Chu c ................... 70

Hnh 3-36. Dng chy trung bnh ma cn trm Kratie ........................................................ 73

Hnh 3-37. Dng chy trung bnh ma cn trm Phnom Pnh .............................................. 73

Hnh 3-38. Dng chy trung bnh ma cn trm Tn Chu .................................................. 73

Hnh 3-39. Dng chy trung bnh ma cn trm Chu c .................................................. 74

Hnh 3-40. Dng chy trung bnh ba thng cn nht trm Kratie ......................................... 76

Hnh 3-41. Dng chy trung bnh ba thng cn nht trm Phnom Pnh ............................... 76

Hnh 3-42. Dng chy trung bnh ba thng cn nht trm Tn Chu .................................... 77

Hnh 3-43. Dng chy trung bnh ba thng cn nht trm Chu c ................................... 77

Hnh 3-44. Dng chy trung bnh thng cn nht trm Kratie .............................................. 77

Hnh 3-45. Dng chy trung bnh thng cn nht trm Phnom Pnh .................................... 78

Hnh 3-46. Dng chy trung bnh thng cn nht trm Tn Chu ......................................... 78

Hnh 3-47. Dng chy trung bnh thng cn nht trm Chu c ........................................ 78

Hnh 4-1. Qu trnh l n Kratie ........................................................................................ 80

Hnh 4-2. Bn ngp lt ng bng sng Cu Long l nm 2000 ................................... 81

Hnh 4-3. Bn ngp lt ng bng sng Cu Long ng vi kch bn A2 nc bin dng 15cm ........................................................................................................... 82



Hnh 4-6. Bn ngp lt ng bng sng Cu Long ng vi kch bn B2 nc bin dng 15cm ........................................................................................................... 83



x

Hnh 4-9. Din tch b ngp tng ng vi cc mc ngp khc nhau-l nm 2000, s dng t hin ti .................................................................................................. 90

Hnh 4-10. Din tch b ngp tng ng vi cc mc ngp khc nhau-l nm 2020 thi k 2020-2029, kch bn A2, s dng t hin ti ............................................... 90



Hnh 4-13. Din tch b ngp tng ng vi cc mc ngp khc nhau-l nm 2021 thi k 2020-2029, kch bn B2, s dng t hin ti ................................................ 91



Hnh 4-16. Bn xm nhp mn kch bn nn ................................................................... 97

Hnh 4-17. Bn xm nhp mn kch bn A2-nc bin dng 15cm ................................ 97



Hnh 4-20. Bn xm nhp mn kch bn B2-nc bin dng 15cm ................................. 99

Hnh 4-21. Bn xm nhp mn kch bn B2-nc bin dng 25cm ................................. 99

Hnh 4-22. Bn xm nhp mn kch bn B2-nc bin dng 30cm ............................... 100

Hnh 5-1. Cc vng tnh ti thuc ng bng song Cu Long ....................................... 103

Hnh 5-2. Tng nhu cu nc ng bng sng Cu Long trung bnh cc thi k ............ 105

Hnh 5-3. Thay i tng nhu cu nc ng bng sng Cu Long trung bnh cc thi k ....................................................................................................................... 105

Hnh 6-1. Quy hoch tng th thy li BSCL trong iu kin bin i kh hu-nc bin dng ........................................................................................................... 118

xi

Danh mc cc t vit tt

BKH Bin i kh hu

BDP Basin Development Planning (Quy hoch pht trin lu vc sng)

BCM Bn o C Mau

TM ng Thp Mi

BSCL ng bng sng Cu Long

DSF Decision Support Framework (Khung h tr ra quyt nh)

GCM Global Circulation Models/ Climate Models or General

circulation models (M hnh kh hu ton cu

KH KTTV& MT Khoa hc kh tng thy vn v Mi trng

IMHEN Vin khoa hc Kh tng thy vn v Mi trng

IPCC Intergovernmental Panel on Climate Change (y ban Lin chnh ph v bin i kh hu)

IQQM Integrated Quantity Quality Model

MARD Ministry of Agriculture and Rural Development (Vietnam)

MONRE Ministry of Natural Resources and Environment

MOST Ministry of Science, Technology

MRC y hi sng M Cng Quc t

PRECIS Providing REgional Climates for Impacts Studies

QL-PH Qun L-Phng Hip

ROMS Regional Ocean Model System (M hnh hi dng vng)

RCM Regional Circulation Models (M hnh kh hu khu vc)

SLR Sea Level Rise (Nc bin dng)

SWAT Soil and Water Assessment Tool

SEA START Southeast Asia SysTem for Analysis, Research and Training

TNN Ti Nguyn Nc

TGLX T gic Long Xuyn

TST T sng Tin

UNFCCC United Nations Framework Convention on Climate Change

(Cng c khung ca Lin Hp Quc v bin i kh hu)

1

M U

ng bng sng Cu Long (BSCL) l mt trong nhng ng bng ln

ca Vit Nam nm h lu lu vc sng M Cng bao gm 13 tnh, vi

tng din tch t nhin khong 3,96 triu ha, chim 79% din tch ton chu

th v bng khong 5% din tch ton lu vc sng M Cng.

BSCL c b bin di trn 700 km, pha Ty Bc gip Campuchia,

pha ng Bc tip gip Vng ng Nam B, pha ng gip bin ng,

pha Nam gip Thi Bnh Dng v pha Ty gip vnh Thi Lan. y l v

tr thun li trong vic pht trin kinh t bin, khai thc v nui trng thy

sn phc v cho nhu cu sn xut, tiu dng trong nc v xut khu. c

bit BSCL c tim nng nng nghip to ln, trong nhng nm qua c

ng gp ng k vo tng sn lng lng thc, gp phn a Vit Nam

thnh mt trong cc nc xut khu go hng u trn th gii.

Bin i kh hu v ang din ra, nh hng su sc n pht trin

kinh t x hi ca c nc ni chung, c bit i vi BSCL ni ring. Bn

bo co trnh by kt qu nghin cu, nh gi tc ng ca bin i kh hu

n qu trnh ma-dng chy, nhu cu nc trong nng nghip, din bin l

lt v xm nhp mn ca BSCL theo cc kch bn B2, A2, trn c s p b

Phn mm Khung h tr ra quyt nh DSF (Decision Support Framework)

do y hi sng M Cng xy dng m Vin Khoa hc Kh tng Thy vn

v Mi trng l c quan c chuyn giao, c bn quyn. Kt qu nghin

cu cp cc vn c bn nht cn quan tm cho BSCL, xut mt s

gii php thch ng ph hp, lm c s cho cc nh qun l hoch nh chnh

sch v cc nghin cu chuyn su tip theo.

2

1. CHNG I. S LC LU VC SNG M CNG

Vi din tch lu vc 795.000 km2, sng M Cng l mt trong nhng

dng sng ln nht trn th gii, xp th 10 v tng lng dng chy nm v

th 12 v chiu di sng.

Bt ngun t cao nguyn Ty Tng (Trung Quc) cao trn 4800 m

so vi mt bin, sng M Cng chy theo hng ty bc - ng nam trn

hnh trnh khong 4.800 m qua lnh th ca 6 nc l: Trung Quc,

Myanma, Lo, Thi Lan, Campuchia v Vit Nam ri ra Bin ng.

Lu vc sng M Cng c chia ra lm 2 phn: Thng lu vc v

H lu vc. Thng lu vc M Cng nm ch yu trn phn lnh th

Trung Quc (v y c gi l sng Lan Cang) v mt phn lnh th

Myanma, c din tch khong 186.000 km2, chim khong 23,4% tng din

tch lu vc sng M Cng, trong 165.000 km2, (chim 20,8%) nm trn

a phn Trung Quc v ch c 21.000 km2 (2,6%) nm trn a phn

Myanma. y, lu vc sng c dng di, hp ngang, a hnh ni cao v

dc; t b xi mn mnh lit v do khong 50% tng lng ct bn ca

sng M Cng c hnh thnh Thng lu vc M Cng; mng li sng

sui km pht trin, trn a phn tnh Vn Nam, Trung Quc, ch c 14

sng c din tch lu vc t 1.000 km2 tr ln (hnh 1-1)

H lu vc M Cng c tnh t ni dng chnh sng M Cng chy

ra khi a phn tnh Vn Nam, Trung Quc vo lnh th nc Lo ti

Chiang Saen. Vi din tch lu vc khong 609.000 km2, chim 76,6% tng

din tch lu vc sng M Cng. H lu vc M Cng nm trong lnh th

ca 4 nc: Lo, Thi Lan, Campuchia v Vit Nam.

Cn c vo iu kin a l t nhin, H lu vc M Cng c chia ra

lm 4 vng di y:

Vng ni cao pha bc

Vng ny tri di trn 500 km t ty sang ng, bao gm Thng Lo

v mt phn lnh th Thi Lan. y, a hnh him tr, chia ct mnh,

thung lng su; cao cc dy ni t 600 m n trn 1.200 m, cao nht n

2.819 m cao nguyn Xing Khong, Lo; dc sn ni khong (30-

45)%; kt cu a cht ni chung l trm tch hay phun tro.

3

Hnh 1-1. V tr a l lu vc sng M Cng

4

Vng ni cao pha ng

Vng ny chy dc sn pha ty dy Trng Sn, di khong 1.000

km, rng 50-300 km, bao gm Trung v H Lo, Ty Nguyn (Vit Nam) v

mt phn ng bc Campuchia. khu vc pha bc v gia vng ny c

nhiu dy ni cao; hng cc dy ni thng l bc - nam hay ng bc - ty

nam. khu vc pha nam, cc nh ni khong 600-1.000 m, cao nht l

nh Ngc Linh trn a phn tnh Kon Tum, Vit Nam. dc cc sn ni

khong (30-40)%. Trong vng ny c cao nguyn bazan rng v kh bng

phng, cao khong (500-1.000)m. Kt cu a cht vng ny ch yu l

c bin cht. Khu vc vi duy nht h lu vc M Cng nm cao

nguyn Khm Mun.

Cao nguyn C Rt

Cao nguyn ny l mt vng i bt p dng lng cho, nghing v

pha ng nam, c bao bc bi cc dy ni Pet-cha-ben pha ty, dy

Phnam ng Rt pha nam v ng nam; Cao nguyn C Rt tri di trn

500 km theo hng bc - nam.

Vng ni cao ty nam

y l vng i ni sn pha bc v ng bc dy ni Con Voi v

Cardaman thuc lu vc sng Tng L Sp Campuchia. Cc dy ni c

cng nin i a cht vi vng ni cao pha ng v cc nh ni to thnh

ng phn nc gia lu vc sng Tngle Sp vi cc lu vc sng chy

ra vnh Thi Lan.

Vng ng bng

ng bng sng M Cng l mt vng t bi t c dng hnh tam gic

vi nh l Phnm Pnh v y l b Bin ng v vnh Thi Lan, ko di

trn 800 km theo hng Bc - Nam v 600 km theo hng ng-Ty; a

hnh thp, kh bng phng; mng li sng ngi, knh rch chng cht. Phn

ng bng sng M Cng nm trong lnh th Vit Nam thng c gi l

ng bng sng Cu Long (BSCL).

T h lu ca sng Tngle Sp, sng M Cng tch thnh 2 nhnh:

nhnh pha ng c gi l sng M Cng v nhnh pha ty c gi l

sng Bassac. Hai nhnh sng ny chy qua bin gii Vit Nam Cm Pu

Chia vo ng bng sng Cu Long. y, sng M Cng c gi l sng

Tin v sng Bassac c gi l sng Hu.

5

Sng Tin chy qua Tn Chu, Sa c, Vnh Long ri chia ra lm nhiu

phn lu, ra Bin ng ti 6 ca: Tiu, i, Ba Lai, Hm Lung, C

Chin v Cung Hu; sng Hu chy qua Chu c, Long Xuyn, Cn Th

ri chia ra lm 3 nhnh ra Bin ng ti cc ca: nh An, Bassac v

Tranh . Nh vy, sng M Cng ra Bin ng ti 9 ca nn phn sng

M Cng chy trong ng bng Vit Nam cng c gi l sng Cu

Long vi 9 ca sng nh 9 con rng phun nc ra Bin ng.

Ngoi ng bng sng Cu Long ra, mt s sng nhnh ca sng M

Cng cng bt ngun v chy trong lnh th Vit Nam. l sng Nm

Rm tnh in Bin, thng ngun sng S Bang Hing tnh Qung Tr,

thng ngun sng S Cng tnh Tha Thin Hu v cc sng S San,

Xr-pc, Ia Hleo v Ia rng Ty Nguyn. Tng din tch lu vc sng

M Cng nm trong lnh th Vit Nam khong 68.820 km2, chim 8,6%

tng din tch lu vc sng M Cng, trong sng Nm Rm 1.650 km2

(chim 2,4%), sng S Bang Hing v S Cng 3.074 km2 (4,4%) v cc

sng Ty Nguyn 30.100 km2 (43,7%) v ng bng sng Cu Long

34.000 km2 (49,5%). Cc sng nhnh ca sng M Cng Ty Nguyn nh

cc sng: S San, Ia. Hleo, Ia rng c coi l sng nhnh ca sng Xr-

pc.

Ti nguyn nc

Sng M Cng c lu lng dng chy trung bnh hng nm l 15,000

m3/s v tng lng dng chy hng nm 500 t m3 ti chu th. Phn b dng

chy nh trn hnh 1-2, chi tit nu trong bng 1-1.

Ngun nc sng M Cng cung cp cho trn 65 triu ngi sinh sng

trong lu vc. Lu vc sng M Cng c tim nng thu in rt ln v pht

trin thu in khu vc ny c kh nng s tng ng k trong nhng thp

nin ti. Hin ti, ch c mt phn nh tng lng nc ca sng M Cng

c khai thc s dng p ng nhu cu ti, i sng, cng nghip v

pht in.

Trong tng lng nc ca sng M Cng, th phn lnh th Trung

Quc, Lo chim mt t l rt ln (hnh 1-3). iu ny cho thy vic khai

thc s dng nc trn lnh th Trung Quc, Lo s nh hng ln n

ngun nc M Cng ni chung v Vit Nam ni ring.

Lu vc sng M Cng hin nay v trong tng lai gi mt vai tr

quan trng khng ch trong pht trin kinh t ca mi quc gia ven sng m

6

cn c trong pht trin hp tc kinh t v chnh tr trong khu vc. Nhu cu

khai thc v s dng ti nguyn nc v cc ti nguyn lin quan trong lu

vc sng M Cng ti cc nc ven sng s ngy cng ln v chc chn s

tng ng k trong tng lai. Do vic s dng cng bng, hp l, pht

trin bn vng v bo v ngun ti nguyn nc v cc ti nguyn lin quan

v ang tr thnh mt nhu cu ln thit thc.

Hnh 1-2. Phn b tng lng dng chy (t m3) trn sng M Cng

123

74

85

142

224

240

306

500

416

7

Bng 1-1. Phn b dng chy trong lu vc sng M Cng

(Ngun: Overview of the Hydrology of the Mekong Basin, MRCS 2006)

Trm thu vn F luvc (km2) Tng lng dng chy

nm (109 m3)

Trung Quc (Trm Jinghong) 74

Chiang Sean (Tam gic vng) 189.000 85

Luang Prabang 268.000 123

Vientiane 299.000 139

Nong Khai 302.000 142

Nakhon Phanom 373.000 224

Mukdahan 391.000 240

Pakse 545.000 306

Stung Treng 635.000 413

Kratie 646.000 416

Ton lu vc 795.000 500

Hnh 1-3. T l ng gp (%) ca cc quc gia vo vo dng chy sng M Cng theo cc ma dng chy

MA

L

MA

CN

8

2. CHNG II. S LC NG BNG SNG CU LONG

2.1. iu kin t nhin

2.1.1. Khi qut c im a l t nhin

ng bng sng Cu Long l phn cui gip bin ca ng bng chu

th sng M Cng, c gii hn bi vnh Thi Lan pha ty nam, bin

ng pha Nam v ng Nam, sng Vm C pha Bc v ng Bc

(hnh 2-1).

ng bng sng Cu Long bao gm ton b hay mt phn a phn cc

tnh: Long An, ng Thp, An Giang, Tin Giang, Bn Tre, Vnh Long, Tr

Vinh, Hu Giang, Sc Trng, Bc Liu, Kin Giang, C Mau, thnh ph Cn

Th.

ng bng sng Cu Long vn l mt min trng Kainozoi M Cng,

c lp y ch yu bng cc trm tch hn hp sng - bin. Ngoi ra, cn

c cc trm tch c ngun gc khc nhau, nh bi tch, trm tch trn cc

ging ct c ngun gc bin, trm tch ngun gc h v trm tch hn hp

m ly - sng v m ly - bin.

Trong ng bng sng Cu Long c 5 nhm t chnh: t phn, t

mn, t ph sa, t xm v t ct cc "ging" ct ven sng v ven bin.

Ngoi ra, cn c mt s t khc nh t vng, than bn.

H thi rng phn b ch yu ven bin bn o C Mau, H Tin v

cc ca sng t ca Tiu n ca Tranh . Mt s loi rng ch yu nh

rng ngp mn, rng ngp chua phn. Ngoi ra, cn c cc cy trng nng

nghip, cy cng nghip v cy n qu.

BSCL l vng ng bng kh bng phng v hi thp, cao ph

bin t 0,3 2,0m, tr mt s i ni pha Ty Bc thuc tnh An Giang,

Kin Giang, ton b t ai cn li c cao di 5 m. Ngoi ra cn c

nhng g t ven sng v cn ct ven bin tng i cao, hai vng trng

nht l ng Thp Mi v T Gic Long Xuyn. B bin thp vi mt s

vnh nh nh mi cao, cc bi bin ngp nc khi triu ln.

9

Hnh 2-1. Bn a hnh ng bng sng Cu Long (ngun B TN&MT 2009)

2.1.2. c im kh hu

Nm trong vng nhit i gi ma nn nn kh hu BSCL quanh

nm nng m v s phn ma kh-m rt su sc tu theo hot ng ca

hon lu gi ma. Ma kh thng trng vi ma t ma, y cng l thi

k khng ch ca gi ma ng-Bc ko di khong t thng XI n thng

IV nm sau, c kh hu c trng l kh, nng v rt t ma. Ma m trng

vi ma ma, l thi k khng ch ca gi ma Ty-Nam ko di t thng V

n thng X, c kh hu c trng l nng, m v ma nhiu.

Kh hu ng bng sng Cu Long c sc thi ring, l kh hu

nhit i m, gi ma cn xch o, nng nhiu, nhit cao quanh nm,

ma ma v c bn l ma h, ma kh xut hin vo cc thng gia v cui

ma ng, u ma h. S tng phn v ma gia ma ma v ma kh rt

su sc.

Bc x tng cng trung bnh nm khong (150-160) kcal/cm2. S gi

nng trung bnh nm khong (2.200-2.800) gi.

Do nn bc x cao, a hnh kh bng phng nn nhit phn b

tng i u trong ng bng sng Cu Long vi nhit khng kh trung

bnh nm bin i trong phm vi (26-29)oC. Nhit khng kh cao nht

10

tuyt i c th ti (38-40)oC. Nhit khng kh thp nht tuyt i khong

(14-16)oC.

Lng my tng quan trung bnh nm khong 7/10 bu tri, tng ln

8/10 bu tri vo cc thng ma ma v gim xung 4-5/10 bu tri vo cc

thng ma kh.

m tng i trung bnh nm khong (70-80)%.

Tc gi trung bnh nm t khong 2 m/s trong ng bng tng ln

trn 3 m/s ven bin. Tc gi ln nht c th ti (25-30) m/s.

Lng bc hi trung bnh nm tng i ln, khong 1.100-1.400 mm.

Lng ma nm trung bnh nhiu nm bin i trong phm vi t di

1400 mm khu vc gia sng Tin - sng Hu cc tnh ng Thp, An

Giang, Vnh Long tng ln trn 2.400 mm bn o C Mau (hnh 2-2).

Ma ma hng nm xut hin vo cc thng V-XI, trong 3 thng c lng

ma trung bnh thng ln nht xut hin vo cc thng VII-IX. Lng ma

ma ma chim khong (88-95)% lng ma nm; 3 thng lin tc ma nh

nht xut hin vo cc thng I-III v ch chim di 3% lng ma nm.

Trong bng 2-1 a ra lng ma nm trung bnh thng v hnh 2-2 l s

phn phi lng ma trong nm ti mt s trm o ma trong ng bng

sng Cu Long.

Bng 2-1. Lng ma trung bnh thng, nm ti mt s v tr trong ng bng sng Cu Long

Tn

trm

Thi k

quan

trc

Lng ma trung bnh thng nm (mm)

I II III IV V VI VII VIII IX X XI XII Nm

Ba

Tri

1979-

2005 3,2 1,0 4,4 47,6 139,2 221,3 219,0 196,8 231,1 288,3 92,2 24,1 1468,0

Cng

Long

1978-

2005 1,8 2,4 11,2 55,7 184,2 205,7 218,8 239,1 254,5 292,0 122,9 35,4 1623,6

M Tho

1979-

2005 2,2 1,1 5,5 49,1 162,0 199,1 171,9 186,1 218,4 270,8 101,9 31,1 1399,3

Cn Th

1978-

2004 6,1 1,9 13,3 36,5 167,7 222,6 239,2 231,0 252,1 275,3 150,1 39,7 1635,6

Sc

Trng 1978-

2005 3,3 3,4 13,0 76,6 228,8 277,5 264,2 301,2 289,7 301,0 136,3 38,6 1933,5

Cao

Lnh

1979-

2004 8,3 7,4 19,4 53,7 150,5 166,5 181,9 176,0 237,1 276,4 145,7 31,0 1453,8

Rch gi

1979-

2005 10,6 12,0 25,7 86,6 239,9 304,9 344,2 360,5 277,6 301,5 205,6 43,5 2212,6

Chu

c 1979-

2007 8,4 2,9 15,5 76,4 154,1 117,7 147,8 168,6 153,9 272,1 148,9 35,2 1301,6

Bc Liu

1980-

2005 3,8 2,5 10,4 53,9 187,3 285,1 272,3 261,5 297,8 310,5 157,6 48,3 1891,1

C

Mau

1979-

2005 22,4 14,3 36,2 110,6 247,2 342,9 330,4 360,0 342,8 376,3 197,2 60,1 2440,5

11

Hnh 2-2. Bn ng tr ma nm ng bng sng Cu Long

2.1.3. Mng li sng ngi, knh rch

Ngoi h thng sng Cu Long, trong ng bng cn c cc h thng

sng chnh sau:

H thng sng Vm C, bao gm hai nhnh Vm C Ty v Vm C

ng. Sng Vm C Ty, bt ngun t vng ng bng tnh Prey Veng,

chy theo hng Ty Bc- ng Nam vo Vit Nam (tnh Long An). Din

12

tch lu vc 1.720 km2, chiu di trong lnh th Vit Nam vo khong 110

km. Sng b thoi ha v sau khi p p Svay Rieng, dng sng khng

cn lu thng vi ngun triu t bin ng. V ma kh, dng chy c bn

rt nh do khng c ngun sinh thy, nhng trong ma l, lu vc sng li

chnh l khu tr v chuyn l trn t Mekong sang Vit Nam; sng Vm C

ng, bt ngun t vng i thp tnh Prey Vieng, chy theo hng Ty

Bc-ng Nam vo tnh Ty Ninh ca Vit Nam. Chiu di sng chnh

trong phn t Campuchia l 54 km, din tch lu vc tng ng l 1.380

km2. on chy gn vo Vit Nam lng sng cn kh su v b nh hng

ca thy triu bin ng.

Nhm sng S Thng, S H, Ci C - Long Kht chy dc theo bin

gii VN-CPC trn a bn cc tnh ng Thp, Long An.

H thng sng Ci Ln-Ci B, hon ton l cc sng vng triu, xut

pht t trung tm bn o C Mau (BCM) v ra bin qua ca Ci Ln.

on ca sng c lng rt rng nhng khng su. Do ni vi sng Hu bi

nhiu knh o ln nn ch dng chy ca Ci Ln-Ci B cng chu nh

hng ch dng chy t sng Hu.

H thng sng M Thanh, gm c sng chnh M Thanh, cc chi lu

C C, Nhu Gia l trc tiu, dn nc mn v cng l trc ng giao thng

thu cc k quan trng ca vng BCM.

H thng sng Gnh Ho, gm c sng chnh l Gnh ho v cc chi

lu Tc Th, m Di v m Chim. Sng l trc tiu, ly nc mn v

cng l trc ng giao thng thy cc k quan trng cho vng BCM.

H thng sng c, bao gm sng c, cc chi lu Ci Tu, Bin nh -

Cn Go, l trc tiu chnh ca vng U Minh.

H thng knh o BSCL c pht trin ch yu trong vng hn 1

th k nay, vi mc ch chnh l pht trin sn xut nng nghip v giao

thng thy. n nay, h thng knh o c xy dng kh dy trn

phm vi ton B 2 cp knh, vi mt khong 3 5 km/knh trc, 1,5

2km/cp 2. H thng cp 3 v ni ng cn pht trin mc thp. H thng

knh trc trong ng bng bao gm:

H thng knh trc ni sng Hu vi bin Ty, sng Tin vi sng

Vm C Ty v sng Tin vi sng Hu. Ngoi ra ti vng ng Thp Mi

(TM) cn c cc trc chy dc t bin gii Vit Nam-Cm Pu Chia vi

sng Tin.

13

2.2. c im thy vn

2.2.1. Dng chy nm

M un dng chy nm trung bnh thi k nhiu nm bin i trong

phm vi t di 10 l/s.km2 khu gia sng Tin - sng Hu tnh ng

Thp - An Giang n 30 l/s.km2 bn o C Mau.

Tng lng dng chy nm trung bnh nhiu nm ca ng bng sng

Cu Long khong 500 km3, trong khong 23,0 km3 c hnh thnh trong

ng bng sng Cu Long, 477 km3 t trung thng lu sng M Cng chy

vo ng bng sng Cu Long.

Mc bo m nc bnh qun trong 1 nm trn 1 km2 din tch ng

bng sng Cu Long ti 14.700.103 m3/km2 v cho 1 ngi 31.560 m3/ngi

(vo nm 2005). Tuy nhin, c ti 95,4% tng lng dng chy nm l t

trung thng lu vo ng bng sng Cu Long, nn nu ch tnh lng

dng chy c hnh thnh ng bng sng Cu Long, th mc bo m

nc bnh qun trong 1 nm trn 1 km2 din tch khong 676.103 m3/km2 v

cho 1 ngi khong 1.450 m3/ngi, vo loi thp so vi cc h thng sng

khc Vit Nam.

2.2.2. Ch dng chy

Ma l hng nm thng xut hin vo cc thng VII-XI. Lng dng

chy ma l chim khong (70-85)% lng dng chy nm. L thng gy

ngp lt ng bng sng Cu Long. Ma cn t thng XII n thng VI

nm sau, lng dng chy ma cn chim khong (15-30)% dng chy nm,

3 thng lin tc c dng chy nh nht xut hin vo cc thng II-IV hay III-

V.

Ch nc sng vng ng bng ven bin cn chu chi phi bi

thu triu Bin ng v vnh Thi Lan vi ch triu tng ng l bn

nht triu khng u v nht triu khng u. Hai loi triu vi ch khc

nhau ny xm nhp vo trong sng ngi knh rch, to nn bc tranh thu

triu rt phc tp. Tuy nhin, thu triu Bin ng chim u th so vi thu

triu t vnh Thi Lan xm nhp vo.

14

Tan Chau station

0

2000

4000

6000

8000

10000

12000

14000

16000

18000

20000

22000

1 3 5 7 9 11

Month

Q (

m3/s

)Chau Doc station

0

2000

4000

6000

8000

1 2 3 4 5 6 7 8 9 10 11 12

Month

Q (

m3/s

)

Hnh 2-3. Phn phi dng chy trong nm ti trm Tn Chu v Chu c

2.2.3. c im l lt

Trn dng chnh sng M Cng, gi tr Qmax ln nht trong thi k t

ti 56.000 m3/s ti Pakse xut hin vo VIII/1978 v 66.700 m3/s ti Kratie

vo IX/ 1939, tng ng vi m un khong 0,102 m3/s.km2 (hnh 2.5). Lu

lng nh l tng ng vi thi k lp li 50 nm, 100 nm v 200 nm ti

Ving Chn tng ng l 24.000 m3/s, 25.500 m3/s v 27.000 m3/s; ti Kratie

tng ng l 70.000 m3/s, 72.500 m3/s v 75.000 m3/s.

Trn l nm 2000 c coi l mt trn l lch s, nguy him nht trong

vng 70 nm qua. Trn l ny gy ra thit hi rt ln chu th M Cng

vi 45.000 km2 din tch b ngp (hnh 2-6), 800 ngi b cht, tc ng xu

n mi trng.

Tuy nhin, nh tc dng iu tit ca Bin H Campuchia lm gim

ng k lng l v lu lng nh l sng M Cng chy vo ng bng

sng Cu Long.

15

Hnh 2-4. Qu trnh mc nc ti Kratie trong cc nm l ln v trung bnh nhiu nm

Hnh 2-5. Qu trnh mc nc ti Chu c trong cc nm l ln v trung bnh nhiu nm

16

Hnh 2-6. nh v tinh khu vc ngp trn l thng 9 nm 2000 ng bng sng Cu Long

L sng M Cng chy vo ng bng sng Cu Long qua sng Tin,

sng Hu v trn qua bin gii vo vng ng Thp Mi, T gic Long

Xuyn v khu gia sng Tin - sng Hu. Tng lu lng nh l trung bnh

chy vo ng Bng sng Cu Long khong 38.000 m3/s.Theo kt qu iu

tra kho st trong thi k 1991-2000, tng lu lng ln nht ca sng M

Cng chy vo ng bng sng Cu Long khong (40.000 - 45.000) m3/s,

trong qua sng Tin v sng Hu khong (32.000 - 34.000) m3/s, chim

(75-80)%, trong (24.000 - 26.000) m3/s qua sng Tin ti Tn Chu,

chim (82-86)%, (7.000- 9.000) m3/s qua sng Hu ti Chu c); trn qua

bin gii khong (8.000 - 12.000) m3/s, trong trn vo T Gic Long

Xuyn (2.000 - 4.000) m3/s, trn vo ng Thp Mi (6.000 - 9.000) m3/s.

Tng lng l sng M Cng chy vo ng bng sng Cu Long khong

350-400) km3, trong (80-85) % qua dng chnh, (15-20)% trn qua bin

17

gii. Trong cc trn l ln nht hng nm, mc nc cao nht sng Tin ti

Tn Chu thng cao hn mc nc sng Hu ti Chu c khong (15 -

45) cm. Mc nc nh l cao nht trong khong 60 nm qua ti Tn Chu

trn sng Tin v Chu c trn sng Hu tng ng l 5,12 m v 4,89 m

u xut hin vo trn l X/1961, ring trn l lch s nm 2000 tng ng

bng 5,06m v 4,90m, xut hin vo ngy 23 thng IX.

Bng 2-2. Lu lng nh l Tn Chu, Chu c trong l ln

Nm Tng (m

3/s)

Tn Chu

(m3/s)

T l (%) Chu c

(m3/s)

T l (%)

1961

1978

1994

1996

2000

2001

36710

3 040

31210

31880

34510

30910

28870

25900

23920

23700

26830

23800

78.6

78.4

76.6

74.3

77.7

77.0

7840

7160

7290

8180

7680

7110

21.4

21.6

23.4

25.7

22.3

23.0

Ln nht 6 710 28 870 78.6 8 180 25.7

Nh nht 0 910 23 700 74.3 7110 21.4

Trung bnh 3 000 25 500 77.1 7 540 22.9

Hng nm vo ma l, l sng M Cng lm ngp gn 2 triu ha pha

bc, ko di 3-5 thng gy kh khn cho canh tc v i sng nhn dn, cc

nm l ln gy nhiu thit hi v nhn mng cng nh ti sn. Tuy nhin l

cng mang li ngun ph sa bi b cho t, ngun thu sn phong ph v c

tc dng tt trong vic v sinh ng rung. Sng M Cng l ngun nc

ngt rt quan trng v c tnh quyt nh i vi BSCL, cung cp cho i

b phn din tch BSCL phc v sn xut v i sng nhn dn.

2.2.4. Cht lng nc sng

c ct bn l lng trung bnh nm ca sng M Cng thng

khong (500-1.660) g/m3 trong cc thng VII-IX. Trn cc knh rch, c

ct bn thng di 50 g/m3, mt s ni ti (70-100) g/m3. Tng lng ct

bn l lng trung bnh nm ca sng M Cng khong 215 triu tn.

khong ho trung bnh nm ca nc sng khong (100-150) mg/l.

Nc sng thuc lp hydro ccbont nhm Canxi kiu I; ion HCO3- chim

(75-80)% tng ng lng cc anion, in Ca++ chim khong 50% tng

ng lng cc cation. pH khong (6,7-7,7). cng khong 1 mg-e/l

hi ln hn kim.

18

Nhn chung, cht lng nc trn dng chnh c s bin i theo ma

r rt. Hm lng cc cht ha tan trong ma cn cao hn trong ma l. Cht

lng nc l dc bin gii cn tt, khng chua, hm lng cc c t

trong gii hn cho php; nhng do phn ln ph sa lng ng trn phn ng

bng thuc lnh th Campuchia, nn khi chy trn qua bin gii vo ng

bng sng Cu Long, hm lng ph sa trong nc l rt thp, thng cao

nht cng khng qu 200 g/m3. Trong vng ngp lt, din bin ca cht

lng nc kh phc tp do b chi phi bi cc yu t kh hu, thy vn v

hot ng ca con ngi. Hm lng cc cht ha tan chnh nh: Na, K,

Ca2+, Mg2+, Fe2+, Al3+, SO42+, Cl-, HCO3- bin i theo ma, ma cn

cao hn ma l; nhng nhn chung vn nm trong gii hn cho php. Tuy

nhin, nc mt ng bng sng Cu Long b nhim vi sinh cao vi

nng Coliform trung bnh khong 300.000 - 1.500.000 con/100ml,

nguyn nhn ch yu l do thi trc tip cc cht thi sinh hot, cng nghip

v thuc tr su vo ngun nc khng qua x l lm sch.

Nc chua l mt vn ln, nht l vng ngp lt. Nc chua ch

yu pht sinh trong vng t phn m trong ng bng sng Cu Long c

khong 1,6 triu ha t phn. Thi gian b b chua thng t thng V n

thng VII, mt s ni n thng VIII, IX. Ring hai vng ngp lt ng

Thp Mi v T gic Long Xuyn cn b chua vo cui ma l, u ma

cn, vo hai thng XII- I. S lan truyn ca nc chua nh hng ln n

cht lng nc v tc ng xu n sn xut v i sng.

Ch thu vn BSCL chu nh hng mnh ca dng chy sng M

Cng, thu triu bin ng, vnh Thi Lan v ch ma ni vng. Do c 2

pha gip bin nn vng ven bin b mn xm nhp mnh, vo ma kh mn

xm nhp su vo ni ng. Nc sng ngi, knh rch v trong ng ven

bin cn b nhim mn, nht l vo ma cn, mn xm nhp su vo trong h

thng sng ngi knh rch v ng rung; xm nhp su nht thng vo

cc thng II - IV, khi lng nc t thng ngun v t.

Tm li, nhn chung nc sng ngi, knh rch trong ng bng sng

Cu Long cn tt, nhng v ang b nhim vi mc khc nhau bi

nc thi v cht thi khng qua x l lm sch t cc khu dn c, cc

th, khu cng nghip, cc tu thuyn trn sng v t ng rung s dng

thuc tr su v phn ha hc. Ngoi ra, nc mt cn b nhim chua phn

v b nhim mn vng ven bin.

19

2.3. c im ti nguyn nc ngm BSCL

Vng ven bin BSCL c ngun nc di t kh phong ph, cha

ng trong cc phc h Holocene, Pleistocene, Pliocene, Miocene, phc h

l hng (ct) v cc khe nt (). Tuy nhin cng nh tnh trng chung ca

BSCL do nhiu vng nc ngm b nhim mn nn tr lng tt b hn

ch v s phn b nc c cht lng tt rt khng u. Theo nghin cu

ca Lin on a cht 8, nc ngm BSCL thuc loi nc ngm c

ngun b sung.

Nc ngm tng nng cha trong tng Holocene, c mi lin quan mt

thit vi nc mn, cht lng nc xu v b nhim mn, phn v nhim

vi sinh. Tuy nhin mt s ni nh Vnh Chu (Sc Trng), Tr Vinh cc

ging ct c th khai thc c nc ngm c cht lng tt s dng c

cho sinh hot, ti hoa mu.

Nc ngm tng su ch yu cha trong cc phc h Pleistocene,

Pliocene, Miocene v c s phn b rt phc tp c v din cng nh chiu

su. Mt cch tng qut s phn b nh sau:

+ Khu vc ven bin v ca sng thuc cc tnh Long An, Tin Giang,

Bn Tre v mt phn tnh Tr Vinh, nc ngm cc tng gn mt t b

nhim mn cao nn phi su trn 300m mi c th khai thc c nc

c cht lng tt. Mt s ni nh Bn Tre, G Cng khai thc nc ngm

cht lng tt rt kh khn.

+ Cc khu vc pha Ty tnh Tr Vinh, Sc Trng, Bc Liu, cc huyn

m Di, Ngc Hin, Th x C Mau (tnh C Mau) khai thc nc ngm

kh thun tin, su khong 100 120m l c th khai thc c nc

ngm cht lng tt.

+ Khu vc ven bin Ty t mi C Mau n Rch Gi kh nng khai

thc nc ngm kh thun tin. Nhn chung su 120 150m c th khai

thc c nc ngm c cht lng tt. Tuy nhin cng c nhng ni cc b

su trn 200m vn cha tm thy nc ngm c cht lng tt.

+ Khu vc ven bin TGLX t Hn t n H Tin khai thc nc

ngm kh khn v cc tng ngm gn mt t b nhim mn cao (hnh 2-8).

20

Hnh 2-7. Bn tim nng tr lng nc ngm lu vc ng bng sng Cu Long.

2.4. c im thy triu BSCL

Thu triu c nh hng su sc n dng chy vng ven bin BSCL.

Vng ven bin pha ng t Cn Gi n mi C Mau chu nh hng ca

thu triu bin ng; vng ven bin pha Ty t mi C Mau n H Tin

chu nh hng ca thu triu bin Ty.

Thu triu vng ven bin ng c ch bn nht triu khng u, mi

ngy nc ln xung 2 ln, c 2 nh v 2 chn. Hai nh triu chnh lch

nhau t nhng 2 chn chnh lch nhau nhiu. Vi dng triu ny s c tc

21

dng a nc vo ni ng nhiu hn. Xu th thu triu ven bin ng l

t Vng Tu n Gnh Ho bin triu tng ln nhng thi gian xut hin

nh triu chm dn.

Thu triu ven bin Ty thuc loi hn hp thin v nht triu. Trong

ngy c 2 nh, 2 chn nhng nhng dao ng ln hon ton chim u th v

thin v nht triu. C ngha l 2 nh chnh lch nhau ng k nhng 2 chn

xp x nhau. Dng triu ny c thi gian duy tr mc nc thp di nn to ra

vic tiu tho nc thun li.

2.5. Tnh hnh kinh t v x hi

2.5.1. Tnh hnh dn sinh

Dn s nm 2007 vng BSCL l: 17.475.764 ngi, chim khong

20,63% dn s c nc.

Dn c trong vng a s sng ch yu v nng nghip, nhng trnh

cn thp, phn ln l lao ng th cng. i ng cn b khoa hc-cng ngh

ch yu tp trung ti cc thnh ph, th x chim khong 80%, nng thn

ch chim 20% nhng ch yu tp trung cc ngnh y t, gio dc, ti

chnh- ngn hng. Lao ng trong cc ngnh nng, lm-thy sn trnh

mc thp.

Nm 2007, bnh qun t nng nghip theo h sn xut nng nghip l

0,87 ha/h, cao hn vng ng bng sng Hng, nn t l lao ng tht

nghip thp hn ng k so vi bnh qun chung ton quc. Thu nhp ca

ngi dn nng thn ch yu t nng nghip, thu nhp cc ngnh ngh

khc ch chim khong 10%. Trong cc sn xut nng, lm thy sn th h

nui thy sn c thu nhp cao hn nhng km n nh, h sn xut la thu

nhp thp nhng kh n nh.

Ngun nc sinh hot ch yu l nc trn cc knh rch, mt s h

dng nc ging khoan, cht lng nc cha m cht lng nc sinh

hot thng b nhim phn, nhim vi sinh trong ma l.

2.5.2. Tnh hnh pht trin kinh t

Ngun kinh t ca cc tnh thuc vng BSCL ch yu l nng nghip,

ngoi ra cn c thy sn, lm nghip, ch bin cc mt hng nng sn thc

phm v thng mi dch v. Gn y, kinh t trong vng c chuyn bin v

pht trin r nt, gi tr sn phm kinh t nm 2007 t 116.488 t ng (gi

22

nm 1994), tng 1,7 ln so vi nm 2000 v trn 2,5 ln so vi nm 1995.

Tc tng trng kinh t lin tc tng, tc tng trng bnh qun nm

2003 t 10,4%, nm 2007 t 14,175% (gi nm 1994), trong khu vc 1

(nng, lm nghip-thy sn) tng 7,16%, khu vc 2 (cng nghip-xy dng)

tng 20,9%, khu vc 3 (dch v) tng 18,52%.

C cu kinh t c s chuyn dch theo hng gim t trng khu vc

nng lm, thy sn, tng t trng khu vc 2, 3. Tng gi tr sn phm cc

ngnh kinh t nm 2007 t 201.300 t ng (gi thc t), trong khu vc

1 l 85.912 t (tng ng 42,68%), khu vc 2: 49.129 t (24,41%) v khu

vc 3: 66.259 t (32,92%), so vi mt bng chung ca c nc th t trng

khu vc 1 cao hn.

a) Pht trin nng nghip

Tnh hnh s dng t

Hin trng s dng t ti BSCL (hnh 2-3) c tm tt trong bng

di y:

Bng 2-3. Tnh hnh s dng t nm 2007- vng BSCL

(Vin QHTL Min Nam)

TT HNG MC Din tch cc loi t (ha)

T T NHIN (*) 4.040.268

I T NNG, LM THY SN 3.376.391

1 t sn xut nng nghip 2.536.295

2 t vn lin nh 219

3 t nui trng thy sn 486.056

4 t lm mui 3.897

5 t nng nghip khc 2.472

6 t lm nghip 347.453

7 t rng t nhin 72.762

8 t rng trng 261.521

9 t vng m 941

II T PHI NNG NGHIP 595.879

1 t 115.458

2 t chuyn dng 268.982

3 t tn gio, tn ngng 1.389

4 t ngha trang, ngha a 2.910

5 t sng rch v MNCD 98.887

6 t phi nng nghip 92.724

III T CHA S DNG 67.998

23

Cc loi hnh s dng t vng BSCL

t 3 v ch yu l 3 v chuyn la; 2 v la +1 v mu hoc 1 la+2

v mu.

t 2 v ch yu l hai v la, theo cng thc ng Xun + H Thu.

t mt v la ma c ri rc cc tnh trong vng ngp l su, b chua

phn ko di vo u ma ma.

Hnh 2-8. Bn hin trng s dng t sng ng bng sng Cu Long

24

b) Pht trin thy sn

BSCL l vng trng im pht trin thy sn xut khu ca c nc,

sn phm thy sn chnh gm tm v cc loi c.

Nm 2007, din tch nui trng thy sn t 657.284 ha, sn lng nui

trng t gn 1.036 ngn tn, trong din tch nui tm l 431,6 ngn ha,

sn lng 221.121 tn.

c) Pht trin lm nghip

Nm 2007, din tch t lm nghip khong 347.453 ha, gim 23.800ha

so vi nm 2004, trong din tch rng t nhin gim ng k. Din tch

t lm nghip nm 2007gim do mt phn din tch t lm nghip

TGLX trc kia quy hoch trng rng nay chuyn sang sn xut nng

nghip.

d) Pht trin giao thng

Giao thng ng b nng thn BSCL pht trin mc thp, chm,

cht lng km v cn nhiu cu th s. Giao thng gia cc tnh ven bin

ng nh Bn Tre, Tr Vinh, Sc Trng cn b t qung, mt s x vng

su vng xa cha c ng t ti trung tm (Hu giang cn 10 x, Bc

Liu cn 18 x). Mt ng b BSCL t 0,2km/km2, thp hn so vi

ton quc (0,342km/km2), mt d dn s c s dng ng b l

0,52km/1vn dn.

Giao thng thy BSCL c li th pht trin, mt ng thy l

0,68km/km2, cao hn nhiu so vi cc ni khc trong c nc. Vi 2 tuyn

ng thy chnh: Tp. H Ch Minh i C Mau, Tp. H Ch Minh i Kin

Lng. Hng ha vn chuyn bng ng thy ch yu l la go, vt liu

xy dng, vt t nng nghip hin chim ti 90% tng sn lng hng ha

c vn chuyn, ring 2 tuyn chnh chim 70-80%.

e) Cng nghip & H tng c s

Cng nghip BSCL cha pht trin, tng gi tr sn phm cc ngnh

cng nghip mi chim khong 24% tng sn phm kinh t (GDP), thp hn

rt nhiu so vi mt bng chung ca c nc (41,5%). Cc ngnh cng

nghip hin c ch yu l cng nghip ch bin nng sn, thc phm, ch

bin thy sn-hi sn, cng nghip khai thc vt liu xy dng a phng,

sa cha nng ng c, lm nc .

25

Hin nay, vng BSCL s dng h thng in nng quc gia, mng

li in quc gia a v tt c cc trung tm huyn v t phn phi

n cc tuyn, im dn c. Hu ht cc tnh nh: Tin Giang, Cn Th, An

Giang, ng Thp, Vnh Long a in v tt c cc x, 100% cc huyn

trong t lin c in t li Quc Gia

2.6. Thc trng h thng cng trnh, thy li

2.6.1. Vng t sng Tin (TST)

Ti BSCL ni chung v vng TST ni ring, cc cng trnh thy li

thng l cc cng trnh phc v tng hp cc nhim v: cp nc ti, tiu

ng x phn kim sot l, xm nhp mn Hin trng cng trnh thy li ti

vng TST nh sau:

a) H thng knh trc, cp I:

H thng knh trc v knh cp I c phn b kh u trn ton vng,

v mt , so vi cc vng khc trong ng bng th h thng knh cp I

vng ny l . Tuy nhin, do cc sng, rch ny c t lu i, i a s

cha c no vt nn b cn do bi lp, v vy cha ch ng p ng c

nhu cu ti, tiu v thot l.

b) H thng knh cp II:

Trong my nm qua nhn dn trong vng no vt v o mi thm

nhiu knh cp II v n nay, h thng knh cp II kh phong ph (khong

994 tuyn, di 3.761km), bnh qun 6,9 m/ha.

Nhn chung, h thng knh cp II, phn b theo cc vng khng u, li

thng b bi lng, thiu nng lc phc v, trong thi gian ti cn phi tip

tc ci to v pht trin thm h thng knh cp II.

c) H thng cng:

Ton vng hin c 22 cng c kch thc B t 5 n 21 m, n nay ch

cn li khong 50% l cn hot ng tt, s cn li cn phi c sa cha.

S phn b cc cng ny cng ch yu tp trung khu vc h lu ng

Thp Mi nh d n Bo nh, Nam Nguyn Vn Tip, vi nhim v

chnh l ngn mn, gi ngt, ti tiu. Cn li cc vng khc hu nh khng

c, nu c cng ch l cc cng bng.

26

Lng cng xy dng c so vi yu cu cn thiu nhiu v cha

ng b nn khng ch ng trong ti, tiu, ngn l. Nhiu ni vn phi

p p thi v trong qu trnh sn xut.

d) Trm bm:

Ch yu c xy dng khu vc Nam knh Nguyn Vn Tip. T

nhng nm u sau gii phng xy dng c 50 trm bm quy m kh

ln, vi nng lc thit k ti 35.420 ha, nhng thc t ch pht huy ti

c 7356 ha, t t l khong 20% nng lc thit k. n nay, hu nh ton

b cc trm bm ln u khng hot ng hiu qu.

Ton vng hin c khong 10.000 my bm xng du cc loi ti

c khong 70-80% din tch canh tc. Cc trm bm in quy m nh ti

100-200 ha cng kh pht trin, khong 20-30 % din tch c bm ti

bng trm bm in quy m nh.

e) H thng , b bao:

Ton vng hin c , b bao, khp kn cho ton b din tch canh

tc vi mt khong 29,6 m/ha. Tuy nhin, phn ln c xy dng vi

quy m vng nh, kch thc cng nh, cu to bng t, hng nm do nh

hng ca l nn hin nay sau mi ma l u b st l, xung cp cn phi

bi p tu sa thng xuyn. Ring vng d n Bo nh h thng ngn

mn xy dng tng i hon chnh, ch cn vng gip ranh gia knh

Ch Go v sng Vm C Ty cn xy dng mi. c bit, vng d n gia

hai sng Vm C, d n 79 v Bc ng, h thng b bao chng l u v

cn rt yu km, gn nh cn phi xy dng mi.

f) H thng ni ng:

Phn ln din tch canh tc ca vng c h thng thu li ni ng

vi mc pht trin cha cao, khng ng u. Cc cng trnh ni ng

c xy dng ch yu l knh dn nc v b bao gi nc, ngn triu. H

thng cng bng cn rt thiu.

2.6.2. Vng T gic Long Xuyn (TGLX)

Vng TGLX hin nay hnh thnh mt h thng thy li bao gm: H

thng kim sot l, cng ngn mn, h thng knh trc, cp 1, cp II (ti,

tiu), h thng bao, h thng trm bm, h thng thy li ni ng.

a) Hin trng h thng bao, b bao:

27

Do qu trnh pht trin v chung sng vi l vng TGLX hnh

thnh 2 loi bao: bao chng l c nm ( bao) v b bao chng l

thng VIII (b bao).

b) H thng knh cp 2:

H thng knh cp 2 c mt trung bnh trn ton vng 5,5 m/ha,

nhng pht trin khng u gia cc khu vc

c) H thng cng v trm bm ti u mi:

Ngoi cc cng ngn mn ven bin, hin nay trong vng hu nh cha

c h thng cng u mi phc v ti. Nc t knh trc, cp 1 c dn

vo cc knh cp 2, c ly trc tip vo rung qua cc cng bng, hoc

my bm nh

S trm bm in tp trung ch yu do cc cng ty ca tnh, cc hp tc

x v mt s t nhn qun l. H thng bm in hin ch p ng c

khong 25% nhu cu ca vng, phn cn li phi s dng bm du do h t

nhn qun l.

Nhn chung tnh hnh u t xy dng h thng trm bm in An

Giang tng ln hng nm, tuy nhin hu ht l cc trm bm nh c cng

sut t 50-100 ha, cc trm bm ln c cng sut ln c hiu qu cao hn

nhng rt kh thc hin do thiu vn u t v h thng in hin cn cha

y .

2.6.3. Hin trng thy li vng Bn o C Mau (BCM)

a) H thng bin ca sng v b bao

Thc trng bin, sng v cc tuyn b bao dc cc knh trc, cp

I.

b) H thng knh rch, cc cp.

H thng trc knh, rch chnh (cp I): Tng chiu di: 4.477km,

mt trung bnh knh trc khong 2,7m/ha. Chiu rng mt bnh

qun cho 2 loi trc chnh trn t 20-45 m, c bit c knh rng 70-

80m. Cao trnh y knh bin i trong khong t -1,5 n -5,5m

(tr sng Ci Ln Ci B, By Hp... rng t 120 n 600m, su t

-5,0 n -8,0m). H thng knh trc thng c no vt nh k

28

khong 7 n 10 nm 1 ln. Tt c cc trc dn ngt u

thng,vung gc hoc song song vi th nc sng Hu.

H thng knh cp II: Knh cp 2 a s c chiu rng mt t 8-

10m; (y = -0,5 n -1,5 m; trung bnh mi knh cch nhau khong

1,5km. Tng chiu di khong 13.496km. Mt knh cp II (tnh

Kin Giang, C Mau, Bc Liu, Sc Trng thuc d n) l 8,0m/ha

t nng nghip.

H thng knh cp III (ni ng): Knh cp III By = 2-5m, (y =

0,0 n -0,5m. Tng chiu di khong 25.580 km. Mt knh

mng cc cp trn ton vng t 6m/ha t nng nghip; phn b

khng u. Nhng ni c mt knh cao nm khu vc sn xut

2 hoc 3 v la v t b nhim phn nh vng U Minh Thng, U

Minh H, Qun L-Phng Hip (QL-PH). Vng Bc knh QL-PH,

Nam Bc Liu, khu vc Tip Nht c mt knh rch cn thp,

cn phi b sung. Nht l khu vc c quy hoch pht trin nui

trng thy sn nc mn.

c) H thng bao ni vng

Cng vi cc dc ven bin, ca sng ln, cn c cc tuyn b bao

dc cc knh trc knh trc cp I. Theo thng k tng tiu vng d n, ton

b cc tuyn b bao dc knh trc, cp I di 1.352km. Tuy nhin nng lc

tr ngt, kt hp giao thng nng thn cn rt hn ch. Kch thc mt ct

b bao cha , cc tuyn cha khp kn, cha c cng, hng nm phi chi

ph p p tm rt tn km.

Nhn chung, h thng cng trnh thy li u t cha khp kn v

khng ng b (h thng bin, ca sng, kim sot l, ni ng). Cha

pht huy kh nng phc v a mc tiu. t c mc tiu tng hp v

ti, kim sot l, tiu nc, bo v vng ven bin ca sng, nui trng thy

sn, ci to t phn..., quy hoch thy li s dng tng hp ti nguyn nc

BSCL c vin Quy hoch thy li Min Nam thc hin (xem nh

hnh 2-4).

29

Hnh 2-9. Bn quy hoch thy li ng bng sng Cu Long

30

3. CHNG III. NH GI TC NG CA BIN I

KH HU LN TI NGUYN NC CA BSCL

Nh nu trn, lng nc chy vo BSCL bt ngun ch yu t

ngoi lnh th Vit Nam. Do , nh gi tc ng ca BKH ln ti

nguyn nc (TNN) ca BSCL, phi nghin cu nh gi thay i ca

TNN trn ton lu vc sng M Cng. y l mt khi lng cng vic v

cng ln m bn thn trong d n ny khng thc hin c. Do , d n

k tha cc kt qu nghin cu ca y hi M Cng, c bit kt qu ca d

n MRC-CSIRO (Reducing vulnerability of water resources, people and the

environment in the Mekong Basin to climate change impacts), trong kt

qu c a ra bo co k thut vo 6/2010 (MRC Technical Paper No29,

Impacts of climate change and development on Mekong flow regimes. First

Assessment - 2009). y l nhng thng tin mi nht c cp nht ti thi

im thc hin D n ny.

Trong nghin cu ca MRCS ch yu ch mi nh gi n dng chy

vo Vit Nam, tc ng phi hp ca nc bin dng, ngp lt v xm nhp

mn cha c xem xt. Nhng i vi BSCL, tc ng ny rt mnh m,

cn phi c phn tch, nh gi mt cch y . D n da trn kt qu

tnh ton dng chy ca MRCS, kt hp vi kch bn nc bin dng v mn

do Vin KH KTTV& MT xy dng tnh ton, phn tch cc tc ng mt

cch su hn cho BSCL.

3.1. Cc m hnh c ng dng trong lu vc M Cng tnh ton tc

ng ca bin i Kh hu ln ti nguyn nc

Phn mm Khung h tr ra quyt nh DSF (Decision Support

Framework) do MRCS xy dng m Vin KH KTTV & MT l c quan c

chuyn giao, c bn quyn, trong cc m hnh c p dng cho cc vng

khc nhau trn lu vc (hnh 3-1).

i vi BSCL, hai m hnh c p dng l IQQM xc nh

nhu cu nc; m hnh thy lc ISIS m phng din bin lu lng, mc

nc trn ton ng bng h lu M Cng t Kratie ra n bin.

31

Hnh 3-1. Cc m hnh p dng tnh ton cho ng bng sng Cu Long

3.1.1. M hnh thy vn

M hnh SWAT (Soil and Water Assessment Tool), mt m thu vn

do B Nng nghip M, c tch hp trong DSF m phng dng

chy da trn cc s liu ngy ca kh hu, a hnh, t theo tng tiu lu

vc. Kt qu ca m hnh SWAT s l u vo cho cc m hnh tip theo.

Ton b lu vc M Cng c chia thnh hn 400 tiu lu vc

3.1.2. M hnh cn bng nc lu vc

M hnh IQQM (Integrated Quantity Quality Model), ban u c

pht trin cho cc lu vc sng Murray-Darling c v c p dng cho

cc lu vc M Cng. M hnh ny m phng, din ton dng chy thng

qua h thng sng lin kt vi cc cng trnh thy li, h, p v h thng

ti. u ra ca IQQM l lu lng trung bnh ngy ti Kratie v lu vc

Tonglesap c lm u vo cho m hnh thy lc.

32

Hnh 3-2. S phn chia lu vc sng M Cng trong m hnh SWAT

Hnh 3-3. S m hnh IQQM cho vng thng lu Kratie

33

Hnh 3-4. S m hnh IQQM cho vng Bin H v BSCL

3.1.3. M hnh thy ng lc

M hnh ISIS l m hnh thu lc, c pht trin bi cng ty Halcrow

Wallingford, m phng thy lc trong h thng sng M Cng t Kratie n

ca sng, v bao gm c h Tonle Sap v h thng sng Vm C. M hnh

m t chi tit s tng tc phc tp gy ra gia thy triu, nh hng dng

chy ngc t sng Tonle Sap v trn b trong ma l.

Mng tnh ton thu lc ISIS vng ng bng sng M Cng c trong

Khung h tr ra quyt nh DSF c cc chuyn gia quc t ti MRC

nh gi l mt cng c tt tin hnh phn tch dng chy trong sng

cng nh vng ngp lt h lu sng M Cng. Mng thu lc ny bao gm

khong hn 10.000 nt tnh ton m t chi tit h thng sng/knh, gn 500

vng ngp ( rung), cc cng trnh cng trn sng ca Cm Pu Chia v

Vit nam. Kt qu ca m hnh l: Mc nc, mn, lu lng ti tng nt c

th xut qua GIS th hin qua dng bn .

Mng tnh ton ly bin trn trn dng chnh ti Kratie, cc bin trn

cc dng nhnh l cc lu vc b phn ca khu vc Bin H. Cc bin di

l mc nc triu ti cc ca bin (thuc lnh th Vit Nam). Lng ma,

lng ly nc khu gia cng c m hnh xem xt tnh ton (hnh 3-5).

34

Hnh 3-5. S thy lc mng sng M Cng

S liu:

S liu a hnh v sng, knh, cng, ng giao thng c cp nht

n nm 2006;

Mc nc v bin mn ti 10 trm chnh (Long Xuyn, i Ngi, M

Thanh, Gnh Ho, ng c, Xo R, Rch Gi...);

S liu ma trn 22 trm chnh (Long Xuyn, Tn Hip, Cn Th,

Rch Gi, V Thanh, Phng Hip, i Ngi, Sc Trng, Bc Liu, C

Mau...). Ma c gn vo cc on v rung tng ng.

35

Ch vn hnh cng theo lch ng m hng nm ca cc a

phng

MRS thit lp m hnh, hiu chnh v kim nh m hnh cho l, cn,

mn v chuyn giao cho cc c quan ca cc nc trong y h sng M

Cng s dng.

3.2. Cc kch bn bin i kh hu lu vc sng M Cng

Kch bn bin i kh hu cho lu vc M Cng ly t sn phm ca

m hnh PRECIS do SEA START (Southeast Asia SysTem for Analysis,

Research and Training) cung cp vi 2 kch bn pht thi cao (A2) trung

bnh (B2) thi k 1985-2050 vi phn gii theo khng gian 0.2 x 0.2

(tng ng khong 22x22km). Trong tng kch bn, cc yu t ma,

nhit... trung bnh ngy c tnh ton n nm 2050.

X l cc kt qu ca m hnh PRECIS c th tnh ton tip thc

hin qua 3 bc:

Tp hp s liu ca cc li, tnh trung bnh cho cc tiu lu vc

Hiu chnh s liu tnh bng PRECIS cho ph hp vi s liu quan

trc thi k 1985-2000.

S dng cc h s hiu chnh thi k 1985-2000 tnh cho thi k

tng lai 2010-2050

Kt qu ton v phn tch tng hp trn ton lu vc th hin trn hnh

3-6 v bng 3-1-3-2.

Bng 3-1. Thay i nhit trung bnh nm, kch bn A2, B2 so vi thi k 1985- 2000, lu vc sng M Cng (Ngun MRC, 2010)

Vng Kch bn

Nhit trung bnh nm (oC) Thay i nhit trung bnh

nm so vi thi k 1985-2000 (C)

1985-

2000

2010-

2025

2026-

2041

2042-

2050

2010-

2050

2010-

2025

2026-

2041

2042-

2050

2010-

2050

Thng lu M Cng

A2

11,9 12,4 12,7 13,6 12,8 0,5 0,8 1,8 0,9

H lu M Cng 26,2 26,4 26,9 27,5 26,8 0,3 0,7 1,3 0,7

Ton lu vc 23,3 23,6 24,0 24,7 24,0 0,3 0,8 1,4 0,7

Thng lu M Cng

B2

11,9 12,5 12,9 13,8 12,9 0,6 1,0 1,9 1,0

H lu M Cng 26,2 26,6 26,9 27,8 27,0 0,4 0,7 1,6 0,8

Ton lu vc 23,3 23,7 24,1 25,0 24,1 0,4 0,8 1,7 0,8

36

Hnh 3-6. Thay i nhit trung bnh nm thi k 2010-2050 so vi thi k 1985-2000 (ngun MRCS, 2010)

Hnh 3-7. Thay i lng ma nm thi k 2010-2050 so vi thi k 1985-2000

Kch Bn B2 Kch Bn A2

37

Bng 3-2. Thay i lng ma nm, ma ma ma (V-X), ma kh (XI-IV), ng vi kch bn A2, B2 so vi thi k 1985- 2000, lu vc sng M Cng (Ngun MRC, 2010)

Vng Kch bn ECHAM4

Lng ma nm (mm) Thay i ca lng ma nm

(mm)

Thay i ca lng ma nm (%)

1985-

2000

2010-

2025

2026-

2041

2042-

2050

2010-

2050

2010-

2025

2026-

2041

2042-

2050

2010-

2050

2010-

2025

2026-

2041

2042-

2050

2010-

2050

Thng lu MCng A2 901 979 1008 1019 999 78 108 119 99 8,7 12,0 13,2 10,9

H lu M Cng A2 1598 1647 1671 1707 1670 49 73 109 72 3,0 4,6 6,8 4,5

Ton lu vc A2 1458 1512 1538 1568 1535 55 80 111 77 3,7 5,5 7,6 5,3

Thng M Cng B2 901 965 1000 982 982 65 100 81.0 82 7,2 11,1 9,0 9,1

H lu M Cng B2 1598 1628 1680 1573 1636 30 82 -25.0 38 1,8 5,1 -1,6 2,4

Ton lu vc B2 1458 1494 1543 1454 1504 37 85 -4.0 47 2,5 5,8 -0,3 3,2

Vng Kch bn ECHAM4

Lng ma ma ma (mm) Thay i ca lng ma ma

ma (mm) Thay i ca lng ma ma

ma (%)

1985-

2000

2010-

2025

2026-

2041

2042-

2050

2010-

2050

2010-

2025

2026-

2041

2042-

2050

2010-

2050

2010-

2025

2026-

2041

2042-

2050

2010-

2050

Thng lu MCng A2 765 794 844 838 823 29 79 74 59 3,8 10,4 9,6 7,7

H lu M Cng A2 1390 1416 1453 1488 1446 26 63 98 56 1,8 4,5 7,1 4,0

Ton lu vc A2 1264 1290 1330 1357 1321 26 66 93 57 2,1 5,2 7,4 4,5

Thng M Cng B2 765 791 822 817 809 26 57 53.0 44 3,4 7,5 6,9 5,8

H lu M Cng B2 1390 1423 1467 1400 1435 33 77 10.0 45 2,4 5,6 0,7 3,3

Ton lu vc B2 1264 1296 1337 1283 1309 32 73 19.0 45 2,5 5,8 1,5 3,6

38

Bng 3.2. (tip) Thay i lng ma nm, ma ma ma (V-X), ma kh (XI-IV), ng vi kch bn A2, B2 so vi thi k 1985- 2000, lu vc sng M Cng (Ngun MRC, 2010)

Vng Kch bn ECHAM4

Lng ma ma kh (mm) Thay i ca lng ma ma

kh (mm)

Thay i ca lng ma ma kh (%)

1985-

2000

2010-

2025

2026-

2041

2042-

2050

2010-

2050

2010-

2025

2026-

2041

2042-

2050

2010-

2050

2010-

2025

2026-

2041

2042-

2050

2010-

2050

Thng lu MCng A2 138 184 165 184 176 45 27 46 38 32,9 19,3 32,9 27,5

H lu M Cng A2 208 230 221 219 224 22 14 11 16 10,6 6,6 5,5 7,9

Ton lu vc A2 194 220 210 212 214 27 16 18 21 13,8 8,5 9,4 10,7

Thng M Cng B2 138 174 180 162 174 35 42 24.0 35 25,5 30,2 17,1 25,5

H lu M Cng B2 208 205 217 169 202 -2 9 -38.0 -6 -1,1 4,3 -18,4 -2,8

Ton lu vc B2 194 199 209 168 196 5 16 -26.0 2 2,7 8,1 -13,3 1,2

39

Theo kch bn A2, khu vc c lng ma tng nhiu nht l thng lu

sng M Cng. y, vo na u ca th k 21, lng ma c th tng

khong trn 13%. H lu sng M Cng, khu vc thuc ng bng sng Cu

Long, c lng ma nm gim t 5 n 8%. Lng ma nm cc khu vc

khc thuc h lu sng M Cng v ngoi lnh th Vit Nam tng t 1-10%

(hnh 3-7).

Nhn chung, cc kch bn BKH cho ton lu vc sng M Cng u cho

thy xu hng tng lng ma vo ma ma (thng V-X) v lng ma nm.

Ring lng ma vo ma kh (thng XI-IV) c s khc nhau gia cc kch

bn: tng trn ton b lu vc kch bn A2 v tng thng lu ng thi

gim h lu sng M Cng i vi kch bn B2 (bng 3-1-3-2). Mc gim

ng k ca lng ma ma kh xut hin vo thp nin 2040.

3.2.1. Kt qu ca Vin KTTV&MT tnh ton bng m hnh ng lc

PRECIS.

Trong nm 2009, Vin KHKTTV&MT hp tc vi trung tm Hardley

(Anh) chy m hnh PRECIS xy dng kch bn bin i kh hu cho Vit

Nam. Min tnh ton ca m hnh PRECIS c m rng hn so vi min tnh

ca SEA START v la chn cc iu kin tnh ton ph hp cho Vit Nam.

Phn tch kt qu tnh ton n nm 2100, cho thy:

Trn ton lu vc sng, nhit nm c th tng 0.9C vo nm 2050 v

tng t 1.2 2.4C vo nhng nm cui th k 21 theo cc kch bn t thp n

cao

Hnh 3-8. S thay i nhit nm (C) trong cc thp nin 2050, 2070 v 2100 so vi thi k 1980-1999 theo kch bn trung bnh B2

40

Theo kt qu m phng thi k 1980-1999 ca m hnh PRECIS, lng

ma nm trn lu vc sng M Cng dao ng trong khong 1000-

2000mm/nm, lng ma trung bnh trn ton lu vc vo khong 1500mm,

tng ng vi s liu tng hp ca y ban sng M Cng. Phn b lng

ma nm khng ng u gia cc khu vc, tng i ln thng lu v t

hn h lu, c bit l phn lnh th Vit Nam, nhiu ni cha ti

1000mm/nm. Nhn chung, phn b lng ma nm trn lu vc tnh ton

bng m hnh PRECIS ca Vin KHKTTV&MT tng i ph hp vi kt qu

ca SEA START (hnh 3.9, 3-10).

Lng ma ma ma trn lu vc chim khong 2/3 lng ma nm, dao

ng t 800 n trn 1500 mm/nm, vi phn b theo khng gian tng t nh

lng ma nm: ma ln hn thng lu v nh hn h lu sng M Cng.

Khu vc t ma nht trong lu vc vn l ng bng Nam B ca Vit Nam.

Lng ma ma kh ch mc di 400mm/nm trn ton lu vc.

a) Kch bn bin i lng ma nm

Theo kch bn B2, lng ma nm trong th k 21 c xu hng tng trn

phn ln din tch lu vc sng M Cng so vi trung bnh thi k 1980-1999,

tuy nhin vn xut hin cc khu vc c lng ma nm gim nh khu vc pha

Nam ca thng lu sng M Cng v ng bng Nam B ca Vit Nam. Xu

hng gim lng ma nm cc khu vc ny ch tn ti n khong gia th

k 21 v trong na sau ca th k 21, xu th tng ca lng ma nm hu nh

nht qun trn ton b lu vc sng M Cng. ng bng Nam B ca Vit

Nam, thp nin 2030 l thp nin c lng ma nm gim nhiu nht, t 20 n

25% so vi trung bnh thi k 1980-1999, nhiu hn hn cc thp nin ln cn

(trc v sau ), khi , lng ma nm ch gim vo khong 5-10% (hnh 3-

9).

Tng t nh kch bn B2, lng ma nm tng u khp lu vc sng

M Cng i vi kch bn A2, mc tng ca lng ma nm ln hn nhiu

so vi kch bn B2. Xu th gim ca lng ma nm ng bng Nam B ch

r rt n thp nin 2020. Vo na cui th k 21, lng ma nm tng t 10 -

20 v thm ch c ni trn 25% so vi thi k 1980-1999.

41

Hnh 3-9. Mc thay i (%) ca lng ma nm trong cc thp nin 2020, 2030, 2050 v 2080 so vi thi k 1980-1999. Kch bn B2

b) Kch bn bin i lng ma ma ma

Theo kch bn B2, din bin ca lng ma ma ma phc tp hn so

vi lng ma nm. Tuy xu th tng lng ma vo ma ma vn chim u

th trn ton b lu vc sng M Cng, nhng xut hin nhiu hn cc khu

vc v thi gian c xu hng gim lng ma ma ma (hnh 3-103-11).

Hnh 3-10. Mc thay i (%) ca lng ma ma ma trong cc thp nin 2020, 2030 so vi thi k 1980-1999, Kch bn B2

42

Hnh 3-11. Mc thay i (%) ca lng ma ma ma trong cc thp nin 2050, 2060, 2080 v 2090 so vi thi k 1980-1999, Kch bn B2

Thp nin 2030 vn l thp nin c lng ma gim nhiu nht, khu vc

gim lng ma m rng ra khp h lu sng M Cng vi mc gim n

20-25% so vi thi k 1980-1999 ng bng Nam B ca nc ta. Sau thp

nin ny, hu ht din tch lu vc sng M Cng c xu th tng lng ma

vo ma ma, ngoi tr Nam B nc ta. Lng ma vo ma ma Nam B

tip tc gim n thp nin 2050 vi mc gim thp hn so vi thp nin

2030, ch vo khong 5-10%, sau lng ma y tng ln khong 0-5%

vo thp nin 2060. Tuy nhin xu th tng ny b gin on bi cc thp nin

2070, 2080 v ch xut hin tr li vo cui th k 21. Tm li, lng ma ma

ma ng bng Nam B c xu th gim n gia th k 21 v tng, gim an

xen nhau trong cc thp nin cn li ca na sau th k. Din bin ca lng

ma ma ma theo kch bn A2 hon ton tng t nh kch bn B2, mc

tng hoc gim ca lng ma cao hn so vi kch bn trung bnh B2.

43

c) Kch bn bin i lng ma ma kh

Theo kch bn B2, lng ma ma kh lu vc sng M Cng c cc

c im ch yu sau y:

Lng ma tng thng lu v gim h lu sng M Cng (hnh

3-11). Nhn nh ny hon ton ph hp vi cc kt qu tng hp ca

y ban sng M Cng trong bo co k thut nm 2010.

Nhn chung theo thi gian, khu vc c lng ma ma kh tng m

rng dn v pha Nam. Trong thp nin 2020, khu vc ny ch gii

hn pha Bc ca thng lu sng M Cng. n thp nin 2030

m rng xung ht Bc Lo v n Bc Cm Pu Chia trong thp nin

2050. Ko di thi gian n thp nin 2080, lng ma ma kh c

xu th tng trn hu khp din tch lu vc sng M Cng.

Trong lu vc sng M Cng, ng bng Nam B ca Vit Nam l

ni c lng ma gim nhiu nht. Lin tc trong nhiu thp nin,

lng ma y gim trn 25% so vi thi k 1980-1999, ch n

thp nin 2080, lng ma ma kh mi c du hiu tng t 0-5%

pha Bc ca ng bng Nam B.

d) Kt lun:

Trc nhng nm 50 ca th k 21, lng ma nm, ma ma ma, ma

kh trung bnh lu vc sng M Cng c xu hng tng, gim khng r rng.

Qua phn tch kt qu tnh ton cho thy, c nhng thp k tng nhng c thp

k li gim, c bit vo nhng nm 30 lng ma nm, ma ma gim r rt.

Lng ma ma kh trung bnh lu vc nhn chung tng phn lu vc t

Pacx tr ln, nht l thng lu M Cng.

i vi BSCL, lng ma nm c xu th gim kch bn B2 v c xu

th tng vo cui th k 21 kch bn A2. Lng ma ma ma c xu th

gim n gia th k 21 v tng, gim an xen nhau trong cc thp nin cn li

ca na sau th k. Trn BSCL, lng ma ma kh gim nhiu nht so vi

ton b lu vc sng M Cng. Trong nhiu thp nin, lng ma ma kh

y gim trn 25% so vi thi k 1980-1999 v ch gia tng cht t vo cui th

k 21.

44

Hnh 3-12. Mc thay i (%) ca lng ma ma kh trong cc thp nin 2060, 2070, 2080 v 2090 so vi thi k 1980-1999. Kch bn B2

45

3.2.2. Kch bn bin i kh hu xy dng bng phn mm

MAGICC/SCENGEN kt hp vi hiu chnh thng k cho BSCL

i vi BSCL, ngoi phng php Downscaling ng lc bng m hnh

PRECSIS nh cp trn, chng ti cn s dng phng php

downscaling thng k vi u vo t m hnh MAGICC/SCENGEN, tng t

cho cc lu vc khc xy dng kch bn bin i kh hu. Kt qu kh ph

hp vi m hnh PRECSIS, nhng c tnh cho cc trm kh tng trong

vng. Tnh ton bc thot hi tim nng, nhu cu nc cho ti ca BSCL s

dng kt qu ca phng php ny.

a) Kch bn nhit

S thay i nhit trn BSCL c th hin trn bng 3-3 v hnh 3-

12. Vo gia th k, nhit c th tng khong 0.8C t thng XII n thng

V v khong 1.1C vo cc thng cn li trong nm. n cui th k, nhit

c th tng ln khong 1.0C theo kch bn thp B1, khong 1.5C theo kch

bn trung bnh B2 v khong 1.9C theo kch bn cao A2 vo cc thng XII -

V. Nhit ma VI - XI c th tng khong 1.4C theo kch bn thp B1,

khong 2.2C theo kch bn trung bnh B2 v khong 2.8C theo kch bn cao

A2.

Bng 3-3. Mc thay i nhit trung bnh nm ti mt s trm kh tng so vi thi k 1980 1999 theo cc kch bn BKH

Kch bn Thi k

Trm kh tng

Chu

c Cao

Lnh

Ba

Tri

Cn Th

Sc

Trng Rch Gi

C

Mau

M Tho

Cng

Long

A2

2030 -2039 0.52 0.54 0.56 0.6 0.46 0.45 0.63 0.24 0.70

2040 -2059 0.86 0.89 0.98 1.09 0.85 0.79 1.17 0.44 1.15

2060 -2079 1.3 1.35 1.52 1.73 1.38 1.25 1.87 0.64 1.75

2080 -2099 1.69 1.76 2.02 2.31 1.86 1.65 2.51 0.83 2.30

B2

2030 -2039 0.52 0.54 0.56 0.60 0.46 0.45 0.63 0.25 0.70

2040 -2059 0.89 0.92 1.01 1.13 0.89 0.82 1.21 0.45 1.19

2060 -2079 1.23 1.28 1.44 1.63 1.30 1.17 1.77 0.62 1.66

2080 -2099 1.47 1.53 1.74 1.99 1.59 1.42 2.15 0.75 1.99

B1

2030 -2039 0.52 0.54 0.53 0.77 0.52 0.53 0.84 0.25 0.55

2040 -2059 0.79 0.82 0.86 1.15 0.83 0.81 1.27 0.45 1.47

2060 -2079 0.97 1.01 1.09 1.42 1.05 0.99 1.56 0.61 2.74

2080 -2099 1.05 1.09 1.19 1.53 1.14 1.07 1.68 0.69 4.11

46

Hnh 3-13. Thay i nhit theo cc kch bn BKH ti mt s trm kh tng

b) Kch bn lng ma

Lng ma nm trn BSCL c th tng t 2,2 2,9% theo cc kch bn

t thp n cao vo cui th k 21 (bng 4-4 4-6).

C Mau

0.0

0.5

1.0

1.5

2.0

2.5

3.0

2000 2020 2040 2060 2080 2100Year

Dt

(oC

)

A2

B2

B1

Cn Th

0.0

0.5

1.0

1.5

2.0

2.5

2000 2020 2040 2060 2080 2100Year

Dt

(oC

)

A2

B2

B1

Chu c

0.0

0.4

0.8

1.2

1.6

2.0

2000 2020 2040 2060 2080 2100Year

Dt

(oC

)

A2

B2

B1

Rch Gi

0.0

0.4

0.8

1.2

1.6

2.0

2000 2020 2040 2060 2080 2100Year

Dt

(oC

)

A2

B2

B1

Sc Trng

0.0

0.4

0.8

1.2

1.6

2.0

2000 2020 2040 2060 2080 2100Year

Dt

(oC

)

A2

B2

B1

Cng Long

0.0

1.0

2.0

3.0

4.0

5.0

2000 2020 2040 2060 2080 2100Year

Dt

(oC

)

A2

B2

B1

Cao Lnh

0.0

0.4

0.8

1.2

1.6

2.0

2000 2020 2040 2060 2080 2100Year

Dt

(oC

)

A2

B2

B1

M Tho

0.0

0.2

0.4

0.6

0.8

1.0

2000 2020 2040 2060 2080 2100Year

Dt

(oC

)

A2

B2

B1

47

Lng ma trn BSCL thay i theo ma r rt, lng ma gim vo

cc thng XII n thng V v lng ma tng trong cc thng t thng VI n

thng XI, trong lng ma 3 thng VI - VIII tng ln tng i t. Lng

ma vo gia th k 21 c th gim khong t 7,5 n 8,0% trong cc thng

XII n V v n nm 2100 lng ma cc thng ny c th gim trn 10%

theo kch bn thp B1, khong 15 - 16% theo kch bn B2 v khong 20% theo

kch bn A2. Lng ma 3 thng VI - VIII c th tng khong 2% vo nm

2050, n cui th k c th tng khong t 3 n 5,5% theo cc kch bn pht

thi t thp n cao. Ring cc thng IX - XI, lng ma tng nhiu nht trong

nm, lng ma ma c th tng khong 6% vo gia th k n khong t 8%

theo kch bn thp B1, khong 12% theo kch bn B2 v khong 15% theo kch

bn A2. S thay i lng ma theo thng trn BSCL gn ging vi lu vc

sng ng Nai.

Bng 3-4. T l thay i lng ma (%) so vi kch bn nn ca cc trm kh tng (kch bn A2)

Trm Thi on

Thay i lng ma (%)

Thng Trung

bnh

nm

Ma

ma Ma

kh I II III IV V VI VII VIII IX X XI XII

Chu

c

2020 -2039 -6.4 -5.3 -7.1 -5.7 -0.4 1.0 1.3 0.4 0.2 7.8 2.9 -2.6 1.7 2.5 -5.1

2040 -2059 -11.0 -9.0 -12.3 -9.6 -0.8 1.7 2.2 0.7 0.4 13.4 4.

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