LI NI U2PHN TH NHT :2CC C IM T NHIN21. iu kin v kh tng thy vn22.
Cht lng mi trng nc3PHN TH HAI8XC NH CC H DNG NC CHNH8I. PHN LOI CC
H DNG NC81.1 Dng nc c tiu hao81.2 Dng nc khng tiu hao8II. HIN TRNG
V NH HNG PHT TRIN CC H DNG NC82.1 Nng - Lm nghip82.1.1 Hin trng nng
nghip8 2.1.2 nh hng pht trin nng nghip8 2.1.3 Lm nghip102.2 Nui
trng thy sn112.2.1 Hin trng khai thc v nui trng112.2.2 Nhu cu nc
cho thu sn142.3 Cp nc dn sinh152.3.1 Hin trng152.3.2 Nhu cu nc sinh
hot16PHN TH BA17HIN TRNG CNG TRNH171. H thng knh to ngun:172. Cc
khu tr nc v iu tit nc:193. H thng bao194. H thng trm bm205. H thng
knh, rch cc cp206. H thng bin, ca sng207. H thng bao ni vng208. Cng
di 209. H thng bm nc2110. nh gi hin trng cc cng trnh thu li phc v
SXNN vng d n:21KT LUN -KIN NGH23
LI NI U
Vng Mn-X No tng i thp v bng phng, nm trong vng Ty sng Hu, c hnh
thnh do nhng hot ng tn kin to cng vi s bi tch ph sa sng Hu v ph sa
bin. Ch thy vn, thy lc ca vng rt phc tp. y l vng t c khai khn tng i
sm, h thng knh rch pht trin kh tt phc v cho vic giao thng v ti tiu
ca vng ny. Tuy nhin s pht trin cng lm tng thm s phc tp ca ch dng
chy trong vng d n .Vng Mn X No b chia ct bi mng li knh rch chng
cht. Ngun cp nc ngt cho vng d n l sng Hu vi lu lng bnh qun ma cn vo
khong 1200 m/s, lu lng bnh qun ma l vo khong 7000 m/s.Tuy khu vc d
n thuc cc tnh Hu Giang, Kin Giang v Thnh ph Cn Th thuc BSCL nm h lu
vng chu th sng Mekong c nhiu thun li, nhng cng tn ti nhiu kh khn hn
ch v iu kin t nhin, li nh hng bi ch thu vn, cc khai thc t thng lu v
dao ng ca thy triu bin ng-bin Ty nn khu vc d n lun phi i mt vi cc
mu thun trong pht trin. Kinh nghim thnh cng ca cc quc gia trong vic
qun l tng hp ngun ti nguyn nc l quy hoch pht trin i i vi quy hoch
qun l. Bo co tnh hnh khai thc, s dng ngun nc khu vc d n Mn- X No s
gp phn phc v tnh ton cn bng cho ton lu vc v vng BSCL.
Bo co gm 4 phn (a) Cc c im t nhin; (b) Xc nh cc h dng nc chnh,
hin trng v nh hng; (c) Cc cng trnh lin quan n khai thc, s dng ngun
nc v (d) Kt lun. PHN TH NHTCC C IM T NHIN1. iu kin v kh tng thy
vnVng Mn X No cng nh ton ng bng sng Cu Long nm trong vng c nn kh hu
nhit i gi ma, nng m v n nh trong mi nm. Hng nm kh hu vng phn ha
thnh hai ma r rt tng ng vi hai hnh thi gi ma: ma ma t thng V n thng
XI v ma kh t thng XII n thng IV nm sau. Cc thng I, II, III hu nh
khng ma. Cc thng cui ma kh (II, III, IV) thng xut hin gi thi lin tc
t hng ng vo lm thy triu v c bit l mn xm nhp su vo ni ng. Ma kh lng
ma ch chim khong 15% lng ma c nm.Cc thng VII v VIII, trong tp trung
nhiu nht l cui thng VII thng xut hin thi k khng ma (khong 15 ngy)
gy hn trong ma ma m dn a phng thng gi Hn B Chn, nguyn nhn ca hin
tng ny l do cc hon lu kh quyn v c ch gi ma gy nn.Ch thy vn, thy lc
ca vng rt phc tp, ph thuc cht ch vo: Ch thy vn sng Hu (on i qua vng
d n) gm ch thy triu bin ng, ch ngun nc thng ngun sng M Kng; Ch thy
triu bin Ty qua sng Ci Ln-Ci T; Ch ma ti ch.2. Cht lng mi trng ncCn
c vo bo co chnh ca Vin Nghin cu Ti nguyn nc pha Nam (SIWRP 2007) v
"Quy hoch qun l tng hp ti nguyn nc ca lu vc sng ti thnh ph Cn Th" v
cht lng nc, sng Hu v nc cc knh vn cha b nhim nng (tr Coliform v E
-Coli). Tuy nhin, du hiu nhim hu c xut hin nhiu ni (sng Cn Th, Mn,
ca cng u knh rch Tham Tng, v c bit l nhng ni t nui c lng ). Trong
tng lai, vi vic m rng quy hoch cc khu cng nghip (theo k hoch t Tht
Nt n Ci Rng) v th ha cng nh hot ng sn xut ngy cng tng, nhim v suy
thoi cht lng s l mi e da quan trng v gy ra nguy him cho vic qun l
cht lng ngun nc, tr khi k hoch chin lc c th v cht thi rn, nc thi v
cch s dng cc tc nhn ha hc trong hot ng sn xut nng nghip c t ra.C
th, theo kt qu gim st nhim hin ti ca S TNMT (thnh ph Cn Th) v s pht
trin ca cht lng mi trng thnh ph Cn Th 1999-2008, gn nh tt c cc knh
mng thot nc v ngun nc cung cp chnh trong thnh ph ang c qu nhiu
nhim, nc chuyn sang mu en v c mi khng khip. Vn nhim nc ti thnh ph
Cn Th tr thnh mt mi quan tm bc xc. Hu nh tt c nc thi ti thnh ph Cn
Th vn cha c x l trc khi thi vo sng Hu. cht thi cng nghip cha c phn
loi v x l. Mt nc trong khu vc nng thn b nhim ch yu l do cc cht hu c
v vi khun. Nc mt b nhim nghim trng gy nhim nc ngm, trong khi nc b
mt ca cc con sng chnh, sng Hu chng hn, b nhim vi cc cht nhim hu c v
vi khun. Ngoi ra, da trn kt qu gim st nhim hin ti ca S TNMT v s pht
trin ca cht lng mi trng thnh ph Cn Th 1999-2008, gn nh tt c cc knh
mng thot nc v ngun nc cung cp chnh u b nhim nng n. Knh rch b nhim
vi nng BOD t 10-15 mg / l vt qu quy chun 2-3 ln, Nng coliform l
4000-160,000 MPN/100ml vt hn 20 ln; v ha cht BVTV chy xung knh rch
v cc knh dn nc mc bo ng.Ngun nc thi x ra sng, rch bao gm: nc trong
khu dn c (h gia nh thi), nc thi t khu cng nghip, tiu th cng nghip
cc xng v cc lng ngh th cng m ngh, v t thy sn, sn xut nui trng thy
sn, nng nghip v cht thi rn. y l nhng ngun chnh gy ra nhim nc mt
nhiu vng ph. cc ngun khc bao gm cc hot ng u ngun trn sng Cu Long v
vn ti ng thy. Trong vi nm qua, nhim ngun nc tr nn ti t c bit l nhim
hu c (BOD v COD) v nhim vi sinh (Coliform). Theo iu tra gn y v kt
qu o (S TN & MT nm 2009; EEPSEA 2009), hu ht cc mu ly t cc khu
vc c th (con sng chnh, knh, mng ni ng, khu vc ch, cc khu cng nghip
v cc cnh ng) c nng BOD, COD v Coliform khng p ng tiu chun cht lng
nc (TCVN 5942 - 1995: Tiu chun cht lng nc - nc mt), v thm ch vt qu
gii hn cho php theo quy nh hin hnh trong Quy chun k thut quc gia v
tiu chun mi trng (QCVN 08: 2008/BTNMT) nhiu ln.Trong nm 2010, ch
tnh ring thnh ph Cn Th s dng 1.081.664 kg thuc tr su cho sn xut nng
nghip. Lng thuc tr su cho la nm 2010 ca tnh Hu Giang l 1.263.783 kg
v tnh Kin Giang l 1.892.800 kg .Mt phn cc cht ha hc c hi c hp th vo
trong, t cy xanh v cc loi c, trong khi mt phn khc c thi vo ngun nc,
gy nhim nc. Trong cc lnh vc nng nghip v nui trng thu sn, ngun nc b
nhim bi vic s dng ngy cng nhiu lng thuc tr su v phn bn. Gia nm 1982
v 1997, vic s dng tng t 40kg n 223kg / ha (EIU 2000a), kt qu l, nng
sut tng lin tc, mc d tng din tch t canh tc gim (Tng cc Thng k Vit
Nam 2007). Cc sn phm quan trng nht trong khu vc l go (90% xut khu
ca c nc), tri cy, v tm, c (MDEC 2008). c bit trong ma l lt hoc cc
trng hp dng chy khc, vt tch ca phn bn v thuc tr su c ra tri lm nhim
nc mt. Hn na, vic tng cng s dng thuc tr su v phn bn ha hc cng dn n
nhim nc ngm.2.1 Mi trng nc mtTrong mi nm qua nc mt sng Hu v mt s
knh rch thot nc chnh tr nn nhim nng n v vt qu cc quy chun hin hnh
trong Quy chun k thut quc gia v cht lng nc mt (QCVN 08:
2008/BTNMT). Ring: Ch s pH vn trong gii hn cho php, dao ng 6,7-7,7
(Quy chun quc gia QCVN 08: 2008/BTNMT, gi tr pH t 6-8,5); Cc gi tr
COD trung bnh trong nc mt tng t 7mg / l ln 15mg/ l, vt qu gii hn
cho php ca quy chun quc gia hin hnh (QCVN 08: 2008/BTNMT); cht rn l
lng (SS) trn sng Hu gim t 74mg / l (nm 1999) xung 43mg/l (nm 2008),
nhng vn cao hn gii hn cho php theo quy nh ca quy chun quc gia (QCVN
08: 2008/BTNMT - Ct A2) 30mg/l; Nng Coliform lun cao hn so vi quy
chun quc gia (QCVN 08: 2008/BTNMT - Ct A2) t 5000 MPN/100ml.
Coliform trong nc mt sng Hu ca dao ng t 44.000MPN/100ml n
51.000MPN/100ml, vt qu gii hn cho php khong 10 ln. Nng trung bnh ca
Coliform trong nc mt ca cc knh chnh thnh ph Cn Th tng ln
62.000MPN/100ml trong nm 2008, vt qu gii hn cho php hn 12 lnNhm kho
st tin hnh kho st cht lng nc mt ti 6 v tr trong khu vc d n vo thng
1-2011.
V tr quan trcCc im quan trc nc mt c ly knh v sng trong vng d n,
gn khu dn c, xung quanh c nhiu cy ci v nh ca.V tr cc im ly mu c
trnh by trong bng 1.1.Bng 1.1: Cc im quan trc mi trng nc mt.
V trThi gian ly muTa Tn mu
Kinh V
Ng ba Mn huyn Mn, tnh Cn Th16h00105o558310o656NM1
Knh Mn, TT. Thi Lai, Huyn C , TP. Cn Th9h45105o321310o428NM2
Knh X No, TP. V Thanh, Tnh Hu Giang14h00105o.39209o4321NM3
im giao knh Tn Hip v X No, huyn Chu Thnh A, tnh Hu
Giang9h30105O34349O5536NM4
X Vnh Ho Hng Nam, Huyn G Quao, tnh Kin
Giang8h30105,42449,7590NM5
Knh Mn, X Ho Li, Huyn Ging Ring, Tnh Kin
Giang15h30105O33159O5240NM6
Cc yu t quan trcCc yu t cht lng nc o c v phn tch bao gm: pH, DO
(oxy ha tan), BOD5, COD, Hg. TSS, Cl-, tng Coliform, Hm lng thuc tr
su Clo hu c, Hm lng thuc tr su ln hu c, hm lng du m. Phng php quan
trcKt qu c th c trnh by trong Bng 1.2:
2
Bng 1.2: Kt qu phn tch cht lng nc mt khu vc d n 1/2011
STTMupHTSS(mg/l)DO(mg/l)COD(mg/l)BOD5(mg/l)Cl-(mg/l)Hg(mg/l)Thuc bo
v thc vt (nhm photpho hu c) (mg/l)Hm lng du m (mg/l)Thuc bo v thc
vt (nhm clo hu c) (mg/l)Coliform(MNP/ 100ml)
1NM16,78653,512,81370VtKhng pht hin(
