KHOA HOC I ^ E S B I B I l ^ B
LU'A CHON CHI SO DlT BAO HAN HAN CHO BONG BANG SONG CUtJ LONG
Bili Vi?t Hirng Trudng Bgi hgc Qudc gia TP. Hd Chi Minh
Tdm tat; Bdng bdng sdng Cicu Long (DBSCL) Id trung tdm san xudt ndng nghiip, nudi trdng thuy sdn tgi Viet Nam. Tinh hinh hgn hdn kit hgp vdi xdm nhgp man tgi khu vuc dien bien ngdy motphirc tgp, dd tgo dp luc bdt lai ldn lin nin klnh ti, mdi trudng vd xd hdi gdy xung dgt trong sic dung nudc. Viec du bdo vd do dgc man tgi DBSCL duac thuc hien thuang xuyin, cdn ddi vai' hgn hdn gap rdt nhieu kho khdn, dgc biet trong cong tdc du bdo. Thdng qua khdo sdt cdc thiit hgi do hgn hdn vd xdm nhgp mdn gdy ra cho cdc tinh thdnh DBSCL, kit hap vdi nghiin ciru xdc dinh chi sd xdc dinh vd du bdo hgn hdn cd tinh tdi yeu td xdm nhgp man, bdi bdo trinh bdy cdc ket qud budc ddu ciia nghien cicu
Tir khoa: h^n hdn, xdm nhgp man, ddng bdng sdng cuu tong, tdc d^ng moi tru&ng, ton thit kinh te, nhiim man, chi so hgn man.
Summary: Mekong Delta is considered the center ofthe agricultural production, aquaculture In Vietnam. Drought situation combines with salinity intrusion is processing complexly In recent years, which caused big disadvantages to pressure on local ecomlc, environment and social sectors and caused the conflicts on water uses So that, the consideration and forecasting salinity intrusion In Mekong Delta is implementing, but it is dlfficuhfor the drought and its impacts, it's specially in the forecasting. Through the surveying of damages caused by drought and salinity Intrusion in Mekong Delta's provinces, as well as the research to Identify the drought Index combined with salinity intrusion factor, the article presents the method and part of initial results regarding to the our research.
Keywords: drought, salinity intrusion, Mekong Delta, environmental impact, economic damages, salinity, drought index.
1. T 6 N G Q U A N DBSCL dugc xem la trung tam san xuit ndng Ddng bing sdng Ciiu Long (DBSCL) la mdt "?'?'??' "^"^ s™ '^^^ Viet Nam vdi cdc san bd phan cua chau thd sdng Me Kdng cd dien P*^™^ ' ^ ' " ^ ' * S?o> fa da tton va tdm. DJy tich 39 747 km', n i m lidn kd vol vvmg Ddng '^™8 la nhirng san p h i m xuit k h i u chu l\rc cua Nam Bd, viing kinh id lan nhit cua Viet Nam "^?S ™ '^"^ V ' ? ' Nam. Tuy nhidn, cac san hien nay, phia B i c giap Campuehia, phia Tay P ' ' ^ " ^ ^ '^™S ^ f * d u kien sdng teong khu Nam la vinh Thai Lan va phia Ddng Nam la '^'i P''^ ^ " ' ' ^ "•* ' ' ^ '^^° ^ ' ™ k'?n tW nhidn.
Bidn Ddng. DBSCL cd vi tri nhu mdt ban dao ^ ' ^ ^ ' ' ' ^ " **" ^^ ' * ! ' ^ ' = BBSCL tuong ddi vdi 3 mat Ddng, Nam va Tay Nam giiSp bidn * " * " ' ' ^ ^^° P'^* ' " ^ " " ° " 8 nghiep, thuy san vdi dudng bd bidn dai tren 700 km. '^™8 • * " '="9<= ^^ng cua ngudi dan noi day
Ngaynhanbai: 14/10/2016
Ngay thdng qua phan bifn: 26/12/2016 > , • »u - • NgayduyeTdang:28/2/2017 nguon lpi thuy san....
nhu mua thuan gid hoa, it bao va Iii tuy Ion nhung khdng dir dpi va mang theo nhidu didu kidn thuan lgi cho phat tridn nhu phii sa
82 TAP CHf KHOA HOC VA CONG NGHE T H O Y LOl S O 37 - 2017
KHQAHOC M I 111 111 III M
4.
Hinh 1. Bdn do dia hinh. thS nhudng vd phdn bo lugng mua ndm tgi DBSCL Tuy nhifin, tai DBSCL cd khdng it cac Ioai
thifin tai nhu Iu lut, hgn han, gidng to,... vd difiu kifin tu nhifin bat lgi nhu nhiem man do xam nhdp mdn tii bifin ciing nhu nhiem phen tir cdc tdng ddt sdu. Ddc bifit trong nhiing nam gdn ddy, trong difiu kifin thay dfii ciia khi hgu toan cdu vd khu vuc, chfi do thdi tifit thay ddi khfing cdn theo quy luat nhu mua trai miia, nang hgn nhay mgt gay gat,... nudc bifin dang day man xdm nhdp sau hon vao ngi dfing va cac con sdng Idn. Han han kfit hgp xdm nhdp mdn da vd dang trd thanh mdi hifim hog tiem an trong khu vgc khi lugng nudc thugng nguon sdng Mfi Kfing vfi ngay mdt suy gidm, lu ngay mgt nhd vd cd thdi gian khdng cd Iii ve. Tat ca da vd dang gdy dp luc ngay mdt tdng Ifin vifc cdp nudc cho sinh hogt va san xudt
ndng nghifip, thuy san va nhifiu nganh kinh tfi khac tgi khu vuc DBSCL. Chinh day la nguyfin nhan ldn nhdt gay tfin thuong cho sdn xudt vd sinh hoat ciia ngudi dan khu vuc ha ngufin sfing Mfi Kdng.
Hgn han la mgt hifin tugng ctia khi hdu, thudng tdi phdt. Hgn han xay ra d hau het cdc vimg khi hau, trong dd cd noi cd lugng mua rat nhifiu va noi cd lugng mua it. Hgn han Id mdt kfit qua cua vifc thifiu nudc cdp hay mua hodc khdng cd mua trong thdi gian dai, do dm trong khdng khi va ham lugng nude trong dat gidm, lam suy giam luu lugng ddng chdy song, miic nudc hd thap hon muc nudc trong tdng chiia nudc nglm gdy dnh hudng xdu dfin sinh trudng ciia cay, nhu suy thoal mdi trudng gay ra ddi ngheo...
Hinh 2. Dudng dong mirc nong man 4%o ndm 2008 - 2009 vd ngdp IU 2000 tgi DBSCL
TAPCHfKHOAHpCVAcONGNGHE-mOYLaiSd 37-2017 83
KHQAHOC l^^SMM^M Han hdn dnh huong rdt ldn tdi mgi ddi tugng
mgi linh vuc ciia ddi song xd hgi. Ngay ca sau thdi ky hgn han, nhiing ddi tugng song phu thuge ngudn nudc thudng phuc hdi trd lgi khd lau do khd ndng cdp/tu phuc hdi ciia ngufin nudc thudng diln ra cham. Thdi gian dfi phye hfii trd lgi tinh trgng ban ddu ddi hay ngdn tuf thudc vao miic do, thdi gian han han va lugng nudc mua nhdn dugc. Nhu vay, nhiing tdc dfing cua ban hdn tdi hdu hfit cac ITnh vuc trong khu vuc, thfing thudng nhiing tac ddng nay cd thfi phdn lam ba nhdm chinh; tdc ddng dfii vdi nen kinh te, tac ddng dfii vdi mdi trudng va tac ddng dfii vdi xd hfii. De xac dinh dugc han han ciing nhu miic do nghiem trgng, chi sfi hgn han thudng dugc su dung.
Tai DBSCL, han hdn cung vdi nhifiu dang thien tai khde nhu Iii lut, giong bdo...xay ra thudng xuyfin va thudng xudt hifn theo miia trong ndm. Nhu miia khd (kift) thudng xay ra han hdn vdi miic do khac nhau. Ddi khi ngay trong mua mua han ban ciing xudt bifn
(han Bd Chdn) vdi thdi gian keo dai tdi 1 thdng gdy dnh huomg tdi cdp nudc cho vu Xudn He va nudc sinh boat do thdi gian nay nudc m§n xdm nhg.p sdu trong ngi ddng.
Trong thdi gian gan day, ciing vdi nhiing anh hudng cua BDKH, tinh hinh ban han tai DBSCL diln bien phiic taip va citng vdi xdm nhap man sdu trong ndi dfing, thift hai trong ndng nghifp ngay mgt tdng cung vdi cac vdn dfi xa hdi, mdi trudng nay sinh nhu thifiu nudc sinh boat, bfinh tat lien quan den nudc va d nhilm mdi trudng nudc kfinh rach. [5]
Han hdn xdy ra tai DBSCL trong qua khii dugc ghi nhan khac nhifiu vdi miic do tac dgng ciing nhu thift hgi rdt ldn cho san xuat cung nhu ddi s6ng ciia ngudi ddn khu vuc.
Trong vdng 40 ndm qua, cd khdng it nhiing ndm ban ndng va ban nghiem trgng. Trung Bd va Nam Bd cd ban trong cac ndm 1983, 1987, 1988, 1990, 1992, 1993, 2003, 2004 ddc bift hgn rdt nghifim trgng vdo ndm 1993 va nam 1998.
Hinh 3. Bdn do hgn cdc ndm 1997, 1998 vd 1999 tgi Viet Nam Ngudn: Tdng c^c thong ke, 1998, 1999
Hifn tugng xdm nhap man tai DBSCL diln ra tugng khu vuc nhu mua, gid. Xam nhap man hang nam va phu thuoc rat ldn vao difiu kifin anh hudng rdt ldn dfin qua trmh phat trifin kinh ddng chay trfin sdng Me Kdng, difiu kifin khi tfi-xa hgi viing ven bifin DBSCL.
TAP CHlKHOA HOCVAc0NGNGHeTHL)YL0iS6 37-2017
KHQAHOC •IJ.IJIJJIel'lJW
Hinh 4. Bdn dd xdm nhdp man tgi DBSCL Nguon: Vien KHTLMN, 2016
lit thang 1 dfin thdng 6 hang nam luu lugng nudc sdng Me Kdng chay vao DBSCL qua sfing Tifin va song Hdu nhd, trong dd luu lugng thang 4 la nhd nhdt so vdi cdc thang trong nam. Ddu thdng 3 va thdng 4 hang ndm Id thdi gian nhu cdu diing nudc Ifin cao cho canh tdc nong nghifp, trong khi muc nudc sdng lai rdt thdp gay thifiu nudc d ddng bang. Van dfi trd nen nghiem trgng khi ddng chdy ra bien khdng du manh dfi day nudc mgn tir bien chay vao. D|c bift vao ky trifiu cudng kfit hgp gid Chudng (gid Ddng Bac) nudc man tifin sdu vdo hfi thdng kfinh rgch ngi dong gay thift hgi cho sdn xudt nong nghifip.
Mua khd hang nam, hai dgng thien tai (han hdn vd xam nhdp man) ciing liic dien ra se tdc dgng rdt ldn tdi sdn xuat va ddi sdng ngudi ddn tai DBSCL. Vifc do vd du bdo xam nhdp man hdng nam trong hf thong sdng kfinh tai DBSCL dugc thuc hien thfing qua khd nhifiu cdc tram khi hrgng thuy vdn.
Tuy nhien, hgn ban chiing ta chi dua tren cdc tac ddng cua nd tdi san xudt va sinh boat (thifiu nudc tudi cho ndng nghifip vd sd hg thifiu nudc sinh hogt) dfi xdc dinh va ddnh gia, cdng tac du bdo rdt ban che, chu yfiu dua
tren sd lifu mi^c nudc sdng kfinh va mua.
Nhu vdy, vifc xdc dinh chi sd ban ban cd tinh dfin yfiu tfi tdc dgng gia tang - xdm nhgp mgn cho vifc danh gid ciing nhu du bdo cho DBSCL rit quan trgng.
2. PHU'ONG PHAP LUAN
Dfi thuc hifn vific danh gid imic do tdc dfing ve mat xa hdi, kinh tfi vd mdi trudng do ban ban kfit hgp xdm nhap man, can thuc hifin mgt sd phuong phdp sau:
Phuang phdp thu thdp vd khdo sat: Thu thdp cdc thdng tin, tai lifu ve cac thifit hgi kinh tfi, mdi trudng ciing nhu cac vdn dfi ve xa hdi hfin quan dfin cac dot thifin tai hgn ban, xdm nhdp man xay ra. Dfing thdi cac chinh sach cua cac cdp chhih quyfin thudc khu vuc nghien cuu da, dang va dg kifin dp dyng cho vifc gidm thifiu tdc ddng hay thift hai do thifin tai bgn hdn, xdm nhdp mgn gdy ra.
Phuang phdp phdn tich thii: bgc AHP: Phuong phdp AHP (Analytic Hierarchy Process) la phuong phap so sanh timg cdp cac tifiu chi ngang cap, sau dd lap ma trdn dfi tinh todn trgng sd. Phuang phap AHP cd thfi xac dinh miic do quan trgng cua timg tifiu chi, quy trinh phan tich theo thii bdc, xem xet nhieu tifiu chi nhd va phan tich ca yfiu td dinh tinh lan dinh lugng. Vi Iy do ndy ma dfi tdi chgn phuong phdp AHP dfi xdc dinh trgng sd cho cdc nguyen nhdn cua cdc tac ddng do hgn ban.
Tren co sd phdn tich nay, nguyen nhdn giam lugng mua va xdm nhdp man sdu Id mgt trong so cdc nguyfin nhdn co ban gdy ra hgn hdn va gia tdng thiet hai [1].
Phuang phdp phdn tich SWOT: phuong phap nay dugc su dung nhdm lua chgn chi sd bgn ban phu hgp nhdt khi dp dung cho DBSCL trong sfi cdc chi sfi ban ban dang dugc sii dung h-ong nhifiu nghien ciiu trong va ngoai nudc.
Mdt sd chi sd ban ban thudng dugc sir dung trong cac nghifin ciiu ttong va ngoai nudc hien nay [2, 5]:
TAP CHI KHOA HQC VA C O N G N G H $ T W C I Y LOI S<5 37 - 2017 85
KHOA HOC
TT 1
2
3
4
5
6
7
S
9
Bang 1.
Ten chi so Chi sd cip nudc mat-SWSI Chi sd khic nghift h?n Palmer
(PDSI) Chi sd chuan hoa lupng mua
(Standardized Precipitation hidex-SPI) Chi so khd cin cuaPahner(PAI) Chi sd Fed
Chi sd khd cin (Aridity Index - J)
Chi sd hifu sudt mua
(Precipitation Effectiveness index - PE)
Chi sd di thudng lugng mua (RAI)
Chi sd can can nudc (K)
Cac chi so va hf s^ xdc dinh va dw bao h^n hdn Ojnh nghia
Chi sd SWSI thih miic dg thieu nudc Chi sfi Palmer sur dung thdng tin vfi nhift do vd lugng mua hang thang.
SPI Id mdt chi so dua vao khd nang cd thfi cua mua cho bdt cfi thang thdi gian ndo.
Chi sd khd cdn, dua ra sii dung bdi Palfai vacs (1995) Chi sd Ped dugc tmh theo cdng thiic (Ped, 1975) Chi sd nay la chi sd khd cdn, nhung ciing cd thfi dugc sii dung dfi tim ra doan hgn han.
Hieu sudt mua phdn loai cdc vimg khi bdu
Chiing dugc coi la lugng mua trung binh cue tri cho di thudng dm vd duong
Han xdy ra khi lugng bdc hoi bat dau vugt qud lugng mua roi xudng
Cdng thirc tinh
aPttn, wvft + fiflniM + cPdftM cMv + '^^'i™ ^"l" " ^°
PDSh = 0.897 PDSIi-i+-Zi
SPlJ'-"'^^
aP.,=Ji^lOO
AT AP Ped =
Gf (Tp
12P ' (T + 1 0 )
n=12 10
P E i n t o = ^ 1 1 5 ( ^ ^ _ J
(.P-P)
E
" = 1
TAP CHl KHOA HOC VA CONG N G H £ T H O Y LOl SO 37 • 2017
TT
10
11
12
13
14
Tfin chi s6 Chi so hgn thuc te(EDI)
Chi s6 ban (Khan)
Chi tifiu nudc cua cay trong nfing nghifp Hf sfi ddng chay nam
Tf sd % lugng ddng chdy thieu hilt so vdi trung binh thdi ky nhifiu ndm
Dinh nghTa Chi sfi EDI Id mft ham s6 cua lugng mua cin cd dfi trd lai difiu kifn chuAn Theo Ddng Khde Rifing, hai yfiu td chi phdi ban thuy van la miic do khd va miic df can
Day la chi tifiu dfi ddnh gid cdy trfing cd bi ban.
Hf sd ddng chdy ndm la ty sd giQa lugng ddng chay ndm vdi lugng mua nam Dfi xem xet miic do thifiu h\it hay du thira ddng chdy trong cdc thdi ky
Cdng thi^c tinh
so,^'"-;" v.tm^tKt"^)/'']
f|iin - V^'*"'"^'!« ' ' " " " ^ " i j ^ ' ^'i'~{^ d j j /
Wo+Pm+Pp
a = Y/X
Qtb
Hifn nay ^ cd rdt nhifiu chi s6 han dS dugc sii dung phfl bifin tr&i thfi gidi va d Vift Nam nhu chi sfl SPI, Ped, K, EDI, SWSL.. ddc bift chi sd SPI, PDSI dd dugc sii dung hong nghifp vu du bao vd canh bao ban d nudc ta va thu dugc nhung kfit qua tflt Tuy nhifin, cdc chi so va hf so bgn ban trfin dfiu cd mgt nhugc difim ldn Id khdng cd yfiu tfi nao lifin quan tdi chit lugng mdi trudng (ddi vdi DBSCL la x§m nh^ rrmn) Iam gja tang bat lgi. Do vdy, cdn xem xet bd sung yfiu td nay vdo cung vdi vifc don gia hod cdc chi sd hgn ban nbSm tgo ffleu kifn thuan Igi cho vifc sir dung cdc tm nguyen sd lifu thu thSp hifn cd [3,4,6].
3. Ktr QUA VA THAO LU^N
Hi$n trgng tdc dgng ciia hgn hdn kit hgp xdm nhdp mgn tgi BBSCL: Trong nhtrng nam gSn
ddy, ban h ^ difin ra trfin difn rgng va difi:
bifin phiic tap, gdy nhifiu thift hgi cho san xudl dgc bift trong san xuat nfing nghifp.
Trong ndm 2013, theo cac bao cao thift ha cua Bd NN&PTNT, cdc tinh thanh DBSCL o khoang 37 ngdn ha liia vd 291 ngan ha thu;
sdn bi dnh hudng bdi tinh trang ban m§n. Difii tich liia vung ven bifin bi anh huong do thifii nudc nggt, nhifiu nhdt tgi Sdc Trdng, Tifii Giang, Ben Tre vdi 10.200 ha, trong do ci hdng tram ba bi mdt trdng. Rieng tai Bfin Tn cd 4.200 ha hoa mdu, cdy dn qud bi giam ndn|
sudt. Huyfn Bmh Dai (Bfin Tre) cho bifit, tron]
vg Ilia ddng xudn, todn huyfn dd xudng 1.151 ha, dfin thdi difim nay dd cd 500 ha bj khfi hgn thifiu nudc, nhiem man...
TAP CHf KHOA Hpc VA C O N G NGH? T H O Y Lpi S(5 37 - 2017 8
I KHOA HOC ^{g«1?H?B!IMi Trong nam 2014, tinh hinh h?ui cd giam trdn pham vi toan d6ng bang, nhung mdt sd noi han cue bd gia tang nhu tmh Bac Lieu vdi tdng thidt li^ len tdi 1,2 ty ddng, 50 ha lua bj nhilm man nang.
Trong nam 2016, theo bao cao cua van phdng Ban clii dao Trung uong ve phdng chdng thidn tai, hrong 6 thang diu nam, t6ng thidt hai ttong san xuit ndng ngliiep tai DBSCL udc tinh khoang 215 ty d6ng cho 9/13 tinh thanh khu vuc. Ciing theo hao cao cua Bd NN&PTNT, san xuit ndng nghidp tai DBSCL thift hai nang nd vdi lua thiet hai 232,95 ha; hoa mau va rau man thidt hai 6.561 ha; cay an qua va cay cdng nghiep bi thidt hai toan vimg la 10.831 ha. Anh hudng tir tinh hinh han hdn va xam nhap m ^ , cd khoang 226.605 hp dan ttong vimg bi thidu nudc sinh hogt.
r 300,000
Hinh 5. Thiet hgi kinh te do hgn hdn vd xdm nhgp man tgi DBSCL
Nguon: Van phdng Ban chi dgo Trung uang ve phdng chdng thien tai, 2016
Theo Vien Khoa hpc Thuy lpi midn Nam, trong thang 4 nam 2016, nuoc man xam nhap sau 70_ km tren 7 nhanh sdng Cilu Long va song Ong Ddc, Cai Ldn thupc viing Ddng bang sdng Cuu Long (DBSCL). Tren sdng Cua Tieu, nudc m^n xam nhap tdi xa Ngu Hiep, huyen Chau Thanh, Hnh Tien Giang.
Tren sdng Cua Dai, man xam nhjp tdi xa Phi Dllc, huyen Chau Thanh, tinh Bdn Tre. Trdn sdng Ham Ludng, man xam nhap tdi xa Long Thdi, huyen Tidu Cin, tinh Tra Vinh. Tren
sdng C6 Cliidn, m$n xam nliap tdi xS My Phudc, huydn My Tii, tinh Sdc Trang. Tren sdng Cung Hiu, mjn xam nhap tcri xa Qudi An, huyen Viing Liem, tinh Vinh Long. Trdn sdng Dinh An, m ^ xam nhap tdi thi tran Tra On, huy$n Tra On, tinh Vinh Long. Trdn sdng Trin De, mjn xam nhjp tdi xa Phii Hiiu, huydn Chau Thanh, tmh Hau Giang. Tren sdng Ong Ddc, man xjm nhap tdi thi ttin An Minh, huydn An Mmh, tinh Kidn Giang. Trdn sdng Cai Ldn, man xam nhjp tdi thanh phd Vi Thanh, ttah H ju Giang.
Nhu vay, hoat dpng san xuit ciing nhu ddi sdng ciia ngudi dan khu v\rc DBSCL cluu tac dpng ldn cua h?n han. Mure dd hdi phuc cua cac nganh san xuat ciing sinh hogt cua ngudi dan sau thdi ky hgn han, tuy thudc khu vuc, nhung thudng keo dai va khd Ichan.
Chi sd hgn mdn dp dung cho DBSCL phuc vu xdc dinh vd dtc bdo mice do:
Trdn the gidi, cd rat nhieu tac gia nghien ciru vd han han. Nhung do tinh phiic tap cua hien tuong nay, den nay van chua cd mdt phuong phap ehung cho cac nghien ciiu vd han han.
Trong viec xac dinh, nhjn dang, giam sat va canh bao han han, cac tac gia thudng sir dung cdng cu chinh la cac chi sd han han.
Tuy nhidn, ehung nhit y nghla cda chi sd han han trong viec theo ddi sir bien dpng cua gia tri cac chi sd han han se giiip ta xac dinh duac sir khdi dau, thdi gian keo dai cimg nhu cuong dp han. Chi sd hgn ban la ham cua cac bidn don nhu lupng mua, nhipt dp, bdc thoat hoi, ddng chay... hoac la tdng hpp cua cac bidn. Mdi chi sd ddu cd uu didm nhuoc didm khac nhau, va moi nudc deu sii dung cac chi sd phii hpp vdi didu kien nudc minh. Vide xac dinh hgn han bang cac chi sd hgn khdng chi ap dyng vdi bd sd lieu quan ttjc ma cdn ap dung vdi bd sd lidu la san pham ciia md hinh khi hau khu vuc va md hinh khi liau toan cau.
Qua phjn tich cac chi sd va h? sd he-- h^«
(bang 1), Chung ta se sii dung chi sd har; han
88 TAP CHl KHOA HOC VA CONG NGHE T H C I Y LOl SO 37 - 2017
cd tinh tdi ydu td gia tang tac ddng mdi mrdng (xam nhjp min), dupe gpi ehung va chi sd han mjn cho viec xac dinh cung nhu d\r bao hgn hjn t?i DBSCL. Chi sd hgn man se sir dimg cac sd lidu dupe do dgc hipn cd tai DBSCL gdm:
- So li$u thuy van (ddng chay, muc nuac);
- Sd lidu khi tupng khu v\rc (mua, b6c hoi);
- Sd Udu vd xam nlijp man (chieu sju xam nhap cua nudc mgn vdi cac nong dp 1 - 4%o);
Sau khi tinh toan thii din cung bidn ddi cdng thirc tinh chi sd/hp sd hgn (bjng 1), chiing tdi iua chpn clii sd han (Khf„) cua Dang BChac Ridng lam ca sd cho vide Ijp chi sd hgn man (.Khm-Kiin)- Cdng thiic tinh toan chl sd hgn man nhu sau:
Trong dd:
Kiiai-mjii: Chi sd hgn-mjn;
KM, KC^ va K,,;^,: tuong iing la chi sd khd, chi sd can va chi sd xam nhjp man, dupe tinh
I KHQAHOC I W . I J I e l J i a n ^
theo cac cdng thiic dudi dSy:
% = i ~ ; f™=(i-|)g;' '''*-('*-T;n
X, Z„: hicmg ling la luang mua va lupng b6c thoat hoi tidm nang ttong thai dogn tinh toan (ttiin, thing);
0 : Lim lupng tiimg bmh cua njm thury;
g,: Lim lupng tgi thdi diem thii i ttong nam;
go: luu lupng trung binh nam trung bmh thdi ky nhidu n jm.
/,: Chidu xam nhap ldn nhit (ling l.Og/l) cua sdng true chinh thdi didm / ttong nam thiij;
k: Chidu xam nhap ldn nhit (iing l.Og/l) cua sdng ttuc chinh khdng gay tJc dpng tdri san xuit va sinh hoat khu vuc.
ITB: Chilu xam nhgp ldn nhit (iing l.Og/T) ciia sdng triic chinh tnmg binh nhidu nam;
Bang xac dinh miic do hgn man trong 6 thang mua khd tgi DBSCL theo chi so han man nhu sau:
Bang 2: B6i v&i thdi doan nam
-•^han-mSn
Tmh trgng han-man
<0,60 Dau hifu hgn ban
, c h i s o Kh,n - m^D
0,6 - 0,9 Han - man nh?
duQ'c phan cap nhu sau:
P^_0,9-l,0 i Hgn-m§n vira
>1,0 f Han - man nSng^
Cach thiic xao dinh hay du bao han man theo chi DBSCL (tinh Sdc Trang) vdi true sdng chinh l\ra sd hgn man ( i ^ _ „sn) cho mdt sd khu vuc chpn la sdng Hju vdi ciia sdng Dinh An nhu sau:
Bang 3: Gia trj chi so hgn ban v^ han Thjng
Klch6 Kcan Kman
K-han - man Khan han
Miic gia tang 1 0.924 0.752 1.039 0.85 0.83 0.02
2 0.985 0.903 1.000 0.94 0.94 0.00
- mjn nam 2011 tren dja b&n tinh Sdc Trang 3
0.911 0.950 1.213 ,, 1.03 ,
0.93 0.10
4 0.556 0.938 1.252 0.81 0.72 0.09
5 0.000 0.864 1.039 0.00 0.00 0.00
6 0.000 0.593 1.000 0.00 0.00 0.00 Miic dp gia tang the hidn miic dp anh hudng Gia tri mirc dp gia tjng thd hipn:
cdng thdm do mjn xam nhgp sau vjo npi ddng.
TAP CHl KHOA HOC VA CONG NGHf T H O Y LOI SO 37 - 2017 89
KHQAHOC n i ^ ^ i M i B r ^
- Khi gia tri Ducmg cd y nghta bdn cgnh tac dpng/thi?t hai do ban han (thidu nudc sJn xuit hay sinh hogt) con cd tac ddng/thi$t hgi do nudc mjn lim khan hidm them ngudn nudc tudi/sinh hogt (bilu hien nay dl nhjn thiy)...;
- Khi gia trj am hojc htog khdng, dilu nay the hien tic ddng ciia han han la vupt ttpi va ttpng didu kidn nay cac bieu hien tac ddng do mjn xam nhap khd phan dinh hon;
Khi miic dd gia tang ban khi tinh tdi xam nhjp mjn njm 2011 tgi tinh Sdc Trjng cd thi dupe bidu didn nhu ttong bidu dd dudi d jy:
• Khan-Tiian i^iKhan
: 0 5 C B 9 4
ll h
Hinh 6. Tinh chi sd hgn vd chi so hgn tich hgp xdm nhgp man cho tinh Sdc Trdng tqi DBSCL Nam 2011 khong phai la nam ban ban nghifim trpng tgi DBSCL, tuy nhifin trong nSm tinh Sdc Trdng ghi nhdn cdc Ihif t hai do ban ban va xdm nhdp mdn gdy ra cho san xudt ndng nghifp va cdp nudc sinh hogt cho ngudi dan. Tmh hinh ndy dien ra trong khodng thdi gian miia khd tgi cac huyfn ven bifin. Can cii vao tinh todn chi sd man vd hgn - man, dfi cho thay ddu hifu hgn hdn nh? va vira. Nhung vdi vifc tich hpp yfiu tfi xdm-nhgp m^, thi miic dp ban ban cd gia tdng ban nhu thang 1 (vdi chi sd K hgn thi ban han d miic df nhp, khi tich hpp yfiu td xdm nhgp man, ban ban - xdm nhdp man d miic vira).
Nhu vay, budc ddu, chi sd hgn mdn tinh cho DBSCL nham xac dinh miic dp hgn ban va du bao hgn cho tuong lai da thfi hifn dupfc miic do gia tdng tdc ddng. Ddng thdi, cac thdng sd tinh toan chi sd tuong ddi gian don va cd sdn trong bfi thong so khi tupng thuy van cua mang cdc
trgm khi tupng thu;^ vdn trong khu vuc.
Tuy chi s6 ndy khdng chi ra dugrc danh gidi hgn khi tupng, hgn thuy vdn, ban ndng nghifp...., nhung do ti'nb da dang trong sii dung nudc khu vy:c DBSCL (ca ndng nghifip, thuy sdn, sii dung nudc smb boat...) cdng vdi vifc nudc man xdm nhdp thudng xuyfin theo quy ludt trifiu thi viec miic dp tdc dpng khdng chi do tiing dang ban ma cdn cpng thfim tdc dpng cua mdn. Vi vdy, vdi muc dp nhdn bifit hgn - man, cfing thiic tinh toan tich hpp yfiu td xdm nhgp man trfin, cd thfi sii dung phu hop cho Ddng blng sdng Cim Long.
4. KET L U ^
Quan ly tdng hpp tdi nguyfin nudc cho DBSCL rdt phiic tap do cac bien ddng ldn vfi difiu kifn tu nhien (bao gfim ca Iii lut, ban ban, dat chua phen va xdm nhdp mdn), tac dong ciia phdt trifin thupmg luu, nhifiu loai co sd ha ting chdng lu lut vd cdc tac dpng cua bifin doi khi hgu. Phiie tgp ndy them trdm trpng bon do nhu cau ldn vfi phat trifin kinh tfi Vift Nam vd Campuehia. Hifn tuong thifin tai ban ban va xam nhdp man sdu vao npi dfing difin ra ngay mdt thudng xuyfin va miic dfi trdm trpng gia tang gdy dp Iuc rat Idn dfin san xudt, sinh hogt va cdng tdc qudn Iy tai nguyfin nudc. Vifc xdc dinh, danh gid tdc dfng gay tdn thdt cung nhu du bdo hgn ban cd tich hop yfiu tfi xam nhap man vao ndi ddng la rai cdn thifit va la nfin tang cho vifc quy hoach, khai thac va sii dung tai nguyfin trong khu v\rc mft each hifu qud, phii hpp vdi difiu kifn thyc tfi ciing nhu trong tuong Iai nhSm phdng chdng bay giam thifiu tdc ddng va thifit bgi.
Trong nghifin ciiu nay, vifc dua ra mfit chi sd ban - man cho DBSCL Id budc ddu tifin. Vdi kha nang dp dung cdc sd lifu do dac sdn cd cua hf thdng tram khi tuong - thuy van va chdt lupng ngudn nudc cda DBSCL, hf sd chi sfi bgn - man dfi dang tinh todn vd cung cdp dii thdng tin cho cdc cap quan Iy cua cdc tinh thanh tgi DBSCL.
90 TAP CHf KHOA HOC VA C O N G N G H £ T H O Y L O I S(5 37 - 2017
I KHnAHOC M I li'l li'l I J I M
T Al LI|;U THAM KHAO
[1] Dwyer, A., Zoppou, C , Nielsen, O., Day, S. & Roberts, S., (2004), Quantifying Social Vulnerability: A methodology for identifying those at risk to natural hazards, Geoscience Australia Record 2004/14.
[2] Dang Dmh Khd, (2011), Nghien ciiu tinh de bj tdn thuong do Iii lut hg luu song Thach Han, tinh Qudng Tri, Lugn van Thac sT khoa bpc, Dai hpc Khoa hpc Tu nhifin - DH Qufic gia Ha Nfii.
[3] Lfi Sdm, Nguyen Van Sang (2010), "Dir bdo nin mgn tgi cdc cira sdng ldn mita khd ndm 2011", Vien Khoa hpc Thuy lpi mifin Nam.
[4] Le Sam, Nguyin Vdn Sang (2009), "Xam nhgp mgn tgi DBSCL mita khd ndm 2009". Vifn Khoa hpc Thiiy lgi mien Nam.
[5] Nguyen Quang Kim, (2009). "^Research development - economic ahd social assessment and forecast demand for water in the basin ofthe Mekong River Delta and Mekong Delta"
The record of the sciential research subject at the country level KC: 08-11/06-10
"Research solutions using rational exploitation of water resources scenarios compatible development projects upstream to drought and salinity in the Mekong delta ". Trudng Dai hpc Thuy Lgi.
[6] Lfi Sdm (2008), '^Studies assessing the drought situation and water shortage during the dry season, plans for warning and drought map of Ninh Thuan province" Dfi tai Tinh. Vifn Khoa bpc Thuy lpi mien Nam.
TAP CHf KHOA HOC VA C O N G N G H E T H O Y LOI sO 37 - 2017 91