NHIỄM MẶN VÙNG CỬA SÔNG TỈNH BÌNH THUẬN

Tiiu ban: Cdc Khoa hgc vi Trdi dat

ISBN: 978-604-413-016-8

NHIEM MAN VUNG CLTA SONG TINH BINH T H U A N
SALINIZATION IN ESTUARIES OF BINH THUAN PROVINCE
Tran Ha Phuong, Nguyin Thanh Hung
Vien Dja ly Tii nguyen TPHCM
1 Mae DTnh Chi, Quin I, TPHCM
Email: pvdialy(^hcm.vnn.vn
Tdm tat:
Trong nhiimg ndm gdn ddy, nhiim man ngudn nuac dugc xem nhu mot nguy
ca, cd tdc dgng xdu din qud trinh sdn xudt vd dai sdng ciia cu ddn viing ven biin,
a hai huyen Bdc Binh vd Tuy Phong ciia tinh Binh Thudn. Phgm vi chju tdc ddng
ciia man, tap trung a viing ven biin - cira sdng cdc sdng Ldng Sdng, sdng Luy. Cd
nhiiu nguyin nhdn ddn din hiin tugng nhiim man ngudn nuac, song chu yiu Id
do phuang thirc van hdnh cua cdc cdng trinh hd chira nuac tir phia thugng luii;
do su gia tdng ciia muc nuac biin ; vd do cdc hogt dgng sdn xudt vd sinh sdng
ciia ngirai ddn.
Bdng cdc phirang phdp nghiin cim vi thiiy vdn, thiiy luc ; phirang phdp dja
vdt ly, dja vdt ly Id khoan,... mdt sd tinh chdt ciia hiin tugng nhiim man ngudn
nude tgi ddy dugc ghi nhdn. Kit qud cho thdy, do man ngudn nuac cd gia tdng,
nhung nuac man khdng xdm nhgp sdu vdo ndi ddng.
Abstract:
In recent years, water salinization is considered as a risk, imposing negative
impacts on the production and living activities of the coastal people, mainly in
Bac Binh and Tuy Phong districts, Binh Thuan province. Salinity-stricken areas
are located in the estuaries of Long Song river and Luy river. Water salinization
can be originated from a wide variety of causes, including the operation modes of
the upstream reservoirs, sea level rise, and production and living activities of the
local people.

Some of the characteristics of water salinization phenomenon are revealed
using hydrologic, hydraulic, borehold and geophysical methods. The results
showed that water salinization is increasing but salt water does not penetrate
into inland areas.

I. M O DAU
Bic Binh, Tuy Phong li 2 huyen ven bien eua tinh Binh Thuin (Hinh 1), cd dieu kien nudi
tdm tren cit khi phat trien hoac lim rudng mudi,... Diy la mdt trong nhirng loai hinh su dung
dit cd tic ddng den khi ning nhiem man ngudn nude mat, ngudn nude ngam ting ndng. Ngoai
ra, nhirng yeu td ty nhien khie nhu han hin, thieu ngudn nude mat, khi ning ding eao eiia myc
nude bien, eiing tao dieu kien cho hien tugng xim nhip man tir bien vio siu trong ndi ddng.
Pham vi chju tic ddng eua man, tip trung d phin ha luu cic sdng Ldng Sdng, sdng Liiy.
Nghien cim niy nhim danh gii tinh hinh nhiem man ngudn nude mat v i nude ngim eiia
hai huyen tren.
274


Hdi nghi Khoa hgc ky- niem 35 ndm Vien Khoa hgc vd Cdng nghe Viet Nam - Hd Ndi 10'2010

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Hinh 1: Khu vuc nghiin cihi
II. TU^ LIEU VA PHl/ONG PHAP NGHIEN CUtJ
De danh gii hien trang xim nhip man, nhiem man nude mat, nude ngim, nhieu dgt dieu
tra, khao sat, thu thip tii lieu, do dac chi tiet da dugc tien hinh, tren pham vi vung nghien
eiiu, dd li:
- Thu thip va xir ly eic tii lieu di ed lien quan den dja chit, kien tao, dia chit cdng trinh,
cdng trinh thiiy lgi, thiiy vin, thd nhudng, hien trang su dung dit ndng nghiep, hien trang khai
thae nude ngim, v.v...

- Dieu tra, khio sit luu vyc sdng Liiy, sdng Ldng Sdng vi tinh hinh xam nhip man vao cac
cira sdng (thing VI vi thing VIII nim 2005).
- Ket hgp vdi Dii Khi tugng Thuy vin Binh Thuin do dac mirc nude, luu lugng, do man
eua sdng Luy (thing IX nim 2005).

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Tiiu ban: Cdc Khoa hgc vi Trdi ddt

ISBN: 978-604-913-016-8

- Thyc hien viec khio sit dja chit thuy vin va khoan 08 lo khoan vao thing 04 nim 2005,
cd do siu lin lugt tuong irng : 15,5 m ; 20,0 m ; 20,0 nri ; 20,0 m ; 20,0 m ; 13,0 m ; 7,5 m ;
9,0 m. Liy mau nude gom : 17 mau phan tich toan phan ; 15 mau phin tich Cl" ; Khio sat
101 dilm gilng nude vio thing IV nim 2005, do dae eic yeu td dja chit thiiy vin khie.
- lfng dung md hinh HYDROGIS de xem xet mue do xim nhip man ting nude mat.
- l/ng dung md hinh ddng chiy MOD-FLOW de xem xet khi ning xim nhip man ting
nude ngim.
- Sir dung thilt bj do dja vat ly, do siu dien, do inh dien (SAS 4000), do dja chin
(Tenalok Mark 6, 24 kenh), gim 4 dgt : (i) Dgt 1 (tir ngiy 28 / 03 / 2005 din ngiy 16 / 04 /
2005) : Do sau dien tren 8 tuyin theo phuong thing gdc vdi bd bien vi phin bd chu yeu d
phin ven biln eua 2 huyen Bac Binh - Tuy Phong. Tdng cdng cd 68 diem do, ed tdng chieu
dii 60 km ; (ii) Dgt 2 (tir ngiy 24 / 06 / 2005 din ngiy 28 / 06 / 2005) : Do siu dien tai 8 lo
khoan vi liy mau nude phin tich TDS, EC, Sal, pH de xac djnh cic tham sd dien trd suit,
diing dl minh giii cic so lieu do dia vit ly ; (iii) Dgt 3 (tir ngiy 11 / 08 / 2005 den ngiy 18 /
08 / 2005) : Do dja chin khiic xa 2 tuyen gin bien : Phan Ri (1,1 km) vi Lien Huong (1,1 km)
; (iv) Dgt 4 (tir ngiy 18 / 12 / 2005 din ngiy 23 / 12 / 2005): Do inh dien trirng vdi 2 tuyin dja
chin vi do siu dien eanh 8 Id khoan trude dd ; do sau dien 2 tuyen Lien Huong vi Phan Ri.
III. KET QUA NGHIEN ClTU VA THAO LUAN

+ Dua tren cic ket qui khio sit, khoan, do dac, phin tich miu vi cac tu lieu nghien cim
trude dd [1], ed the nhin thay: Tren luu vyc sdng 2 huyen Tuy Phong, Bic Binh dang dien ra
nhirng thay ddi manh me trong cii tao vi khai thie tii nguyen nude mat. Nude ngim ciing
dien bien theo xu the cd lgi hon. Cic cdng trinh tieh nude deu cd tic ddng lim cho xam nhip
man thay ddi, man cd the xim nhip manh hon do viee tich nude phye vy tudi tieu. Tuy viy,
do ddc long sdng d diy li yeu td quyet djnh chieu dai xam nhip man tdi da, vi do dd viec
quan ly van hanh co che xi nude (lii) ciia cic hd chira phia thugng ngudn ddng vai trd quan
trgng trong viee lim giim khi ning xim nhap cua nude bien.
+ Ket qui do dja vit ly cho thiy: Ciu tnic dja chit eua viing ven bd cd inh hudng den su
van ddng cua nude man duge the hien qua hinh thii be mat di gdc, cac ddi dip vd, nirt
ne,...Cu the li:
- Mye nude ngim nim dudi myc nude bien khoing tir - 5 den -12 m trong miia mua
(thing VIII nim 2005) ; Trong di gdc cd bieu hien ciia cic ddi dip vd ; Nin diy cua hai
thung liing sdng Liiy vi sdng Ldng Sdng deu nim dudi myc nude biln khoang - 60 m. Cae
yeu td ty nhien vira neu, cd the li dieu kien thuin lgi eho su xim nhip cua nude bien vao cac
ting chira nude.
- Ting chiia nude man day khoing 3,6 m Urong ung vdi thung liing ciia sdng Liiy, tin tai
02 dang ngudn nude man gin lien vdi cic thanh tao trim tich: (i) Nude man trong cac trim
tich sdng tudi Holocen (aQ2^"^), Id dien tren bl mat, cich bd biln khoing 4,5 km; (ii) Nude
man trong trim tich bien tudng viing vjnh - ven bd (mQi^^), phin bl xuyen suit hi bd biln
trd vao den 10 km.
- Ddi vdi sdng Ldng Sdng, tang chua nude man tuong irng trong trim tieh biln tudng viing
vinh - ven bd (mQi ), phin bd hi bd bien trd vio din khoang 5 km. Ting chira nude nay Id
ra tren mat phia bd bien, diy trung binh khoang 44 m va mdng din ve phia trong dit liin.
Phan tren mat, nude cd dg man kem hon phin dudi sau.
- Tuyen do siu dien cit ngang qua thung liing sdng Liiy, ciirig cho thiy cd 2 dang nguIn
nude man: (i) Trong trim tich sdng (aQa^) vi trim tieh sdng biln (amQ:''^) tuli Holocen, Id
dien tren be mat. Cich bd biln > 3 km; (ii) Trong trim tieh bien tudng vung vjnh - ven bd
(mbQi ), phan bd siu ben trong dit liin din cich bien khoing 8 km.
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Hdi nghi Khoa hgc kv niem 35 ndm Vien Khoa hgc vd Cdng nghe Viet Nam - Hd Ndi 10'2010

+ Theo cic nghien cim d khu vyc Pei-kang thudc bd bien phia Tiy cua Dii Loan [2]. khi
khao sit eic ting chira nude trong cic thinh tao trim tich trude vi sau bien tien 6000 nim
trudc diy, da ehirng minh mdt ddi ed gii trj dien trd suit li 1,5 Qm hoac nhd hon, dugc xem
la ddi xim nhip ciia nude biln. Dii chilu vdi ket qui do dac tai viing nghien cim cho thay :
- Ranh gidi nude man (ed dien trd suit < 10 Qm ) eua ting chira nude Pleistoeen keo dii tir
bien trd vio khoing 10 km d khu vyc sdng Ldng Sdng, khoing 5 km d khu vyc sdng Liiy.
- Ranh gidi nude man ciia ting chira nude Holocen, chii yeu trong trim tieh sdng (aQ2^)
va trim tich sdng bien (amQ2'"^), Id dien tren be mat vi cich bd bien > 3 km tren sdng Liiy.
- Ranh gidi nude man "tin du" eua ting chua nude "khdng phan chia" tdn chu yeu d khu
vyc Nlii Dit vi VTnh Hio.
- Ranh gidi duge xem li nhiem man tir nude bien (cd dien trd suit 1,5 Qm hoac nhd hon)
eua ting chira nude Pleistoeen li < 1 km cich bd bien thude khu vyc sdng Liiy va < 500 m
thudc khu vyc Phude The.
- Ranh gidi duge xem li nhiem man tir nude bien cua ting chira nude Holocen la < 500 m
cich bd bien thudc khu vyc sdng Liiy.
+ Ddi chieu vdi ket qui do siu dien nim 1988 theo sd lieu eua Lien doin Dja chit Thuy
vin - Dia chat cdng trinh mien Trung cho thiy, dien bien man - nhat ciia nude dudi dit khi
phire tap trong khoing thdi gian giiia nim 1988 vi nim 2005. Tuy nhien, cd the thiy do man
ciia nude dudi dit ting eao hon, tip trung d hai khu vyc li ha luu sdng Liiy vi sdng Ldng
Sdng, trong dd sdng Liiy bieu hien ndi bit nhit, song pham vi phin bd nude mat lai giim so
vdi nam 1988.
+ Bieu hien myc nude bien ding eao hon, dugc the hien rd net qua hien tugng xdi Id bd
bien cua viing niy. Dieu dd, ciing li tien de thuin lgi de nude bien ed khi ning xim nhip vio
cic ting chira nude ven bien.
+ De lim giim nhe khi ning nhiem man, ngoii cie giii phip da cd de cap trong eic
nghien cuu khie [3] mang tinh chit viing, khu vyc hoac cd tinh chien luge liu dii, mdt sd

giii phap cu the duge de xuit nhu sau :
- Xay dyng cic hd thugng luu de dieu tiet ddng chiy: giim bdt lii, ting ddng chiy miia
kiet, cap nude eho cic ddi tugng dimg nude li viee lim cin thiet.
- Khu vyc sdng Liiy se dugc bd sung tir thuy dien Bic Binh vdi luu lugng binh quan 25
mVs (ldn hon tdng luu lugng cua tit ci cic con sdng Bic Binh, Tuy Phong edng lai). Luu
lugng niy lai khdng thay ddi theo thdi gian (Q = 25 m /s). Diy li mdt ngudn nude rit quy gii,
can khai thie de phuc vu phit trien cho toin vung.
- Viing ha luu eic sdng Liiy, sdng Ldng Sdng khdng ldn, chieu dii xam nhap man chi
khoing 8 km (sdng Ldy). Ldng sdng khdng siu, bd sdng khdng cao, do dde ldng sdng ldn nen
man len khdng xa, vdi luu lugng ddng trieu len khdng Idn. Do dd, viee xi nude diy man de
dat din hieu qui. Ket qui nghien cim cho thiy trong thdi ky nude kem chi cin mdt luu lugng
khoing 10 m/s li ed the diy man xudng xa 3 - 4 km phia ha luu (sdng Liiy), giim bdt do
man trong sdng, nit ngin thdi gian nhiem man, gdp phin nggt hda mdt doan sdng ding ke
(gin mdt nira chieu dii doan sdng bi nhiem min).Viec sir dung ngudn nude bd sung de diy
man tren sdng Luy (sdng Ldng Sdng) cd the tao dieu kien tdt cho viec bd sung nude ngam
khu vyc ha luu 2 huyen Bic Binh, Tuy Phong.

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Tiiu ban: Cdc Khoa hgc ve Trdi ddt

ISBN: 978-604-913-016-

IV. KET LUAN
- Xim nhap man cua nude bien theo sdng li do miia khd, nude sdng can kiet khien nude
biln theo cac sdng, kenh din vio sau trong ndi ddng giy man.
- Xim nhip man vio viing cua sdng Liiy, sdng Ldng Sdng se nghiem trgng hon do vifc
liy nude d thugng luu phuc vu tudi, xay dyng cic hd. Tuy viy, man khdng len xa bon do dieu
kien dja hinh (do die ldng sdng) khdng che, 2 ben sdng ciing khdng cd cic viing triing thip cd

nguy eo ngap man. Mirc do nghiem trgng cua xim nhap man trong trudng hgp niy chi xiy ra
theo hinh thirc: man len sdm hon, do man cao hon vi thdi gian ngap man keo dii hon, giy d
nhiem ngudn nude, dit dai va nude ngim.
- Tren luu vyc sdng Liiy xim nhip man manh me hon sdng Ldng Sdng, do cira sdng Ldng
Sdng bj lip vio miia khd va cd do ddc cao hon so vdi sdng Liiy, ban che nude bien chay vao,
trong khi tren sdng Liiy nude bien van ed the lin siu vio ndi ddng, xam nhip man vao nude
ngim.
- Ciu tnic dja chit vi thinh phan trim tieh ed vai trd gdp phan cho viec duy tri man trong
cac ting chua nude.
- Nude ngim trong pham vi thung liing sdng Liiy cd bieu hien "man hon" ngay trong miia
mua, do trong thdi gian niy nude sdng tir thugng ngudn khdng dii khi nang day liii nude
bien, din den xim nhip ngang, thim qua bd.
- Thdi gian duy tri nude bien xam nhip theo sdng vao ndi ddng cing lau, cang lim ting
khi ning nhiem man eua cic ting ehiia nude.
- Khi so sinh 2 thdi diem 1988 vi 2005, thi do man ciia cac tang chua nude cd phin ting
cao bon, song pham vi phin bd nude man lai giim ding ke so vdi trudc day.
Ldi cam on
Tap the tic gii xin cim on Vien Khoa bgc va Cdng nghe Viet Nam da cip kinh phi trang
bi cic thilt bj dja vit ly (SAS 4000, Terralok Mark 6 24 kenh) va Sd Khoa hgc va Cdng nghe
tinh Binh Thuin di ho trg kinh phi de thyc hien cdng trinh nay.
TAI LIEU THAM KHAO:
1. Nguyen Thanh Himg vi nnk. Dieu tra dinh gii tinh hinh nhiem man ngudn nude viing
ven bien Bac Binh va Tuy Phong - Tinh Binh Thuan. Bao cao tdng kit dl tai - Sd
KH&CN tinh Binh Thuin (2008).
2. Chieh-Hou Yang, Lun-Tao Tong, Ching-Feng Huang, Combined Application of dc
and TEM to Sea-water Intrusion Mapping. Geophysics, Vol.64, No.2, March-April
1999, p. 417-425.
3. Dao Xuin Hgc vi nnk., Nghien cim cic giii phip giim nhe thien tai ban ban d cac
tinh duyen hii miln Trung (tir Hi Tinh din Binh Thuan). D I tii Khoa hoc cip Nha
nude, Bd KHCN&MT vi Bd NN&PTNT, thing 07 / 2001.

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