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 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 phuang thirc van hdnh cua cdc cdng trinh hd chira nuac tir phia thugng luii; su gia tdng ciia muc nuac biin ; vd 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, 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 huyen ven bien eua tinh Binh Thuin (Hinh 1), cd dieu kien nudi tdm tren cit phat trien hoac lim rudng mudi, Diy la mdt nhirng loai hinh su dung dit cd tic ddng den 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, ning ding eao eiia myc nude bien, eiing tao dieu kien cho hien tugng xim nhip man tir bien vio siu ndi ddng Pham vi chju tic ddng eua man, tip trung d phin 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 ^••^^•-^•"•^l \ NINH THU.4N L.4M D6NG "^ T U Y PHO^fCJ r?G~ BXC BINH \ ^ I '.^y.l.^l•^n [ H A M THU>VN BAC ^ R^^ LM5» vtt'c sort^ hu'^ L6liboan Litu vUc song Long Song 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, 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 dac mirc nude, luu lugng, man eua sdng Luy (thing IX nim 2005) 275 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 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, dae eic yeu td dja chit thiiy vin khie - lfng dung md hinh HYDROGIS de xem xet mue xim nhip man ting nude mat - l/ng dung md hinh ddng chiy MOD-FLOW de xem xet ning xim nhip man ting nude ngim - Sir dung thilt bj dja vat ly, siu dien, inh dien (SAS 4000), dja chin (Tenalok Mark 6, 24 kenh), gim dgt : (i) Dgt (tir ngiy 28 / 03 / 2005 din ngiy 16 / 04 / 2005) : Do sau dien tren tuyin theo phuong thing gdc vdi bd bien vi phin bd chu yeu d phin ven biln eua huyen Bac Binh - Tuy Phong Tdng cdng cd 68 diem do, ed tdng chieu dii 60 km ; (ii) Dgt (tir ngiy 24 / 06 / 2005 din ngiy 28 / 06 / 2005) : Do siu dien tai 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 dia vit ly ; (iii) Dgt (tir ngiy 11 / 08 / 2005 den ngiy 18 / 08 / 2005) : Do dja chin khiic xa tuyen gin bien : Phan Ri (1,1 km) vi Lien Huong (1,1 km) ; (iv) Dgt (tir ngiy 18 / 12 / 2005 din ngiy 23 / 12 / 2005): Do inh dien trirng vdi tuyin dja chin vi siu dien eanh Id khoan trude dd ; sau dien tuyen Lien Huong vi Phan Ri III KET QUA NGHIEN ClTU VA THAO LUAN + Dua tren cic ket qui khio sit, khoan, dac, phin tich miu vi cac tu lieu nghien cim trude dd [1], ed the nhin thay: Tren luu vyc sdng huyen Tuy Phong, Bic Binh dang dien nhirng thay ddi manh me 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 viee tich nude phye vy tudi tieu Tuy viy, ddc long sdng d diy li yeu td quyet djnh chieu dai xam nhip man tdi da, vi dd viec quan ly van hanh co che xi nude (lii) ciia cic hd chira phia thugng ngudn ddng vai trd quan trgng viee lim giim ning xim nhap cua nude bien + Ket qui 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 - den -12 m 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 tao trim tich: (i) Nude man cac trim tich sdng tudi Holocen (aQ2^"^), Id dien tren bl mat, cich bd biln khoing 4,5 km; (ii) Nude man 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 trim tieh biln tudng viing vinh - ven bd (mQi ), phin bd hi bd bien trd vio din khoang km Ting chira nude Id tren mat phia bd bien, diy trung binh khoang 44 m va mdng din ve phia dit liin Phan tren mat, nude cd dg man kem hon phin dudi sau - Tuyen siu dien cit ngang qua thung liing sdng Liiy, ciirig cho thiy cd 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 > km; (ii) Trong trim tieh bien tudng vung vjnh - ven bd (mbQi ), phan bd siu ben dit liin din cich bien khoing km 276 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] khao sit eic ting chira nude 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 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 km d khu vyc sdng Liiy - Ranh gidi nude man ciia ting chira nude Holocen, chii yeu trim tieh sdng (aQ2^) va trim tich sdng bien (amQ2'"^), Id dien tren be mat vi cich bd bien > 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 < 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 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 phire tap khoing thdi gian giiia nim 1988 vi nim 2005 Tuy nhien, cd the thiy man ciia nude dudi dit ting eao hon, tip trung d hai khu vyc li luu sdng Liiy vi sdng Ldng Sdng, 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 ning xim nhip vio cic ting chira nude ven bien + De lim giim nhe ning nhiem man, ngoii cie giii phip da cd de cap 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 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 luu eic sdng Liiy, sdng Ldng Sdng khdng ldn, chieu dii xam nhap man chi khoing km (sdng Ldy) Ldng sdng khdng siu, bd sdng khdng cao, 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 thdi ky nude kem chi cin mdt luu lugng khoing 10 m/s li ed the diy man xudng xa - km phia luu (sdng Liiy), giim bdt man 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 luu huyen Bic Binh, Tuy Phong 277 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 miia khd, nude sdng can kiet khien nude biln theo cac sdng, kenh din vio sau ndi ddng giy man - Xim nhip man vio viing cua sdng Liiy, sdng Ldng Sdng se nghiem trgng hon vifc liy nude d thugng luu phuc vu tudi, xay dyng cic hd Tuy viy, man khdng len xa bon dieu kien dja hinh (do die ldng sdng) khdng che, ben sdng ciing khdng cd cic viing triing thip cd nguy eo ngap man Mirc nghiem trgng cua xim nhap man trudng hgp niy chi xiy theo hinh thirc: man len sdm hon, 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, cira sdng Ldng Sdng bj lip vio miia khd va cd ddc cao hon so vdi sdng Liiy, ban che nude bien chay vao, 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 tri man cac ting chua nude - Nude ngim pham vi thung liing sdng Liiy cd bieu hien "man hon" miia mua, thdi gian niy nude sdng tir thugng ngudn khdng dii nang day liii nude bien, din den xim nhip ngang, thim qua bd - Thdi gian tri nude bien xam nhip theo sdng vao ndi ddng cing lau, cang lim ting ning nhiem man eua cic ting ehiia nude - Khi so sinh thdi diem 1988 vi 2005, thi 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 24 kenh) va Sd Khoa hgc va Cdng nghe tinh Binh Thuin di ho trg kinh phi de thyc hien cdng trinh TAI LIEU THAM KHAO: 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) 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 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 278