JOURNAL OF SCIENCE OF HNUE DOI 10.18173/2354-1059.2017-0020 NatuialSci 2017, Vol 62, No. 3, pp 160-170
This paper is available online al http;//stdb hnuc.edu.vn
KHAI THAC BEN VUNG TAI NGUYEN Nu6C DU6l DAT VUNG VEN BIEN QUANG TRI TRONG BOI CANH BIEN DOI KHI HAU
VA MUC NU6C BIEN DANG
N g u y e n S a n ' va T o n g P h u c Tuan^
Phong Tdi nguyen nu&c du&i ddt. Viin Dia Li. Vien Khoa hgc vd Cong nghi Viet Nam Phdng Dia mgo - Dia dpng luc Viin Dia Li, Viin Khoa hoc vd Cdng nghi Viet Nam
Tom tat: Bien doi khi hau va muc nudc bien dang gay ra nhieu thach thflc trong quan li va khai thac tai nguyen nudc dudi. Quang Tri c6 viing ven bien vdi vai tro dac biet quan trong trong phat trien kmh te xa hpi va viec danh gia tai nguyen mot each toan dien nham to chuc khai thac ben virng trong bdi canh myc nudc bien dang duac dat ra ia cap thiet. Sfl dung mo hinh Visual ModFlow xac dinh dugc luu lugng khai thac nudc ben vung cua vung nghien cflu la 77600 ni /ngay dem. tai 2 cym gieng khai thac va xac dmh myc nudc ha Ihap d lung gieng khoan sau moi 3 nam khai thac trong chu ki 27 nam. Lan dau lien de tai da ti'nh den anh huang cua bien doi khi hau den kha nang khai thac ben vflng tai nguyen nirdc dudi dat.
Tirkhda: Trfl luang khai thac (Qkt), nudc dudi dat, dia chat thuy van.
1. Mofdau
Vflng ven bien Quing Tri gdm 4 huyen ven bien (VTnh Linh, Gio Linh, Tneu Phong, Hai Lang) va thanh phd Quang Tri, dugc gidi han ve phia Ddng ben Bien Ddng, phia T i y Ii vflng go ddi, phia Nam l i tinh Thfla TMen - Hue, pMa Bac la tinh Quang Binh (Hinh 1). Day la tryc ddng lire phit trien kinh te - chiMi trj - xa hdi quan trpng cfla tinh, ngi tap trung cac dd thi, khu dan cu, ca sd s i n xuat, ha t i n g dich vy Men [1], nhung cung la vung chiu i n h hudng nang ne nhat cua bien ddi kM h | u va m y c nude bien dang [2], NgMen cflru nudc dudi dat (NDD) vflng ven bien Quing Tri da cd gdm: Tim kiem N D D Tay Ddng Ha, chu bien Le Quang Manh, 1990. Tham dd NDD viing Gio Linh, chfl bien Nguyen Trudng Giang, 1995. Dac diem dia ehat thuy van vflng thi xa Dong Ha, Nguyen Trudng Giang 1999. Tai nguyen N D D tinh Quang Tri, Doan Van C i n h va Le Tien Dflng, 2002. Quy hoach quan li, khai thac sfl dung va bao ve tai nguyen NDD mien ddng bing linh Quang Tri, chu bien Nguyen Thanh Son, 2008.
Cac nghien ciiu trudc nam 2000, su dung chfl yeu p h u a n g phap khoan tuy dugc xem l i chinh x i c nhat nhung cd nhugc diem ve thdi gian va kinh pM thuc hien, cflng nhu khd khan trong dieu cMnh k h i nang khai thae cho cac kich ban phit trien kinh te xa hdi. Nhung nghien cflu sau nam 2000 da flng dung md hinh Visual ModFlow trong tinh loan, nhung cdn cd mdt sd v i n de can de c$p: Doan Van Canh (2002), chua dnh d i n lac ddng cfla bien ddi kM hau trong md hinh dnh loan;
Nguyen Thanh Son (2008), mdi linh Iru lugng dpng ty nhien, chua litfli ldi trfl lugng khai thac.
Ngay nhan bai; 18/1 /2017. Ngay nhan dang: 27/2/2017.
Tac gia lien he: Nguyen Son, e-mail; [email protected]
Khai thdc ben virng tdi nguyen nu&c dudi ddt viing ven bien QudngTii trong boi cdnh bien doi khi hdu...
Thdng sd khi hau duac sfl dyng de danh gii tru lugng khai thac nudc dudi dat. Theo kich bin bien ddi khi hau, lugng mua hang nam cfla (^uang Tri trong cac thdi dtem nam 2020, 2030, 2040 lang 1,6%, 2,4%, 3,3% so vdi thdi ki 1980 - 1999 [2]. Vdi lugng mua trung binh nam cfla cic tram kM tuang vung ven bien Quang Tri kit hap vdi he sd tang lugng mua do biln doi khi hiu, cho phep xac dinh lugng mua vung ven bien sau 27 nam ke rtr nam 2016 li 2400 - 2500 mm/nam.
Lupng bdc hai 1500 - 1600 mm/nam.
Dac diem dia Mnh lu nMen vi nhan lic Vung ven bien Quang Tri gop phin lam gia lang lac dpng lieu cyc efla BDKH. Cac dii cat ven bien ndi cao sS bj xdi mdn do myc nudc biln dang, lam giam ngudn tai nguyen nudc ting khong ip. He Ihong dudng ven bien cit qua cac doi cit cflng gop phin lim suy giam ngudn nudc cdn cit He thdng dudng bp, dudng sit tren be mat dong bing cflng ty bien minh thinh nhflng de nhan lao, lac ddng phflc tap vao ngudn tii nguyen nudc, ma trudc lien la nudc khdng ap. Tinh phin minh trong phat irien lanh thd lam suy giam kha nang ty lim sach cfla tu nMen ngay cing lam suy thoai han ngudn nudc khdng ip dugc sfl dyng liu ddi trong khu vue. Them vio do, die diem cac sdng vung ven bien Quang Tri cd lugng ddng chiy bien ddi manh gifla cic mua cflng nhu gifla cac nam nen it cd khi nang dip flng nhu cau phit tnen cfla khu vyc.
Nhu vay, Ihyc tien phat trien trong bdi eanh bien ddi khi h^u va myc nude bien dang cho thay ngudn nudc khdng ap tai ven bien Quing Tri chiu sue ep manh, can tMet phai dm kiem giai phap ben vung d cic ting chfla nudc khac, Nghien ciiu lan dau den xac dinh trfl luang khai Ihac ben viSng cd dnh den anh hudng cfla bien ddi khi hau Ihdng qua lugng mua va cap dp chi tiet d ludi dnh toin trong md hinh dat tdi muc cao nhat so vdi nhflng ngMen cflu tnrdc day (50 m x 50 m), 2. Noi dung nghien cihi
2.1. Phu-gng phap nghien cihi
Viec sfl dung md hinh Visual ModFlow trong ngMen cflu NDD chua thyc su phd bien d nudc ta, bdi vay trudc khi ip dung md Mnh, chung tdi gidi thieu tdng quit ve ban chit vi linh ning md hinh, lim eo sd ap dung trong ngMen cfln. Nhflng thdng sd kM hiu dau vao md hinh dugc trich xuat theo kich bin bien ddi khi hau; cac thdng sd Meu chinh md Mnh dua iren cac Id khoan da cd cflng nhu quan trie cfla de tai
Bp phin mim Visual Modflow bao gdm ba phan mem chinh (Modflow, ModPath, MT3D)vi nhieu md-dun phu trg [3]. Phin mem Modflow dflng de tinh toin trfl lugng, chil lupng va phin bd ddng chiy ngam; Phin mim ModPath cd chuc nang tinh hudng ya tie dp cic dudng ddng khi nd van ddng xuyen qua he thdng cac Idp t:hfla nudc; Phin mem MT3D phdi hgp vdi Modflow cd chflc nang tinh loan qui yinh khulch tin va van chuyin cflng cic phin flng hoi hpc khac nhau cfla cac vat chit hoi tan trong he thdng ddng chiy ngam.
Trong nghien cfln niy sfl dung phin mem Modflow
Thyc chit phin mim ModFlow la giai phuong trinh dao him rieng vl su bien tMen dp cao myc nudc dudi dat [3]:
dx\"dx) dy{"dy) dz\"dz) dt (I) trotigdd: T,s', Tyy , 1.^ li cic he sd dan nudc theo phuang x, y va z Chilu z la chilu thing dflng,
h la cdt cao myc nudc l^i vi tri (x, y, z) d Ihdi dilm t, W la cac gia Iri bd cap hay thoil cfla nudc NDD l?i Vl tri (x, y, z) d Ihdi diem I. W = W(x, y, z, I) la ham sd phy thudc Ihdi gian t vi khdng gian (x, y, z), Ss la h? so nhi nudc, Ss = Ss(x, y. z), K,,, = Kx,(x, y. z), Kyy = Kyy(x, y, z), Ki; = Ki^x, y, z) cic ham phy thudc vao vi tri khdng gian x, y, z.
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Nguyin Son va T6ng Phuc Tuin
De giai phuang trinh (I), phii tim ham so h(x, y, z.t) thoa man (1) va thoa man cac dieu kien bien. Sy bien ddng cfla gia tri h theo thdi gian xae dinh bin eliit ddng chay, tfl dd tinh duac trfl lirgng ldp chua nude va cac hudng ddng chiy. Viee dm ldi giii giai tich h(x,y,z,l)cs^z.
phuang trinh (1) chi thyc hien dugc khi miln nghien ciru dugc md phdng tudng minh bing ham toan hpc. Tuy nhien trong thyc te, mien tham cd dieu kien rit phflc lap, do dd ngudi ta huge phai giai bing cac phuang phap gin dung Cd nMlu phuang phap giii phuang trinh (1), va trong md Mnh Modflow su dung phuang phip sai phin hun han theo 3 CMIU [4].
Cac dilu kien bien li tham sd khdng thi tMlu trong linh loan va dugc chia Ihanh 3 nhdm:
nhdm bien theo phuang ngang (cic bien xung quanh efla mien tinh toin chfl yeu la cic bien mo ti su gia nhap cfla eac ddng ngam tu eac vung lin can); nhdm bien "ndi" tren be mat (ddi lug^
va dieu kien cap/thoat nudc dudi dit; mye nudc khdng ddi cua bien, hd ldn; cic gieng hflt hcac ep nude); nhdm bien theo phuang dflng lien quan tdi cae yeu td kM tupng (lugng bdc thoit hoi nudc va bd cap).
2.2. Ket qua nghien cihi danh gia trii lirrrng khai thac nu'd^c dvoi dat
Danh gia tru lugng khai thac bang phuang phap md Mnh sd dua Iren co sd giii phu'ong trinh vi phan, sfl dyng phuang phip sai phin hun han Iheo 3 cMeu trong mdi trudng 16 hdng khdng lien tuc. Hien nay cd nMeu chuang trinh may tinh dugc viel dl gii quylt van dl nay, d day chung tdi sfl dung phim mim MODFLOW cfla Cdng ti Waterloo Hydrogeologic Hoa Ky di kem vdi bg phin mem Visual ModFlow. Ndi dung ngMen cflu dugc thyc Men qua eac budc: md hinh hoa Uudng tham, Meu cMnh md Mnh phfl hgp vdi he thdng gieng klioan da cd tfl cic de tai trudc day va cua de lii [5] vi dua ra ket qua cua md hinh.
2.2.1. Mo hinh hoa trudng tham
Tren co sd tdng hgp, phin tich tai lieu dieu Ira tham dd dia ehat, dia chil thuy van linh Quang Tri tfl trudc den nay chung ldi lien hinh md Mnh hoa dieu kien dia chit thuy van vflng nghien cuu nhu sau.
* Tren binh do
Vflng ngMen cuu dugc gidi han pM'a Ddng li bien, phia Tiy li gd ddi, dia Mnh eo xu hudng ddc ve phia bien. Phin trung tim dong bang la nai phat trien cfla hai he thdng sdng, he thdng song Ben Hii va he thdng sdng Quang Tri. Cic ting chua nude va cich nudc deu cd xu hudng ddc ve pMa bifin, vflng nghien cflu dugc sa do hoa nhu sau.
Bien gidi phia Ddng tang chfla nudc tiep sflc vdi bien dugc md hinh hoi la bien loai I vdi H = const. Cdt cao myc nudc tren bien li H = 0 ra.
O phia Tay, nai dia Mnh nfli cao, cac tang chfla nudc Id hdng gdi len lang chua nudc khe nut khdng ddng deu hp tang Long Dai dugc md Mnh hoa thanh bien loai II. Bien cd the li Q = 0 hoic Q = const, se dugc chinh xac hoa bang viec giii bii loan ngugc tren md hinh.
Hp thdng sdng Bin Hai va Quing Tri se dugc so do hoa thanh bien loai 1 hoac bien loai III tuy thugc vao kel qua chinh li bai loan ngugc.
* Tren mat cdt
Mat cit ngMSn cuu dugc md hinh hoa thanh he Ihong gdm 5 Idfp chfla nudc va each nudc [1].
Lgp 1 la tang chua nudc Holocen bao gdm loan bd tram tich phan bd khdng lien tuc.
Thanh phan thach hpc la cat thach anh mau xam trang, xim vang, cil bpt ngudn gdc bien, sdi^
sdng bien, gid bien. Chieu diy tfl 2,5 den 20 m, Irung binh 12 m. He sd thim bien ddi tfl 0,47 den 16,31 m/ng, trung binh 5,22 m/ng. He sd Mia nudc trpng Iyc 0,005.
Lap 2 la ldp cich nude ylu tram dch Holocen phan bd khdng lien tuc. Thinh phan gdm chu ylu la set, set bdt miu vang, cat bpt miu xam den ngudn gdc sdng bien amQ2*"\ amQz'-
Khai thdc ben vimg ldi nguyen nirdc du&i ddt vimg ven Men QudngTri irong boi cdnh bien dot khi hgu..
Chieu d i y thay ddi 10 - 20 m, trung binh i 5 m , he sd tham r i t nhd t u 0.0001 - 0,001 m/ng, he sd nha nudc 0,0001.
Ldp 3 la tang chfla nude gdm trim tich thdng Pleistoeen phan bd lien lue tren loan vflng nghien eflu. Thanh phan thach hpc gdm eit thach anh m i u x i m trang, xam den, cit lan san m i u ving, eugi sdi. cat set ngudn gdc sdng, bien, sdng bien m Q / , mQt', aQi, aQi' va amQi'. C M I U day tfl 1 0 - 2 5 m, hesd thim thay ddi lfl2,04-30.95 m/ng, trungbinh 9,2 m/ng, he so nha nude 0.0085.
Ldp 4 la lang chua nudc tram tich Neogen phan bd khdng lien tuc. Thanh phin thach hpe gdm c i t l i n set, cit hat thd mau x i m trang, xam tro, san sdi. O trung tam cd cMeu day ldn keo dai ra bien, pMa N a m v i Bac tang chfla nudc cd cMeu day rat mdng hoac bi b i o mdn toin bd. CMeu day bien ddi tfl 10 den 60 m. H e s d Iham Ihay ddi tfl 8,06 - 3 7 , 6 9 m/ng, trungbinh 15,53 m/ng, he sd nha nude 0,03.
Ldp 5 lot dudi l i n g chfla nudc Neogen la tram tich O3 - S| he l i n g Long Dai Thanh p h i n thach hgc la cat ket, bdt kel chfla nude khdng lien tuc, phy thudc v i o sy phat trien eac he thdng dut gay. Trong gidi han dong bang chua cd Id khoan n i o gap nudc trong lang nay nen dugc so dd hoi thinh ldp each nudc.
* Lu&i sai phdn
Sfl dung ludi sai phin dang d vudng 250 x 250 m vdi 5 ludi tuang flng 5 Idp theo mat cat dung, phfl loan bd dien lich vung nghien cuu khoang 1200 km^. Nhiing vi tri can nghien cfl'u ehi del han duae sfl dyng ludi nhd han, kich thude 50 x 50 m.
* Yiu td dja hinh
C i c yeu td ve dia Mnh gdm cdt cao be m|Lt dia Mnh, cdt cao day cac ldp tang chfla nudc dugc lay Iren ca sd ban dd dia Mnh d le 1:50000 he toa dd va cao do n h i nudc, do cao va toa dp cac Id khoan tham dd dia chit, dia chit thuy van, cfla c i c p h u a n g an trudc day.
* Yiu to khi tugng, thuy vdn
G i i tri bd cap cua lugng mua v i bdc hai lay theo lai lieu quan trie cfla tram khi tugng thuy van Ddng Ha. Cac gia tri dua vao mo Mnh d u a c lay theo so lieu trung binh 41 nam (1973-2013) cfla cac ylu to klii lugng, vdi gia tri tdng lugng mua trung binh nam la 2366,7 mm/iiam; lugng boc hai trung binh nam 1303,9mm/nam [2]. Myc nudc tren cac song dupc l i y iheo sd lieu quan trie cfla cac tr^m thuy van B i n Hai, Ddng Ha, Thach Han, Q u i n g Tri [3].
Hinh 1. Sa do hinh chieu bdng mgng sdng suoi vd hp so tham K viing nghien ciru
Nguyen San va Tong Phuc Tuin
Mat cat nghien ciiu dugc md Mnh hoa thanh he thong gdm 5 ldp chua nudc va each nudc (Hinh 2 vi Hinh 3). Hp sd thim vi he sd nha nudc dugc lay tu so lieu cua Bio cao tim kiem NDD vung Hd Xi, Ddng Hi, Tay Ddng Hi, Gio Linh [6-8].
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Hlnh 3. Mat cdt ngang (B~B) trin mo hinh theo he sd tham K 2.2.2. Hieu chinh md hinh
Trudc kM dy bao trfl lugng khai thac NDD, chung ldi tiln hanh giii bai loan ngugc dS cMnh xic hoa cac ihdng so dia chit thfly van da dugc xac djnh bing thi ngMem thim d ngoai trdi, kiem tra cac bien va dieu kien bien da cho.
Do dieu Id^n tai lieu khong cho phep, d day ehung tdi chi lien hinh giii bii loan ngupc on dinh de cMnh li he sd thim vi dieu kien bien. He sd nhi nude dugc lay theo tai lieu hut nudc thi nghiem chum cfla phuang an tham dia chat thuy van trudc day, ddng thdi do vung n^ien cflu khdng cd mang ludi quan trie ddng thai muc NDD, nen myc nudc dua vao md hinh de chinh li chung tdi lay iheo myc nudc tinh do dugc tai cac Io khoan tham dd dia chat, dia chil thuy van lir cac phuong an' thSm dd trudc diy [9, 10] va lay theo ket qua cua dot khao sal thyc dia mdi nhat nam 2016 cfla dl tai [5]. Sau dd dya vio cdt cao be mgt dia Mnh tfl do ti'nh chuyin lu myc nudc linh sang cdt cao muc nudc cua lang chfla nuoc de chinh li.
Bii loan ngugc dn djnh dugc giai bing phuang phap Ihu din. Ban diu dua cac sd li§u dau vao gom he sd thim, lugng mua, bdc hai vi dieu ki?n bien. Sau dd lien hanh chay rad hinh de cho ra kit qua phan bd mue nude. So sinh myc nude nhin dugc tren md Mnh vdi mye nude quan 164
Khai thdc ben virng tdi nguyen nu&c duoi ddt vimg ven bien QudngTri Irong bdi cdnh bien ddi khi hdu...
trie dugc d ngopi thyc te, nlu sai sd gifla md Mnh voi thyc tl vugt qui gia tri cho phep dii lai lap l?i tu dau, bing each thay ddi gia tri eic thdng sd tham vi dieu kien bien. Qua trinh lap di lap lai nMeu lin den kM nao sai sd gifla myc nudc tren md Mnh va thuc te dat dupc gii in cho phep thi dling lai vi ket thflc bai toan. Trong qua trinh giii bai loan ngugc dn dinh, bien phia Tay dugc gan eho dieu kien Q = const.
Nghien ciiu nay da sfl dyng 20 lo khoan de hieu ehinh. Do cic Id khoan nay phii phan bd theo phuong ngang vi theo phuang thing dflng tren eac ling chua nudc vi nguon so lieu ed h^n nen khdng lay dugc theo cflng mdt thdi diem, d cung mpt bao cao dm kilm NDD ma lay theo cac bao cao dm kiem NDD cfla cic phuang in tham dd trudc diy [9, 10] va liy theo ket qui cua dpi khao sit thyc dja mdi nhat nam 2016 efla dl tii [5]. Bd thdng sd cin M?u cMnh bao gdm he sd ihim iheo phuang ngang va phuang Ihang dflng. Myc nudc linh loan cua rad Mnh duge so sanh vdi lii lieu thyc do ve muc nude trong cac lo khoan. Kit qua tinh toan dugc trinh bay tren (Bing l)va(Hinh5), vdi sai sd RMS la 10.83 %, dat yeu ciu.
Bdng 1. Muc nu&c ngam trong Id khoan quan sdt vd Id khoan tinh todn stt
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
Ki hieu lo khoan
LK604 LK610 LK404 LK608 LK605 LK405 LK423 LK424 LK429 IIIB IVB VB QT3 QTll QT LK432
QT14 VA UA IIIA
T^a dfi lo khoan X
716972 713245 710490 724179 716725 725194 732691 739057 728761 744423 748004 739188 718821 722461 723577 726376 726695 741646 742980 745677
V 1894003 1888710 1891436 1884229 1880314 1870163 1863108 1858975 1855916 1852189 1854321 1853189 1869858 1871802 1871584 1873339 1869090 1854313 1848571 1851689
L 3 khoan quan sat (m)
0.80 1.75 1.90 1.00 2.00 3.00 2.10 2.00 4.00 2.20 1.70 3.00 3.00 2.20 2.10 2.20 2.10 2.10 3.00 2.00
Lo khoan tfnh toan (m)
8.50 1.80 1.95 1.10 1.70 3.50 1.70 2.40 3.54 2.35 1.40 2.60 3.30 2.00 1.80 2.50 2.45 2.40 2.75 2.10
Nguyen San va Tong Phflc Tuin Gii tri chenh lech gidi han cho phep dugc xic dinh tfl cic sai sd:
- Cac sai sd tu sd lieu nhap vao md hinh do do bang may GPS cam tay; dp eao mat dat, dp cao muc nudc, dp cao mii, diy cflng nhu chieu diy tang chfla nudc, he sd thim nam ngang va thing dflng. lay sai sd = 0,3 m;
- Cac sai sd trong tinh loin cac IhaMi phan can bang nudc do sai sd tfl lupng mua, lugng hoc hai, lugng nudc cung cap Ifl sdng, dp cao myc nudc gin d cac bien lay - 0,2m.
Vdi nhan xet nhu Iren thi gii tri chenh lech cho phep la ± 0,5m.
Calculated vs. Obserued Head
Hinh 5. Sai so mirc nu&c tinh todn trong cdc Id khoan quan trdc 2.2.3. Ket qua danh gia tru luong khai thac nirdc dudi dat
Sfl dung bien lugng mua, bdc hai theo kich bin bien ddi kM hiu, hieu cMnh md hinh dya theo lai lieu lo khoan da ed kll hgp vdi bd sung cua dl tai, va thay ddi lu 3 cum lo khoan (Doin Van Cinh, 2002) sang 2 cum Id khoan cho Ihay ket qua ranh gidi xim nhip man dugc giam di trung binh tfl 200 - 500 m, rat cd y nghta trong bdi cinh muc' nudc bien dang. Cic kel qui cy the cfla md Mnh gdm:
* Bo tri cum Id khoan
Dua vio sy phin bd vi die diem lang chfla nudc trien vpng, dya vao dac diem phan bd^_
cu, dua vio nhu ciu sfl dung nudc cfla dia phuang, ling chua nudc Pleistoeen - Neogen dupe'lif^
thac bdi 2 bai gieng tip trung vdi cdng suit khai thae duge trinh bay trong Bang 2 va Hinh 6.
Stt 1 2
Bdng 2. Thiit ki khai thdc bdi giing Gio Linh vd Hdi Lang Ten bai gieng
Gio Linh Hai Lang
So luong LK khai thac
11 30
Cong suit khai thac mVneav
17600 60000
Khai thdc ben virng tdi nguyen nu&c du&i ddt viing ven bien QudngTri trong boi cdnh bien doi khi hdu...
Hinh 6. Sa do bo tri cdc bai gieng khai thdc trong tdng chua nu&c Pleistoeen - Neogen viing dong bdng tinh Qudng Trf
Nhu vay, mang ludi bd tri eic lo khoan khai thac tren bai gieng Gio Linh dugc gifl nguyen nhu bai gieng Men lai gdm 11 Id khoan khai thae (LKKT) dugc bd tri tren hai tuyen song song.
Khoang each giua cac LKXT va gifla cac tuyen LKKT li 500 - 700 m, vdi cdng suit khai thie giai doan dau la 17600 m^/ngay. Cae gieng khoan khai thie dugc ki Meu la G.
Bai gieng Hii Lang dugc bd tri mdi gdm 30 LKKT tren ba tuyen song song vdi true dudng tinh ip ehay gifla dong bing. Khoing each giiia cic LKKT va giua cac tuyen LKKT la 900 - 1000 m.
Cdng suit khai thie efla bai gieng niy li 60000 m'/ngay. Cic gieng khoan khai thac dupc ki hieu la Q (Hinh 6).
* Banh gid biin dgng muc nudc
Kit qua du bao tru lugng khai thie vi bien dpng cdt cao muc nudc ddng trong thdi doan 27 nam vdi cac ehu ki 3 nam dugc yinh biy trong Bang 3 vi bien ddng cdt cao muc mudc dgng trong khdng gian lanh tho d cac thdi diem 12 va 27 nam Irong Hinh 7.
Bdng 3. Cot cao mffc nu&c dpng tinh todn trong cdc Id khoan khai thdc (tru&ng hgp biin Q = const)
'
SHLKGl G2 G3 G4 G5 G6
-im \agng (nV'ne)
1000 1700 1700 1700 1700 1700
c6[ cao rntrc nirdc dpng tinh loin (n) 3 nam
-1.61 -5.68 -5 68 -6.58 -6-58
^ 5 8 6 -3.76 -SIM -8.04 -8.90 -8.90 -6.75
9 mm -4.94 -9 24 -9 24 -10 05 -10.05 -7.84
12 nam -5 65 -9.94 -9 94 -10-73 -10.73 -8.47
„n.™
-6 09 -1038 -10,38 - I I 14 - I I 14 -8 85
IS nam -6 38 -10,65 -10 65 -1140 -1140 -9 10
21 nam -6 56 -10 82 -1082 -11 57 - I I 57 -9 25
24 -6.69 -10.94 -10,94 -11.68 -11.68 -9.36
27 nam -6.78 -tl.02 -11,02 -11-76 -11,76 -9 43
C6l cao MNcho phep -8.19 -16,33 -16.33 -20,18 -20.18 -23,15
Nguyen San va Tdng Phuc Tuin
SHLK
G7 G8 G9 GIO G i l Q1 02 Q3 Q4 Q5 Q6 Q7 Q8 Q9 QIO Q l l Q12 QI3 014 015 016 017 QI8 019 020 Q2I 022 023 Q24 025 Q26 Q27 028 029 030
.uu lugng Im'/ng)
1500 1500 1700 1700 1700 • 2000 2000 2000 2000 2000 2000 2000 2000 2000 2000 2000 2(100 2010 2000 2000 2000 2000 2000 2000 2000 2000 2000 2000 2000 2000 2000 2000 2000 2000 2000
C6l cao myc nudc dSng tfnh loan (m) 3 nam
-5 58 -5 58 -6-26 -6 26 4.09 -16 97 -15.01 -12 97 -11.83 -1143 - I I 37 - I I 90 -13.49 -15.81 -18,48 -17 73 -1535 -13 49 -12.77 -11.45 -11 57 -11,62 -12 82 -14 86 -16,99 -17,27 -15 94 -14.38 -I3,5fi -12-70 -12.64 -13 I I -1435 -16.36 -1840
6 -7.79 -7 79 -8-45 -8.45 -6,14 -13.37 -12,13 -1036 -9.18 -8.70 -8 54 -9 19 -10.88 -12 80 -15 00 -14 72 -13 80 -1223 -10.16 -8.74 -8 73 -8,95 -11 30 -12.93 -14 02 -13.62 -13.04
• 11.18 -9,36 -8 57 -SS4 -9,69 - U 31 -1330 -14 63
9 nam -8.95 -8 95 -9.56 -9.56 -7 19 - I t 82 -11.25
• -9,98 -8.75 -7 84 -7 69 -8 78 -10.45 -11.70 -13 24 -13 62 -13 36 -12 24 -9,73 -8,33 -7 88 -8,32 -11.31 -12.27 -12.69 -12 11 -11.94 -10.31 -8.56 -7 06 -7 77 -8,84 -10 67 -12.21 -13,09
12 nam -9.64 -9.64 -1022 -10,22 -7.80 -11.12 -1102 -10,23 -9 12 -8.06 -8 06 -9,30 -10.58 - l l 35 -12 58 -13 20 -13 29 -1261 -10,07 -8.85 -8 25 -8,81 -11.59 -12.16 -12.12 -11 45 -1147 -10.15 -8,49 -7 11 -7 94 -9.12 -10 83 -1190 -12 42
, 5 * -10,07 -10.07 -10 62 -10 62 -8,18 -10.67 -10.94 -10 47 -9 60 -8.5i -8 60 -9,86 -10 84 - I t 31 -12 22 -12 95 -13 29 -12 98 -10,57 -9-38 -8.75 -9 44 -11 83 -12-16 -11.75 - I t 03 -11,20 -I0,!0 -8,69 -7 54 -8.46 -9 64 -11 12 -11.79 -11,97
18 nam -10 34 -10 34 -10.88 -10.88 -8.42 -1045 -11.02 -10 76 -10 18 -9 34 -9 46 -10.51 -11.28 -11.46 -12 17 -12 87 -13.45 -13 43 -11.16 -10-15 -9 57 -10.28 -12.19 -12-31 -11.61 -10 81 - t l 10 -10 27.
-9 31 -8 37 -9.29 -10.33 -11.60 -11.93 -11.78
21 nam -10.52 -10 52 -11 05 -1105
-8 58 -1037 -11 19 -11.10 -10 77 -to IS -10.30 -1129 -11.71 -11-63 -12,17 -12.87 -13-70 -13 94 -11,75 -11,00 -10 50 -n.05 -12 62 -12.48 -11.61 -1073 -\i 02 -10.44
-9 90 -9 22 -10.14 -11.01 -12 02 -12.10 -11.70
24 nam -1063 -10 63 -11 16 - I t 16
-8 68 -10 39 -11 37 -11,49 -11 44 -11.07 -11 19 -11.97 -12.17 -11,87 -12,20 -12.87 -13 96 -14.42 -12.36 -11.79 -11.37 -11.80 -13.02 -12,66 -11.61 -10 72 -11.10 -10.78 -10,57 -10.11 -11.03 -11.69 -1248 -12.40 -11,72
27 nam -1072 -10 72 -11 24 -11,24 -8 76 -10 46 -1157 -11,88 -12.09 -11.94 -12 06 -12 64
•12.65 -12.15 -12 29 -12,97 -14 24 -14 911 -12,95 -1258 -12.22 -1254 -13,44 -12 88 -1168 -10 74 - I I 23 -11 19 -11.24 -10.98 -11.87 -12.34 -12,94 -12 73 -11.79
est CBO MNcho
phep -13.77 -13.77 -23-15 -23,15 -21,50 -20 00 -19 50 -19 30 -18,50 -17 JO -17-00
•17.50
•17.40 -16 50 -18 50 -17 50 -15 70 -15 80 -16 00 -16-50 -1700 -1750 -18 00 -18,50 -19.50 -19.00 -18.50 -17,00 -16 50 -1600 -15,80 -15 70 -15,60 -16.00 -18,50
Theo kll qua tinh toan dua ra d (Bang 3) va cic dudng ding cMeu sau ha diip myc nudc tfl (Hinh 7), cMeu sau ha thip mue nude tinh loan vio cac thdi diem khai thac, nhit la thdi diem khai thac lau nhat la sau 27 nim diu nhd han gia Iri cho phep Nhu v^y cong suit tMet kl cfla cae 16 khoan khai thie li cd ihl chip nh|n dupe lam trfl lupng khai thac nudc ben vung cho vung ngMen eflu,
Khai thdc hen viing idi vung lai nguyet •c dual dat viing ven bien QudngTri trong hdi canh bien doi khi hdu..
Hinh 7. Cdt cao mgc nuac dpng tinh todn sau 12 ndm (trdi) vd 27 ndm (phdi) khai thdc
3. Ket luan
Nude dudi dit tang chua Pleistoeen va Neogene li ngudn cd ihl dap ung nhu ciu phit triin kinh le x5 hdi efla Vflng ven bien Quang Tn, trong kM nudc cic tang khdng ap bi anh hudng ngay cing ning ne han cfla bien ddi khi hSu va myc nudc biSn ding.
Dinh gii trfl lugng khai thac thdng qua md hinh ModFlow la mot phugng phip edn kha mdi d nudc ta, tiep can vdi hudng nghien cfln hien nay tren the gidi. Md hinh dupc van hanh vdi cac bi&i khdng gian, ciu trflc dia chat vi die linh cac Idp dat da, cung nhu cae tham sd hieu chinh tu cic gieng khoan va cfla quan trie cua de tii [5], cflng vdi cac thdng tin ve nhu ciu sfl dung nudc hien lai eung nhu trong cic quy hoach la ca sd de xual bd tri 41 gieng khoan phin bo irong 2 cym tap Irung d Gio Linh va Hii Lang. Da xac djnh duge luu lugng khai thac nudc ben vflng cua vflng nghien ciiu li 77600 mVngiy dem. Theo kich bin nay, sau 27 nam, muc nudc d viing cap nudc van cdn d dp sau -10 m (chua den mii ting chfla nudc cd ip Pleistoeen}, Ii dam bio an loan cho lang chfla. Ddng thdi vdi kich ban tren, da xic dinh cot cao myc nude dpng d lung gieng khoan sau moi 3 nam khai thac trong chu ki 27 nam,
Trong nghien cuu niy. ylu td bien ddi klii hau mdi chi tinh ldi sy cM phdi cfla lupng mua.
My nhien anh hudng cua myc nudc bien ding cflng cin dugc danh gia do thieu hyt tai lipu ve mye bien ding va inh hudng cfla chflng toi cac ting chua nudc. Vi vay. nhimg ngMen cflu tiep theo can dupe trien khai nham danh gia loan dien anh hudng cua bien ddi khi hiu ldi kha ning khai ihac ben vflng nudc duoi dit vung ven bien.
L&i cdm an, Tliay mat tap the tic gia xin chan thanh cam an de tai "Nghien cuu ddnh gia tdi nguyen nuac du&i ddt vd xdc dinh cdc phuang dn khai thde hap li ddi ven bien linh Qudng Tri"
cap Vien han lam Khoa hgc vi Cdng nghe Viel Nam da ho irg chflng ldi thyc Men nghien cuu nay.