• KHOA HQC CONG NGHg '
ANH HU-dNG CUA CONG TRJNH THUY DIEN AN KHE - KANAK D^N SU" HA T H A P MUG NU-dC DU-dl D A T
d^VUNGHADU
Lft THJ THANH TAM Vien D/a If
Tom tit: Tren ca sa xii ly vd phdn tich cdc kit qud Men cd, trong bdi bdo ndy trinh bay su suy gidm trii luang nude dudi ddt a khu vuc hg du cua cong trinh do su dnh hudng ctia thuy dien Art Khi - Kanak vd hogt dpng chuyin nude tir sdng Ba sang sdng Cdn cua cdng trinh ndy (thdng qua su hg thdp muc nude cua cdc tang chtia nude). Kit qud nghien dm cho thdy, tic khi thity dien di vdo hoat ddng hdu hit muc nude trong cdc tdng chua nude dudi ddt a hg du cdng trinh deu bf ha thdp.
Diiu ndy da vd dang gdy khd khan khdng nhd cho cdng ddng dan cu trong sinh hogt hang ngdy vd cdc hogt dong sdn xuat
Tir khoa: s\r suy giam trii lugng nir6c dudi dat, thuy dien An Khe - Kanak
Abstract: Based on processing and analysing of the existing data, this paper presents the decline of groundwater reserves in the area behind the damdue to the impacts of An Khe - Kanak Hydropower Plantand the scheme which transfer water fromBa River to Con River (through the lowering of water table of the aquifers). The results _^offi this studyj/iow that from the time when An Khe - Kanak hydropower project was put into operationin June 2011 most of water tables of the aquifers in this area have been lowered. As a result, this has created considerable difficulties for communities in daily life and the production activities.
Keywords: decline of groundwater reserves. An Khe - Kanak hydropower project
1. MO DAU chinh thuc bi chan ddng de lam thuy dien An Thuy dien An Khe - Kanak nim a thucmg Khe - Kanak, s6ng Ba - con song dai nhjt chiy ngu6n song Ba thugc tinh Gia Lai gdm co hai qua dia ban 2 tinh Gia Lai va Phu Y6n da thay h6 chila: H6 Kanak va H6 An Khe. Hd Kanak dOi hoan toan, chiing tro th&nh mot ddng nuoc nSm d huyen Kbang co dung tich 313,7 triju m' nhd vao miia khd va lam xuit hien tugng hp v4 di$n tich luu v^c 833 km^, luru lugng binh han a khu v\rc h? du vol miic do ngay cang quan den tuySn cdng tinh 18,7 mVs. Ho chiia tang. Tmoc tinh trang tren, Bp Cdng Thuong da An Khe (ntai 6 huy?n An Khe), dung tich 15,9 cd quy dinh bu0c nha may thuy di$n An ICh6 • triSu m each hd Kanak khoang 30 km vd phia Kanak phai mo cua xk nude vd sdng Ba vdi Imi hj luu, di$n tich luu vuc 1.246 km^ luu lugng lugng khdng nhd hon W / s trong dieu ki?n binh quan den toyen cdng trmh 27,8 m'/s.Tuy binh thuong. Tuy nhien, vi muc dich san xuit nhien, sau khi tich nude 6 hai hd chiia nay, phfci dien nen nha may da nhieu lin khdng dam bio Idn nude sdng Ba dugc dua qua h$ thdng kenh dugc luu lugng nude quy dinh dd tra vd cho chuyen^nudc sang luu vuc sdng Cdn - Binh sdng Ba, dieu nay da tac ddng manh dSn chat Dinh de phat dien va tudi tieu cho khu vvc nay. lugng va trtt lugng cac ngudn nude bao gdm ca Viec khai thac nude sdng Ba cua thuy dien An nude m|t va cac ting chila nude dudi dit Khe - Kanak da trii vdi quy luiit tu nhien gay (NDB), luu lirgng cua ddng mat giam di rit Idn, hSu qua Idn ddn mdi trudng sinh thai. Kd tir khi tham tri cd thm didm khdng cdn d mgt vai noi,
32 T A P C H I T A I N G U Y £ N N U O C S 6 4 - 2 0 1 8
' KHOA HQC CONG NGHE *
ben canh do muc nude trong cac tang chira nude (TCN) bi ha thap ro ret sau khi cdng trinh di vao hoat ddng. Hien tugng nay da anh hudng nghiem trpng den su sdng cua cac loai thuy sinh trong sdng va ddi sdng, san xudt cua cu dan d khu vuc ha du.
2. KHU VirC NGHIEN ClTU VA TAI LIEU SU" DUNG
2.1. Khu vyc nghiSn cihi: Bao gdm 11 huyen va thi xa cua tinh Gia Lai ndm d xung quanh hai hd chua va phia ha du cdng trinh thiiy dien An Khe- Kanak, the hien qua so dd sau:
2.2. Tai lieu su* dung: Bai bao dupe hoan thanh dua tren cac k8t qua nghien ciiu thu dupe cua du an "£)/eu tra, ddnh gid dnh huang cua thuy dien An Khe - Kanak den tdi nguyen nuac vung hg lim luu vice song Ba'\ mg so:
VAST.DTCB.01/17-18 ma tac gia true tilp tham gia [4,5], eae ket qua nghien cuu eiia eac tac gia Doan Van Canh [1], Hd Minh Thp [6], Sd Tai nguyen & Mdi trudng Gia Lai [2] va eiia Trung tam Quan trac tai nguyen nude eiia Bp TN&MT [3].
Hinh 1. So do vung nghien cuu
3. BAC DIEM CHINH CUA CAC TANG CHITA NUOfC CO TRIEN VQNG 6 VUNG NGHIEN CUtJ
Tir k6t qua nghiSn ciiu cua cac tac gia [1] va [6], cd thS thay d vung nghien cim ed eae TCN sau day ed triin vpng cap nude eho san xuat va sinh ho^t eua cdng ddng:
3.1. T^ng chii-a nirdc lo faSng trong cac thanh tao bd rdi Hoiocen (Qiv) - (qh): Co ngudn gdc aQiv^; abQiv^"^ va aQiv''^, phan bd dpc thung liong sdng Ba, la Ayun va eae sudi Idn. Tang ed dien tich hep, chi6u day nhd, kha nang chira nude tir ngheo den trung binh, thupe loai nude nhat, cd y nghia cung cap nude vdi quy md nhd, don le.
3.2. T^ng chihi nude lo hong trong c^c thanh tao Pleistocen (qp): Phan bd chu yeu dpc thung liing sdng Ba, la Ayun, thupc loai ngheo nude, ddi noi la trung bmh, la nude nhat. Tang nay chi cd kha nang cap nude vdi quy md nhd.
3.3. Tang cfaii-a nude via lb hhng trong tram tich Neogen (N): Cd di?n phan bd va chieu day Idn, miic dp chiia nude tir trung binh den giau, thupe nude nhat. Tang ed kha nang cung cdp nude vdi quy md trung binh, ddi noi la Idn.
3.4. Tang chira nude phun trao bazan Pleistocen trung (pQu): Thupc h? tang Xuan Loc (PQiix/) va he tSng Dai Nga (^Qndn). Miie dp chira nude tir ngheo den trung binh, thupc nude nhEit. Tang cd y nghia ddi vdi cung cap nude quy md nhd.
3.5. Tang chira ntrdc phun trao bazan Pliocen - Pleistocen pCNi- Qi): Thupe he tang Titc Tung (PN2- QI tt) phan bo d hau khap viing.
Nude khdng ap, ddi noi cd ap cue bp, kha nang chiia nude tot. La TCN quan trpng nhat d lim vuc sdng Ba ndi rieng va tinh Gia Lai noi chung, cd kha nang cung cap nude tap trung quy md vira den Idn.
4. ANH HirCJNG CUA THUY DIEN AN KHE - KANAK DEN M^TC NU^6C DU'OfI DAT 6 VUNG NGHIEN ClTU
Sau khi thiiy dien An Khe - Kanak di vao
TAP C H f T A l N G U Y E N N U C C S O 4-2018 33
• KHOA HQC CONG NGHE •
hoat ddng (thang 10-2011) da cd nhiing anh hudng khdng nhd din NDD d vimg nghien cuu, dae biet su suy giam vS trii lugng cua cac TCN d khu vuc ha du eac bd ehiia. D§ thay dugc su thay ddi v6 trii lupng eua eae tdng chiia NDD trong khu vuc do anh hudng ciia thuy dien An Khe - Kanak, chiing tdi theo ddi su bidn ddng ve mue nude eiia eac TCN trong khu vuc nay trong cac khoang thdi gian trudc va sau khi thiiy dien di vao boat dpng. Tic sd lieu quan trac muc NDD (trong thang 4 - dac trung eho miia khd va trong thang 10 - dae tnmg cho miia mua) trong eae Id khoan ciia mang Quan trae qude gia [3]
chung tdi thSy, cd su biSn ddng rd r?t ve muc nude cua cac TCN trong nhiing nam qua. Thuc te cho thay, viec chan ddng tieh nude tren hai hd chiia K Bang va An Khe, dae biet viec chuyen nude tir song Ba sang sdng Cdn da lam giam rat ddng ke luu lupng nude tren sdng Ba, do do lam giam lugng nude cung cap tir sdng Ba eho eae TCN gay ra hien tupng ha thdp muc NDD D d khu vuc ha du. Cd the thay dieu nay thdng qua cac dd thi ha thap muc nude eiia eae TCN trong khu vuc nay nhu sau:
4.1. Anh hirdng d ^ myc nude cua tang chiia nirdc tram tich D^ tu (Q) trong khu vurc
Tii ket qua quan trac mue nude trong cac lo khoan trong TCN trim tich De tii tir nam 2007 - 2016 tai cac lo khoan LK IIT, 12T d huyen Mang Giang; LK14T, LK15T d huyen Dak Po va LK C7a d huyen Phii Thien, chiing tdi ve dupe do thj bien ddi muc nude eiia TCN nay trong cac nSm nhu sau:
Hmh 2. Bieu do dao dpng muc nude theo thai gian tgi 16 khoan UT
34 T A P C H I T A I N G U Y E N NUOC 5(54-2018
Hinh 3. Biiu dd dao dong muc nude theo thdi gian tgi Id khoan 1ST
.,
.1 J -•
.
J
'
W
« H
«.
lim ma n i l^ ^ ^ - s ^ . - - -
-»-lli;enu*tTWnB<
IDU 101) t o u
- » - l l i f t nuAt TMny 10 uns
Nin
»><
Hinh 4.Bieu do dao ddng muc nuac theo thai gian tgi Id khoan C7a Tir cac dd thi tren chung ta thdy: muc nude trong cac lo khoan quan trac deu cd xu the giam ti: nam 2011 va 2012; d huydn MSng Giang muc nude giam tu 1 - 1,7m (miia khd) va tit 0,8- 1,5m (mua mua). Muc nude 6 huy^n Bak Po giam tit 0,2 - 0,8m. Dac bi^t huyen Phii Thi?n d phia Nam vung nghiSn ciiu, hifn tugng ha thap muc nude dien ra manh me hon, cu thd giam tir 2m ddn 3,2ni.
Nhu vjiy, cd thd thiy cang v^ cudi ha luu sdng Ba su anh hudng cua dap thiiy dien den muc NDD cang ro net.
4.2. Anh hirdng den mvc nvd'C ciia tang chira nirdfc Neogen (N) trong khu vyc
Hifn mang quan trie qude gia cd 3 l5 khoan quan trie trong TCN Neogen nam d huy$n Phii Thien, do la cac LK C7b, C7c va C70, cac dd thi bidn ddi muc nude trong cdc lo khoan nay dugc trinh bay qua cac bieu dd dudi day:
• KHOA HOC CONG NGHE •
Hinh 5. Bieu do dao dong muc nude theo thdi gian tgi Id khoan C7b
Hinh 6. Bieu do dao ddng m^cc nuoc theo thdi gian tgi 16 khoan C7c
^ -
4 4
• *
HOT
N|mJ IDN
r:\^-., ^^
-»-IIWnif*cTWng* -^lli^nu*cThiiiBlll FUn.
"' "«
trong vimg nghien cim. Dieu nay cho thay cang ve phia ha luu (noi nam xa cdng trinh thuy dien) thi miie dd ha thap mire nude trong cac TCN xay ra vdi miie dp ngay cang tSng.
4.3. Anh hu-dug d^n myc nirdc cua tang chira nirdc Bazan (PN2-Q1) trong khu vyc
Cd eae lo khoan sau day quan trac TCN trong Bazan d khu vuc nghien ciiu: LK lOT d huySn Dak Doa; LK 66T; LK 67T va LK 169T nlm d huyen Chu Se. Tir cac sd li^u thu thap dugc chung tdi da ve dd thi dao dpng muc nude trong cac lo khoan nay nhu sau:
Hinh 8. Bieu do dao ddng muc nude theo thdi gian tgi Id khoan lOT
Hinh 7. Bieu do dao ddng muc nude theo thdi gian tgi 16 khoan C7o Qua cac dd thi tren cho thay, muc nude trong 3 l5 khoan tren deu giam tic nam 2011 vdi miic dp giam tir 2,5- 6,2m trong mua khd va tir 2,2 d6n 3,6m trong miia mua. Cd thS thay day la khu vuc cd mirc dp suy giam mue nude Idn nhdt
Hinh 9. Bieu do dao dpng mtfc nude theo thai gian tgi Id khoan 67T Qua eac do thi tren chiing ta th4y: m\rc nude trong lo khoan d huy?n Dak Doa bat ddu giam tir nam 2012 vdi miic dp giam din 5m trong miia khd. 6 huyen Chu Se, tai l5 khoan LK67T
TAP CHf T A I N G U Y E N N U O C S6 4-2018 35
• KHOA HOC CONG NGHE •
muc nude bat dau giam td nam 2011 vdi miie dp tir 1 d8n 3,5m.
Ben canh hien tupng ha thap muc nude trong cac lo khoan quan trie, cdn la hien tupng suy giam lim lupng eae mach Id trong TCN nay d khu vuc nghien ciiu. Cd the thay rd dieu nay qua cac dd thi tai diem Id DL3 thupc huyen Dak Doa va diem Id DLl 1 d huyen Chu Se:
Hinh 10. Bieu do dao ddng luu luang nude theo thdi gian tgi Id khoan DL3
Hinh 11. Biiu dd dao ddng luu luang nude theo thai gian tgi Id khoan DLll Cac maeh Id tren cd hien tupng suy giam luu lupng tir nam 2012 vdi miic dd giam tir 0,6 dkn l,5m^/s.
Chung ta biit riing TCN trong Bazan la ting san pham chinh phuc vu khai thae cho sinh hoat va san xuat d vimg nghien eiiu ndi rieng cung nhu d toan Tay Nguyen ndi chung. Vi vay, hien tugng suy giam muc nude trong eae Id khoan va
eae diem xuat Id cua TCN nay la anh hudng rSt Idn den trii lupng ngudn NDD trong vimg.
5. DE XUAT MOT SO GIAI PHAP N H A M GIAM THIEU HIEN TU'gfNG H^
THAP M y c NDD Ct VUNG NGHIEN COtJ De cd the giam thieu hien tugng ha thap mirc NDD d khu vuc nghien ciiu, can tien hanh ngay va ddng thdi eae cdng viec sau day:
- DS gdp phan eiiu mdi trudng ty nhien d khu vuc nghien eiiu, eae co quan chiic nang ciia tinh Gia Lai can tinh toan lai lugng nude tdi thi^u dk duy tri ddng chay moi trudng tren sdng Ba dh lam can cii bat bupe nha may thiiy dien An Khe - Kanak tra nude lai cho sdng Ba dam bao luu lupng tdi thieu, ddng thdi can giam sat chat che viec xa nude nay, dac biet trong miia khd.
- Nang cao cdng tac quan ly Nha nude vl khai thac NDD, dae biet vdi Ipai hinh khai thac nhd le trong cdng ddng - la hinh thiic khai thac phd bien nhat trong vimg. Ddng thdi nang cao kien thiie ve dia chdt thiiy van khu vuc cho cac co sd hanh nghd khoan khai thac NDD trong vung.
- Tim kiem cac giai phap tang eudng lupng bd cap eho NDD de nang cao trii lupng nude trong khu vuc. Chung ta biit, NDD trong khu vire dugc bd c$p chii yeu td nude eua cac dong mat va nude mua nglm tir tren mat dit. Tuy nhien, chi ed mpt phan lugng nude rmy dupe giir lai trong TCN cdn phin Idn lai thoat ra mang sdng sudi ciia dia phuong trong mua kho.
Vi vay, cd the cai tao eae hd, dhxi hogc cac dja hinh triing trong vimg de lam noi giit NDD thoat ra trong mua khd va cung la noi luu giii nude mua trong mua mua dk cung eip nude tuci trong miia khd ddng thdi lam tang ngudn b6 sung eho NDD.
6. KET LUAN
Chiing ta khdng thi phu nhan nhOng Ipi ich ma eae cdng trinh thuy dien mang lai eho ddi sdng sinh hoat va san xuat cua cdng ddng noi chung va ciia tinh Gia Lai ndi rieng, tuy nhien ben CEinh nhung lgi ich dd edn la nhimg anh hudng khdng nhd do tac ddng eua cac cdng
36 TAP CHlTAl NGUYEN N U d C S(5 4
• KHOA HQC CONG NGHE • trinh nay mang lai. Vdi thuy di?n An Khe -
Kanak tir vi?c chuyin nude tir sdng Ba sang sdng Cdn da lam anh hudng nghiem trpng den tai nguyen nude d vimg ha du bao gdm ca nude mat va NDD. O khu vyc hg du nhiiu doan sdng Ba hi khd han vao miia khd, do lupng nude sau dap tra vl ha du khdng dat 4mVs da biie tii nhieu khuc sdng nay lam anh hudng din sy sdng eua eae loai sinh vgt trong sdng va din sinh hogt va san xuat ciia cdng ddng. Diiu nay da dupe chdng minh bang su suy giam muc nude trong cac TCN d khu vuc ha du tir khi thuy dien An Khe - Kanak di vao hoat ddng.
Qua cac sd lieu trSn chiing ta thdy, eac TCN da va dang la doi tupng khai thac phuc vu sinh hoat va san xuat cua cdng ddng (tang qh; qp; N va PN2-Q1) d vung nghiSn cuu dSu chiu tac dpng cua cdng trinh thuy dien An Khe - Kanak. Hdu het muc nude trong eac lo khoan va diem Ip quan trac d nhung khu vuc nam dudi dap thuy di^n deu bi hg thap tir nam 2012 va 2013 do lupng nude bd cap tu sdng Ba vao eae ting chua NDD giam. Hien tugng suy giam muc nude trong eac TCN la biSu hien suy giam tru- lupng eua eac TCN trong khu vuc do anh hudng ciia viec ngan ddng tich nude va chuyen nude sang sdng Cdn cua cdng trinh thiiy di6n An Khe -Kanak.
Bk giam bdt hien tupng suy giam tru lupng NDD, eae co quan chiic nang cua Gia Lai can phai thuc Men ddng bd mpt sd cdng tac sau:
Dua ra luu lugng tdi thieu cua sdng Ba bat budc thuy dien An Khe - Kanak phai tra lai eho ddng sdng nay dl dam bao ddng chay mdi trudng;
Phai quan ly chat che viec khoan khai thac NDD cua dan cu trong vimg; ddng thdi tim ra cac bien phap nham luu giii nude mua de cung cap eho cac TCN.
xay dyng cac giai phap luu giii nude mua vao Idng dat phuc vy chdng hgn va bao v$ tai nguyen NDD vimg Tay Nguyen". MS sd DTDL.2007G/44. Luu trie BQ Khoa hgc vd Cdng ngh$, Hd Ndi
2. Sd tai nguyen & Mdi trudng Gia Lai, 2012. Bao eao "Nhung net ehinh ve cdng trinh thuy di?n An Khe- Kanak".
3. Trung tam Quan trac Tai nguyen nude qude gia - Bp tai nguySn & Mdi trudng, 2017.
Bao cao "Ket qua quan trac nude dudi dat vung Tay Nguyen trong cac nam 2007 den 2016".
4. Le Thi Thanh Tam &nnk. Bao cao chuyen de "Tai nguyen nude dudi dit vimg Tay NguySn"
thupc dd tai **Nghidn ciiu co sd khoa hpe cho giai phap tdng thi giai quylt cac mau thuin lgi ich trong vice khai thac va sii dung tai nguyen nude lanh tho Tay Nguyen". Luu trie Vien Dja ly, 2014
5. Le Thi Thanh Tam & imk. Bao cao chuySn de "Diiu tra, ddnh gid S{c suy gidm tdi nguyen nude duoi ddt a viing nghien cicu trudc vd sau khi xdy dgp thuy di^n An Khe - Kanak" thupe Dy an "Dieu tra, danh gia anh hudng eua thiiy dien An Khe - Kanak den tai nguyen nude vimg hg luu luu vyc sdng Ba". Ma so:
VAST.DTCB.01/17-18.
6. H6 Minh Thp & nnk, 2014. Bao cao dl tai
"Qi^ hogch tdi nguyen nude tinh Gia Lai din nam 2025". Lien doan Quy hogch va Dieu tra TNN miin Trung. 2014.
TAI lApJ THAM KHAO 1, Doan van Canh &nnk, 2010. Bao cao kit qua dl tai: "Nghien ciiu co sd khoa hpc va
Ngudi phdn bi^n: PGS.TS Ha Linmg Thuan Phdn bienxong: 8/2018
TAP CH( TAl NGUYEN NUCfC SC 4-2018 37
