NGHIEN CUU ANH HUONG CUA BIEN DOI K H I HAU DEN BIEN DONG DONG CHAY MAT LUtJ VlTC SONG
NAM MlfC
Truffng Van Anh, Trinh Xuan Manh Truang Dai hoc Tai nguyen va Moi truong Ha Noi Tom tat
Song Nam Mire la mot phu km lan cua dong chinh song Da, co vi tri dia ly.
dia hinh vd dieu Men lu nhien khdphuc lap. Dong chdy song ngoi tren km virc bien doi do nhimg dien bien bd( hri cua cac yeu to khi hau cUng nhu thuy van. Bdi bao nghien cmi su bien dong ciia dong chdy mat tren luu vuc song Nam mi'rc dual tac dong cua bien doi khi hau dua tren viec phan tich chudi so lieu thuc do vd su dung cong cu mo hinh toan thuy van MIKE NAM. Hai kich ban RCP4.5 vd RCP 8 5 cho hai giai doan 2016 - 2035 vd 2045 - 2065 duac sir dung. Ket qua nghien cmi cho thdy luu licang trung binh im'ia kiet thai ki ddu vd giua the ki co xu the tang so vai giai doan nen. Luv luang trung binh miia lu cung co xu the tang va tang lan nhdl trong giai doan giira the ky. Nguyen nhan duac xdc dinh Id do luang mua mua ha cua hai kich ban nay deu tang so vai thai ki ca sa.
Tu- khoa: Bien doi klii hau; Dong chay mat; Liru vuc song Nam Mirc; N4IKE NAM Abstract
Study on the impacts of climate change on surface water resources in Nam Muc river basin
Nam Muc River is one of the largest tributaries of the Da River basin located in a veiy complicated area of geography, topology and natural conditions. Surface water resources in this basin changed due to the negative variability of climatic and hydrological factors. This paper concentrates on the fluctuation of surface water in the Nam Muc river basin under the impact of climate change by analyzing observed data as well as using MIKE NAM numerical model. RCP4.5 and RCPS. 5 scenarios were applied for periods of 2016 - 2035 and 2045 - 2065. Tlie results indicate that the annual mean discharge in dry season will increa.se in both study periods compared to The base period. Annual mean discharge in the wet season will increase and obtain a biggest value in the second period compared to the base and first periods. The causes is determined as the forecast rainfall in The dry season of
the RCP4 5 and RCP8.5 scenarios will both increase compared to the base period.
Keywords: Climate change; Surface water flow: Nam Muc river basin; MIKE NAM 1. Mo" dau doi hoi phai dau tu' nhieu thai gian va B i 6 n d 6 i k h i h a u ( B D K H ) d u o c x a c " S " ^ " '^c bofi ngu6n dij Heu hien nay dinh la sir bien d6i trang thai cua khi hau phuc vu cho cong tac nghien cuu t^i so vai trung binh va/hoac dao dong cua Viet Nam con thieu hoac rat han c h l khi hau duy tri trong mot khoang thai Tai Viet Nam. trong nlwng nam qua da gian dai, thuang la vai thap ky hoac dai co rat nhi6u chuang trinh nghien cuu hon [1]. Vi vay, viec danh gia tac dong nham dua ra cac giai phap giam nhe va cua BDKH den tai nguyen nuac luon ung pho vai BDKH tren cac quy mo
, . 3 Tap chi Khoa hoc Tai nguyen vd Moi tru&ng - So 20 - nam 2018
Nghien cuu
khac nhau [1]. Cac cong cu mo hinh toan hien dai nhu mo hinh khi hau. mo hinh toan thuy van dong vai tro rat quan trong trong nghien cijru, danh gia tac dong cua BDKH. Nhieu mo hinh toan thuy van - thuy lire, thuy dong lire dugc ung dung thanh cong vai do chinh xac cao trong danh gia tac dong cua BDKH trong ITnh \ y c thu>' van - tai nguyen nuac. Trong nghien cuu nay, mo hinh thuy van MIKE NAM duac lua chpn d^ tnih toan va nghien cmi lugng dong chay du tinh cho tuang lai dua tren cac kicli ban BDKH duac lira chon tu do dua ra nhung phan tich va danh gia bien dong cua dong chay mat tren Imi \ u c song Nam Muc.
2. Tong quan luu vuc va phu'ong phap nghien cihi
2.1. Liru vuc song Nam Muc
Hinli I: Ban do luu vuc song Nam Muc Nam Muc la song nhanh 1cm nhit nam 6 ba phai cua song Da. Song bat ngu6n tu viing nui cao tren 1500 m tren dat Lao, chay vao tinh Lai Chau theo huong rir Tay Nam len Dong B4C.
do vao song Da tai ban Hu6i Muc cac cua song Da 409 km, co tdng dien tich la 2740 km-. Dia hinh luu vuc song Nam Muc la dia hinh viing nui. viing d6i va viing dit hep ven cac su6i. Vd dac
diem khi hau, nliiet d6 trung binli nam tren luu vuc song Nam Muc khoang tCr
16-2:VC.
Nhin chung cac s6 lieu quan trie cho thay dong chay Ion nhat tren song Nam Muc Ion hon tren song Nam P6 va Song Nam Na. Luu luong lan nhat da xuat hien trong nhung nam gan day la 4480 mVs ung vai mo dun dong chay Ion nhat la 1672 1/s.km- quan trac duoc tai tram thuy van Nam Muc. Cung tai Nam Muc bien dp muc nuoc Ion nhat do duac la 7.57 m [2].
2.2. Kich ban biin ddi khi h^u a Viet Nam
Kich ban BDKH va nuac bien dang cho Viet Nam nam 2016 duac cap nhat theo 16 trinh da dugc xac dinh trong Chien luge qu6c gia ve BDKH, nham cung cap nhung thong tin moi nhat ve dien bien.
xu the bien doi cua khi hau va nuac bien dang trong thai gian qua va kich ban BDKH va nuac bien dang trong the ky 21 o Viet Nam. Kich ban BDKH co xet den su bien doi ciia cac yeu to khi hau nhu nhiet do (nhiet do trung binh nam. miia va nhiet dp cue tri), lugng mua (mua nam, mua trong cac miia. mua cue tri) va mot so hien tugng khi hau cue doan. Nam 2013, Uy ban Lien chinli phu v^ BDKH (IPCC) cong b6 kich ban cap nhat, duong phan bo nong dp khi nha kinh dai dien (Representative Concentration Pathways - RCP) dugc su dimg de thay the cho cac kich ban phat thai khi nha kinh SRES (Special Report on Emission Scenarios).
Cac RCP dugc lya chgn sao cho dai dien dugc cac nhom kich ban phat thai va dam bao bao gom dugc khoang bien doi cua nong dp cac khi nha kinh trong tuong lai mot each hgply []].
Theo kich ban BDKH va nuoc bien dang moi nhit do Bp Tai nguyen va Moi
= ^
Tap chi Khoa hoc Tai nguyen va Moi truong -So 20-
rvgitien cuu
truofng cong bo thi cac kich ban phat thai khi nha kinh dugc chon de tinh toan xay dung kich ban cho khi hau 7 viing ciia Viet Nam gom kich ban phat thai trung binh (kich ban RCP 4.5) va kich ban phat thai cao (kich ban RCP 8.5).
dua vao cac dieu kien tu nhien. tinh hinh kinh te xa hoi. dan so va muc dp quan tam den moi truang cua khu vuc. Trong nghien cuu nay lua chon 2 kich ban danli gia muc dp anh huong ciia BDKH den tai nguyen nuoc bao gom kich ban phat thai cao (RCP 8.5) va kich ban phat thai trung binh (RCP 4.5) tu' kjch ban BDKI^
dugc Bp TNMT ban hanli nam 2016 de tinh toan. Dua vao cac gia tri thay doi ciia lugng mua va nhiet dp trung binh miia cho vung nghien cuu (Dien Bien, Lai Chau, Son La), tien hanh tinh toan lugng mua ciio thai ky tuong lai tuang ling vai gia thiet tram khi tugng nam trong tinli nao se co gia tri bien doi cua tinh do dugc lay tu kich ban BDKH hien hanh. Sau do phan phoi mua mua thanh mua ngay dua tren gia thuyet phan phoi mua se khong thay doi giiJa thoi ky c a so va kich ban BDKH. tir do se co dugc kich ban mua ngay trong tuong lai.
2.3. Mo hinh mua - dong chdy MIKE NAM
Mo hinh NAM dugc xay dung lai Khoa Thuy van, Vien Ky thuat Thuy dong lire va Thuy luc thupc Dai hpc Ky thuat Dan Mach nam 1982. Trong mo hinh NAM cac thong so va cac bien la dai dien cho cac gia tri dugc trung binh h6a tren toan luu vuc. Mo hinh tinh toan qua trinh mua - dong chay theo each tinh lien tuc ham lugng am trong be chfe rieng biet co tuong tac lan nhau [6]. Mo hinh NAM da dugc ung dung rpng rai a Viet Nam, dugc kiem chiing phu hop voi nhieu luu vuc 6 nuac ta.
Cau triic mo hinh NAM dugc xay dung
tren nguyen tac cac ho chua theo chieu thang dung va cac ho chiia tiiyen tinh.
gom 5 be chua theo chieu thang dung gom be chira tuyet tan. be chira mat. be chua tang duai. be chira ngam tang tren va be chua ngam tang duai.
Hien nay trong mo hinh thu} dong lire MIKE 11 (do Vien Thiiy Luc Dan Mach - DHI xay dung) mo hinh NAM da dugc tich hgp nhu mot modun tinh qua trinh dong chay tir mua. Hinh 2 mo ta cau tnic ciia mo liinh NAM.
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Hinh 2: So' do nguyen ly mo hinh NAM 2.4. Thih lap mo hinh MIKE NAM DO lieu dau vao cho mo hinh bao gom so lieu khi lugng nliu nhiet dp, dp am, so gio nang, gio. mua va so lieu luu lugng trung binh ngay. Chuoi so lieu khi tugng thiiy van tren luu vuc song Nam Muc dugc thu thap dong bp va keo dai tir nam 1970 - 2004 ciia cac tram do trong va lan can gom tram Lai Chau, Quynh Nhai va Dien Bien. Do nhirng kho khan trong viec thu thap cac tai lieu khi tugng thuy van tai luu vuc Nam Mirc phan dien tich thupc Lao. nghien cim nay giai
Tcip chi Khoa hQC Tai nguyen vd Moi truang-So 20 - nam 2018
Nghien cuu
han chi sir dung cac so lieu ciia cac tram thupc Viet Nam. S6 lieu tai cac tram nay dugc dimg d^ hieu chinh va kiem dinh mo hinh MIKE NAM. Theo do. thoi gian dimg de hieu chinh mo hinh tir nam 1994 d^n 2001, bp thong s6 toi uu tim dugc trong buac hieu chinh se dung de ki^m dinh mo hinh cho thoi ki tir nam 2001 dSn 2004. Ngoai ra. boc hoi tien nang ET^ sir dung trong mo hinh MIKE NAM dugc xac dinh qua cong cu ET^, Calculator. Tram Nam Muc dugc su dung lam tram kiem tra va xac dinh bp thong s6 mo hinh vi day la tram duy nhit CO do luu lugng dong chay trong
nliieu nam ciia luu vuc nay. Viec hieu chinh thong so mo hinh chii yeu dugc tien hanli bang phuong phap thir sai.
Ket qua hieu chinh cho thay giija tinh toan va duong thuc do la tuong doi phii hgp nhau voi sai so lech dinh ve gia tri va thai gian la khong nhieu. Hinh 3 the hien ket qua hieu chinh cho thay giira hai duong qua trinh tinli toan va thuc do tuang doi bam sat nhau \ e ca pha dao dong va gia trj dinh. Ngoai ra chi tieu NASH tuang d6i tot. Ion hon 0.8 va he s6 PBIAS va RSR deu o muc dam bao m n l u o t l a - 0 . 0 1 I 6 v a O , 3 5 5 9 .
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Hinh 3: Qua trinh luu luotig thuc do va tinli toan hieu chinh mo hinh (tir nam 1994 - 2001}
Sau khi buoc hieu chinli mo hinh cho ket qua tot. mo hinh MIKE NAM dugc tien hanli kiem dinh cho cac nam tir 2001 dan 2004. Ket qua kiSm dinli thuy van cho luu vuc Nam Miic the hien trong hinh 4 la tuong doi kha quan, co the nhan thay giiia duong tinh toan va duong thuc do la kha tucmg dong nhau.
Chenh lech giua luu lugng Ion nhk giiia tinh toan va gia tri thuc do khong dang ke. Sai so lech dinh tai cac tram ki^m tra nam trong pham \i cho phep. K^t qua tinh toan chi ti^u NASH tuong d6i tdt 6 —
(0,8) va he so PBIAS va RSR deu nho,
\m lugt la 2.6533 va0,4588. V a i k i t qua tren bg thong so mo hinh co dp tin cay cao va CO the ap dung vao du tinh dong chay trong tucmg lai theo cac kich ban BDKH. Nhu vay. thong qua hai buac hieu chinh va kiem dinh, nghien cim da xac djnh dugc bg thong so toi uu cho luu vuc Nam Muc vai cac gia tri thong s6 chinh nhu C^^^ - 0,73; CK1.2 - 33,8, 5 6 : L ^ ^ = 1 0 6 ; U , , ^ ^ = 1 0 .
3. Danh gia dong chay liru virc song Nam Mirc trong diiu kien BDKH
Tap chi Khoa hoc Tai nguyen vd Moi truang -So 20- nam 2018
Nhu da trinh bay, hai kich ban BDKH gom kich ban phat thai cao (RCP 8.5) va kich ban phat thai trung binh (RCP 4.5) dugc dimg de tinh toan. Theo do, cac kich ban bien doi lugng mua va boc hoi theo thoi doan ngay cho cac tram tr8n va gan luu virc song Nam Muc dugc thu thap cho cac thai doan nam tii 2016 - 2035 va 2046 - 2065 tuong ung voi dac tnmg cho cac giai doan dau th6 ki va giiia th8 ki. Voi gia thiet ve dieu kien v$t ly cua toan luu vuc
Nehien cuu la khong doi (cac thong so cua mo hinh MIKE NAM se khong thay doi theo thai gian), mo hinh MIKE NAM da dugc kiem dinh se dugc dung dk mo phong cac kich ban g6m: Thoi ky co so (1986 - 2005);
thai ky 2016 - 2035 (giai doan I) theo kich ban RCP 4.5; thoi ky 2016 - 2035 (giai doan I) theo kich ban RCP 8.5; thoi ky 2046 - 2065 (giai doan II) theo kich ban RCP 4.5 va thoi ^ 2046 - 2065 (giai doan n) theo kich ban RCP 8.5.
Hinh 4: Qua trinh luu lupng th^ do va tinh toan kiem dinh mo hinh (tir nam 2000 - 2010)
Hinh 5: Duong lay tich tong /irpWg dong chay tai tr^m Ngm Muc theo kfch ban RCP 4.5 cua thoi ki co- so* va thai ki dau thi ki
Tap chi Khoa hoc Tai nguyen va Mot truang -So 20- nam 2018
Nehien cuu
Kgt qua danh gia bien dong dong chay song Nam Miic trong giai doan dau the ki ciia kich ban RCP 4 5 va RCP 8.5 cho thdy Trong thoi ky ki?t kich ban RCP 4.5 CO lugng dong chay Ion hon so vol thai ky co so. Tuy nhien trong kich ban RCP 8.5 lugng dong chay kiet lai xu huong giam di so voi thoi ky ca sd.
Trong thai ky lu, dong chay cua kich ban RCP 4.5 la lan nhat, nguyen nhan do mua cua mua ha trong kich ban RCP 4.5 tang nhieu nhat (9,2% so vai thai ky CO so) va nhiet dp thi tang it hon kich ban RCP 8.5 (tai nhi?t dp tai Dien Bien, RCP 8.5 tang 1"C, RCP 4.5 tang Q,TC).
Luy tich dong chay theo thai gian (hinh 6) cung th8 hi^n tong lugng dong chay se tang manh trong kich bdn RCP 4.5.1 khoang 4,67% con trong kich ban RCP 8.5 thi tang it hem, khoang 1,17%.
Doi voi giai doan giua the ki (2046 - 2065) theo kich ban phat thai thdp RCP 4.5, so sanh vai giai doan nen va dau
the ki thay rSng trong thai ky ki?t lugng dong chay trong thai ki nay lan hon cac giai doan con lai. Nguyen nhan co the do nhi^t do cua mua dong va xuan cua kjch ban RCP 4.5 giai doan II cao hon kich ban RCP 4.5 giai doan I (nhiet dp tai Dien Bien, kich ban RCP 4.5 giai dogn I tang 1,6''C, giai doan II tang 0,7''C). Trong khi do mua ciia kich ban RCP 4.5 trong giai dogn II giam 9,7%
va trong giai doan I tang 17%. Ngoai ra, trong thoi ky lu, dong chay ciia kich ban RCP 4.5 trong giai doan II la Ion nhat. Nguyen nhan do mua cua mua ha trong kich ban RCP 4.5 giai doan II tang nhi6u nhat (16,6% so vai thai ky co so).
Luy tich dong chay theo thai gian (hinh 7) thiy rang t6ng lugng dong chay se tang manh trong kich ban RCP 4.5 giai doan I, vao khoang 4,67% so voi thai ky CO so. D6i voi kich ban RCP 4.5 giai do?in II thi tang nhi6u hon, vdo khoang 15,32% so voi thai ky co so.
Hmh 6: Qua trinh dong chdy thang va duamg cong th&i dogn luu Itrgrng t^i Nam Muc trong th&i ki cff sa, va giai do^n 2046 - 2065 cua kfch ban RCP 8.5
Tap chi Khoa hoc Tai ngiiyen va Moi truang - So 20 - nam 2018
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WnA 7: Du&ng luy tich tong lucmg dong chay tai tram Nam Muc theo kich ban RCP 4.5 ciia thai ki ca sa vd thoi ki dau the ki
Hmh 8: Qua trinh dong chdy thang vd du&ng cong thoi doan luu luiptg tai Nam Muc trong thai ki cas&, va giai doan 2046 - 2065 ciia kich ban RCP8.5
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Hmh 9: Bu&ng luy tich tong lu^tg dong chdy tai trpm Nam Mirc theo kjch ban RCP 8.5 ciia thai ki ca sd va thai ki d&u the ki
Tap chi Khoa hoc Tai nguyen va Moi truang -So 20- nam 2018
Nghien cuu
N g h i e n ciru sir bien d o n g d o n g chay song N a m Miic trong hai giai d o a n dSu v a giiia th6 ki ciia kich ban phat thai c a o R C P 8.5 n h a n thdy r a n g trong t h a i k y kiet giai d o a n II l u g n g d o n g chay se Ion h o n t h a i k y c a s a . Tuy nhien l u g n g d o n g c h a y n a y trong giai d o a n I se n h o h o n t h a i ky c a so. N g u y e n n h a n d o nhiet d o ciia m u a d o n g va x u a n ciia kich b a n R C P 8.5 giai d o a n II c a o h o n kich b a n R C P 8.5 giai d o a n I. T r o n g thai k y lu, l u g n g d o n g chay trong giai d o a n II la Ion nhat, d o m u a ciia miia ha kich b a n R C P 8.5 trong giai d o a n II tang n h i e u nhat ( 1 9 , 3 % so v a i thai k y c o s a ) , kich b a n R C P 8.5 trong giai d o a n I tang it h o n ( 8 . 8 % so voi thai k y c a so) Liiy tich d o n g chay t h e o thai gian (hinh 9) the hien ro tong l u g n g d o n g chay se tang m a n h trong kich ban R C P 8.5 giai d o a n I, v a i m u c tang khoang 1,17% so v a i t h a i k y c a s a v a kich b a n R C P 8.5 giai d o a n II thi tang nhieu h o n , vao k h o a n g 13,99% so voi thoi k y c a s o .
4 . Ket luan v^ kien nghi N g h i e n ctru da lira c h p n hai kich b a n phat thai c a o R C P 8.5 va trung binh R C P 4.5 d e danh gia bien d o n g d o n g chay m a t tren luu v u c song N?im Miic b a n g m o hinh toan thuy v a n M I K E N A M . K6t qua cho thdy kich b a n R C P 4.5 trong giai d o a n I co t6ng l u g n g tang 4.67%. va giai doan II t6ng l u g n g tang 15,32%. Kich ban R C P 8.5 giai doan I CO t6ng l u g n g tang 1,17% v a giai d o a n II t6ng l u g n g tang 13,99% so v o i thoi ky CO so.
Nghien cuu nay m 6 i chi x e m xet bien d o n g cua d o n g c h a y m a t tren luu 10 -
v u c s o n g N $ m M u c trong m p t b a i toan k h a i q u a t c h u n g c u a tiru v u c , c h u a xet d e n n h i i n g nhSn to gSy a n h hudmg den d o n g c h a y m a t n h u h o c h u a , cac c o n g irinh k h a i thac n g u o n n u o c k h a c hay sir d u n g n u a c ciia cac n g a n h kinh te trong t u a n g lai. D a y ciing la d i e m h a n c h e trong n g h i e n c u u n a y v a se d u g c dinh h u o n g k h a c p h u c t r o n g cac n g h i e n cim tiep theo.
T A I L I E U T H A M K H A O [1]. BO Tai nguyen va Moi truang (2016). Kich ban bien doi khi hau va nwifc bien dang cho Viet Nam 2016.
[2]. Vi?n khoa hpc thiiy l(?i (2015), Nghien cuu xay difng mo hinh quan ly tong hpp tai nguyen vd moi truang liru vuc song Da.
[3]. TrSn Thanh Xuan, Hoang Minh Tuyen, Le Tuan Nghla, Luang Hftu Dung (2011). Tac dong cua Bien doi khi hau den dong chdy trong song. Tuyen tap Bao cao Khoa hoc ISn thu XIII, tx. 146 - 153.
[4]. D. Labat, Y. Godderis, J. L. Probst (2004) Evidence for global runoff increase related to climate warming. Advances in Water Resources, 27, pp. 631 - 642.
[5]. Todini, Ezio (1988). Rainfall- runoff modeling ' past, present andfiiture.
Journal of Hydrology.
[6], Fuji technology press ltd (2014).
Impact of Climate Change on River Flows in the Black Volta River. JDR Vol.9 No.4 pp. 432-442doi: 10 20965/jdr.2014.
p0432(2014)
[7]. DHI (2011). MIKE NAM manual.
[8]. http://ssl.tamu.edu/media/1312/
MoriasiModelEvaLpdf
B B T n h a n bai: 0 7 / 3 / 2 0 1 8 , P h a n bien x o n g : 16/5/2018
Tap chi Khoa hoc Tai nguyen vd Moi tnrcmg - So 20 - nam 2018
