Tap chi Khoa hoc va Cong nghS Bien; Tap 14, S6 3; 2014: 272-279 DOI; 10.15625/1859-3097/14/3/3795 http;//www.vjs.ac.vn/index.php/jmst
MO PHONG LAN TRUYEN CHAT 6 NHIEM KHU VUC PHA TAM GIANG - CAU HAI, THl/A THIEN - HUE BANG MO H I N H DELFT-3D
Cao Thi Thu Trang'*, Pham Hai An', Tran Anh Tu', Le Dure Cudng', Tran Dm; Th^nh', Trinh Thdnh^
' Vi?n Tai nguyen vd Moi tradng bien-Vien Han ldm Khoa hgc vd Cdng nghe Viet Nam Vien Khoa hge vd Mdi tradng-Dai hgc Bach Khoa Hd Npi
'Email: [email protected] Ngdynhanbai: 19-3-2014
TOM TAT: Dua tren cdc so lieu khdo sdt va thu thdp ve khi tugng - thiiy van. chdt lupng nu&c khu v^ec dam phd Tam Giang - Cdu Hgi, Thieg Thien - Hue da mo phong truang thuy dpng luc va lan truyen chdt 6 nhiem trong dam phd sit dung mo hinh Delft-3D. Cdc kit qud mo phong cho thdy dong chdy trong ddm phd co gia tri l&n nhdt tgi khu vuc cua Thugn An. vdo mua mua dgt din 1,0- 1,2 m/s,_ dong chdy nho nhdt xudt hien lgi khu vuc ddm Cdu Hgi. Ty le trao ddi nuac trong ddm phd kha thdp, dat khodng 31.7% tai phd Tam Giang. 25,8% lgi ddm Sam - Thuy Tit va 5,33% tgi ddm Cdu Hgi. Nong dp cua cac chdt 6 nhiem cao tgi cdc khu vuc ciea song nhu song Huang, Tniii.
Thudn An. 6 Lau vd Tu Hien, thgm chi vupt gi&i hgn cho phip (GHCP) Tu khoa: Mo hinh, ddm pha, chdt 6 nhiim. chdt lugng nu&c. mo phdng.
MO DAU
Dam phd Tam Giang - Cdu Hai (TG-CH) thupc tinh Thira Thien - Hue (TTH) la he dam pha ldn nhdt d Viet Nam, co toa do dia ly:
16°15'00" 16''42'00"B, l67"22'0d"
107"57'00"D, dientich mat nude 216 km", chieu ddi 68 km, chieu rong 10 km, dp sdu trang binh 1,6 m va sau nhat 4,2_m He ddm phd cd hai cira: Thudn An d phia Bdc vd Tu Hiln d phia Nam, thupc loai thiiy vuc gdn kin, nude lg vd lg - nhat va eo tinh phdn tdng manh [ 1 ].
Khu vuc dam phd Tam Giang - Cdu Hai chiu dp lyc rdt ldn tir cdc hpat dpng phdt triln ven ddm pha nhu nudi trdng thuy san, ddn cu - du lich, ehan nuoi gia siic, gia cdm ... Nguin thai ra ciia cac boat dgng ndy chu ylu la nhung chat thai thong thudng gom cac chdt dinh dudng vd hiiu ca. Cdc chdt nay khi di vdo thuy vyc se Ian fruyln, phdn tan, ldng dpng hoac luu gid lai trong nudc tiiy thupc vdo cac dieu kien
thiiy ddng luc vd cae ngudn gdy 6 nhilm. Dl mo phong lan tmyen ehdt 6 nhiem frong khu vyc dam phd Tam Giang - Cdu Hai (tinh Thua Thien Hul), da su dung mo hinh Delft-3D fren ca sd chay mo hinh thuy dpng lyc (Delft- FLOW). Cae doi tugng chinh duge mo phong Id cac ngudn chdt hiiu ca (till hien qua thong so BOD5, COD).
Bai bao trinh bdy radt s6 kit qua nghi6n cuu m6 phong lan fruyln chdt 6 nhiira trong khu vuc ddm pha Tam Giang - Cdu Hai nhdm dua ra biic tranh phan b l chdt 6 nhiem trong khu vyc. Cac ket qua nghien ciiu nay da the hien dugc^phan nao quy luat lan tmyln chdt gay 6 nhilm d vimg TG-CH vdi su tdc dpng ciia nhieu yeu td khac nhau, frong do nguon cung cap tir luc dia, tai lugng nudc song va che dp thiiy dpng lyc, dae biet la qud tiinh trao dii nudc giira he thdng ddm, phd vd bien la nhung yeu td anh hudng hudng true tiep va quyet dinh
Mo phong lan tmyln chdt 6 nhiem . den ndng d6 va pham vi khong gian phan bo
ciia cac chat hiru ca.
TAI LIEU VA PHUONG PHAP NGHIEN CUtJ
Tdi Ii6u
Dia hinh: so lieu dp sau vd dudng bd cua khu vuc nghien ciiu dugc so hod tir cdc ban do dia hinh UTM ty le 1:50.000. Ngodi ra, dia hinh vimg bien Thira Thien Hue va cac viing ldn can khi thiet lap m6 hinh diing de NESTHD con duac tham khdo vd bd sung tir co sd dii li?u dia hinh E T 0 P 0 5 va GEBCO-1.
Khi tugng: sd lieu vl khi tupng su dung bao gdm buc xa mat frdi, dp am tucmg doi, lugng mdy, nhiet dp khong khi eo gia tri tmng binh theo miia (rnua khd - thang 5 vd miia mua - thang 11). So lieu gio eua thdng 11 nam 2011 vd thdng 5 iiam 2012 quan frde 6h/lan tai Hue lam dir lieu ddu vao cho mo hinh tinh toan [2].
Thuy hdi vdn: phia cua song sir dyng sd lieu luu lugng theo gid tai tram tren song Huong, sd lieu luu lugng trang binh thang fren sdng O Lau va sdng Tmdi (so lieu do Tmng tam Khi tugng Thuy van Thira Thien Hue cung cdp ndm 2012), so lieu do dac muc nudc vd dong chdy, nhietj muoi tai 3 tram lien tyc; phia ngoai sii dyng hdng sd dieu hod thuy^frieu cho cac bien md, dugc tinh todn tir chuoi sd lieu quan frac muc nudc tir mgt so de tdi, du an eiia Trung tdm Khi mgng Thuy van bien, Vien Tai nguyen vd Moi tmdng bien, Tmdng Dai hoe Thuy lgi, nhiing diem bien long phia bien khong CO so li$u quan frac thi tham khdo ket qua tinh toan tir md hinh NAO-TIDE (chuang trinh du bdo thuy trieu eua Ddi Thien van Quoc gia Nhdt Bdn NAO) [3].
Phvorng phap
Phirang phdp dieu tra khdo sdt biin vd phdn tich trongphdng thi nghidm
Hinh 1. He thdng pha Tam Giang - Cdu Hai va cac tram khdo sdt
Ba fram khdo sat lien tiic 24h tai 3 vi fri pha lugng nudc frong hai raiia: mua mua (thdng Tam Giang ddm Sam - Thuy Tii vd ddm Cdu 11/2011) va miia kho (thdng 5/2012) (hinh I).
Hai dupe bd fri d l khdo sat thuy vdn va chdt Toe dp va hudng dong chdy dugc do bdng may
Cao Thi Thu Trang, Pham Hai An,...
tu ghiJDNC-2M cuaAnh, SD30 cua Na Uy) ...; mau nudc dugc lay lien tuc 2h/6p, sau do dua ve phong thi nghiem de phdn tich cac thong so BOD5, COD. Cdc phuang phdp phdn tich tuan theo cac tieu chudn Viet Nam da ban hanh (QCVN-08/2008/BTNMT).
PhiTffng phdp mo hinh
Sii dung mo hinh DELFT - 3D [4, 5] dl md phong qud trinh thuy dpng luc va qua trinh lan tmyen chdt 6 nhiem trong khu vye tai hai thdi diem: hien tai va dy bao nam 2020.
Mien vd lu&i tinh: kich thude mien tinh c6 pham vi 70 km theo hudng Bac Nam va 1 - 10 km theo hudng Dong Tay. Toan bd khu vyc tinh todn bao gom 95x503 6 ludi (hinh 2).
Mien tinh eo ede bien long phia bien la; cira Thudn An va ciia Tu Hien; ngoai ra con c6 cac bien long song: song 6 Lau, song Huong vd song Traoi.
Tai bien song: sir dyng luu lugng tirng gid trong thang tren s 6 n | Huang, luu lugng frung binh thang fren song O Lau va song Tmdi.
Tai tat cd cae bien ldng deu sir dyng vd tham khdo cac ket qua quan frac nhiet muoi frong cdc dgt khdo sat nam 2011 vd 2012 (01 tai TTH.2011-KC.l 1) tai khu vyc he ddm pha Tam Giang - Cdu Hai.
Kiem chirng md hinh
Doi vdi vi6c md phong lan tmyen chat gay 6 nhiera, da tien hanh hieu chinh vd ddnh gid dp chinh xae cua mo hinh bang viee so sanh kit qua eua md hinh thuy dpng luc (dong chdy) vol sd lieu quan frac thyc te. Cac ket qud sau ldn hieu chinh cudi cung ciing da eho thdy sy phu hgp tuang doi giira tinh todn vd so lieu quan trac thue te (hinh 3).
Hinh 2. He thdng ludi tinh cua md hinh Thai gian tinh todn: md hinh dugc chay theo hai miia: miia khO vd raua mua. Miia mua bdt ddu tinh todn tir OhOO, ngay 01/11/2011 vd kit thiic luc 23h00, ngdy 31/11/2011. Miia kho bdt dau tinh toan tir OhOO, ngay 01/5/2012 va kit thiie lue 23hOO, ngay 31/5/2012. Budc thdi gian de chay md hinh la 1 phiit.
Dieu kiin bien:
Tai cac bien nid phia biln (Thuan An, Tu Hien); dimg ede hang so dilu hod thuy trilu da dugc tinh toan vd npi suy phu hgp vdi dilu kien dia phuang.
V(ms)
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Hinh 3. So sdnh dong chay tinh todn va quan trac tai khu vuc phd Tam Gang trong miia mua
(11/2011)
(tren; van toe theo phuang nggng-U, du&i: van toe theo phucmg thdng dimg-V)
Md phong lan tmyen chat 6 nhiem ...
Md hinh chdt tugng nu&c
Md hinh Ian tmyln chdt lugng nude (Delft- WAQ) duae triln khai vdi cac thdng s6 COD, BOD5. Mien, ludi tinh, thdi gian tinh todn, eae dieu kien ban dau vd dieu kien bien tuong ty nhu mo hinh thuy ddng lue. Ngoai ra, cac tham
so dau vao cua md hinh chat lugng nude duge ldy tir edc ket qua phan tich vd ede gia fri tham khdo theo hudng ddn cua mo hinh.
Hieu chinh mo hinh bang each so sdnh ket qua md phong vdi ket qua quan frac lien tyc ngodi thue dia (bang 1).
Thdng so BODs (mg/l) COD (mg/l)
B a n g l So sdnh gia tri ldn nhdt gida mo hinh va quan trdc - phdn tich Mua miFa Miia kho Mo liinh Quan trie Md hinh Quan trie
5,5 6,58 6,0 4,54 20,0 21,97 25,0 14,06 KET QUA NGHIEN ClTU
Mo phong thuy d^ng lure Dong chdy
Ket qud mo phong tdc dp dong chdy khu vuc dam pha Tara Giang -Cau Hai duge trinh bdy trong hinh 4.
Sy tuong tdc cua cac thdnh phan: dong trieu, ddng chay bien ven bd, dong nude sdng vd tac ddng cua gid ben tren mat nudc cua chinh thuy vuc da tao nen dong chdy tdng hgp trong he ddm pha. Dong chdy he ddm pha TG- CH tuang doi phuc tap do su tuang tdc cua cac thanh phan fren cdng vdi sy bat dong deu cua hinh hge dudng bd thuy vyc nude va phdn bo do sdu cua no cung co nhung anh hudng, lam cho biic franh ddng chay tdng hgp rdt khde nhau fren khdng gian vung nudc.
Trong miia mua (thang 11/2011) van tic dong chay cd gid tri ldn nhat dat l,0-l,2m/s tai cua Thuan An, dat gia hi nho nhdt tai khu vuc ddm Cdu Hai, dat 0,15m/s. 6 cira Tu Hiln do bi tiiu hep vd nong nen van tie dong ehay ca khi trilu len vd xuing deu yeu. 0 khu vuc ddm Thuy Tii tic dp ddng chdy cue dai dat 0,18m/s, pha trilu chdm hem I gid so vdi eiia Thudn An vd 20 phiit so vdi cua Tu Hien. Do vdo miia mua, luu lugng nudc song Huang ldn nen dong chay tii trong song chdy ra phia ngodi cua van chilm uu thi trong pha trieu len, khoi nudc biln chu ylu di vao tiong khu vyc dam pha va it khd nang xdm nhap sau vdo tiong song.
Hinh 4. Trudng toe dp dong chay trong thdi ky a) nudc rong-miia raua; b) nudc Idn-miia mua;
Cao Thi Thu Trang, Pham Hdi An,...
Vdo miia kho (thdiig 5/2012), van tdc dong chdy dat gid tii ldn nhdt khoang 0,7-0,8 m/s tai cira Thudn An, dat khoang 0,06 m/s tai khu vuc ddm Cdu Hai va dat khoang 0,09-0,28 m/s d khu vuc ddm Thuy Tii. Van tic dong chay tai khu vye Tam Giang dat 0,03-0,1 m/s, pha tiieu chdm 40 phiit so vdi cira Thuan An, tioiig pha trilu xuong lugng nudc song Huomg phdn ldn chay ra cira Thudn An va mgt phdn chdy vao khu vuc ddm Thuy Tii, khoi nudc trong pha Tam Giang chay ra theo hudng Dong Nam din cita Thudn An gap khoi nudc song Huong vd dupe day ra ngoai bien qua cua Thuan An.
Trao doi nudc
Cdc kit qua vl lugng nudc vd ty le frao dii nudc qua mgt ngay dem tai ba khu vyc co ddc dilm sau: ddm Cdu Hai cd di?n tich va thi tich ldn nhdt sau dd din Thuy Tii va J a m Giang la nho nhdt. Tuy nhien, ty le trao ddi nude frung binh ngay (%) lai cd xu thi ngugc lai, Tam Giang la khu vyc co gid tri ldn nhdt, sau dd ldn lugt Thiiy Tu, Cdu Hai. Dieu nay hodn toan diing so vdi thyc te, khu vuc dam Cdu Hai co luu lugng song nho va cira Tu Hien hep, tiong khi khu vuc Thiiy Tu co cira Thudn Aji vd Tam Giang co luu lugng sdng dang ke dd vao. Su chenh lech giiia thdi gian chay ra va thdi gian chdy vao eua cac khu vuc dugc the Men fren bang 2.
Bang 2. Lugng nudc va ty le frao doi nudc qua mdt ngay dem tai ba khu vyc Tam Giang - Thuy Tu - Cdu Hai
•c trao dof Irung binh ng^y (%)
31,7 21,5 21,5 43,0 .^,^ 25,8 17,1 17.1 34,2 102 163,0 5,95 2,74 8,69 3,21 4,42 3,51 7,93 0,90 3,65 1,68 5,33 2,71 2,15 4,86 42,5 75,
60.0 95,
10,7 24.2 2,9 16,5 16,4 32,9 0,04 17,8 14 12,2 24,6 0,13 16,3 16,3 32.6 „ „ ^ 12,9 12,8
Theo ket qua tinh todn tir mo hinh cho thay sy trao doi nudc frong ddm pha chu yeu do dong chdy, ddng chdy van chuyen nudc tir vimg nay tdi vimg khac, hinh thdnh su trao doi nude theo mat r6ng cua vye nude. Tai dam Cdu Hai, tiong dieu kien khong co lii ldn, lugng nude tiong ddm luon cdn bang va van chuyen uu the ve _phia cira Thuan An so vdi ve phia cira Tu Hien. Tai dam Thuy Tii, vdo cd 2 miia raua va kho, cdn bang nude deu chdy ve phia Tam Giang, chirng to lugng chdy song Huang hdu nhu khong dnh hudng den dara Cdu Hai, ke ed khi mua lii. Tai pha Tara Giang lugng nudc ludn can ban_g vdo miia kho va edn cdn luu lugng lech han ve phia lugng chdy ra so vdi chay vdo trong miia mua.
Ve miia khd, do luu lugng eac song rdt nhd, lugng chdy tir bien vao dam phd ldn, luu lugng
ldn nhat tai cira Thudn An theo ti'nh toan cua mo hinh dat 975 ra Is va cua Tu Hien dat 15 m^/s. Ve raiia mua, do luu lugng cac song do vao ddm phd chiem uu the ve thdi gian chay ra phia bien, luu Iugng ldn nhat tai cira Thuan An theo tinh toan cua mo hinh dat 1.877 mVs vd eiia Tu Hien dat 67 mVs. Thdi gian chdy ra tai ciia Thudn An gap 4,8 ldn thdi gian chay vdo yd thdi gian ehay ra tai cira Tu Hien gap 2,7 ldn thdi gian chdy vdo frong mua mua.
Theo nghien ciiu trong ludn van thac sy ciia ttac gia Nghiem Tien Lam (2002) tinh todn bang mo hinh DUFFLOW nam 2000 tai ciia Thuan An gia tn cyc dai cua luu lugng dat 2.400 m Is vd tai cira Tu Hien gid tit cue dai ciia luu lupng dat718mVs.
Mo hinh chat luong nirdc Nhu cau oxy sinh hda (BODs)
Mo phong lan tmyen chdt 6 nhiem . Trong miia mua, ndng d6 BOD5 co gid tri
1,5-6,5 mg/l (gid tri quan trac thuc te frong khoang 1,72-6,58 mg/l). Tai cdc khu vuc ciia sdng vd cira bien nong dp BOD5 eo gia tri cao hem cac khu vuc khac, tiong dd khu vyc cita sdng Huang va cua Thudn An BOD5 co gid tri ldn nhdt dat 6,5 rag/I, tai eita sdng O Ldu dat gia tii ldn nhdt 5,0 mg/l va cua Tu Hiln la 4,5 mg/l, con lai cac khu vye khac nong dp BOD5 thudng khdng vugt qua 2,0 mg/l tiong cd pha trieu xudng va len.
- ^
Hinh 5. Mo phong lan tmylnBODs (mg/l) khi:
a) tiilu len-miia mua;b) trieu len-miia kho
Mua kho, nong do BOD5 bien doi frong khoang 1,2-6,2 mg/l (gid frj quan trac thyc te tiong khodng 3,38-4,64 mg/l) trong ea pha trieu xuong va pha trieu len (hinh 5b). Tuy nhien, miia kho nong do BOD5 ldn nhdt xudt hien tai khu vuc cira Tu Hiln (frong cd hai pha trieu), khu vuc cua song Huong vd eua Thuan An;
ning doBODj cyc dai la 5,8 mg/l trong pha trieu xuong va 6,0 mg/l tiong pha trieu len, khu vuc cira song O Ldu vd song Tmoi co gid tri cyc dai trong khoang 3,0-5,0 mg/l. Cdc khu vyc khac nong dp BOD5 khong vugt qua 3,8 mg/l trong pha trieu len vd 4,5 mg/l trong pha frieu xudng.
Du bdo den nam 2020 nong do BOD5 khu vyc nghien ciiru bien doi frong khodng gia tri 2,0-10,0 mg/l tiong miia kho va co the dat gid tri fren 10 mg/l trong miia mua. Trong mua mua CO sy xdo trpn manh hem so vdi mua kho, dac biet tai tai ciia song Huong vd cira Thudn An, noi eo su frao doi nudc manh giira song va ddm phd, giira ddm pha vd bien. Cdc khu vyc khac CO sy biln dpng khong ddng ke.
Nhu cdu oxy hda hgc (COD)
Trong mua mua, nong do COD khu vuc nghien ciiu bien doi trong khoang gid tn 3- 20 mg/l trong ea pha trieu xuong va pha trieu len, nong do COD eye dai tron^ ca hai pha trilu la 20,0 rag/1. Khu vye eo nong do COD ldn nhat tap tmng tai cua song Huang va cua sdng Tmdi, khu vuc Ddm Sam ndng do COD dao dgng trong khodng 7-! 3 mg/l, khu vuc pha Tam Giang dao dpng trong khoang 4-12 rag/1, va khu vuc cua Tu Hien, ddm Cdu Hai va Thiiy Tii cd gid tri thdp hon so vdi eae khu vuc khde (khdng vugt qua 4 mg/l).
Miia kho, nong dp COD khu vuc nghien cim bien ddi frong khodng gia tri 3-22 mg/l trong cd pha trieu xuong va pha trieu len (hinh 6b). N6ng do COD cyc dai tap frung tai khu vuc ciia Thudn An, khu vye Thudn An den Tam Giang, sau do den khu vye cira sdng Huong CO gid tii ldn nhat 17 mg/l trong pha trilu len va 19 mg/l trong pha trieu xuong.
Dy bdo din nam 2020 ning do COD khu vuc nghien ciru co the gap doi gid tii hien nay vd bien dii tiong khodng 5-50 mg/l. Khu vuc
Cao Thi Thu Trang, Pham Hdi An,...
tmng tam dam Cdu Hai hdu nhu khong cd su xdo trpn frong ca hai miia. Cae khu vue cua song Huang, Traoi vd eua Thudn An c6 sy xdo tron manh vdo ca hai miia.
"^
Hinh 6. Mo phong lan tmyen COD (mg/l) khi:
a) trieu len-miia mua; b) trieu len-miia kho KET LUAN
Su lan tmyen ciia edc chat hiiu ca phy thupc nhieu vao che do dpng luc eiia khu vyc nghien ciiu. Cac khu vye eo su bien ddng manh ve nong dp la nhirng nai eo su tuang tac manh giua nudc song-dam phd, bien-dam pha. Nong
dp BODs cira song Huang, Thuan An co gia hj ldn nhdt, sau do din cac khu vuc ciia song 0 Ldu, Tu Hiln, Tmdi, Ddm Sam yd Thuy Tii.
Vdo raua kho, khu vyc ciia Tu Hien, ciia song Huang va cua Thuan An ed gia tri BOD5 ldn nhdt so vdi edc khu vyc khac. Vdo mua mua, ndng dp COD tai cua sdng_ Huang, Truoi va Ddm Sam ed gia tri ldn nhat, sau do ldn lugt din pha Tam Giang, Tu Hien, dam Cau Hai vd Thuy Tu. Tuy nhien, vao mua khd, ndng dp COD khu vue Thudn An, Tam Giang co gid trj ldn nhdt, sau do den cira sdng sdng Huang va cac khu vyc khde.
Cdc kit qud tinh toan, du bao cua mo hinh da the hien dugc phdn nao quy ludt lan tmyen chdt gay 6 nhilm d vung TG-CH vdi sy tac done cua nhieu yeu td khac nhau, frong do ngudn cung cdp tir luc dia, tai lugng nudc song va che do thuy dpng lyc la nhiing yeu to anh hudng hudng trye tiep va quyet dinh den nong do va phan bo cua cac chat hdu eo tiong nudc, LM cam en: Bdi bdo dugc hoan thanh dudi su hd frg cua dl tai TTH.2011-KC.il va dl tai KC09-17/11-15. Cac tac gia xin trdn trpng cam an.
TAI LIEU THAM KHAO
1. Trdn Due Thanh, Trdn Dinh Ldn, Nguyen Hiru Cu vd Dinh Vdn Huy, 2010. Tien hod va ddng lyc he ddm pha Tara Giang - Cau Hai. Nxb. Khoa hgc Tu nhien va C6ng nghe. Ha Ndi. 225 tr.
2. S& Khoa hgc vd Cong nghe Thira Thien Hue, 2004. Ddc dilm Khi hau- Thuy van tinh Thira Thien Hul. Nxb. Thuan Hoa.
3. Matsumoto, K., T. Takanezawa, and M.
Ooe, 2000. Ocean tide models developed by assimilating TOPEX/POSEIDON altimeter data into hydronamical model, a global model and a regional model around Japan J.Oceanogr, 56, 567-581.
4. WL\ Delft hydraulic, 1999, 2003. Delft3D- WAQ User Manual version 3.1, Delft, the Netherlands.
5. WL\ Delft hydraulic, 1999, 2003. Detailed description of processses. Delft3D-FL0W Technical Reference Manual. Delft, the Netherla.
Md phdng lan tmyen chat d nhiem . . .
POLLUTANT TRANSPORT SIMULATION IN TAM GIANG - CAU HAI LAGOON, THUA THIEN - HUE PROVINCE
BY USING DELFT-3D MODEL
Cao Thi Thu Trang\ Pham Hai A n \ Tran Anh T u \ Le Due Cuong', Tran Due Thanh', Trinh Thanh^
'institute of Marine Environment and Resources-VAST
^Institute of Science and Environmental Technology-HTU
ABSTRACT: Based on collective and survey data on hydrometeorology and water quality in Tam Giang - Cau Hai lagoon, Thua Thien - Hue Province, hydraulic and pollutant transportation in lagoon system had been simulated by using Delfl-SD model. The study results show that the current velocity is highest in Thuan An inlet, it reaches 1.0-1.2 m/s, the lowest velocity is in Cau Hai lagoon. The water exchange rale in lagoon is quite low with the values of 31.7% in Tam Giang, 25.8% in Sam - Thuy Tu lagoon and 5 33% in Cau Hai lagoon. Concentration of pollutants is high in river mouths and inlets such as Huong, Truoi, Thuan An, O Lau and Tu Hien. The simulation results show that the values of nutrients and organic mailers in water are high in these areas, even higher than limitation value.
Keywords: Model, lagoon, pollutants, water quality, simulation.
