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sO KHOA HgG CONG NGH~ VA MOl TRUONG TRUNG TAM KHOA HOC TU NHIEN VA CONG NGH~ SOTHU'LQI • Qu4c SIA • - ? HQI THAO KHOA HQC E AM Hi THUA THIEN - DE SEMINAR ON COASTAL LAGOON OF THUA THIEN - HUE Hai Phong 07 - 08 Nov 1994 - , HQI THAO KHOA HQC VE DAM PHi THOA THIEN - HUE Co quan chu tri: PHAN VI~N HAl DUONG HOC TAl HAl PHONG De tai cap nha ruroc KT.03-11, chuang trlnh KT-03 Co quan to chuc: - vu PHAT TRIEN CeJNG NGH~, TRUONG 80 KHOA HOC CeJNG NGH~ vA MeJl - PHAN VIEN HAl DUONG HOC TAl HAl PHONG, TRUNG TAM KHOA HOC TU NHIEN VA CeJNG NGH~ ouoc GIA - TRUONG DAI HOC THUY LOI, Ban 80 THUY LOI to chuc: - KS Truong Trl Tan, Trl.fong ban - PTS Nguyen Chu Hai, - PTS Trinh Quang Hoa, Uy vif§n Uy vh§n - PTS Tran Dire Thanh, Thu ky thl.f6'ng true MVC lVC Trang Loin6idau Truong Chi Tan Tam quan tronq ve khoa h9C va kinh te xii h9i vunq pha Tam Giang Nguyen Chu Hoi Tiep can nghien Cl1USLr dl:mg hop IV tai nquyen va phat tri~n lau ben rnoi tnronq dam pha Tam Giang - Cau Hai Ho Nqoc Pha Tam Giang - nci h9i tu cua nhieu van de khoa h9C Nguyen Dinh Hoe va nnk M9t s6 dac di~m dia d9n9 hrc n9i sinh hi$n dng kinh te quan tronq, mang lai qia tri tai nquyen cu the va vo hlnh to Ion mot phvong dien nao d6, c6 the n6i, su ton tal cua dam pha anh hu'ong quyet dinh den sir phat trien kinh te· - xa h(>i cua Thua Thien - Hue Tuy nhien, nhan thuc ve ban chat tu nhien va qia tri tal nguyen h$ sinh thai dam pha TG - CH nhieu han hep Do d6, viec SLt dunq khai thac dam pha chua hop Iy, chua hieu qua, kh6ng lau ben, da noi com len cac doi khanq IQi lch sir dunq, nguy co can kiet tai nquyen, thoai hoa rnoi truonq NhGng van de quan Iy rnoi trvong va che ngl! tai bien tro len cap bach nhu ng~p lut, nhiern ban, nhiem man, ach tac giao thong chuyen, lap cua VI the yeu cau phai c6 mot mo hlnh Slr dunq hop Iy va lau ben dam pha TG - CH De dat muc tieu can phai c6 nhO"ng hieu biet co ban ve rnoi tnrcnq tu nhien, sinh thai va tai nquyen dam pha Bai viet danh gia t6ng quan va c6 h$ thong nhunq van de dua tren nhO'ng tai li$u da c6, dac biet la nhieu tai li$u dieu tra khao sat moi cua de tai KT.03.11 Phan vi en Hai duonq h9C tai Hai Phonq chu trl voi sir tham gia cua cac can b(>chuyen men cac truonq Dai hoc t6ng hop Ha N6i va Hue a V! TRi H~ SINH THAI DAM PHA TG - CH TRONG H~ THONG DAI VEN 80' VI~T NAM Dam pha ven bo la m6t nhO'ng doi tuong dune dac bi$t quan tam tren the gioi [7,9,16] Duci cac g6c khac dam pha TG - CH da dune dieu tra khao sat tir lau [1,8,15], nhunq chi den gan day mci ducc ghi nhan la mot loai hlnh thuy vue co ban va tieu bieu ven be nuoc ta [4,12,14] l.an dau tien de tai KT.03.11 n6 duoc nqhisn cuu v6i tv each la mot h$ sinh thai ven be doc lap ngang cap vci cac h$ sinh thai cira song chau th6, cua song hlnh pheu va cac vinh ven be a Viec nhan thuc dung dan kieu loai h$ sinh thai da tao nhGng dinh hvong dung dan ve phucnq phap dieu tra khao sat, n(>i dung nqhien ciru va muc tieu su' dung, quan IY He dam pha TG - CH la mot vung bien (lagoon) 16n nhat, tieu bieu nhat so 12 dam pha phan bo khoang vi d(> 11 - 170B mien Trung Vi$t Nam va cOng thuoc loai co Ion tren the giai N6 thu6c kieu cau true gan kin, c6 cira thong, theo phan loai cua Nichols [7] a 52 VI tri va tinh dia doi, H$ dam pha TG - CH la mot lagoon nhiet dci, nuoc 19, narn d phia tay Bien Dong, noi co hu'ong qio thinh hanh huang dong vci tan xuat 56 % thai dai trang thanq Khac voi hau het cac dam pha khac.con lai narn d cac vung mua it hoac trung blnh d Trung 8(>, Tam Giang - Cau Hai narn a' phia bac deo Hai Van thuoc mien ven bo tay vinh Bac 8(>, noi co luc;mg rnua thuoc loai Ian nhat nucc ta, tren duoi 3000mm/nam [10], Sl/ trung h9P giO'a rnua kho vao rnua he nong va mua mua vao rnua dong lanh cunq vci nhO'ng khac nghiet ve thai tiet anh huang sau sac den rnoi trucnq tu nhien va sinh thai h$, cAc HO'P PHAN TV' NHIEN CUA H~ Hinh thai va cau true H$ dam pha rang 21600 keo dai 68km, rang nhat 8km, hep nhat O,6km, co d(> sau trung binh 1,5 - 2m va ducc chia pharr Phla bac la pha Tam Giang, doan giO'a la An Tuyen Thuy Tu va phia nam la dam Cau Hai Vl/c rurcc co the tlch trung blnh 300 trieu m3, co rnua 10 tren 400 trieu m3 Phia sau vue rurcc la dong bang cat Holoxen, chan truce vue nucc la dai can dun cat cao - 10m den 60m, Vl/c ruroc dam pha thong voi bien qua cira Tu Hien a phia nam va Thuan An a phia bac 'Cua Tu Hien rang 50 - 100m, sau - 2m va thinh thoanq b] boi lap Cira Thuan An r(>ng 250 300m, sau den - 7m va co huonq dich len phia bac the ky qua [13] Do vao dam pha co cac song Ian nhu song Hucnq, 80, Dai Giang, Truoi Tnrcc cira song Huonq, 80, phat trien cac cau true vi chau tho trang lagoon Cac delta trieu phat trien a phia trang cira Tu Hien, phia nqoai cua Thuan va phia nam Thuy Tu Hai phia dam pha phat trien cac them, bai lagoon cao - 4m Cau tao bang cat, cat bot D,a chat khu vue va tram tfch nen day H$ dam pha phat trien tren nen kien true Hecxinit co be day Holoxen co the dat 50 - 60m, nhung nhieu cho tram tich Pleixtoxen 1(>gan be mat He dam pha hlnh va phat trien trang thai gian Holoxen Pha Tam Giang phat trien theo co che cua mot lagoon thuc thu Khu cua song Hucnq phat trien cau true chau tho nhu mot h$ phu Dam Thuy T0 phat trien ke thtra tren long song co Dam Cau Hai phat trien ke thtra tren nen vong kien tao rat tre Su phan di theo chieu doc cau true tao nen sir khac biet sau sac cac yeu to tu nhien va sinh thai h$ SU' phan bo tram tich day dU'9C phan biet theo tieu khu vue phan anh tuong tac song bien a Tieu khu Lau - Truoi - Cong Ouan dac trung bot Ian va bun bot nho xarn den qiau rnun ba huu co b Tieu khu Dam Sam la cat hat nho, bot Ian xarn den c Tieu khu cua lagoon Tir Hien, Thuan An cat mau vang Ian vo sinh vat d Tieu khu Tam Giang - Thuy T0 va cac bai ngap trieu ven dam Cau Hai tram tlch rnin dan theo chieu sau, rnau nau vanq, xarn nau e Tieu khu Cau Hai bun bot nho xarn xanh Cac tieu khu a va b dac trung cho moi truonq chau tho; tieu khu c - rnoi truong tach cira: tieu khu d - cho rnoi tnronq kenh trieu, bai trieu lagoon; tieu khu e - rnoi tnrcno ho lagoon 53 ; • Ve dia hoa tram tfch, I au het dam pha c6 qia trj Fe3+/Fe2+ ng vat noi, dong vat day dam pha Thua Thien Hue Thong tin khoa hoc va conq nghe Ban khoa h9C va ky thuat tinh Thira Thien - Hue T Nichols M and Allen G., 1981 Sedimentary process in coastal lagoons UNESCO Tech Papers in marine science No 33 Ton That Phap, 1993 Cau true phan loai va mot so dan li$u sinh thai khu h$ thuc vat thuy sinh pha Tam Giang tinh Thua Thien - Hue Thong tin khoa h9C va conq nqhe Ban Khoa h9C va ky thuat tinh Thua Thien - Hue T Phleger F.B,1978 A review of some general fearure of coastal lagoons in "Coastal lagoon research Present and future" Proc of Seminar Duke Univ 10 Le Khac Pho, 1993 Khl hau dong bang khu vue Hue So van hoa, Thong tin - Th~ thao - Hue 11 Va Van Phu, 1993 Thong tin khoa h9C va conq ngh$ Ban khoa h9C va ky thuat tinh Thua Thien - Hue 12 Tran Dire Thanh, Nguyen Due Cu va NNK, 1985 Dac di~m dia chat - dia mao dai ven be phia Bac Viet Nam Bao cao de tai 48.06.14 Liru trCr tai Phan vien Hai duonq hoc tai Hai Phonq 13 Tran Dire Thanh, 1985 cCra Thuan An va Tu Hien NhCrng phat hien rnci ve khao c6 hoc narn 1985 Vien khao co Ha Noi 14 Tra~ Due Thanh, 1991 D~c di~m co ban cua cac bon tich tu hi$n dai tieu bi~u dai be tay vinh Bac B¢>.Tai nquyen va moi tnronq bi~n T NXB Khoa h9C va ky thuat Ha Noi 15 VO Trung Tang va Dang Thi Sy, 1977 Nguon linghl khoa h9C bi~n toan quoc Ian I, Nha Tranq 16 URA 1355 (Unite de recherche associe'e), 1992 Ecosystems lagunaires Organisation biologique et fonctionnement Universite' de Montpellier II SUMMARY PRINCIPAL PROBLEMS ON NATURAL CONDITIONS, ECOLOGY AND RESOURCES OF THE TAM GIANG - CAU HAl LAGOON Tran Due Thanh Nguyen Chu Hoi With an area of 21,600 ha, length of 68 km and mean depth from - m, Tam Giang - Cau Hai is a coastal lagoon typical in Vietnam It is a brackish water lagoon situated in the region with high rainfall (about 3,000 mm a year) Having two inlets, it belongs to the nearly closed type of structure The formation and development of the lagoon are as a result of the interaction of recent tectonic movements, runoffs, waves and sea level changes exposed in morphology and sediment distribution patterns 62 The river influence on the lagoon is important but unequal with season and space, the wave role is great but the tidal role is small Hydrochemical factors change in a wide range within a day, with season, depth and length of the water body The water circulation is very restrictive, exposed clearly in the water stratification that never has been seen before in the coastal zone of Vietnam The phytoplankton flora is abundant in species (171) but poor in biomass On the contrary, the zooplankton fauna is poor in species but rather rich in biomass too and hydrophyte flora and benthos fauna are poor in species but rich in biomass In the lagoon, there are 182 marine, brackish and fresh fish species of which Ciprinus centralis is an endemic species Nutrients are often poor in water but rather rich in bottom sediments and provided mainly by the rivers With an output from 70 - 280 mgC/cub.m a day, the primary production of phytoplankton is of significance Meanwhile, the water grass playa very important role in the lagoon ecosystem because of its high primary production The fact that there exists a short food chain has made the output of the ecosystem rather high Stratifying water, moving and closing inlet and sedimentation are dynamic characters of the lagoon The closing of the Tu Hien inlet has made serious influences on lagoonal environment, ecology and economy The lagoon has, in resources, a very great potential for developing fishery, waterway transportation, tourism, etc The most valuable resources is, however, a habitat for over 300,000 people among which 195,000 people have their life closed to the lagoon There have been many urgent problems on the lagoonal environment which need to be managed such as flood, inundation, freshening process in rainy season, salt intrusion in dry season, enclosing inlet, pollution and exploitation of aquatic living resources Besides these, the benefit conflict has emerged from economic activities A master plan is, therefore, necessary for sustainable environment development and the suitable resource utilization of the Tam Giang - Cau Hai lagoon 63 ... rurcc co vai tro tien phong chuyen hoa dinh du'ong va co cua he dinh dvong hO'u co bang each tieu thu va chuyen hoa true tiep dinh duong va co tu nen day Buoc dau, nang xuat so cap thuc vat noi... cho tren 30 van dan cu tren va ven dam pha lien quan den vunq dat c6 di$n tlch 89.000 trang d6 c6 26.000 mat rurcc dam pha, 49.000 dat dong bang va 19.000 dat cat (con dun bai) ven bien Nho c6 ... keo dai, co hai cira thong voi bien, cau true gan kin va co su phan di sau sac theo chieu dQCthe hien tfnh ke thira cua cau trucdia chat va quan h$ tuong tac cua cac yeu to dong lire: chuyen d( >ng