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BAD VE• MOl TRUUNG VA NGUON LIJI THUY SAN • Hai Ph6ng, 14 - 15/01 /2005 ~ NHA XUAT BAN NONG NGHI~P 44 33 NGHIEN COD CONG NGHe NUOI GIUMOT SO LoAI SINH VAT BIEN QUY HIEM G6p PHAN BAo ve DA DANG SINH HOC Pham Thi Nhan 34 366 V va nnk NGUON LQI cA TAP BIEN VIeT NAM: THANH PHAN, sAN LUQNG, cAc HudNG SU'DVNG CHiNH VA TiNH BEN vONG KHI LAM THOC AN TRONG NUOITRONGTHUYsAN 45 C 379 Bl Le Anh Tudn 35 PH{JC HOI vA BAo ve cAc THAM co BIEN -MO HlNH QuAN LY VA PHAT TRIEN BEN vONG vUNG BIEN VEN BO Nguyin 36 37 C( 46 D 388 47 D uo« Dt;li Cl QuAN LY VA PHAT TRIEN NGUON LQI THUY sAN VUNG NGAP LV CUA DONG BANG SONG cUD LONG TRONG TiNH HlNH Mdl t.e Xuan Sinh 397 QuAN LY NGUON LQI TREN Cd sa CONG DONG: NGHIEN CW DIEM a RAN TRAo (KHANH HOA) vA PHU LONG (HAl PHONG) 416 48 49 Bui Dinh Chung / 38 SU'DVNG HQP LY He SINH THAI co BIEN VIeT NAM 426 Nguyin Van 39 40 50 SU'DVNG TAl LIeU ve TINH NGHIEN CW PHAN BO, BIEN DONG MUA cAc THONG So MOl TRUONG (CHL-A vA TSS) LIEN QUAN DEN PHAN BO cAc NGlJTROONG VlNH BAc BO Trdn Van Dien, Trdn Dinb Lan, Do Thu Huang 434~ UNG DVNG cAc KET QuA NGHIEN CW TUONG QUAN CA-MOI TRUONG TRONG xA Y Dl)NG VA TRIEN KHAI MO HiNH mr BAo cA NGU DAI DUONG 447 Dinh Van Clu,Doan Van 41 ru« ~ cAc PHUJNG PHAp tnc 51 52 e», Chu Tien vte« TiNH TRULUQNG cA BIEN VIeT NAM D{ing Van Thi, Nguyin Viet Nghia, Vii 457 53 vt« na H 42 ntnc DAU DANH GIA TAc DONG CUA HO HoA BlNH DOl vor NGUON LQI cA BIEN VEN BO 472 Trdn Due Tht;lnh,Do Dinh Chien 43 Billc DAU LUQNG GIA KINH TE CUA MOT SO THAM co BIEN VEN BIEN PHlA BAc VIeT NAM Nguyin tt« Thu 10 , ,-' 54 N 488 ABSTRACT PRELIMINARY ASSESSMENT COASTAL ON EFFECTS FISHERY OF HOA BINH DAM ON RESOURCES Tran Due Thanh, Do Dinh Chien Haiphong Institute of Oceanography Analyzing data on current, salinity, bottom topography and sediments, and suspended sediments shows that the water volume and accompanied maters from the Red River appear to influence on the whole Tonkin Gulf, however, strong effect on the depth of 30m and obvious effect on the depth of 50m In the Tonkin Gulf, the best fishing grounds are distributed in the Vietnamese sea part and in shallow water less than 50m deep The spawning season is from April to September, and the fishing season is from June to November Due to building and operating Hoa Binh Dam, the change and loss of a great volume of fresh water, sediments and nutrients, which are discharged from the Red River into the sea have made serious impact on resources and the environment in estuary and coastal sea The reduction of coastal fish resources is one of the heaviest impacts It is a combined consequence of reducing nutrients; change in ecological factors (current, salinity, tllrbidity etc.); loss or degradation of habitats and breeding grounds, block of bearing migration of some fish species, and pollutant concentration in coastal environment An initial calculation shows that during the last years, fish stock in Vietnamese seaof the Tonkin Gulf has been reduced by 185,500 ton equal to 24.6% of the original stock The impacts of building and operating Hoa Binli Dam have contributed to reduce 42,665 tOI1 of fish, of which 3,710 tons have been reduced by decreasing nutrients discharged directly from river; 24,115 tons by decreasing phosphorous nutrient moved from seabed upwardin the situation of fresh water store in the dam during the rainy season; and 14,840 tons due to other reasons This assessment needs to be referral to the bigger hydroelectric damof Son La whish is under preparation upstream the Hoa Binh Dam BVOC DAU DANH GIA TAc DONG CUA HO HoA BINH DOl Val NGUON LOI cA BIEN VEN BO Do Tran Due Thanh va Dinh Chien Phdn vien Hdi duang 1z9Ctai Hdi Phong MO DAU Theo thong ke narn 1998, trai dat co 47.655 ho mrcc Ian a tren 150 ruroc, d6 nhieu ho chira da gay thiet hai Ian cho nghe ca bien yen ba (WCD, 2000) Viet Nam, tir sau 1975, viec xay dung cac ho phat trien kha manh mroc da co khoang tren 650 h6 Ca 472 ABSTRACT PRELIMINARY ASSESSMENT COASTAL ON EFFECTS FISHERY OF HOA BINH DAM ON RESOURCES Tran Duc Thanh, Do Dinh Chien Haiphong Institute of Oceanography Analyzing data on current, salinity, bottom topography and sediments, and suspended sediments shows that the water volume and accompanied maters from the Red River appear to influence on the whole Tonkin Gulf, however, strong effect on the depth of 30m and obvious effect on the depth of 50m In the Tonkin Gulf, the best fishing grounds are distributed in the Vietnamese sea part and in shallow water less than 50m deep The spawning season is from April to September, and the fishing season is from June to November Due to building and operating Hoa Binli Dam, the change and loss of a great volume of fresh water, sediments and nutrients, which are discharged from the Red River into the sea have made serious impact on resources and the environment in estuary and coastal sea The reduction of coastal fish resources is one of the heaviest impacts It is a combined consequence of reducing nutrients; change in ecological factors (current, salinity, turbidity etc.); loss or degradation of habitats and breeding grounds, block of bearing migration of some fish species, and pollutant concentration in coastal environment An initial calculation shows that during the last years, fish stock in Vietnamese sea of the Tonkin Gulf has been reduced by 185,500 ton equal to 24.6% of the original stock The impacts of building and operating Hoa Binb Dam have contributed to reduce 42,665 ton of fish, of which 3,710 tons have been reduced by decreasing nutrients discharged directly from river; 24,115 tons by decreasing phosphorous nutrient moved from seabed lipward in the situation of fresh water store in the dam during the rainy season; and 14,840 tons due to other reasons This assessment needs to be referral to the bigger hydroelectric dam of Son La whish is under preparation upstream the Hoa Binli Dam BlfOC DAU DANH GIA TAc DONG CUA HO HoA BiNH DOl Val NGUON LQI cA BIEN VEN BO Do Tran Drrc Thanh va Dinh Chien Phdn vien Hdi duang hoc tai Hdi Phong MO DAU Theo thong ke nam 1998, trai dat co 47.655 he mroc Ian a tren 150 mroc, a nhieu he chira dii gay thiet hai Ian cho nghe ca bien yen be (WCD, 2000) Viet Nam, tir sau 1975, viec xay dung c~c he phat trien kha manh Ca mroc dii co khoang tren 650 472 he co Ion va vira, tren 3.500 ho COnho (ADB, 1993; WB et al, 1996) Cac ho co sire chira Ion tap trung tren hru vue song Hong va Dong Nai, ho Hoa Blnh, Thac Ba va Tri An diroc xep van nhom 18 ho Ion nhat chau A co dung tich chira tren ty rrr' mroc Cong trinh ho Hoa Binh khoi cong 6/11/1979 va t6 may so bat dftu van hanh tir 30/12/1988 Hd Hoa Blnh co dung tich chira 9,45 ti rrr', thuoc loai Ion tren the gioi va dirng hang thir ur chau a (tlnh den 1995) Tac dong tieu cue cua ho Hoa Blnh tren hru vue dil diroc danh gia qua mot so cong trinh nghien CUu(Nguyen Thuong Hung va nnk, 1995; Vii van Tuan, 1999) Tuy nhien, viec danh gia anh huang cua cluing tai moi tnrong cira song va yen bo rat han che (Trdn Dl(C Thank va Do Dinn Chien, 2002) SI! thay d6i phan bo va mat di mot hrong Ion mroc ngot, tram tich va dinh duong tu song Hong dira bien xay dung ho Hoa Blnh dil gay nhirng hau qua nghiem nhieu mat ve moi tnrong, tai nguyen vung cira song va bien yen bo nhir thay d6i che d¢ dong chay, xoi la bo bien, xam nhap man, mat noi cu tni, bai giong va baide cua sinh vat, suy giarn dinh dirong va giam sire san xuat cua vung bien yen bo, dan den thiet hai ve da dang sinh hoc va nguon lei thuy san danh bat, nuoi a Bai viet trinh bay ker qua phan tich, danh gia hau qua cua cong trinh ho thuy dien Hoa Blnh doi voi nguon loi nghe ca bien yen be tay Vinh BAc B¢ (VBB) Viec suy giam nguon lei nghe ca bien yen bo rat nhieu nguyen nhan va viec danh gia hrong suy giam ho Hoa Blnh dua thee phtrong phap chu dao la phan tfch va tinh di~m so tac dong moi tnrong, ket hop sir dung kinh nghiern danh gia cua Chen T.A.C (2000) cho tnrong hop ho Tam Hiep tren song Truong Giang Do han che ve tai lieu, nhirng ket qua trinh bay a day moi chi la biroc dau, co tlnh ban dinh hrong, nhirng co y nghia dinh hirong cho nhfrng nghien cull tiep'theo, nhat la danh gia tac dong cua he thong bac thang thuy dien song Da (Nguyen Van Trang va nnk, 2000) PH~M VI ANH HlfONG CUA DONG V~ T CHAT SONG HONG DEN VUNG CUA SONG V A BIEN VEN BO T A Y V~NH BAC BO 2.1 Liru vue song va dong vat chat tit he thong song Hong Cac song d6 van bo' tay VBB co th~ phan chi a luu vue chinh: hru virc cac song vung Dong bac; hru vue he thong song Hong va Thai Blnh, hru vue cac h~ thong song Mil song Ca va luu vue he thong song Gianh - Tri-Htrong Theo hlnh thai dia hlnh, dai ba tay VBB diroc chia vung yen bo: Mong Cai- Do San; Do San - Lach Truong (ven be chau th6 song Hong hien dai); Lach Tnrong-Mili Ron va Mfii Ron- Hai Van (Tran Dire Thanh va nnk, 1985) Khi d6 bien, cac nhanh song cua cung mot he thong hru vue co th~ d6 van cac vung bo khac nhau, tao nen su khong dong nhat giira hru vue va vung yen be chiu anh huang Truce day, nhfrng tinh toan co ban cho VBB thuong chi tinh gioi han den khoang Mili Lay, het dia phan Quang Blnh Do vay, nghien ciru chap nhan gioi han vira neu d~ tien so sanh so lieu Theo do, hru lirong mroc song Hong-Thai Blnh chiern khoang 78% tong hru luong mroc d6 van be tay VBB (125km3/nam so voi 160 krrr'znarn) va dien tfch hru vue chiern 73,6% tong dien tich cac hru vue bo tay thu mroc van vinh (155.000km2 so voi 210.624 krn") 473 Hang nam mroc cac song d6 VBB tir be tay thuoc dia phan Viet Nam chiem 94,5% va tir yen bO' Trung Quoc chi 5,5% (Doi dieu tra Lien hiep Viet-Trung, 1965) Theo Nguyen Viet Ph6 (1984), trung blnh hang nam cac song phia Viet Nam d6 vao vinh 179 krrr' mroc va 125 88 trieu tan bun cat lo lirng Neu uac tinh ca bun cat di day chiem ty l~ 10% so vdi bun cat lo lirng thl tong bun cat tir song d6 khoang 138,6 trieu tan H~ thong SOng Hong va Thai Blnh hang nam d6 bien mot khoi hrong mroc khoang 125 ty rrr', mang 116 trieu tan cac chat ran, 70 trieu chat tan ran hoa tan va mot hrong dang ke chat gay a nhiem heat dong dan sinh-kinh te d9C theo cac trien song Dinh dirong cung cap cho vung yen be chau th6 song Hong (Cl'SlI) tir nhieu nguon khac Nguon tir song hang nam khoang 40.296 tan t6ng nito khoang hoa tan, 1.200 tan photpho khoang hoa tan, 17.600 tan silic khoang hoa tan Nguon dinh duong khoang nito hai dang N03' va N02- tir mroc mira cung cap true tiep cho vung cira song khoang 1.066 tan/nam RUng ngap man yen bo hang nam cung cap tir 6.237 tan nito va 205.435 tan ChIc (Nguyen Duc Cl! va nnk, 1998) 2.2 Hinh thai dia hlnh yen be chau thb song Hong VBB rong khoang 150.000km\ sau trung blnh 50m va cue dai 107m tai, mot triing sau gan cira vinh D9C doi bo vinh, co mat cac vilng vinh, chau th6, cira song hlnh pheu va cac darn pha Tong dien tich hru vue cac song d6 vao vinh khoang 300.000 krrr', e6 155.000km2 hru vue cua song Hong phia bo tay Cac dao vinh tap trung vung ven bo tay bac voi so hrong tren 2000 dao Ian nho Phfa ngoai vinh, ria them luc dia narn dQ sau 120m Dia hlnh day vinh kha thoai voi goc gee nho hon SO, hiern tai 10-30° Dai yen bo CfSH gom cac chau th6 n6i, chau th6 chim va tnroc chau th6 Dei chau th6 n6i (dong bang chau tho) co dien tfch khoang 17 nghln km", Trong do, phan chau th6 hien dai duoc hlnh khoang 3.000 nam qua, co dien tich 6.000 krn", dlnh nam phan Hung Yen, day trai dai khoang 150 km tir ban dao Do San den Lach Truong Dien tich chau th6 n6i de khong can chiu anh huang thuy trieu, rong 4500 krn" Phan chau th6 n6i ngoai de, hay la vung trieu,"r¢ng tren 500 krn' Dei chau th6 ngarn (delta front) la phan day nong, kha bang phang nam tnroc cira song chau th6, gioi han ngoai d¢ sau 6-12 m ruroc, dien tfch khoang tren 1000 krn", rong 5-15 km va keo dai tir Do San den Lach Truong Phia ngoai chau th6 ngam la dci truce chau th6 (prodelta), khoang sau 20-30 m Tai day d¢ doc tang, bun cat song dua lang dong rat It, vai tro cua song cling nhir cua song day giam h~n, v~t lieu tir luc dia dua chu yeu la cac san pharn rat nhir bun set nau hong, tich tu nho dong hai hru yen vinh Bac B¢ (Tri'in DL(C Thanli nnk, 1986) va 2.3 Dong chay yen bo' Dong chay tong hop yen bo crSH rat phirc tap va gem cac phan dong trieu, dong song, dong gio Moi dong phan phat huy iru the mot khoang nhat dinh cat ngang bo Dong chay trieu thuan nghich va co iru the vung mroc sat bo, trung binh d¢ sau m tro vao, co noi den 12 m Dong chay song phat huy doi song va bo, e6 huang phu thuoc vao huang gio, dia hlnh bo va bien d6i theo mua Dong chay gio co toe dQ khong Ion, thtrong 5-15 cm/s, irng voi toe gio ph6 bien 4-5 m/s yen bo, huang dong 474 a phu thuoc vao hirong gio, thirong phat huy chi tang mat tren khong gian rong, dong gop tich cue vao dong chay mua a yen bo Dong chay yen bo phat huy a d¢ sau 10 m den 25-30 m mroc va co tfnh chat mua, huong chay thirong song song voi bo Dong yen ba co vai tro quan doi vci di chuyen bun set lo lirng va dinh duong tren pharn vi rong, den d¢ sau 30 m va virot khoi ranh gioi phia tay nam, dong bac cua yen bo Cl'Sll Toe d¢ dong chay yen bo 10-15 cm/s huong ve phfa bac va dong bac vao mua he; 20-~0 cm/s, huong ve phfa nam va tay nam vao mua dong Hoan hru VBB co hirong chay d9C yen bo xuong phia tay nam quanh narn 2.4 Ngu truong vimg bi~n yen be tay vinh Bac Bthi se lam giam manh dinh dirong photpho dua len tang mat, nang suat SOcap va san lirong ca se giam nrong irng la 9% Voi ket qua cua cong trinh nghien ciru nay, co the danh gia dinh hrong nhirng thiet hai nghe ca bien he>.thuqng nguon gay Neu t6ng luong rnroc ngot mua mira li1cac song d6 vao VBB, phan bien Viet Nam tfnh den het pham vi Quang Blnh la 127 ti m' (75% ca nam), thi khoi lirong trung blnh tich mroc 479 mua mira lil va xa mroc mua kho cua ho Hoa Blnh la 5,65 ti rrr' (nrong duong dung tich hiiu Ich cua he), bang 4,45% tong hrong Mac du ho xa mroc vao rnua kho tiep theo, nhimg viec giam hru luong ruroc mua mira lil (thang 6-9) lam giarn dinh dirong, nang xuat sa cap va sinh khoi, dt dut mat xfch lien tuc chu6i thirc an Day la thai gian ca de va sinh tnrong manh Theo che d¢ van hanh hd, rmrc mroc +91m ±2m diroc trl thai ky Iii som 15/6- 15/7 hang nam, nam gitta mua ca di cu vao gan bo di de Tac dong gay thieu hut dinh dirong va thirc an vung cira song va bien yen ba vao thai ky gay tac dong 16'11 den nghe ca eft nam Luong mroc ngot tich lai ket thiic rnua mira lil diroc xa phat dien vao mua kho dira bien se co tac dung nhat dinh doi voi san hrong nghe ca nhirng khong Ian VI nhtrng ly sau: mot hrong mroc ngot dang ke diroc sir dung nroi v6 mua kho nho di6u tier mroc ho; hrong lai dira cira song yen ba chi tap trung sat cira song, khong du dong nang dira xa vao khu vue bien yen bo, nen tac dung dinh dirong chi pham vi rat hep sat bo: thai gian xa mroc phat dien mua kho khong phai la mua sinh de va phat trien manh cua cac loai thuy san (mira tom ca de thang 4-9) Cac chat dinh dirong mroc song dira dai yen ba ton tai b trang thai tan, phu va nam chat rAn lo lirng Chac chan xay ho, trfl ruroc, dinh dtrong dang huyen huyen phu va chat ran se bi giif lai luong dang ke Tham chi, dieu kien hoa ly ho cling co the lam thay d6i ham hrong dinh dirong tan mroc va hru giG"mot phan tai ho Trong s6 cac chat dinh dutmg, quan nhat la nguon phot pho, duoc danh gia Ia tai hrong 14.860 PO/" tan/nam doi voi he thong song Hong (Pham Van Ninh, 1995) Viec hru giff khoang 5,65 ti rrr' ruroc ho vao mira lil cling co nghia la lam giam di mot hrong dinh dirong dang ke song tai luc dia, nrong dirong 736 tan phospho tan Luong phospho nay, neu tham gia vao chu6i dinh dutmg cua he sinh thai co the tao hang ngan tan thuy san Thea Chen A.T.C (2000), luong ca mat di giam tnrc tiep dinh dirong tir song Truong Giang lien quan den thieu hut phospho dong cua ho chira chiern khoang 7% so voi t6ng hrong ca bi mat di tac Gia tang khd ruing a nhiem wing cua song Cung voi sir gia tang khoi hrong chat thai cac hoat dong dan sinh kinh te tren hru sir giam tai mroc se lam tang ham hrong chat gay nhiem mroc song d6 bien, dan den mire d¢ tap trung cao cua cluing b yen ba tai cac bAy nhiem, tac dong xau den V\!C, cac he sinh thai yen bo phia bac Tlnh trang nhiem mot so yeu t6 moi tnrong nuo'C hien va tram tich cira song yen bo, dii nhan thay co su tich tu cao cac kim loai nang va bieu bi nhiern dong, chl, kern, thuy ngan co the sinh vat, nhat Ia cac loai hai manh vo co tap tinh an 19C co kha nang tich tu cac kim loai nang cao hem cac loai khac (Luu van Diiu va nnk, 2001) 3.3 Danh gia t6ng hop cac tac dong d6i v6i nguon lQ'i ca bi~n yen bo, Cac tac dong chinh, khong gian tac dong (theo cap rat Ion, Ion, vira va nho) va mire d¢ tac dong cua chung (rat manh, manh, trung blnh, yeu) ciia ho Hoa Blnh toi vung song va bien yen bo diroc tong hop tren bang 480 cira Sang Tc5ng hop cac tac dQng phat sinh dH~utiet ho thuy di~n Hoa Sinh Khong IT gian tac d9n9 Loai tac d9n9 rat Ion Ion vua Muc d9 tac d9n9 nho rat manh manh trung binh X X Mat nol cu tru Mat hoac anh hllang xau den bai giang, bai de va chan dllong di cu di de Giam bun cat dira ven bo Giam nguon bien yen boo Thay d6i can bang, phan ba ruroc, bun cat 10 Ilrng va dong chay cac cua song Thay d6i phan ba d(> man vung cira song Han che kha n~ng phan tan v~t chat W song di xa Tanq kha n~ng tap trung chat nhiem vung cira song dinh dllong x X X vung a " yeu X X X x X X X X X x X Nhir vay, suy giam da dang sinh h9C va suy giam nguon loi thuy san danh bat, nuoi lien quan den h6 Hoa Binh thong qua cac tac nhan nhu: chan duong di cu di de, mat bai giong, biii de va mat noi cir tni; dao 19n can bang sinh thai va cac yeu to moi tnrong lien quan den dieu tier hd; thieu hut dinh ducng: t~p trung chat gay nhiern ven bo va cac tac dong true tiep hoac gian tiep khac Su suy thoai cac he sinh thai mat noi cir tni, nhiem va dao 19n cac yeu to sinh thai dii dan den suy giam da dang sinh h9C va nguon loi thuy san danh bat, nuoi DANH GIA TON THAT NGUON LOI cA BIEN VEN BO DO CONG TRINH HO HOABINH 4.1 Dien bien thirc te Nguon lei nghe ca vung cira song ven bien co xu huong giam r5 ret nhieu nguyen nhan, chac chan co nguyen nhan xay dung h6 tren hru vue Khoang 50% trii' hrong tom, cua ca, mroc 1'1 va bien nong bi giam sau thai gian xay h6 Hoa Binh San hrong ca chay Macerura reeverssi song Hong, cira Ba Lat, cira Bach Dang khoang thai gian tir 1962-1964 la 8-15 nghln tan/nam, den khong khai thac San hrong ca moi Clupanodon thrisa tren song Hong thai gian 1964-1979 la 40-356 tan/nam, den ding khong khai thac Do nhieu 19 do, san hrong ca khai thac nr nhien dong bang song Hong chi 1.000 tan/nam so voi tnroc day la 5.000 tan/nam Nguon loi mo tom Cat Ba- Ba Lat giarn 50% so voi tnroc dap h6 Hoa Binh va h6 tren thirong nguon co th~ la mot nguyen nhan quan (B9 Thiry san,1996) a a 481 Trti hrong trung blnh ca n6i VBB (ph an bien Viet Nam) khoang 390 nghln tan va kha nang khai thac 156 nghln tan (B¢ Thiry san, 1996) Tnr hrong ca tang day tinh trung blnh theo nhieu tac gia tir 1958 den 1985 khoang 456 nghln tan va kha nang khai thac 226 nghln tan T6ng cong trft hrong ca VBB tnroc 1985 la 846 nghln tan va kha nang khai thac 456 nghln tan Theo Bui Dlnh Chung va nnk (2001), vung bien Viet Nam thuoc VBB, trti hrong ca n6i nho 390.000 tan, ca day 291.166 tan, tong 681.166 tan Nhirng narn gan day (1997-2002), trti hrong ca bien VBB phan thuoc Viet Nam duoc danh gia trung blnh khoang 567.353 tan, kha nang khai thac ben vfrng hang narn trung blnh 226.942 tan Nguon 19i ca giam siit, dac bier vung mroc yen be San hrong khai thac mot so loai ca co gia tri kinh te cao nhir chim, thu, nhu hang, ca giam manh, ca tap lai tang nhu mien sanh hai gai, tic, trich ve v.v Tnroc nam 1990, cac ket qua danh gia trii luong ca day khoang 420-560 nghln tan, theo ket qua cua du an ALMRV narn 2002 chi 167 nghin tan, giarn di khoang 60-70% (Dew Mann Son, 2002) Tnr hrong ca tang day VBB co xu huang giam di, duoc danh gia khoang 37-56 van tan (Le Trong Ph/in, 1974), 50 van tan (Pham Thuac, 1977), 33 van tan (Nguyen Xudn L9C, 1985), 17,5 van tan (Le Van Dang va Dao Van T~(, 1994) va 11,6 van tan (Pham Thuac, 2000) Ngoai trir phircng phap danh gia khac nhau, co rat nhieu ly dan den suy giarn manh me nay, dac bier la danh bat qua mire Tuy nhien khong the khong ghi nhan moi quan h~ hlnh thirc la trfr lirong ca day giam di gan hai Ian khoang thai gian 1985-19941a ho thuy dien Hoa Binh di vao hoat dong Nang suat khai thac cua nhieu loai nghe giam Nghe ca n6i co san hrong chiern gan 60% san luong khai thac nhirng san hrong cua nhieu nh6m ca dii virot ngirong cho phep, dan den so hrong don vi nghe khai thac giam mien BAc So hrong don vi nghe vo ket hop anh sang giam tren 90% so voi nam 1977 Nang suat khai thac tren don vi tau thuyen giam Nghe vo ket hop anh sang tnroc nang suat dat 100 tan/vang/nam chi 3040tan/vang/nam San hrong binh quan cua mii lire may tau narn tir 0,92 tan/cv nam 1981, chi 0,36 tan/cv nam 2001, giam 61% San hrong ca day cling giam tci 30-36% Nhieu loai nghe khai thac ca n6i khac cling giam nrong tu, Ty l~ cac loai co gia tri kinh te cao nhu: ca sao, ca hong, ca moi, ca de, ca song, ca su giarn di nhieu so voi truce day, nang suat danh bAt a nhieu khu Vt!C giam di r5 ret (Pham Thuac, 2002) a o T6m danh bAt giarn ca ve san luong va kich ca bai torn Mi Mieu, san luong thang nam 1975 dat 5,88 kg/gio, thang nam 1995 chi 2,65 kg/gic Mat san hrong thang narn 1975 dat 120 kg/km", thang nam 1995 chi 54kg/km2 (R9 Tlucy sdn, 1996) Trong dot khao sat vao thang 3-4 nam 2002 tir Quang Ninh toi bac Nghe An, tir 30 m mroc tra vao ph fa tay vinh, so voi tnroc day co bien dong Ian ve cac loai torn nh6m torn he iPenaeus}, khong thay xuat hien torn su (Penaeus monodon), torn he mua (Penaeus merguiensis), torn he An D¢ (Penaeus indicus) va torn he phuong dong (Penaeus orientalis), Noi chung, nang xuat danh bAt torn giam tir be khoi va giarn r5 ret khoang d¢ sau 20-30 m mroc tra (Nguyen Cong Con va nnk, 2002) Vac tfnh trii hrong 482 tom vung bien phia tay vinh Bac B¢ (thang 3-4 nam 2002) la 1.322 tan, dai d¢ sau diroi 20 m (13.700 krrr') la 494,5 tan, dai 20-30 m (16.250 krn") la 684, tan va dai 30-50 m (20.640 krrr'jla 143,1 tan Tnt IUQ'ng va kha nang khai thac d¢ sau duoi 30m giam 23,44% so voi thoi ky 1975-1988 (1.540 tan) Nang xuat khai thac thap, trung blnh a dat 2,9 kg/gio Mat d¢ tom tren toan vung bien khao sat la 40,77 kg/km", cua thai ky 1975-1990 Thanh bang 57,64% cua cac loai tom kinh te thap (Nguyen ph an san luong Cong Con va nnk., 2002) a Danh gia chung, co th~ thay rang nang suat danh bat cac 10C;lihai san vung bien yen be tay VBB giarn khoang 40-50% so sanh thai ky 1988-1990 so voi nhieu nam tnroc, Nhirng nguyen nhan suy giarn co ban la khai thac qua rmrc, mat bai giong-bai de, mat noi cir tni, nhiern tai ch6 va nguon thai tir dat lien, dao Ion dieu kien sinh thai cira song yen be va suy giam dinh duong Trir khai thac qua rmrc, cac nguyen nhan lai mire khac nhau, deu lien quan den xay dung va dieu tiet ho Hoa Binh a 4.2 Danh gia ton that nguon loi ca bi~n yen bo Viec tinh t6n that triI hrong ca bien yen bo tay VBB dira vao phuong phap tinh diem s6 tac dong moi tnrong ket hop voi kinh nghiern cua Chen T.A.C (2000) cho tnrong hop dap Tam Hiep tren song Truong Giang d6i vci bien Dong Trung Hoa Bang Ma tr~n xac djnh di~m tronq so cac yeu t6 tac dnglam giam trfr 1l.t9ng ca vjnh B~c B(phan Vi~t Nam) TT Tac d9n9 tren h~ thong luu vue ba tay vinh Biic B9 Di;;m tn;mg so Do ho Hoa Binh Khai thac qua mire va danh bat huy di$t nguon 1c;1i 50 Giam dinh dlfong cua s6ng va vung bi~n ven be 20 15 (2 giam true tiep dinh dlfong tlt s6ng va 13 giam ngu6n phospho tlt day giam rurcc nqot tlt s6ng) Mat nc1i elf tru, mat hoac tac d9n9 den bai giang, bai de va chan dlfong di elf di de: 12 Gia t~ng va tap trung chat nhiem Thay d6i ehe d9 thuy van va sinh thai cua s6ng ven bo (dong chay, d9 man, d9 due) 6 Bien d9n9 khf hau-thuy van (nhiet d9, rmra, bao, s6ng, ruroc dang v.v.) T6ng c9n9 100 23 D~ tinh thiet hai ho Hoa Blnh gay cho nghe ca bien, can phai xac dinh duoc t6ng thiet hai tat ca cac nguyen nhan gay va tinh theo s6 tirng nhan tac (Bang 2) Do tinh chat qua plnrc tap cua cac moi quan he nhieu chieu, bai toan chi co th~ giai diroc nho xac dinh s6 cua cac yeu t6 gay tac dong theo ma tran quan h~ theo phirong phap danh gia tac dong moi tnrong Viec hra chon diem s6 th~ hien tinh logic va tinh thirc tien cua cac yeu t6 tac dong moi quan he tac dong va ket qua tinh toan phai phu hop voi 483 nhirng thong so co kha nang xac dinh duoc bang khao sat thuc tien Vi du, tru hrong ca tinh theo cac thai diem nrong doi xac dinh, ty l~ suy giam tru hrong va nang xuat danh b~t theo thai gian Ap dung nghien CUu cua Chen T.A.C (2000) cho ho Hoa blnh tren song Hong, thi phan trfl hrong ca VBB phia Viet Nam giarn giam nguon phospho cung cap tir day se la: xP PI = 4,4488% x k X k' (1) trang do: P: trfr hrong ca ban dau cua vung bien yen bo tay VBB PI: tru luong ca bien bi giam tich mroc ngot ho Hoa Binh dan den giarn dinh duong phot cung cap tir day bien 4,4488% la he so gifra dung tich mroc hiru Ich cua ho Hoa Binh (tich mua mua lG d~ xa phat dien mua kho) so voi tong hru hrong tat k = 0,9 la he so co k' = y nghia: 0,8 la he so co y ca cac song bo tay d6 vao vinh khoi hrong nuoc giam 10%, san pham ca giarn 9% nghia: neu san pham ca bi mat tich mroc mua mua lG la 100%, thi san pham ca diroc bu lai xa mroc mua kho la 20% Tong hop, san pham ca chi mat 80% Can cir vao diem so tren bang 2, ta co he phuong trinh: PI =A x P2IB (2) P-P2=P3 (3) a day: P2: luong ca vung bien yen bo tay VBB bi suy giarn t6ng cac tac dong khac P3: tru luong ca vung bien yen ba ray VBB lai, (j day chon P3 = 567.353 tan (theo tai lieu cua Dao Manh Son, 2002) A: so diem tac dong giam dinh duong phospho ngot tru lai ho cho phat dien mua kho, tir day bien nguon mroc a day A = 13 B: tong so diem gay tac dong suy giarn tnl hrong ca bien yen bo tay VBB day B =100 Tinh ta diroc: P = 752.853 tan; P2 = 185.500 tan va PI = 24.115 tan Nhu vay, qua nhieu nam, tru luong ca bien yen ba giam di 185.500 tan, nrong irng giam 24,6% tong tru hrong ca ban dau Trang do, dieu tiet ho Hoa Blnh lam giam 42.665 tan (nrong irng giam 5,66% t6ng tru luong ca ban dau) va rieng tac dong hru gift rnroc tai he phatdien mua kho gay thieu dinh du6ng lam giam 27.825 tan ca (do giarn true tiep dinh dirong tir mroc song 3.710 tan va giam nguon 484 cung cap photpho tu day bien yen br 24.115 tan) Thier hai moi tinh cho doi nrong ca, chira tinh den cac doi nrong khac nhu tom, m\fc v.v Neu tinh san lirong danh bat cho phep hang nam bang 50% trfr luong, ho Hoa Binh lam giam san luong ca bien danh bat 21.332,5 thiet hai cho danh bat ca tan/nam Neu tinh gia 20 trieu dong cho moi tan, bien hang narn la 426,65 ti dong Viet Nam, nrong duong 27,6 trieu USD Ngoai thiet hai ve san hrong danh bat, can thiet hai dau nr chi phi dieu kien nang suat danh bat giarn Trong ty l~ giam nang suat danh bat 40-50%, tac dong cua ho Hoa Binh d6ng g6p 9,2- 11,5% C6 nghia la, ho Hoa Binh can lam tang chi phi danh bat nghe ca bien vinh Bac BQ (phuong tien tau thuyen, ngir cu, dau mO', nhan cong) len 9,2- 11,5% Cang vao nhfrng nam kho han, kha nang tich mroc ho rang tang va thiet hai ve san hrong va chi phi danh bat nghe ca bien rang 100 KET LU~N Viec xay dung va dieu tier ho Hoa Binh lam mat mot khoi lirong bun cat 100 va thay d6i phan bo liru lirong mroc ngot, bun cat va dinh dutrng tir song dua bien, da gay tac dong Ian den moi tnrong va tai nguyen khong chi cira song rna tren khong gian rong 100 cua vung bien ven bo tay VBB MQt nhirng hau qua tac dong 100 nhat la suy giarn nguon loi nghe ca bien ven bo giam dinh dirong vung cira song va bien ven bo; thay d6i dieu kien sinh thai cira song ven bo (dong chay, dQ man, dQ due v.v ); mat noi hoac tac dong den bai giong, CU tni, mat bai de va chan dirong di cu di de mot so loai thuy san; gia tang va tap trung chat nhiern moi tnrong ven bo Bang phuong qua nghien phap danh gia tac dong moi tnrong, cho diem so va sir dung ker ciru cua Chen T.A.C (2000), ket qua tinh roan cho thay qua nhieu narn, tru luong ca bien ven bo VBB phan Viet Nam giarn di 185.500 tan, bang khoang tru luong ca ban dau Trong giarn tru hrong 42.665 24,6% t6ng d6, viec xay dung va dieu tiet ho thuy dien Hoa Binh lam tan (3.710 tan giarn dinh dirong true tiep tir mroc song, 24.115 tan giam nguon cung cap phospho tir day lien quan den ho tru mroc ngot mira mira lil va 14.840 tan cac tac dong khac cua ho) Neu tinh san hrong danh bat hop ly bang mot nira tnr luong ca bien, ho Hoa Binh lam giam san hrong danh bilt 21.332,5 gid 426,65 tdnlndm, tri ti dong Vi¢t Namlndm, tuang duang 27,6 trieu USD/nam Hau qua tac dong cua ho can lam tang chi phi danh bat (phuong tien tau thuyen, ngu cu, dau md va nhan cong) len 9,2- 11,5% Nhu cau dien nang, chong li1 va mroc nroi nrong lai doi hoi xay dung bac thang thuy dien song Da, d6 c6 thuy dien San La 100 nhat, Vi the, sue ep doi voi moi tnrong sinh thai cira song ven bitin ho thirong nguon rang tang va t6n that doi voi nghe ca bien ven bo se rang 100 Trong bai toan quy hoach quan ly tai nguyen mroc luu vue song Da n6i chung va xay dung dap thuy dien San La n6i rieng, can c6 danh gia chi tiet tac dong den nguon lei ca bien ven bo dti c6 nhfrng giai phap irng thfch hop, xu 485 TAl LI¢U THAM KHAo Ban chi dao phong chong lut bao trung uong, 1997 Quyet dinh Gtta Truong ban chi dao peLB trung uang ve' viec phe duyet "Quy trinh van hank ho thu» dien Hoa Binb va cdc cong trinn cdt gidm lii song Hong maa mua lii hang ruim", Quyet dinh so 57 PCLBW/QD 12 thang nam 1997 BQ Thuy san, 1996 Nguon lai thicy sdn Vi¢t Nam NXB Nong nghiep, Ha NQi Tr 1-616 Bui Dlnh Chung, Chu Tien Vinh, Nguyen Hiru Due, 2001 Nguon lai ca bii'n- co sd phdt trien clla nghe' ca bie;l V iet N am Tuy~n tap cac cong trinh nghien ciiu nghe ca bien Tap II Nha xuat ban nong nghiep Ha NQi Tr 199-210 Dao Manh Son, 2002 Tinli hinn nghien cuu nguon 10 hdi sdn va moi truang a vinl: Bdc B9 nhiing nam qua Tuyen tap bao cao khoa hoc hoi thao "Dieu kien nr nhien, tai nguyen va moi tnrong vinh HAc BQ" Hai Phong, 2002 Tr.54-61 DQi lien hiep Viet-Trung, 1965 Bao cdo die'u tra t6ng hap vinli Bdc B9 Liru trfr tai Phan vien hai dirong hoc tai Hai Phong Hoa Manh Hung, 2001 Dong luc hinlt thai cira song ven bii'n dong bang Bae B9 Vi¢t Nam phuc vu khai thdc va su dung hap If tai nguyen moi truang dra song ven bii'n Tom tM luan an tien sy Dia lY Ha NQi Tr 1-21 Luu Van Dieu, Nguyen Thi Phuong Hoa va nnk, 2001 Danh gid muc d9 nhiem nguon thai tit luc dia, de' xudt gidi phdp hi'm soat, qudn If a nhiem wing bii'n ven bo phia bdc (Ut Quang Ninli den Thanh Hod) Liru tru tai Phan Vien Hai Duong hoc tai Hai Phong 486 Luong Phuong Hau, Trinh Viet An va Luong Phuong Hop, 2002 Dong chdy dta song vung dong bang Bdc B9 NXB Xay Dung Ha NQi, tr.I-172 Ngo Trong Thuan, 1997 Dien bien long song Da dnb huang van hanli h6 Hoa Binb nhiing ndm ddu Khi nrong thuy van so Trang - 10 Nguyen Cong Con, Pham Quoc Huy, Lai Duy Phuong, 2002 Nguon lai tom wing Vinh Bdc B9 ndm 2002 Tuyen tap bao cao hoi thao khoa hoc " Dieu kien tu nhien, tai nguyen va moi tnrong Vinh B~c BQ" Hai Phong, 2002 11 Nguyen Due Cu va nnk, 1998 Dieu tra khdo sat chat Luong moi truang va dong thai dinlz duiing vung cira song chdu tlz6 song Hong Bao cao de an dieu tra co ban cap nha mroc hai nam 1997-1999 Luu trfr tai Phan vien Hai duong hoc tai Hai Phong 12 Nguyen Kien Dung, 1999 Boi ldng bun cat ho' Hod Binli giai doan ddu tich nude, Khi nrong Thuy van No.6 (462) Ha NQi Tr.1O-15 13 Nguyen ThUQ'IlgHung va nnk, 1995 Nghien 14 Nguyen Viet Ph6, 1984 Dong chdy song ngoi va du bdo bien dong clla m6i truang va de' xudt cac dinb huang phdt trien kinli te' -xii hoi tai vung thuang va du cong trtnb thuy dien Hoa Binh Bao cao khoa hoc d~ tai nha ruroc KT-02-l4 CULt vt« Nam NXB KH va KT Ha NQi Van Trang, Nguyen Tai SO'I1va nnk, 2000 Quy hoach bdc thang thLiy dien tren song Da Bao cao hru trlt tai Cong ty Tu van Xay dung dien T6ng Cong ty Dien Lire Viet Nam 15 Nguyen 16 Nguyen Huy Yet, LUll Van Dieu, Nguyen Dang Ngai, Lang Van Ken, 2000 SI/ suy thodi h¢ sinh thai san vinn Ha Long-Cat Ba thai gian gdn day Tai Nguyen va M6i tnrong bien Nxb, KH&KT T.VII Ha N9i Tr 146-59 nhiem bien song tdi Pharn Van Ninh, 1995.6 - 03 - 07 Ha N9i 18 Tran Dire Thanh va nnk, 1985 Dia chat dia mao ddi ven biln phia bdc Vi¢t Nam Bao cao chuyen de De tai 48.06.14: "Nghien ciru d~c diem dieu kien tu nhien va kha nang nguon lei dai ven bien Viet Nam, de xuat bien phap su dung hop ly va bao ve nguon lei" LUll trlt tai Phan Vien Hai dUO'I1gh9C tai Hai Phong 19 Tran Duc Th~nh, Dinh Van Huy va Tran Dlnh Lan, 1996 D(zc diem pluit trien clla vung ddt boi ngdp trieu ven ba chdu tluS song Hong Tap chi khoa h9C ve trai dat So 18 (1), trang 50-60 20 Tran Duc Th~nh, I"Q Bao cao tong ket M tai KT 17 Nguyen Duc Ct;r, Nguyen Hiiu Cu, Do Dlnh Chien va Nnk, 2000 N ghien cuu du bao, phong chong sat !d ba bie;1Bdc be) tlf Quang Ninli tai Thanh H6a Bao cao du an KHCN-5A LUll trlt tai Phan Vien Hai dUO'I1gh9C tai Hai Phong 21 Tran Due Thanh va Do Dlnh Chien, 2002 A.nh huang CLlacac ddp chua tren hat VI/C den moi truang sinh thai ven boo Tai nguyen va M6i twang bien Tap IX NXB KH&KT Ha N9i 22 Trung tam Tai nguyen nuoc va M6i tnrong, 1999 Nghien cuu bien dong chat luang nude mdt h¢ thong song Hong vd Thai Binh Bao cao M tai Luu trlt rai Vi~n Khoa h9C Thuy lei 23 Vfi Van Tu an , 1999 Ddnh gia dnh huang cLia ho Hod Binh tai moi truang Tuyen tap cac bao cao khoa h9C tai hoi nghi moi twang toan quoc narn 1998 Nxb KH&KT Ha N9i Tr 486-507 24 ADB, 1993 Vietnam environment sector study Technical 25 Chen-Tung report pp 1-116 The Three Gorges Dam: Reducing the Upwelling and thus Productivity in the East China Sea Geophysical Research Arthus Chen, 2000 Letter, Vo1.27, No.3, p 381-383 26 WCD (The World Commission on Dams), 2000 Dams and Development A new framework for Decision-Making The report of from: http://www dams org/report/ 27 WB, ADB, FAO, UNDP, NGO Water Resources Group and Institute of Water Resources Planning, 1996 " Vietnam Water Resources Sector Review" Intergrated Report 487 ... luong ca bien bi giam tich mroc ngot ho Hoa Binh dan den giarn dinh duong phot cung cap tir day bien 4,4488% la he so gifra dung tich mroc hiru Ich cua ho Hoa Binh (tich mua mua lG d~ xa phat dien... tinh thiet hai ho Hoa Blnh gay cho nghe ca bien, can phai xac dinh duoc t6ng thiet hai tat ca cac nguyen nhan gay va tinh theo s6 tirng nhan tac (Bang 2) Do tinh chat qua plnrc tap cua cac moi... Thuac, 2002) Ca tang day co nhieu loai quan nhir ca phen, ca moi, ca trac, ca mien sanh, ca hong, ca v.v Trir hrong ca day phan vinh phia Viet Nam diroc danh gia khac thee thai gian va tac gia: 44-88