KY YEU "CAC DE TAl NGHIEN COU KHOA HOC C6NG NGHE NGANH TAl NGUYEN VA MOI TRLfONG GIAI BOAN 2002 2006" DETAI D A N H G I A T A C D O N G C U A T H I E N T A I D E N N A N G S U A T , S A N L U O N G C[.]
KY YEU "CAC DE TAl NGHIEN COU KHOA HOC- C6NG NGHE NGANH TAl NGUYEN VA MOI TRLfONG GIAI BOAN 2002-2006" DETAI: D A N H GIA TAC DONG C U A THIEN TAI D E N N A N G S A N L U O N G C U A M O T SO C A Y L U O N G T H U C C H I N H B A N G N A M BO V A C A C BIEN P H A P Q N G SUAT, DONG PHO Ca quan chu tri: Vien Khi tuong Thuy van C h u n h i e m de t a i : TS NCVC Nguyin Van Liem Cac t h a n h v i e n : PGS TS Nguyin Van Viet KS Ngo Sy Giai ThS Ngo Tien Giang CN Ngo Thi Chien CN Dao Thi Thoan CN Nguyin Hong Son TS HoangMinh Tuyen - Vien Khi Vien Khi Vien Khi Vien Khi ViBn Khi Vien KM Vien KM tuong thuy tuong thuy tuong thuy tuong thuy tuong thuy tuong thuy tuong thuy van van van van van van van Muc tieu cua de tai: 1- Nghien ctiu dien bien va danh gia tac dong cua thien tai l u lut, ngap ung, ngap man va nan han den dien tich, nang sua't, san lugng cua mot so cay luang thuc chinh tirng mua vu a dong bang song Cuu Long (DBSCL); 2- Kien nghi ve chuyen doi ca cau mua vu gieo cua mot sd cay luang thuc chinh, tirng budc nang cao, 6n dinh nang sua't, san lugng tirng mua vu Noi dung nghien curu: 1- Tong quan dieu kien tu nhien, cac dang thien tai va nhung chi tieu danh gia tac dong cua thien tai ddi vdi nang sua't, san lugng cua mot sd cay luang thuc chinh tirng mua vu gieo tr6ng; 2- Nghien cuu diSn bien cua thien tai lu lut, ngap ling, ngap man va han han; 3- Danh gia tac dong cua thien tai l u lut, ngap ung, ngap man, han han den nang sua't, san lugng cua mot sd cay luang thuc chinh tirng mua vu; 4- Kien nghi cac giai phap ve ca cau thdi vu gieo phu hop ddi vdi mot sd cay luang thuc chinh Tom tat bao cao: Ket qua nghien cuu cua de tai, ngoai phan m d d i u va ket man ra, p h i n noi dung chinh dugc trinh bay chuang sau day: Chuang I : Tong quan dieu kien tur nhien, cac dang thien tai va nhung chi tieu danh gia tac dong cua thien tai ddi vdi nang sua't, san lugng cua mot sd cay luang thuc chinh tirng mua vu gieo tr6ng d dong bang song Ciru Long; Chuang II: Dien bien cua thien tai lu lut, ngSp ung, ngap man va han han d vimg 805 KY YEU "CACflgTAI NGHIEN CUU KHOA HOC- CONG NGHg NGANH TAI NGUYEN VA MOI TRUdNG GIAI BOAN 2002-20 d6ng bang song Cuu L o n g ; Chuong I I I : Danh gia tac dong cua thien tai l u lut, ngap ung, ngap man, han han ddi vdi nang sua't, san luong cua mot sd cay luong thuc chinh tirng mua vu d vung ddng bang song Cim Long; Chuang I V : K i e n nghi cac giai phap ve co ca'u thdi v u gieo phu hop ddi voi mot sd cay luang thuc chinh K e t qua nghien c u u : CHUONG I: TONG QUAN DIEU KIEN TU NHIEN, CAC DANG THIEN TAI VA N H O N G C H I T I E U D A N H G l A T A C O N G C U A T H I E N T A I D O I VCJl N A N G SUAT, SAN L U O N G C U A MOT SO CAY L U O N G T H U C CHINH T R O N G TUNG MUA V U GIEO TRONG D O N G BANG S O N G CUD LONG 1.1 DIEU KIEN TUNHIEN 1.1.1 Dac diem dia ly dia hinh DBSCL la phan luu chau tho song Mekong nam tren lanh tho Viet N a m , trai dai tit 8°30 den 11° v i Bac va 104°30 kinh Dong, phia Bac giap Campuchia va phd Ho Chi M i n h , phia Nam va Dong giap bien Dong, phia Tay giap v i n h Thai Lan DBSCL kha bang phing va co cao tha'p, su chenh lech ve cao khong dang k& ( l c m / k m ) , ngoai trir mot sd diem co nui cao nhu d vung A n Giang, K i e n Giang 1.1.2 Dac diem hau thuy van a) Dac diem hau: Co nen nhiet tuang ddi cao, biic xa mat trdi doi dao va it bien dong theo cac thang nam Lugng mua bien dong nhieu theo khong gian va thoi gian Mua mua t i l thang den thang 10 va mua kho tir thang 11 den thang nam sau Lugng mua trung binh cac thang mua mua vao khoang 130 - 150 m m va vai chuc mm cac thang mua kho Lugng mua trung binh nhieu nam ( T B N N ) dao dong khoang 1.330 - 3.067 m m b) Dac diem thuy van: Cac song chinh, bao gom: (1) Song M e k o n g (song Tidn va song Hau); (2) Song V a m Co Dong; (3) Song V a m Cd Tay; (4) Song Cai L d n ; (5) Song Cai Be; ngoai khu vuc co mot he thong kenh rach chang chit Che thuy van cua khu vuc chiu anh hudng manh me cua che thuy van song Mekong va phan chia hai mua ro ret M u a l u : tir thang den thang 11 va mua kiet: tir thang 12 den thang nam sau DBSCL cung chiu anh hudng cua che dd thuy trieu Bien Dong va vinh Thai Lan 1.2 CAC DANG THIEN TAI KHI HAU Thien tai l u , lut, ngap man va han han 1.3 CHI TIEU DANH GIA Chi tieu danh gia tac dong cua ngap lut, ngap man va han han ddi vdi nang sua't, san 806 KY YgU XAC BE TAl NGHIEN CPU KHOA HOC- CONG NGHg NGANH TAl NGUYEN VA MOI TRUflNG GIAI BOAN 2002-2006" lugng cua mot sd cay luang thuc chmh cac mua vu, bao gom: + Thdi gian ngap lien tuc thdi gian dai d cac tieu vung co anh hudng cua l u lut; + M u c nude l u ( H > 3,0 m) tai tram Tan Chau; + M u c nude trung binh thang cua cac tram thuy van khu vuc noi dong; + Chi tieu man S = 4%o (do man lam lua va hoa mau d i e t ) ; + V i t r i va thdi gian xua't hien man S > 4%o; + Chi tieu phan loai han theo tan suat xuat hien va tuan kho lien tuc; + He sd thuy nhiet cai bien ( K ) : K i= I = Trong do: R - Lugng mua ngay, Z m I= ] - Lugng bde hai tiem nang Cac ngudng dung di danh gia va phan loai han nhu sau: K < 0.4: Han rat nang; K = 0.4 H- 0.5 : Han nang; K = 0.5 -s- 0.6 : Han vira; + Chi tieu giam nang sua't trung binh cua cay cua Prd-se-rd'p: a) Han rat nang, mtic giam nang sua't cua cay dat tren 50% so vdi nang sua't trung binh nhieu nam (TBNN); b) Han nang (mure giam nang sua't cua cay dat tren 20% so vdi nang sua't T B N N ; c) Han nhe - M u c giam nang sua't cua cay dat den 20% so vdi nang sua't TBNN 1.4 CHI TIEU DANH GlA TAC DONG CUA THIEN TAI KHI HAU Danh gia tac dong cua thien tai k h i hau ddi vdi nang suat lua va cac cay mau luang thuc chinh vu dong xuan, vu he thu va vu mua thong qua he sd bien dong C d cac k tinh He sd bien dong C dugc tinh theo cong thu:c: k _tfl H n-1 Trong do: C - He sd bien ddng cua nang suat cay dao dong thdi thdi tie't Don vi tinh % k va d\ = ^ f (1.2) n-\ Trong do: Y j - Nang suat cay cua vu (i) nao do, dan v i ta/ha; Y - Nang sua't cay trung binh cua ca thdi ky n vu,(ta/ha); Y x t - Nang sua't x u the cua cay trong vu i , dan v i ta/ha; n - Sd vu dugc xem xet 807 KY YEU -CAC BE TAI NGHIEN CUU KHOA HOC- CONG NGHE NGANH TAI NGUYEN VA MOI TRUdNG GIAI BOAN 2002-2 C H U O N G II: D I E N B I E N C U A T H I E N T A I L U L U T , N G A P U N G , N G A P M A N V A H A N H A N V U N G D O N G B A N G S O N G CCfU L O N G II LU LUT VA NGAP UNG Tir nam 1926 den nam 2001, da co 41 nam co l u chmh vu v o l muc nude dinh lu tai Tan Chau tir 4,2 m (bao dong cap I I I ) , co 24 nam co dinh lu ldn hem 4,5 m (chiem 31,6%) D i n h l u nam 1961 cao nhat (5,12 m ) , sau den cac nam 1966, 2000 Lu cua cac nam 1961, 1966, 1978, 1991, 1996, 2000 va 2001 co dang l u dinh, co mot dinh phu xuat hien vao thang 7, Dac biet anh hudng cua E l - N i n o 1997 - 1998 nen nam 1998 la nam co l u nho nhat, muc nude dinh 1Q tai Tan Chau chi dat 2,81 m va tai Chau Doc 2,55 m , ung vdi tan suat khoang 95,5% Dac biet l u lich sir nam 2000 (t6ng 1ugng ldn nhat, thdi gian lu dai nhat va l u sdm nhat) Tit thang 5, mua gio mua Tay N a m da tao nen l u dau mua, nude song bat dau len va cho den thang 7, thi dat tdi dinh, sau dd l u xudng cham thdi gian ngan, roi tiep tuc len va dat dinh l u cao nhat Trong thang 8, tham chi la thang 7, cd lh£ xuat hien mot "dinh phu", tao l u dinh rieng biet (lu 1978, 2002) K h i lu ngoai song cao (H = 3,0 m trd len tai tram Tan Chau va Chau Doc), nude lu tir song Tien, song Hau va tir Campuchia tran vao D T M va T G L X D i n h l u thudng xuat hien vao tir cudi thang den cudi thang 10 M u a l u thudng keo dai den thang 11 L u lut d D B S C L len xudng cham vdi cudng suat trung binh - cm/ngay va cao nhat cung chi d mire 20 - 30 cm/ngay Ket qua tinh toan tan suat xuat hien dinh l u ldn nhat nam nhu sau: - C u d i thang ( - / ) : 4% - Dau va giua thang ( - 20/9): 17% - Cudi thang den cudi thang 10 (21/9 - 20/10): 69% - Cudi thang 10 den cudi thang 11 (21/10 - 20/11): 10% Ket qua tinh toan cho tha'y: V d i chi tieu H > 3,0 m tai Tan Chau nude lu d s6ng Mekong tran vao cac vung trung D T M thi thdi gian t r i muc nude H > 3,0 m tai Tan Chau cac nam dao dong tir 15 den 138 va thdi gian ngap sau d cac vung trung D T M cung dao dong tuang ung khoang thdi gian noi tren V a thdi gian dat dinh lu tai cac tram k h u vuc noi dong D T M thuoc tinh L o n g A n so v d i tram Tan Chau < 10 Thai gian dat dinh l u cua cac tram Thuy van k h u vuc noi dong thuoc phia Bac D T M (tinh Dong Thap va A n Giang) so v d i tram Tan Chau, Chau Ddc < Ve ngap lut co the phan vung ngap lut DBSCL bdn tieu vung ngap lut nhu sau: Dai dat cao ven Bien Dong tir Go Cong qua Ben Tre, Tra V i n h , Soc Trang den Bac Lieu, co cao trung binh khoang - m , co nhieu song chay qua nhung khong bi ngap lut l u song V u n g trung D T M nam d phia ta ngan song Tien tit Bac Tien Giang den bien gidi Viet Nam - Campuchia, co cao mat dat 0,5 - m , xung quanh dugc bao bgc bdi dai dat cao la bd bien d Go Cong, bd song Tien va bd dat cfl D o n g N a m Bo V u n g la vung trung va ngap lut nang ne nhat d DBSCL V u n g Tu: giac L o n g Xuyen nam d phia huu ngan song Hau, phia thugng luu rach Cai San, cao mat dat thap va ddc nghieng tir bd song Hau den vinh K i e n Giang V u n g cung la vung thudng xuyen bi ngap lut Vung dat thap va chua man U M i n h - Ca M a u co cao mat dat thap, chi cao han muc nude tridu mot it, song nam sat bien nen khong bi ngap lut bdi nude song ma chi bi 808 KY YEU 'CAC BE TAI NGHIEN CUU KHOA HOC- C6NG NGHE NGANH TAI NGUYEN VA MOI TRl/CING GIAI SPAN 2002-2006" ngap man Do sau va thdi gian ngap ling tai cac tieu viing d D B S C L nhu sau: d vung ngap sau, sau ngap lut tren m , thdi gian ngap - thang, thudng tur thang den thang 11 Vung ngap trung binh co thdi gian ngap - thang, keo dai tir thang den thang 11, sau ngap - m V u n g ngap nong co sau ngap 0,5 - 1,0 m , keo dai tir den thang Thdi gian ngap ling d DBSCL dugc phan biet lam loai chinh: Ngap lien tuc (gin nhu lien tuc lu); Ngap lien tuc (hay gan nhu hen tuc mua); Ngap khong hen tuc trieu II.2 DIEN BIEN CUA THIEN TAI NGAP MAN Mua kiet lugng nude nggt tir thugng nguon chay ve rat han che nen che thuy van vung DBSCL chiu su chi phdi manh cua thuy trieu Bien Dong va vinh Thai Lan D d ddc long song nho, dia hinh tha'p, co nhieu cira song, kenh rach thong bien tao dieu kien man xam nhap sau vao noi dong d DBSCL co nguon man xam nhap vao: (1) Nguon man true tiep tir Bien Dong va (2) Nguon man tir vinh Thai Lan X a m nhap man vao DBSCL thudng xay tir thang den thang 5, mire xam nhap man nguy hiem nhat la vao thang Dudng ranh gidi man % cua cac tuan thang bien thien khong theo mot xu the nhat dinh sudt tren ca vung Tir viing Go Cong den Soc Trang, thudng thang van la thdi gian qua trinh xam nhap cua dd man % vao dong (trtr song Hau vi chiu anh hudng mua sdm tren viing thugng luu) Trong liic do, tinh hinh xam nhap man d vung ven bien K i e n Giang thang thi ngugc lai Tile la tuan cua thang cd dudng ranh gidi man 4%o vao sau nhat Dac biet d viing ven bien K i e n Giang co nam mua sdm nen tuan cudi cua thang lai la thdi gian co man 4%o vao sau han so vdi cac tuan thang 0 II.3 DIEN BIEN THIEN TAI HAN HAN Ket qua tinh toan cho tha'y tai Ben Tre, Tien Giang, V i n h L o n g , Soc Trang, Bac Lieu, Ca Mau, Kien Giang: Ngay bat diu mua mua sdm nhat va muon nhat xa'p x i tren dudi 1,5 thang so vdi trung binh nhieu nam ( T B N N ) , nhung sd nam co bat dau mua mua muon han T B N N nhieu han Ngay ket thuc mua mua sdm nha't va muon nhat xap x i 0,5 -1 thang so vdi T B N N , nhung sd nam co ket thuc mua mua muon hon T B N N nhieu han Con tai Dong Thap, Can Tha: Ngay bat diu miia mua sdm nhat va muon nha't dudi thang so vdi T B N N , nhung sd nam co bat dau mua mua muon han T B N N nhieu han Ngay ket thuc miia mua sdm nha't va muon nha't xa'p x i 0,5 thang so v d i T B N N , nhung sd nam co ket thuc mua mua muon han T B N N it han • Lugng mua tich luy trudc va sau mdc thdi gian dugc chon (ngay 01 thang 01 hang nam) De tai da tinh dugc thdi gian lugng mua tich luy sau mdc dat 75 m m , 200 m m va trudc mdc 500 m m , 300 m m va 100 m m ting v d i cac sua't bao dam 20%, 50% va 80% tai cac tram k h i tugng d cac tiiu vung V i du: Tai Rach Gia, lugng mua tich luy sau mdc, dat 75mm vdi sua't bao dam 20%: 11/3, 50%: 20/4, 80%: 9/5; dat 0 m m vdi suat bao dam 20%: 24/4, 50%: 18/5, 80%: 01/6 va lugng mua tich luy trudc mdc, dat 500mm v d i suat bao dam 20%: 14/10, 50%: 2/10, 80%: 18/9; dat 300mm vdi sua't bao dam 20%: 11/11, 50%: 26/10, 80%: 8/10; dat 100mm vdi suat bao dam 20%: 3/12, 50%: 27/11, 80%: 3/11 Tai M o c Hoa, lugng mua tich luy sau mdc, dat 75mm vdi suat bao dam 20%: 18/3, 50%: 5/5 80%: 9/5; dat 200mm, 20%: 29/4, 50%: 17/5, 80%: 9/6 va lugng mua tich luy trudc mdc 500mm vdi suat bao dam 20%: 12/10 50%: 1/10, 80%: 25/9; 300mm vdi sua't bao 809 KY YEU "CAC D£ TAI NGHIEN CUU KHOA HOC- CONG NGH.E NGANH TAl NGUYEN VA MOI TRLfONG GIAI BQAN 2002dam 20%: 31/10, 50%: 20/10, 80%: 16/10; dat 100mm vdi suat bao dam 20%: 22/11, 50%: 14/11, 80%: 7/11 Tai Ba T r i , luong mua tich luy sau moc dat 75mm vdi sua't bao dam 20%: 18/4, 50%: 13/5, 80%: 19/5; dat 200mm, 20%: 13/5, 50%: 28/5, 80%: 3/6 va luong mua tich luy trudc mdc 500mm vdi sua't bao dam 20%:4/10, 50%: 25/9, 80%: 20/9; dat 300mm vdi sua't bao dam 20%: 27/10, 50%: 10/10, 80%: 7/10; dat 100mm vdi sua't bao dam 20%: 21/11, 50%: 2/11, 80%: 31/11 • Tan sua't xuat hien tuan kho va tuan kho lien tuc: Trong nhung thang d i u va giua mua mua tai M o c Hoa, Cao Lanh, Cang L o n g , Ba T r i , Chau Ddc, M y Tho, Soc Trang, Can Tho, Bac L i e u , Ca M a u , Rach Gia xac sua't tuan k h d lien tuc tuan 2, thang va tuan thang dao dong khoang 10 - 65% T a i M d c Hoa, Cao Lanh, Chau Ddc, M y Tho tuan thang va tuan , , thang xac sua't tuan kho lien tuc dao dong khoang 10 - 35% va tuan thang 7, tuan thang dao dong khoang - 19% Xac sua't tuan khd lien tuc tai cac dia diem noi tren tuan 2, thang va tuan thang dao dong khoang - 64% Trong tuan thang va tuan 1, thang tai M o c Hoa, Cao Lanh, Chau Ddc xac sua't tuan kho lien tuc dao dong khoang - 17% Ket qua tinh toan theo chi tieu giam nang sua't cay cua Prd-se-rdp ddi vdi lua thdi ky 1976 - 2002 nhan tha'y d cac tinh: Trong vu dong xuan: Han lien tuc xay cac nam 1976 - 1985 Dac biet la d tinh Kien Giang: han nang da xay vao cac nam 1977 - 1981 (chi so giam nang sua't lua dao dong khoang tur -50,5 den -69,6%) Trong vu dong xuan nam 1978 la nam xay han nang o hau he't cac tinh thuoc DBSCL, nam 1993 han cung xay d phan ldn cac tinh thuoc DBSCL nhung muc han it nghiem hon so v d i nam 1978 (chi sd giam nang sua't lua dao dong khoang tir - 1,7% den -27,4%, ngoai trur vung Tra V i n h (chi sd giam nang sua't lua dat -60,2%) Nhung nam g i n day han van thudng xay vu dong xuan nhung mire it nghiem hon Trong vu he thu: han lien tuc xay cac nam 1976 - 1982 tai Long A n , Kien Giang, Can Tho, Tra V i n h Trong cac nam 1976 - 1984 tai A n Giang, Dong Thap, Kien Giang Dac biet la vao cac nam 1977 - 1981: han lien tuc xay d A n Giang, Tien Giang (chi sd giam nang sua't lua dao dong khoang tir -50,5 den -69,6%) Nhung nam g i n day han van thudng xay vu he thu nhung ve muc han cd tha'p hon Trong vu mua: Han lien tuc xay cac nam 1976 - 1987 d h i u he't cac tinh Dac biet vu miia 1978, han nghiem da xay d cac tinh L o n g A n (chi sd giam nang sua't lua dat -91,5%), d Dong Thap (chi sd giam nang suat lua dat -60,6%), d A n Giang (chi sd giam nang suat lua dat -76,6%) va o Tra V i n h (chi sd giam nang sua't lua dat -66,9%) V u mua nam 1992, han nang xay d tinh L o n g A n (chi sd giam nang sua't lua dat -92,0%), han trung binh xay d tinh Dong Thap (chi sd giam nang sua't lua dat 22,6%) va han nhe xay d tinh Ben Tre (chi so giam nang sua't lua dat -2,9%) Ridng vu mua nam 1993, han xay d muc trung binh va gay thiet hai cho lua mua chu ye'u d cac tinh Long A n (chi so giam nang sua't lua dat -37,3%), T i e n Giang (chi sd giam nang sua't lua dat -34,8%), va d K i e n Giang (chi sd giam nang sua't lua dat -0,8%) Con d cac tinh khac han anh hudng khong dang ke N h u n g nam gan day han van thudng xay vu mua d D B S C L nhung mire dd bdt nghiem hon • Bdc thoat hoi tiem nang: Luong B T H T N nam cua D B S C L dao d6ng tur 1341 m m 810 KY YEU "CAC 0£ TAl NGHIEN CUU KHOA HOC- CONG NGHE NGANH TAI NGUYEN VA MOl TRLfflNG GIAI BQAN 2002-2006" (Ca Mau) den 1498 m m (Ba Tri) Luang B T H T N tha'p nha't vao thang 12 (100 - 106 m m ) , luong B T H T N cao nha't vao thang va (144 - 156 m m ) De tai cung da tinh toan tin sua't xuat hien han (%) vu he thu va mua cac tinh thuoc DBSCL CHlfONG III: DANH GlA TAC DONG CUA THIEN TAI LU LUT, NGAP UNG, NGAP MAN, HAN HAN DOI V l NANG SUAT, SAN L U O N G CUA M O T SO CAY LONG T H U C CHINH T R O N G TL/NG M U A V U V U N G D O N G B A N G S O N G CU\J L O N G DBSCL hang nam co vu san xuat chu yeu: dong xuan (tir thang 10 den thang - nam sau), he thu (tit thang den thang - 10) va vu mua (thdi vu sdm: gieo vao thang - , thu hoach vao thang 10 - 11; thdi vu la: gieo vao thang - , thu hoach vao thang 12; thdi vu muon: gieo vao thang - , thu hoach vao thang va nam sau) Cac nhom gidng lua va cay mau gieo trong cac vu, bao gom: N h o m gidng lua ngan co thdi gian sinh trudng (TGST): 90 - 105 ngay, nhom gidng lua trung cd TGST:105- 115 ngay, nhom gidng lua dai cd TGST: 130- 150 Cac cay mau l u ang thuc cd TGST: - 120 III MUA SINH TRUC-NG CUA CAY LUA VA MOT SO CAY MAU LUONG THUC Miia sinh trudng (MST) la thdi gian cay cd the sinh trudng nhd nude trdi, la thdi ky luong mua vuot qua 0,5 luong bdc thoat hai tiem nang (PET), cong them khoang thdi gian tieu hao 100 m m , t r u luotig am dat D d i v d i nhung viing b i l u lut ngap sau giua miia mua, thi M S T dugc chia giai doan: giai doan trudc l u , giai doan l u ngap sau va giai doan sau l u Giai doan trudc l u thuoc ve thdi gian canh tac vu va giai doan sau l u thuoc thdi gian canh tac vu Trir vung canh tac lua mua (liia ndi) d D T M Nhung vung, mua khd dong rudng bi man va phen t h i dau mua mua man, phen cao nen viec gieo ca'y vu thudng t r i han so vdi bat dau MST Nen k h i tinh toan can trir di khoang thdi gian dd Ve cudi mua mua, neu dong rudng cd bd g i u nude, se cd kha nang keo dai them MST tren thuc te III.2 DANH GIA TAC DONG CUA THIEN TAI NGAP UNG, NGAP MAN VA HAN HAN DOI V l N A N G SUAT, SAN LUONG CUA CAC C A Y LUONG THUC C H I N H 1) Danh gia tac dong cua thien tai ngap ling: L u lut thudng xuyen xay ra, cudng suat lu khong ldn, thdi gian ngap lut keo dai va dd sau ngap lut ldn L u sdm, l u m u o n va l u l d n chinh vu ddu gay thiet hai nghiem trgng T h d i gian t r i mile nude dinh l u la mot nhung yeu to han che l d n nhat D a phan lam loai ngap chinh n h u sau: V u n g ngap lau va ngap ra't sau (ngap l u tren 2,0 m , keo dai tir - thang, trung binh la 3,5 - 4,0 thang lien tuc, tir thang - 11) V u n g ngap lau va ngap sau trung binh (ngap sau tur 1,0 - 2,0m, keo dai - thang, tir thang - 1 , mot so viing tha'p tir thang - 12) V u n g ngap lau nhung ngap ndng (ngap sau tir 0,5 - , m , thudng keo dai 2,5 - 3,5 thang, t u thang - ) Dua tren muc nude lu ( H > 3,0 m ) tai Tan Chau nude l u d song Cuu Long tran vao cac vung trung D T M va thdi gian t r i muc nude H > 3,0 m tai Tan Chau dd t i m thdi gian t r i ngap lut d cac vung trung D T M v d i dd chenh lech trung binh khoang 10 811 KY YEU -CAC BE TAI NGHIEN CPU KHOA HOC- CONG NGHg NGANH TAl NGUYEN VA MOI TRUONG GIAI DOAN 2002-2 Dong thdi, dua vao muc nude trung binh thang d cac tram thuy van d k h u vuc noi dong de t i m mire ng&p lut d cac vung trung D T M Phan tich danh gia thiet hai ve dien tich gieo lua va hoa mau tac ddng cua ngap lut cho tha'y: a) D d i vdi lua he thu va miia: N a m co l u trung binh dien tich lua b i ma't trang ngap ung vao khoang hang chuc ngan N a m co l u ldn l i c h sir 2000 la 401.342 ha, b i mat trang khoang 46.402 b) Ddi vdi hoa mau: Nam co lu trung binh dien tich hoa mau bi mat trang vao khoang hang chuc ngan Nam co lu ldn lich sir (2000)dien tich hoa mau bi ngap 85.234 ha, mat trang la 609 2) Danh gia tac dong cua thien tai han han: Dien tich b i han m i vu san xuat dao dong khoang tir 4.000 den 230.000 va dien tich b i mat trang tir 1.000 den 39.000 Dac biet nam 1998 dien tich lua he thu b i han len t d i g i n 274.850 ha, bi mat trang han 32.000 3) Danh gia tac dong cua thien tai ngap man: Nhung chi tieu sir dung 6i danh gia, bao g6m: a) D d i vdi lua: Dung chi tieu man S%„< % (la td't ddi vdi cay lua), chi tieu S%o > 4%o (la hai ddi vdi lua), chi tieu S%o > 10 ° a c % „ (la tai hoa ddi v d i cay lua) n b) D d i vdi hoa mau: Diing chi tieu dp man S % „ < % (la tot ddi v d i cay hoa mau), chi tieu S % > % (la hai ddi vdi cay hoa mau), chi tieu S °/ > 10 hoac % - la tai hoa ddi vdi cay hoa mau d tieu vung bi nhiem man () (X) III.3 KET QUA TINH TOAN HE SO BIEN DONG CUA NANG SUAT LUA TRONG VU DONG X U A N , HE T H U V A M U A CAC T I N H He sd bien dong chung cua nang suat lua (Q,) vu dong xuan, he thu va mua d DBSCL dao dong khoang 19,8% - 21,2% Trong he sd C vu he thu la ldn nhat (21,2%) va vu mua la nho nhat (19,8%) He sd thdi tie't ( C ) dao dong khoang - 4% D d i vdi tirng tinh nhung vu cu the cac he sd C va C cd gia t r i rat khac Ket qua tinh toan he sd C cho tha'y: Nhung tinh nao cd he so C cao cd nghia la tac ddng cua cac loai thien tai ndi tren den nang suat lua d cac tinh dd l d n v k v k k k III.4 KET QUA TINH TOAN HE SO BIEN DONG NANG SUAT VA HE SO THC-I TIET CUA M O T SO C A Y M A U LUONG THUC C H I N H (NGO, K H O A I L A N G , D A U TUONG) d CAC TINH Ddi vdi dong bang song Ciru Long, he sd bien ddng chung cua nang sua't ngo, khoai lang, san va dau tuong (C ) nam dao ddng khoang 18% - 41,2% D d i vdi tirng tinh va ddi vdi tirng cay mau cu the nam deu tinh duoc he sd C va C v v k Ill THIET HAI DO THIEN TAI LU LUT, NGAP UNG, NGAP MAN VA HAN HAN GAY RA D O I VC5I SAN X U A T N O N G NGHIEP Ngap ling la mot nhung yeu td lam giam nang suit hoac lam cay bi chet khong cho thu hoach va l u lut keo dai cd the lam cham trd cac mua vu m d i L u sdm gay anh 812 KY YEU "CAC DE TAI NGHIEN COU KHOA HOC- C&NG NGHE NGANH TAl NGUYEN VA MOI TRUONG GIAI DOAN 2002-2006" hudng den san xuat lua he thu va thai gian l u rut sdm hay muon cung anh hudng den thai vu xudng gidng cua lua ddng xuan va cac cay mau luang thuc, dong thdi neu l u rut muon thi se anh hudng den thdi gian gieo sa vu Ilia he thu nam sau d nhung viing ngap l u Do man cua nude song, cac kenh rach va rudng vao thdi k y cudi miia kho va dau miia mua thudng nam khoang thdi gian cd man cao nhat nam (thang va thang 5) va v i t r i cua ranh gidi gidi han man - g/1 hay - g/1 Vao nhung thdi diem trieu cudng manh nha't nam lam tran nhieu cua cong ngan man, nude man tran vao dong rupng gay thiet hai cho san xuat nong nghiep d nhung vung Thiet hai cua san xuat nong nghiep han han cac vu vu dong xuan, he thu, mua la rat ldn Cu the nam 1981: V u dong xuan 150 ha, he thu 11054 ha, vu mua 4042 ha; nam 1987: V u he thu 21427 ha, vu miia 8357 ha; nam 1992: V u dong xuan 1250 ha, he thu 39062 ha, vu miia 7835 ha; nam 1998: V u dong xuan 19414 ha, he thu 32109 CHLTONG IV: KIEN NGHI CAC GIAI PHAP VE CO CAU THCfl VU GIEO TRONG P H U H O P D O I VCfl M O T S O C A Y L U O N G T H L / C C H I N H IV.1.THC5I VU LUA a) Lua d6ng xuan: D d i vdi tidu vung khong chiu anh hudng cua l u : (1) Tra lua sdm: Sa thang tit 20/10 den 30/10; (2) Tra lua trung: Sa thang tut 1/11 ddn 25/11 D d i vdi tieu viing chiu anh hudng cua l u , nude rut cham: Sa thang tir 10/11 den 10/12 b) Lua he thu: Ddi vdi tieu vung anh hudng cua lu vd sdm: Sa thang tir 20/4 den 10/5, thu hoach trudc 20/8 D d i vdi tieu vung khong anh hudng cua l u : Sa thang tir 20/5 den 10/6, thu hoach xong trudc 15/9 c) Lua mua: D d i v d i tidu vung anh hudng cua l u vd sdm, dat chua phen, ngap ung sau: Sa thang tir 20/5 den 30/6, thu hoach vao cudi mua mua dau mua kho (thang 12 hoac thang nam sau) D d i v d i tieu vung khong anh hudng cua l u : Sa thang tir 20/5 den 30/6, thu hoach vao thang 10 va 11 M u a trung gieo ma thang 6, cay thang 7, thu hoach thang 11 Miia muon gieo ma tir 15/6 den 15/7 ca'y tur 20/7 den 15/8 thu hoach thang 12 va thang nam sau d) Cay mau luang thuc (ngo, dau tuong, khoai lang, san): Thai vu cua nhung cay chu yeu dua vao tich luy mua dau mua duoc 75 m m v d i sua't bao dam 80% Nhung gidi han sau cua cac cay mau phai tinh toan thdi vu de thu hoach trudc xuat hiSn muc nude dinh l u chinh vu vdi sua't bao dam 20% d nhung vung thudng xuyen ngap ting sau Con d nhung chan van cao phai thu hoach k h i miia mua ket thuc IV.2 CO CAU LUAN CANH CAY LUA VA CAY MAU LUONG THUC 1) Co cau miia vu cay d nhung tieu vung sinh thai nong nghiep cu the d DBSCL dd tai de xuat dat dugc mtic hgp l y , hieu qua va kha t h i phai ne tranh dugc tac dong tdi da cua cac loai thien tai nhu l u , ngap ung, ngap man va han han (vdi suat bao dam 80%) 2) Ve kha nang tang hoac giam vu gieo d DBSCL: Ddi vdi nhung noi thuy lgi da co thd chu ddng tudi tieu t h i kha nang tang vu la ra't cao va co thd gieo v u hoac 813 KY YEU "CAC S£ TAl NGHIEN CUU KHOA HOC- CONG NGHE NGANH TAI NGUYEN VA MOl TRUCJNG GIAI DOAN 2002-2 vu m i nam D d i v d i dong rudng trung thich hop vdi co cau vu: M a u (he thu) + Lua (mua) + Lua ( D X ) Con nhung noi dia hinh thoat nude tot co the sir dung co cau: Lua (He thu) + L u a ( M u a ) + M a u ( D X ) Neu nhu tren dat vu lua khong 6n dinh ve nang sua't san lugng t h i nen chuyen doi co cau luan canh nhu sau: a) v u lua: D o n g xuan - he thu tren dat trung nude l u rut cham, chan ruong chua phen D d i v d i nhung chan ruong kien quyet khong cho gieo vu thu dong; b) vu lua va m o t v u mau: Lua dong xuan - mau he thu (ngd, khoai lang) - lua mua tren dien tich chd vao mua Theo chung tdi, ddi vdi chan ruong d tieu vung nhidm man ven Bien Dong va vinh Thai Lan co the xem dudng ranh gidi man 4%o cua tuan thang cung la dudng ranh gidi giua vung co kha nang tang vu va vung mot vu (trir trudng hgp d ngoai dudng ranh gidi man 4%o nhung noi nao khong b i ngap man, mua sdm, g i u dugc nude mua) Tai nhung chan ruong tur trudc den v l n chi canh tac mot v u lua mua mua mua, nang suat tha'p va bap benh t h i co the chuyen sang nudi thuy san (torn su) cd gia tri kinh te cao hon Rieng ddi vdi cac chan ruong trung, nhidm phen, ngap sau va thdi gian ngap keo dai nhieu thang thuoc tidu vung D T M neu dugc d i u t u cao, ap dung tie'n bo k y thuat, ngoai vu lua mua noi (sir dung gidng co TGST trung ngay) cd thd them mdt vu mau (virng, dua hau, dau tuong) vao cudi va sau vu lua Con d d i v d i nhung noi canh tac nhd nude trdi ve l y thuyet deu co kha nang gieo m i nam v u , chu yeu mua sinh trudng IV.3 XAC DINH CO CAU GIONG PHU HOP V6l MUA VU GIEO TRONG CAC CAY LUONG THUC • TiSu vung sinh thai nong nghiep phu sa ngqt 1) Lua dong xuan: Tidu vung khong chiu anh hudng cua l u : (1) Tra lua sdm: Sa t h i n g tir 20/10 den 30/10, (2) Tra lua trung: Sa thang tir 1/11 den 25/11 Tidu viing chiu anh hudng cua l u , nude rut cham: Sa thang tir 10/11 den 10/12; 2) Lua xuan he: Thudng dugc b d t r i tren chan ruong chu dong nude va lam vu nam Sa thang tir 20/3 ddn 10/4 va thu hoach xong trudc 15/7; 3) Lua he thu: d nhung noi khong chiu anh hudng cua lu, sa thang tur 20/5 ddn 10/6 va thu hoach xong trudc 15/9 O nhung noi chiu anh hudng cua l u ve sdm: Sa thang tir 20/4 den 10/5 va thu hoach trudc 20/8; 4) Lua mua: d nhung noi khong chiu anh hudng cua lu: Lua mua sdm sa thang tir 20/5 den 30/6 va thu hoach thang 10 va 11 L u a mua trung (mua Id) gieo ma thang ca'y thang va thu hoach cudi thang 11 Lua mua m u o n gieo ma tir thang 15/6 ddn 15/7 ca'y tir 20/7 den 15/8 thu hoach thang 12 va thang nam sau 6" nhung noi chiu anh hudng cua l u : gieo ma thang ca'y tir 25/7 den 10/8 thu hoach thang 12 va thang nam sau • Tieu vung sinh thai nong nghiep Dong Thap Mixdi 1) Lua ddng xuan: Tidu vung chiu anh hudng cua lu, nude rut sdm: (1) Tra lua sdm: Sa thang tit 20/10 den 30/10, (2) Tra lua trung: Sa thang tur 1/11 den 25/11 Tidu vung chiu anh hudng cua l u , nude rut cham: Sa thang tir 10/11 den 10/12; 2) L u a xuan he (hoac lua he thu sdm): T h u d n g dugc b d t r i tren chan rudng chu ddng nude va l a m v u hoac v u nam Sa thang tur 20/3 den 10/4 va thu hoach xong trudc 15/7; 814 KY YEU 'CAC BE TAI NGHIEN CUU KHOA HOC- CONG NGHE NGANH TAl NGUYEN VA MOI TRUONG GIAI BOAN 2002-2006" 3) Lua he thu: d nhung noi chiu anh hudng cua l u : Sa thang tu: 20/5 den 10/6 va thu hoach xong trudc 15/9; 4) Lua mua: d nhffng noi chiu anh hudng cua l u sdm, lua mua sdm sa thang tir 20/5 den 30/6 va thu hoach thang 10 va 11 O nhung noi chiu anh hudng cua l u chinh vu: Lua mua muon gieo ma t u thang 15/6 den 15/7 cay tir 20/7 den 15/8 thu hoach thang 12 va thang nam sau D d i vdi trudng hop vu lua thu dong (vu lua thu: 3) nang sua't khong on dinh (hay bi l u lut chup k h i vao giai doan gan thu hoach) t h i nen chuyen ddi co cau luan canh nh sau: (1) vu lua + vu mau (dau hoac viing), va (2) v u lua + torn d nhung chan ruong trung • Tieu vung sinh thai nong nghiep Titgiac Long Xuyen 1) Lua dong xuan: Tieu vung khong chiu anh hudng cua l u : (1) Tra lua sdm: Sa thang tir 20/10 den 30/10; (2) Tra lua trung: Sa thang tit 1/11 den 25/11 Tieu viing chiu anh hudng cua l u , nude n i t cham: Sa thang tir 10/11 den 10/12 2) Lua xuan he (hoac lua he thu sdm): Thudng duoc bd t r i tren chan rudng chu dong nude va lam vu nam Sa thang tir 20/3 den 10/4 va thu hoach xong trudc 15/7 3) Lua he thu: d nhttng noi khong chiu anh hudng cua l u : Sa thang tir 20/5 den 10/6 va thu hoach xong trudc 15/9 O nhung noi chiu anh hudng cua l u ve sdm: Sa thang tur 20/4 den 10/5 va thu hoach trudc 20/8 4) Lua vu mua: d nhung noi khong chiu anh hudng cua lu: Lua mua sdm sa thang tur 20/5 den 30/6 va thu hoach thang 10 va 11 Lua mua trung (mua l o ) gieo ma thang ca'y thang va thu hoach cudi thang 11 Lua mua m u d n gieo ma tir thang 15/6 den 15/7 ca'y tir 20/7 den 15/8 thu hoach thang 12 va thang nam sau O nhung noi chiu anh hudng cua l u : gieo ma thang ca'y tur 25/7 den 10/8 thu hoach thang 12 va thang nam sau • TiSu vung sinh thai nong nghiep Ven bien Dong Lua mua sdm + L u a thu ddng, do: V u Lua mua sdm: Gieo ma: 25/5 - 10/6; Ca'y: 15/6 - 30/6; thu hoach: 30/8 - 15/9; V u Lua thu ddng: Gieo ma: 20/8 - 5/9; Ca'y: 10/9 - 25/9; thu hoach: 10/12 - 25/12 D d i vdi viing dat vudn, dat r l y thuoc Go Cong D6ng va Go Cong Tay, cac xa vung dudi thuoc huyen Cho Gao nam co thd tien hanh vu dau Tidu vung sinh thai nong nghiep Dong Thap M u d i Dau tuong he + Dau tuong thu dong ( V u dau tuong he: Tria: 25/5 - 10/6; thu hoach: 10/8 - 25/8 V u dau tuong thu ddng: Tria: 20/9 - 10/10; thu hoach: 10/12 - 30/12 Hoac luan canh ltia miia sdm + dau tuong dong xuan (Gieo: 10/5 - 25/5; ca'y: 1/6 - 15/6; thu hoach: 20/8 - 5/9 V u dau tuong d6ng xuan: Tria: 20/9 - 5/10; thu hoach: 10/12 - 25/12 Vung gan bidn, chu yeu cay mdt vu lua mua vi man rut muon, thdi gian xam nhap cua no lai sdm O day vu lua miia: Gieo; thang 6; ca'y thang 7; thu hoach: cudi thang 11 V i man cd the anh hudng nen du co thu hoach m u d n qua thai gian tren nhung khong dupe qua 15 thang 12 • TiSu vung sinh thai nong nghiep Tay Song Hau 1) Lua ddng xuan: Tidu vung khong chiu anh hudng cua l u : (1) Tra lua sdm: Sa t h i n g tit 20/10 den 30/10; (2) Tra lua trung: Sa thang tir 1/11 den 25/11 Tidu viing chiu 815 KYYEU "CAC TAI NGHIEN CUU KHOA HOC- CONG NGHE NGANH TAI NGUYEN VA MOI TRUONG GIAI SPAN 2002-20 anh hudng cua l u , nude rut cham: Sa t h i n g tir 10/11 den 10/12; 2) L u a xuan he (hoac Ilia he thu sdm): Tren chan ru6ng chu dong nude va lam vu nam: Sa thang tir 20/3 den 10/4 va thu hoach xong trudc 15/7; 3) L u a he thu: d nhung noi khong chiu anh hudng cua l u , sa t h i n g tir 20/5 den 10/6 va thu hoach xong trudc 15/9 d nhung noi chiu anh hudng cua l u ve sdm, sa t h i n g tur 20/4 den 10/5 va thu hoach trudc 20/8; 4) Lua mua: d nhung noi khong chiu anh hudng cua l u : L u a mua sdm sa t h i n g tir 20/5 den 30/6 va thu hoach thang 10 va 11 L u a miia trung (mua Id) gieo ma thang ca'y thang va thu hoach cudi thang 11 Lua mua muon gieo ma tir thang 15/6 den 15/7 ca'y tir 20/7 den 15/8 thu hoach thang 12 va thang nam sau O nhung noi chiu anh hudng cua lu: gieo ma thang cay tir 25/7 den 10/8 thu hoach thang 12 va thang nam sau • Tieu viing sinh thai nong nghiep Kien Ban dao Ca Mau (Viing nhiSm man Ca Mau - Giang) a) Vung da't tuong ddi cao: Lua he thu + mau ddng xuan Trong dd: Lua he thu: Gieo: 1/5 - 25/5; ca'y: 21/5 - 15/6; thu hoach: 10/8 - 5/9 M a u ddng xuan: Dau tuong ddng xuan: Tria: 20/10 - 30/10; thu hoach: 10/1 - 20/1 (TGST: 82 ngay); b) Vung dat cd dd cao trung binh: Dau tuong he + lua mua mudn Trong dd: Dau tuong he: Tria: 25/5 - 10/6; thu hoach: 10/8 - 25/8 (TGST:76 - 77 ngay) L u a miia mudn: Gieo: 5/8 - 20/8; ca'y: 1/9 - 15/9; thu hoach: 1/12 - 15/12; c) Vung da't tha'p: Trudc mat chu yeu ca'y mot vu lua mua: Gieo vao thang 6; ca'y vao thang 7; thu hoach vao thang 11 IV.4 KIEN NGHI CAC GIAI PHAP UNG PHO DOI VOl CAC LOAI THIEN TAI TRONG SAN XUAT C A Y LUONG THUC I V Cac giai p h a p ung p h d d d i v d i t h i e n t a i 10 l u t , ngap u n g , ngap m a n 1) Thdi vu gieo ltia he thu phai dam bao cd the thu hoach dupe lua trudc lu chinh vu xay 2) Dap bd bao bao ve lua he thu k h i l u ve sdm tai nhung vung ngap l u vira va sau, khdng nen gieo vu lua thu ddng d nhung vung 3) Can theo doi chat che cac ban t i n d u bao, canh bao l u , ngap ung va ngap man cua cac Trung tarn D u bao K h i tuong Thuy van dia phuong ket hop v d i can cu" khoa hoc cua dd tai de xuat di cd quyet dinh dung d i n ddi v d i vide thu hoach sdm trudc k h i b i l u chup ddi vdi lua he thu V a cd bidn phap ngan xam nhap man huu hieu bang each d i p va ddng cac cira ngan man d cac tinh ven Bidn Ddng va vinh Thai Lan vao nhung thdi diem can thiet IV.4.2 Cac giai phap img phd ddi vdi thien tai han han Dua vao bit diu mua mua irng vdi suat bao bam 80%, luong mua tich luy ling vdi cac suat bao dam khac trudc va sau mdc va xac suat xay mdt tuan k h d , hai tuan khd lien tuc d cac dia phuong thudc ddng bang sdng Cuu L o n g di bd t r i thdi vu gieo trdng 816 KY YEU "CAC BE TAl NGHIEN CUU KHOA HOC- CONG NGHE NGANH TAl NGUYEN VA MOI TRUflNG GIAI BOAN 2002-2006' Dua tren co sd cac ket qua tinh toan ta co thd hoan toan chu dong ngu6n nude de tudi nude bo sung cho lua va hoa mau k h i co han xay KET LUAN VA KIEN NGHI Nhung thiet hai ve san xuat nong nghiep d DBSCL lu lut, ngap ung, ngap man va han han nhung nam gin day la rat dang ke M t i c dd tac dong cua m d i loai thien tai ddi vdi cac cay luong thuc chinh dupe gieo d m i tidu viing sinh thai nong nghiep cung rat khac nhau; Ket qua tinh toan bat diu mua mua ung v d i sua't bao bam 80%, thdi gian ung vdi sua't bao dam P = 80% cua luong mua tich luy sau mdc tinh dat 75 m m , 200 m m va lupng mua tich luy trudc mdc dat 500 m m , 300 m m , 100 m m d cac dia phuong va xac sua't va tuan kho lien tuc va tan sua't xuat hien han cung nhu thdi gian t r i dp man: S = %o tuan d tirng mua vu gieo cu the tai cac dia phuong thuoc DBSCL la co sd khoa hoc dd bd t r i co ca'u mua vu gieo cac cay luong thuc chinh; Chi nen m d rpng dien tich gieo ca'y lua he thu d nhung chan ruong chu dong nude tudi vao giai doan diu va giua vu Chu dong nguon nude dd tudi bd sung cho lua va hoa mau co han xay ra; Thdi gian t r i dp man: S = - 20 %o rat phu hop vdi nudi T o m su, nhung lai la tham hoa ddi vdi lua va cac cay mau luong; Muc nude l u trung binh thang dac tai cac tram thuy van ndi ddng la dac trung quan bieu thi mire dp ngap lut la can cu khoa hoc dd dap b d bao bao ve lua he thu tranh lu vd sdm chup; Nhting dien tich b i ngap man hien dang canh tac lua dat hieu qua tha'p, nang sua't lua bap benh nen chuydn sang nudi thuy san theo quy hoach chi tie't tong thd t h i hieu qua se dat cao hon; He sd bien ddng nang sua't cua cac cay luong thuc chinh k h i hau tao nen cac mua vu d cac dia phuong rat khac nhau; Co ca'u mua vu cay d cac tidu vung sinh thai nong nghiep dupe xay dung ddi vdi lua ddng xuan sit dung muc nude l u rut 20 cm muc nude mat rudng lam xudng gidng ddi vdi cac viing dau nguon va khoang 2,5 m ddi v d i cac vung luu Ddi vdi vu he thu va vu mua: Gieo sa k h i miia mua thuc su bat dau (ting v d i sua't bao dam 80%) Chu ddng nude tudi k h i xay han "Ba chang" T h u hoach ltia he thu trudc k h i l u vd (trudc 15/7) d nhung vung trung ngap lut sau; D d i v d i cac tinh thudc vung DBSCL chi ndn m d rpng dien tich gieo ca'y lua he thu va cac cay mau luong thuc d nhung chan rudng t d i tieu chu ddng k h i cd han nang va ngap ung xay K h o n g nen gieo vu ltia thu ddng (vu he thu mudn) d nhung noi khong cd dd bao bao ve an toan k h i l u ve; 10 Viec khai thac tong hop va bao ve tai nguyen nude la bien phap co ban dd phdng tranh va giam nhe thiet hai thien tai lu, lut, ngap man va han han gay 817 ... Tir nam 1926 den nam 2001, da co 41 nam co l u chmh vu v o l muc nude dinh lu tai Tan Chau tir 4,2 m (bao dong cap I I I ) , co 24 nam co dinh lu ldn hem 4,5 m (chiem 31,6%) D i n h l u nam 1961... 1997 - 1998 nen nam 1998 la nam co l u nho nhat, muc nude dinh 1Q tai Tan Chau chi dat 2,81 m va tai Chau Doc 2,55 m , ung vdi tan suat khoang 95,5% Dac biet l u lich sir nam 2000 (t6ng 1ugng ldn... cac nam 1976 - 1985 Dac biet la d tinh Kien Giang: han nang da xay vao cac nam 1977 - 1981 (chi so giam nang sua''t lua dao dong khoang tur -50,5 den -69,6%) Trong vu dong xuan nam 1978 la nam