HIEN TRANG VA DUBAO XU THE HOANG MAC HOA CJ CAC TINH NINH THUAN VA BINH THUAN CUA VIET NAM LE VAN KHOA* I KHAI NifeM VA DINH NGHIA \ t SA MAC HOA, HOANG MAC HOA - Theo Cdng udc chd'ng sa mac hda ciia Lien hgp qud'c dugc thdng qua tai Hdi nghi thugng dinh ciia Lien hgp qud'c ve mdi trudng va phat trien tai Rio de Janeiro nam 1992 thi sa mgc hda Id su suy thodi ddt dai tgi cdc viing khd hgn, bdn khd hgn, vung dm nua khd hgn cdc nguyen nhdn khde nhau, CO biin ddi hdu vd cdc hogt dgng ciia ngudi gdy - Theo tir dien bach khoa Viet nam, hoang mac hda la qua trinh va hien tugng dat trd khd cdn, cay cd tu nhien khdng mgc lai dugc, cay trdng khdng trdng lai dugc Do ddt rtrng, lien tie'p chan tha qua miic, dai sir dung khdng hgp ly va nhiing dieu kien ban ban keo dai hang nam nen da trd hoang mac - Theo Uy ban Khf hau (WMO) cua Lien hgp qud'c, hoang mac hda la su thoai hda ciia he sinh thai va su xuai hien ciia mdi trudng sa mac tren cac viing khd ban, ban khd ban va mdt sd vung am udt, Qua trinh hoang mac hda dugc bieu thi bdng su thieu hut am, su tich mudi dat, su suy giam mau md ciia dai, su giam siit che phu, su thay ddi gidng, loai va su banh trudng ciia cac bai cat hoac su xam la'n ciia cac cdn cat di ddng - Theo FAO (2008), hoang mac hda la qua trinh tu nhien va xa hdi pha vd can bang sinh thai ciia dai, tham thuc vat, khdng khf va nudc d cac viing khd ban ban khd ban va ban am udt, Qua trinh xay lien tuc, qua nhieu giai doan, ddn de'n giam siit hoac mai hoan toan kha nang dinh dudng ciia dat trdng, giam thie'u cac dieu kien sinh sd'ng va tang them canh hoang tan Mac dti cd nhiing khai niem nhin nhan vdi gdc khac ve sa mac hda (SMH) hay hoang mac hda (HMH) nhung deu cd nhan dinh chung dd la qua trinh suy thoai dai (thoai hda dai) ddn de'n giam siic san xuat ciia dat mdt each nghiem trgng hoac tham chi lam mat di sire san xuat sinh hgc cua dai Nguyen nhan chil ye'u dac diem bie'n ;ttdi hau, cac dieu kien tu nhien ciia viing (dac diem khf hau, lugng mua, dat dai, dia hinh, tham thuc vat, ) va tac ddng boat ddng ciia ngudi (dan cu va phan bd, cac kieu sir dung dai, cac chfnh sach quan ly dat dai, ) FAO-UNEF (2008) cho biei, SMH hay HMH dien chii ye'u qua cac qua trinh sau: (i) qua trinh thoai hda tham thuc vat; (ii) qua trinh xdi mdn nudc; (iii) qiia trinh thdi mdn dd gid; (iv) qiia trinh nhiem man; (v) qua trinh suy giam chai hiiu co dat; (vi) qua trinh kei von, da ong va (vii) qiia trinh tfch liiy ddc to dat Ngoai ra, yeu td bien ddi khf hau thdi gian gdn day nhu khd han, mua bao ldn d nhieu viing, nudc bien dang xuat hien nhieu hom la nhu'ng nguy co ddn tdi hoang mac hda manh ban Chi tieu quan trgng de xac dinh SMH la chi sdkhd hgn - ty le lugng mua hdng nam, so vdi lugng bd'c thoat hoi tiem nang thdi gian nhat dinh (thang, nam), bie'n ddng tu 0,05-0,65 (Cdng udc chd'ng sa mac hda) Hien nay, SMH the hien rd nhat tren dai trdng ddi trgc, khdng cdn ldp phii thuc vat, dia hinh dd'c, chia cdt, nai cd lugng mua tha'p (700 800 mm/nam); lugng bd'c hoi tiem nang dat 1000 - 1800 mm/ nam Chi sd khd han cua Penman tfnh theo cdng thiic: PET H,=R PET la lugng nudc bd'c hoi tfnh theo phuang phap Peiunan (mm) R, la lugng mua (mm) Ca'p khd ban dugc phan chia theo bang dudi day Le Van Khoa GS.TS., Dai hoc qud'c gia Ha Ndi Le Van Khoa - Hien trang va dif bao xu the hoang mac hda BANG Cap han dugc phan chia theo chi sd khd han Cap han Rai am udt Am udt Chi so' kho han 7,0 Dua vao ty le giiia phdn thu (lugng mua) va phdn chi (bd'c hoi) ciia can can nudc, ta cd chi sd khd han K, nhu sau: ^ = E^ R Trong dd Ej la lugng bd'c hai tiem nang, R; la lugng mua cting thdi ky Cac chi tieu cu the cua K| de danh gia mirc khd ban phu thudc vao ttrng vting Tren lanh thd Viet Nam, chi sd khd ban nam phd bie'n la 0,3 den 1,0 Chi sd khd ban nhd ban 0,3 cd d mdt sd trung tam mua ldn nhu: Mudng Te, Sapa, Bdc Quang, Tam Dao, Tra My, Ba Ta, Bao Ldc, Mdt sd noi cd chi sd khd han ldn ban 1,0 nhu Bach Long VT, Bach Ma, Nha Trang, Ayunpa Bdc Quang vdi lugng mua ldn nhai (4802 mm) cd chi sd khd ban be nhat (0,13), Nha Hd lugng mua be nhat C794 mm) thi chi sd khd ban ldn nhat (2,09) Ngd Dinh Tuan (2009) cho biei: theo lugng mua sinh ddng chay, d Viet Nam chua cd vimg nao dat tieu chudn hau khd ban (Xo < 250 mm/nam) hay ban khd ban (Xo < 500 mm/nam) Nhu vay, d Viet Nam khdng cd qua trinh sa mac hda ma chi cd qua trinh hoang mac hda- mdt dang thap cua sa mac hda Nhiing viing cd lugng mua tha'p, dac biet la d tinh Ninh Thuan va Binh Thuan, ddng thdi la tinh cd dien tich dai cat bien va cdn cat di ddng kha ldn nen cang tang cudng nguy ca bi hoang mac hda n HIEN TRANG HOANG MAC HOA TINH NINH THUAN VA BINH THUAN Cac tinh Nam Trung Bd, dien hinh la Binh Thuan va Ninh Thuan dugc coi la vting khd ban, thie'u nudc thudng xuyen Tinh hinh ft mua va ndng nhidu nen ban thudng dien gay gdt Dac biet nhiing nam gdn day, anh hudng cua bien ddi hau (BDKH), tac ddng ciia hien tugng El Nino, mua mua thudng de'n mudn hem va kei thiic sdm hon so vdi binh thudng nen miic ban han va thie'u nudc dd'i vdi san xuat ndng nghiep va sinh boat d tinh cang trdm trgng Nhu vay, neu xet de'n lugng mua, lugng bd'c thoat hoi, nhiet trung binh, thi Ninh Thuan - Binh Thuan thudc viing hau kho ban va hoang mac hda chi xay cue bd tren mdt sd vung, vdi dien tfch khdng ldn chii yeu d ven bien va vimg dai trdng ddi trgc Theo kei qua kiem ke dai dai nam 2008 ciia Sd Ndng nghiep va Phat trien ndng thdn (NN&PTT^) cac tinh Binh Thuan va Ninh Thuan, dien tich dai dang bi thoai hda va hoang mac hda (trinh bay d bang 2) phan bd tap trung nhat d cac huyen Ninh Phudc, Ninh Hai (tinh Ninh Thuan); Tuy Phong, Bdc Binh, Ham Thuan Bdc (tinh Binh Thuan) phan anh sir suy thoai dai kha rd net, chua ke de'n su suy thoai ve chai lugng, su mat dinh dudng dai BANG Dien tich da't hoang mac hoa d tinh Binh Thuan va Ninh Thuan Binh Thuan: Dien tich tur nhien: 783.255 Dai trdng hoang hda Trong dd ddi mii trpc Dien ti'ch hoang mac hda Ninh Thuan: Dien tich tu nhien: 336.000 Dien tfch dai trdng ddi niii trpc Dien tfch hoang mac hda Dien tich thi hien hoang mac hda nang 255.492ha 106.343ha 89.995ha Chiem 31,96% Chiem 13,31% Chiem 11,3% II4.900ha 8I.021ha 15.632ha Chiem 33,5% Chiem 23,6% Chiem 4,6% Nguon: Sd NN&PTNT Binh Thuan va Ninh Thuan, 2008 Nqhien ciru Phat trien ben vdnq so (30) - Thanq 3/2011 Le Van Khoa - Hien trang va dif bao xu the hoang mac hda Viet Nam tdn tai nhieu loai hinh HMH, nhung d tinh qua kei qua nghien ciiu khao sat theo cac mat cdt va cac diem chia khda cung nhu phan tfch cau triic eiia ban dd canh quan sinh thai cho tha'y cd dang hoang mac CO ban sau : Hoang mac cat (cat bay, cat chay, cat trugt Id); Hoang mac da (da Id - lan Id); Hoang mac dai cdn tra san sdi, dai bac mau thoai hda; Hoang mac mud'i tan du d xa bien va ven bien Hoang mac cat mdt phdn the' hien tinh nguyen sinh ciia qua trinh tich tu cat hien dai Cdn hau hei cac dang hoang mac khac mang tfnh chai thii sinh khai thdc qua mirc va khdng hgp ly dai dai Thd'ng ke sa bd dien tich hoang mac hda d hai tinh dugc trinh bay bang dudi day: BANG Dien tich hoang mac hda d hai tinh Binh Thuan- Ninh Thuan STT Dang hoang mac Binh Thuan (ha) Ninh Thuan (ha) Hoang mac cat 56.740 9.103 Hoang mac da 9.355 21.468 Hoang mac mud'i - Ven biin - Luc dia 1.870 9.540 525 5.882 Hoang mac dai can 12.490 44.043 Tong cpng: Ti le % so v&i dien tich tu nhien 89.995 11,3% 81.021 23,6% Nguon: Dl tai DTDL, 2008G/05 m CAC TifeU CHi DANH GIA HOANG MAC HOA Tieu chi danh gia hoang mac hda d cac nudc Yeu td khf hau, chu yeu la lugng mua tha'p so vdi lugng bd'c hoi ddn tdi hinh cac viing khd ban, ban khd ban, ban am vay dat bi ban han manh Mdt vting dugc coi la hoang mac hda the hien cac bien tugng sau: - Lugng mua rai ft so vdi lugng bd'c hoi hoac lugng mua khdng ft nhung phan bd khdng hgp ly, cd mdt mua khd keo dai, nhieu thang lien tuc lucmg mua dudi ngudng khd ban; trung binh nam dudi 200-300 mm; lugng mua chi bdng 1/5 lugng bd'c hai hoac ft hon niia; - Khdng cd kha nang cung cap nudc cho cay trdng bdng ngudn nudc tu nhien va tir he thdng tudi miia khd; - Vao mua mua, xay qua trinh xdi mdn dai mua va vao mua khd xay qua trinh thdi mdn, qua trinh man hda tir phfa bien vao ndi ddng; - Cac hoat ddng khai thae rung va sir dung dai canh tac ndng nghiep, chan tha gia siic khdng hgp ly; - Dai thoai hda rd ret, ngheo miin, thieu dinh dudng; - Xuai hien thuc vat tu nhien chi thi khd han; - Bien nhiet ldn; am thap; gid cd the gay xdi mdn, gay cat bay, cat chay, tao phong thanh; nudc mua tao xdi mdn; lu rat nhanh, rai ngdn - Yeu to ve che phii rung de dam bao ngudn sinh thiiy Khd'i lugng vat chat hiiu ca dai khdng cd rtrng ft ban 10 ldn so vdi dai rtrng; cac hg cay hda thao, hg rau mud'i chiem uu the'; hdu nhu khdng cd reu va dia y; cd bui thua thdt, gdn nhu tra trui Cay lau nam gdm cd hai tang re, tdng tren ndm gdn mat dat de sir dung nudc vao miia xuan, tang dudi sau Nqhien ciru Phat trien ben vifnq so (30) - Thanq 3/2011 §s Le Van Khoa - Hien trang va da bao xu the hoang mac hda ban, lan rdng de tim hiit nudc ngdm La thu nhd de tranh bd'c thoat hoi, la ciing, vd day, cd loai khdng la, cd loai la bie'n gai; than cay cd kha nang quang hgp, than chiia nudc nhieu Dd'i vdi cay mdt nam, cay tha'p (30-40cm); cd chu ky sinh trudng ngdn (2- 2,5 thang, cd loai chi 2-3 tudn) - Yeu td dai dai: dia hinh cd dd'c ldn, dat dai ngheo kiet va bi xdi mdn manh, dl phat sinh ldp dai mat khd ciing, suy giam cac dac tfnh vat ly, hda hgc, sinh hgc va kinh te' ciia dai, mai tham thuc vat tu nhien lau dai, (Cdng ude chd'ng SMH) - Ye'u td xa hdi lien quan ngheo ddi va qua trinh sir dung dai: dan so ddng, sinh sd'ng dua vao canh tac tu nhien, sir dung dat khdng ben viing, gia tang siic ep vao tai nguyen thien nhien, Cac tieu chi danh gia cac loai hinh hoang mac hda d Binh Thuan va Ninh Thuan O Viet Nam chua cd nhu'ng tieu chf thd'ng nhat de danh gia cac loai hinh HMH, nhung pham vi nghien ciiu Di tdi DTDL, 2008GI05 de xuat mdt sd tieu chf co ban cho cac loai hinh HMH d tinh Ninh Thuan va Binh Thuan nhu sau: 2.1 Hoang rrmc cdt: gdm tieu chi cabdn: a) Loai dat: cdn cat (trdng, vang, dd) va ddt cat ven bien (trdng,vang, dd); Xuat hien cac hien tugng: cat bay, cat nhay, cat chay (theo nudc) d miic khac nhau; Dai cd phan CO gidi nhe, rat ngheo dinh dudng b) Thuc vat uu the' hay sinh vat chi thi: cac loai cd khd ban va cay bui ehie'm 40% trd len Tren nhiing dun cat, bai cat dge bd bien, ngoai nhu'ng khu vuc trdng rtrng phdng hd va sd it dien tich cd cay trdng ndng nghiep, thao mdc thien nhien neu cd chi mgc lua thua toan la nhu'ng loai cd gai la mudt hoac la nhgn va sd ft loai cd than tha'p- re dai bam chat vao cat nhu cay gai chd'ng (Tribulus terrestris), xuong rdng ba (Opuntia dilleni), cdt khf hoa tfm (Tephrosia purpurea), dau dao bien (Canavalia maritima), cay sam dai {Boerhaavia repens), cd chan thd (Fimbristylis miliacea), cd chdm chdm {Spinifex littoreus), rau mudng bien {Impomea pes-caprea), c) Ye'u td hau thdng qua lugng mua va lugng bd'c hoi: Khu vuc Mien Trung chi sd khd han nam khdng cao nhung cd miia khd ban rai vao dau va giua miia he, cang ve phfa Nam cang cd nhieu thang khd ban gay gdt; Binh Thuan va Ninh Thuan cd chi so khd ban nam tuong ddi cao, mua khd ban triing vdi miua ft mua, nhieu thang cd chi sd khd han vao loai cao nhai nudc (Nha Hd'), cd nam lucmg mua ft (794mm), chi so khd han dat tdi 2,09 2.2 Tieu chi hoang mgc man a) Ye'u td hau: chi so khd ban tuong dd'i cao va la dieu kien thuan lgi cho xam nhap man tir bien va nudc ngdm man dang len theo cac mao quan lugng bd'c hoi tang vao mtia khd Le Huy Ba (2008) cho biei, nhiem man nudc mat xay tren tai ca cac cira sdng cua khu vuc mien Nam Trung Bd Ve mua mua, ranh gidi nhidm man chi each cua sdng den km nhung ve mua khd, ranh gidi nhiem man bi day sau vao ndi ddng tir de'n km, tdng khoang hda kha cao 3- 30g/l nen nhieu noi khdng the' su dung cho muc dfch ndng nghiep Toan bd dien tfch viing Phan Rang Thap Cham bi nhidm man, 15% dien tfch ddng bang Ninh Thuan va Binh Thuan cung bi nhidm man, dac biet la viing ven bien nhu Ca Na, Lien Hucmg, Phude The, Phan Rf b) Tieu chf dat: Ninh Thuan cd bd bien dai 105km va Binh Thuan cd i92 km bd bien nhung bai cat ehie'm uu the' va dai man cd quy md nhd chi chiem tren dudi 1% dien tfch tu nhien (DTTN) d mdi tinh Chia ra: - Dai man nhieu (Mn), thudng cd tdng sd mud'i tan >1% va EC > 4ms/cm, dai cd phan ling kiem; - Dai man trung binh (M) cd tdng sd mud'i tan dao ddng ttr 0,5-1,0% , EC < ms/cm (thudng tir 0,15 - 3,0 ms/cm ), dai cd phan ling trung tfnh, ft chua; - Dat man ft (Mi) cd tdng sd mudi tan < 0,25% va EC < 4ms/cm Rieng tinh Binh Thuan cd 122 dai man kiem (dat man luc dia- dai Ca Rang) SB Nqhien cdu Phat trien ben vdnq so (30) - Thanq 3/2011 Le Van Khoa - Hien trang va di/bao xu the hoang mac hda c) Tieu chi thuc vat: Nhin chung, da't man nhieu tfch luy nhieu chat gay hai cho cay trdng ke ca cay trdng lam nghiep Vi vay kha nang phat trien ndng lam nghiep tren nhirng loai dai la rat han che Hien dang sir dung de lam mud'i cdng nghiep va nudi thuy san nudc man Dai man trung binh va ft ngoai han che' ve man ngam., va dang dugc sii dung trdng liia va hoa mau, nhung rai khd khan ve ngudn nudc nggt Mdt sd loai sinh vat chi thi nhu : - Say (Neyraudia arundinaceae) Loai say thudc hg boa thao (Gramineae), la loai cay ed sd'ng lau nam mgc bui, cd cao de'n 4m, than dac va to d gdc, mgc hoang d vung dai man it, nai dm udt quanh nam - Ldc hen (Scirpus grossus), thudc hg cdi (Cyperaceae), la loai cd sdng dai, cao den 2m, than cd canh nhgn va mat ldm, la dai, thon nhgn; Phat trien manh d bun noi cd anh hudng ciia thuy trieu - Ldc vdi dep (Cyperus platystylis), thudc hg cdi, la loai cd sd'ng dai, than ciing cd canh; la cd phien mau luc tuoi hay mdc, mep la rat sde; mgc rdng rai d bai lay man 2.3 Hoang mgc ddt cdn tra sgn soi a) Tieu chf dai: chii ye'u nhdm dai xam tdng dai mat rai mdng (< 10 cm), kei von da ong ndi tren mat dai ehie'm tren 60%, phan bd d nhiing dd'c khac nhau, xdi mdn mat da va dang xay nghiem trgng Cd noi xuat hien xdi mdn ranh rd ret b) Tieu chf thuc vat: thuc vat khd ban ehie'm uu the' nhu cac loai cd, cac khdm le nhd phan bd rai rac hoac cay bui chiu ban, cd gai xuat hien Tren phan ldn cac dat xam, dai tdng mdng khd can, tham thuc vat thudng rat cdn cdi, chii yeu la cay Itim bui thua thdt xen trang cd phan nhieu la nhirng cay cd gai nhu xuong rdng ba (Opuntia dilleni), tao gai dai (Zizyphus africanus, Zizyphus cenoplia), cay cap gai {Capparis thoreli, Capparis beneolens), cay ddina {Odina wodier), cay cdc rtrng {Spondias nangifora), cay mun (Diospyros mun), miing quan (Flacourtia, Fluggea microcarpa), quao Nqhien cifu Phat trien ben vifnq so (30) - Thanq 3/2011 niii (Stereospermum cylindricum), ngii trao (Vitex negundo) Cac loai cd thudng gap la den ddng {Amaranthus caudaius, Amaranthiis spinosus), cd ga, cd chi (Cynodon dactylon), cd gimg (Panicum repens), bim bim dai (Evovulus alsinoides), cdc man (Polycarpaea arenaria), cd tim lan (Triantliema poifulacastrum) cd gau (Cyperus rotondus), cd lac (Cyperus castaneus) c) Tieu chi hau: dat khd ban, chat, thdi gian khd ban tren thang lien tuc nhieu nam Vting dai cd lugng mua thap 700-1000mm hoac cao ban va chiu anh hudng manh cac hien tugng bien ddi khf hau ddn tdi khd han Chi sd khd ban > 2.4 Hoang mgc dd a) Tieu chi dai va dd'c: niii da hoac da ndi tren mat dai, dd'c cao, thudng > 25°; Da Id chiem tren 60% dien tfch ; Dai xen ke vdi da, khd, chat, khd canh tae b) Thuc vat tu nhien: dat trdng, cd va cay bui mgc rai rac Hoac cay bui xen cay gd nhung ty le che phii < 20%, phan bd khdng deu c) Tieu chf ve khf hau: thdi gian khd ban tren thang lien tuc nhieu nam Vting dai cd lugng mua thap 700-1000 mm hoac cao ban va chiu anh hudng manh cac hien tugng bien ddi hau ddn tdi khd han Chi sd khd ban > IV NHUNG GIAI PHAP GIAM THIEU HOANG MAC HOA TRONG Dl£u KlfiN BifeN DOI KHi HAU Cac giai phap cap qud'c gia Phat trien cac cdng trinh thuy lgi , trdng mdi va bao tdn quy rung Phdng chd'ng hoang mac hda la mdt van de mang tfnh chie'n lugc vtra cap bach, vira lau dai ddi hdi su phdi hgp ddng bd ciia nhieu nganh, nhieu linh vuc Trong dd giai phap khoa hgc - cdng nghe thuy lgi la trung tdm, cac giai phap ve dat, rtrng, la phdi hgp Day la nhirng giai phap can ddu tu ldn va Nha nudc cd trach nhiem chfnh Cap dja phuong ^ Le Van Khoa - Hien trang va dubao xu the hoang mac hda - Tuyen truyen va nang cao nhan thiie ciia ngudi dan ve tinh trang bie'n ddi khf hau va tac ddng ciia nd dd'i vdi qua trinh HMH dang didn vimg Canh bao sdm nhirng tac ddng ciia bien ddi hau va HMH de chuan bi ve mat tinh thdn cho ngudi dan san sang chap nhan tdn that va thuc hien cac bien phap thfch irng xuai hien nhiing tinh hudng xau - Khoanh nudi, trdng mdi va bao ve nghiem ngat dien tich rung tu nhien ft di tren cac khu vuc mii cao dd'c, tri, gia tang che phii dat, han che' qua trinh xdi mdn, rira trdi tren nhung vting dai dd'c - Tranh thu cac ngudn vd'n va ngoai nudc de ddu tu cho viec thiei ke' xay dung mang ludi hd chira cting vdi viec bao tdn cac khu rung ddu ngudn de giii nudc mua mua, ban che' lu quet, kei hgp nudi trdng thiiy san nudc nggt va cai thien dieu kien vi khf hau vd'n rai quan trgng dd'i vdi nhirng viing dang cd nguy ca hoang mac hda nhu Ninh Thuan va Binh Thuan - Nghien ciiu cac phucmg an kha thi lap mdi cac khu bao tdn thien nhien, khu du trii sinh quyen hoac vudn qud'c gia de tri, tdn tao sinh canh, bao ve rung, quy gen va da dang sinh hgc, ddng thdi gdp phan giii dai giii nudc, cai thien dieu kien mdi trudng va han che tac ddng ciia qua trinh bie'n ddi khf hau de'n hoang mac hda ciia viing - Cd nhu'ng bien phdp nghiem ngat khdng cho phep khai tbac dat ddi niii d nhirng noi xung yeu, cd dd'c > 25°, hoac dai dd'c > 15° va cd tang dai mdng < 50cm de sir dung vao muc dfch ndng nghiep, ddng thdi cd ke' hoach trdng, bao ve va tu bd rting tren nhiing viing dai - Cd nhiing bien phap kien quyei, kha thi de tang cudng bao ve va phue hdi rtrng phdng hd ven bien nhdm ban che' qua trinh hoang mac cat vdi qua trinh cat bay, cat chay va di chuyen ciia cac cdn cat ven bien va giam siit siic tan pha cua gid bao, xam nhap man nhdm bao ve an toan cho cac viing dat khu vuc ndi dia Cac dai riing phdng hd ven bien nhu mdt tam chdn xanh ngan chain va lam giam dang ke td'c gid - Trien khai xay dung cac hd ao nhd de trii nudc tai chd vdi quy md phii hgp, dp dung giai phap che phii ban che' bd'c hoi tao ngudn nudc mat va tang nudc ngam, tiep tuc thuc hien chuang trinh kien cd hda kenh muong, giam tdn thai nudc qua trinh truyen ddn, ling dung nhiing ky thuat tudi hien dai, tiei kiem nudc nhu: tudi phun mua, nhd gigt cho nhiing cay trdng cd gia tri kinh te' cao, chgn cac loai gidng cay trdng phii hgp, sir dung ft nudc vdi thdi gian gieo trdng thfch hgp, xay dung cac dap ngam dge ven bien nhdm han che' thoat nudc nggt bien, tang trii lugng nudc ngam V DU BAO XU THfi DifiN BifiN HOANG MAC HOA BINH THUAN VA NINH THUAN De du bao xu the' didn bie'n HMH theo kich ban bie'n ddi hau (BDKH) trung binh, bao cao dua tren can cii: quan trgng: (i) Kich ban Bie'n ddi khf hau trung binh (B2) cho Nam Trung Bd; (ii) Do che phii rimg va (iii) Thiiy lgi Kich ban bie'n doi hau Theo kich ban trung binh (B2) ve BDKH ciia Bd Tai nguyen va Mdi trudng (TN&MT, 2009) dd'i vdi Nam Trung Bd so vdi thdi ky 1980-1999 thi: - Nhiet trung binh cd the tang 0,4°C (nam 2020); 0,9°C (2050) va 1,9°C vao nam 2100; - Lugng mua cd xu the' bie'n ddi theo chieu hudng gia tang 0,7% (2020); 1,7% (2050) va 3,2% vao nam 2100 vao mua mua, nhung lai giam 10-15% vao mua khd ; - Muc nudc bien dang trung binh tren toan dai bd bien Viet Nam cd the dang len 0,12cm (2020) de'n 30cm (2050) va 75cm vao nam 2100 Do che phu riing Hien trang ve che phu rimg ciia tinh dd'i vdi nhiing huyen cd nguy ca HMH cao dugc ddn d bang va Nqhien cdu Phat trien ben vdnq so (30) - Thanq 3/2011 Le Van Khoa - Hien trang va dif bao xu the hoang mac hda BANG Do che phu rimg theo huyen dang cd nguy co HMH cao cua tinh Ninh Thuan (dv: ha; Huyen DT tunhien DTco rimg Toan tinh Ninh Hai Ninh Phudc 336.000 57.122 90.802 147.536 15.140 22.096 Rumgtu nhien 139.657 12.221 19.094 Chia Rimg Tdng ^ tuoi 7.879 598 2.919 359 3.002 107 Dai khong CO rimg QH choLN Dai khac 76.864 16.676 30.038 111.600 25.306 38.668 Do che phii (%) 43,7 25,9 24,2 Nguon: Bd NN&PTNT, 2006 BANG Tdng hgp che phii rimg theo huyen dang cd nguy co HMH cao tinh Binh Thuan (dv: ha) Huyen Toan tinh Bac Binh Ham Thuan Bdc Tuy Phong DT tir nhien DTco rimg 783.255 182.310 131.803 53.491 319.353 83.852 52.792 7.055 Rimg tu nhien 291.688 82.205 50.064 4.318 Chia Rimg ^3 Tong tudi 8.854 27.665 852 1.647 1.018 2.728 2.738 2.169 Dai khong CO Dai khac rimgQH choLN 86.091 12.403 16.978 1.976 377.811 86.055 62.032 44.460 Dp che phu (%) 39,6 45,5 39,3 9.1 Nguon: Bd NN&PTNT, 2006 So lieu cho thay, nhiing huyen ven bien cd nhieu dat cat ciia Ninh Thuan nhu Ninh Hai, Ninh San, Ninh Phudc va thi xa Phan Rang Tliap Cham chi cd 25 rtmg vdi mat che phu 0,3%, dudi xa ngudng an toan sinh thai Tucmg tu, cac huyen Bdc Binh, Ham Tan, Ham Thuan Bdc, Tuy Phong va TP Phan Thiei ciia tinh Binh Thuan, che phii rtmg cd ldn hon cac huyen ven bien ciia tinh Ninh Thuan, nhung dien tfch rtmg phdng hd dai ven bien cung rai thap, TP Phan Thiet chi dat 12,3 % che phii Nhu vay, vdi tham thuc vat ngheo nan, rung phi lao phdng hd bi chat pha de nudi tdm tren cat deu la nhtrng nguy ca xiic tien qua trinh HMH Du bao de'n 2020 thi nudc man miia khd, se xam nhap sau 10-15 km va 20-25 km nam 2050 vao ddng bang Binh Thuan va Ninh Thuan chiem dien tfch tuong iing 80-85%, va 100% tdng dien tfch cac ddng bang Cdn thiei phai cd nhiing giai phap bao ve, trdng mdi, dac biet ddi vdi rtmg phdng hd, rtmg dau ngudn, rtmg phdng hd ven bien, nang mat che phu rtrng toan tinh len 60% thi mdi ban che' dugc qua trinh HMH giam lu va luu chiia nudc phue vu tudi tieu, sinh boat miia khd, ddng thdi ciing la giai phap phdng chd'ng ban dai va ban khdng Sau nam 1975, d tinh da xay dung them mdt loat hd chira vira va nhd Trong dd, d Ninh Thuan cd cac hd dang chii y nhu: hd Tan Giang; hd Sdng Sdt; hd Sdng Trau; hd Lanh Ra; hd Tra Van; hd Ta Ranh; hd Tan My (dang thiei ke"); d Binh Thuan cd cac hd nhu: hd Sdng Quao; hd Ca Giay; hd Ldng Sdng; hd Sdng Luy; Thiiy dien Ham Thuan - Dami; he thd'ng thiiy lgi TaPao (dang thiei ke), Tuy vay hien vdn chua dap irng ngudn nudc can sir dung ciia hai tinh Dd dd can thiei phai thiei ke' va xay dung them cac hd chiia mdi./ Do dia hinh tinh dd'c thoai bien nen cac hd khdng cd tinh da nang ma chi lam nhiem vu TAI LIEU THAM KHAO Bd Tai Nguyen va Mdi trudng: "Kich ban Bien ddi hau, nudc biin dang cho Viet Nam"; 2009 Nguyin Diic Ngir: "Bien ddi khf hau vdi han han va hoang mac hda d Viet Nam"; Hdi thao BDKH toan cau va cac giai phap iing phd ciia Viet nam; Ha Ndi, 2008 Ngd Dinh Tua'n: "Phat trien va sir dung hpp ly ngudn tai nguyen nudc"; Hdi thao khoa hoc \'l BDKH; Ha Ndi,2007 Vien Quy hoach va Thiet ke ndng nghiep: "Quy hoach sir dung dat Binh Thuan va Ninh Thuan"; Bao cao khoa hoc, 2006 Nqhien ciru Phat trien ben vifnq so (30) - Thanq 3/2011 m Thuy lgi