Hoi Dia ly Viet Nam Dai hoc Thdi NguyS"
PHAN TICH ANH HU'CfNG CUA RUI RO THIEN TAI LEN HE SINH T H A I DAM P H A T A M G I A N G - CAU HAI, TINH T H I T A THIEN HUfe
Nguyen Huy Anh', Le Van Thang Abstract
Analyze impact of natural disasters on Tam Giang - Cau Hai lagoon ecosystem, Thua Thien Hue Province
Tam Giang - Cau Hai lagoon ecosystem in Thua Thien Hue province is rated as one of the unique ecosystems in the Central coastal. So far. people have found some 400 species, including 250 species of phytoplankton. 54 species of bottom algae, 43 species of algae. 18 species of aquatic plants, 31 species of terrestrial vegetation. The extreme weather events such as big floods, typhoons and waves that cause to freshening, salinization of lagoon water. These processes will create extreme conditions, unfavorable habitat for ecosystem creature and processes m lagoon; change ecosystem structure, affect on gen resources and biodiversity.
l.DATVANDE
Dam Phd Tam Giang - Cau Hai (TG-CH) phan bfi ti:Bn chifiu dai gin 70km, cd dien tich khoang 22.000 ha, vdi ngufin tdi nguyen sinh hpc phong pfaii va ddng vai trd rat quan trpng doi vdi nudi trfing thuy sdn, giao thdng - cang, du Ijch, nong nghiep, difiu hod khi hau, difiu hoa nude mua trong cac dgt lu lyt, gidm xdm nhgp man qua cac cua song khi cd trieu cudng. TG- CH cung la kfau vyc nhgy cdm dfii vdi nhiing tac dgng ciia thien tai nhu lu lyt, bao, nuac bifin dang, han hdn. Thien tai dang ngdy cang dien bifin phiic tap, khdng theo quy luat da dnh hudng xau dfin ddi song, sinh hoat cua cu ddn, tac dong xau dfin chit lugng nude vd lam cho hp sinh thai (HST) cua dam phd ngdy cdng suy thoai. Nghien ciiu phdn ticfa dnfa hudng cua nii ro thien tai dfin he sinh thdi dam phd dugc thyc hien ttong nam 2012 vdi 2 ngi dung cfamh la: tfing quan vfi he sinh thai khu vuc dam dam pha TG-CH; phan tich vai ttd ciia HST doi vdi phdng chfing nil ro thien tai.
2. PHUONG P H A P NGHIEN CUTJ
- Phuang phdp thu thdp vdphdn tich tdi lieu: Day la phuang phap quan trong trong qua trinh trifin kfaai faoat dpng ngfaien ciiu nay, giiip tiet kipm dugc thdi gian vd kinh phi. phuang phap ndy duge su dyng dfi phan tich cac ngufin tdi lipu cd lien quan dfin HST va rui ro thien tai d dja bdn nghien ciiu.
- Phirang phdp tham vdn cdng ddng: Trong qua trinh nghien ciru, su dyng phucmg phap nay dfi phdng van cac cap chfaifa quyen dia phuong vd mgt so hd dan vfi tinh fainfa thien tai, vfi he sinfa thai, ve sinh kfi cung nhu nhihig quy dinh, chinh sdch ciia cdc cap vfi phdng tranh, giam nhe thien tai cho ngudi dan. Su dyng cdc bdng hdi dfi lay thong tin tii chinh quyen dja phuong va cac fag dan song tren dja ban nghien ciiu. Dong thdi dieu tra tnrc tiep cdn bd va nhan dan dfi tao su trung thue vd cfainh xdc cho nguon sfi lieu vfi tinfa hmh kmh te - xa fagi, rui ro thifin tai, HST ciing nhu cae yeu to ty nhien, mdi trudng khac.
3 K^TQUAVATHAOLUAN
3.1. Tfing quan ve he sinh thdi dim pha Tam Giang - C i u Hai 3JJ. Khu hS thuc v0t
^ Hp tiiuc vgt dim phd da phat hign dugc khoang 400 lodi, bao gom 250 loai time vat pfaii du, nguon goc nude ngpt, man, lg, 54 loai vi tdo day, 43 loai rong tao, 18 loai tiiuc vat tiniy sinh, 31 loai thuc vat can [13,14].
Thanh phdn tdo: Theo nghien cira cua Vd Van Phu va cdng su [8], da phat hipn 357 Ioai tao pfaii du (Phytoplankton) tiiuoc 6 ngdnfa: Cyanopfayta 19 lodi; ngdnh Heterokontophyta 241 loai"
nganh Chlorophyta 3 lodi; nganh Dinophyta 72 loai; nganh Euglenophyta 2 loai; ngdnh Cfaloropfayta 20 lodi
' Vi^n Tdi nguyin vd Mdi tru&ng - Dgi hpc Hue
Ky yiu Hdi nghi Khoa hgc Dia lp todn qudc ldn tha 7
Hoi Dja iy Vift Nam Bai hgc Thai Nguygn
~rX'biin: Vuc nude ciia he dim phd TG - CH den nay da biet 5 Ioai chinh la cd Nan lU Innhila beccarii), cd Xoan (Halophila avails), cd Luon {Zostera japoniea), co He ttdn iHalodule pmlfoba), cd Kim {Ruppia maritime), thugc 4 chi, 4 hg, Cae loai uu the la cd Luon (Z aoonica) cd He trdn {H. pmifolia). Loai thudng gap la cd Kim {R. maritime), co Nan {H.
heccani) Loai it ggp la co Xoan {H. ovalis), chi thay d ciia Tu Hien, Hgp Chau va vyng Hda Dudn (6 101 Day la nhiing noi cu tni quan trong cua cac thuy sdn, dgc biet la nhirng lodi cd gia tn kmh te trong dim phd.
Thuc vdt nggp man: Thyc vat ngap mgn (TVNM) d viing dam pha TG - CH hipn tap trung thdnh 2 khu vyc chinh. Khu vuc Rii Cha, Tan My. Trong dd, dipn tich TVNM d khu vyc Ru Cha hien co dien tich khoang Il,25ha, khu vuc Tan My khoang 2,48ha, Cac lodi thudng gdp la Gid (Excoecaria agallocha), Sii {Aegiceras comiculatum), O ro (Acanthus ilicifolius), Nggc nil bien (Clerodendrum inerme). Rang bien (Arcostichum aureum), Cdc vdng (Lumnitzera raeemosa). Vet khang {Bmguiera gymnorrhiza). Dude vdi {Rhizophora stylosa), Mdm bien (Avicennia manna) [12].
3.1.2. He ddng vgt
a. Bdng v^t khong xuang sdng (Invertebrata)
- Ngdnh giun dot: Trong nganh giun dot d dim phd TG - CH hiu nhu chi ggp cac loai (23 loai) cua ldp giun nfaifiu to Polychaeta [12].
- Ngdnh nhuyen the: Ket qud dieu tra cfao tfaay cd 18 Ioai nfauyen the thudc bg chan byng tmng (Mesogastropoda), bp chan riu mang sgi (Filobrancbia) va bg chan riu mang tam (Eulamellibranchia), trong dd thanh phan loai uu ttgi thugc vfi bg chan riu mang tam.
- Nganh chdn khdp: Trong nganh chan khdp da phdt hiSn cdc lodi thuoc bg rau nganh (Cladocera), bp cfaan cfaeo (Copepoda) cua gidp xac pfaii du (33 loai) va cac bp Ampfaipoda, Tanaidacea, Isopoda, Decapoda thugc gidp xdc bdm ddy (12 lodi).
b. Khu he cd ddm phd [4, 9, 13]
Nhin chung khu he cd dam pha ndm trong 4 nhdm sinfa thdi theo nguon goc (lien quan dg mgn) ciia chiing dudi day:
- Nhdm ca nude Ig: Cd sfi Ioai ddng nhat vd Id nhdm chu yfiu cua khu he ca dam phd. Dai dipn nhdm ndy gfim cac loai ca thupc cac hg: Clupeidae, Engraulidae (bg Clupeiformes - bg ca Trich), Atfaeriiudae (bp Atheiiniformes bp cd Sufit), Hemirhamphidae (bo Belonifoimes), Mugilidae (bg Muguiliformes - bg cd Doi), Tfaeraponidae, Leiognathidae, Gobiidae, Siganidae (bp Perciformes - Bg cd Vugc).
- Nhdm ca nguon goc bifin. Da sd thupc bg cd Vugc sfing d vung bifin nhipt ddi va cd so lupng nhieu. Tuy nfaien, nhifiu lodi thugc bg cd Hpp Muoi nen thudng xuat hien trong dam pha vao miia kho.
- Nhdm cd nude nggt: Nhdm sinfa thai nay cd thdnh phan lodi hgn che. Trong miia mua lu vdi dg man tfaip (5-10%o) thudng gap tdi 30 lodi cua cdc hg: Cyprinidae (bp Cypriniformes - bd ca Chep), Notopteridae (bg Osteoglossiformes - bg cd That Lat), Clariidae (bg Siluriformes - bg cd Nheo), Symbranchidae (bg Symbranchiformes - bp Luon), Anabantidae, Ophiocephalidae (bp Perciformes - bg ed Vugc).
—=-Nh6m-ca di cuJuy-thugc-giai dogn sinh trudng cua cd the, mpt sd lodi di cu den cac thuy vyc khac vdo tirag tfadi gian nhat dinfa faang nam Pfain ldn cdc loai di cu vao dam phd de kiem moi node sinh sdn nfau ca mdi cd, ca dfii Id, ca cam bifin...
Theo mgt nghiSn cira cua Vd Van Phii va cpng su [8] da xac dinh dugc 171 lodi cd, gom 100 giong, nim ttong 62 fag, tfaugc 17 bg ca khac nhau song trong dam phd TH-CH,
c Khu h$ chim
Khu fap chim kha phong phii (chu yfiu cac lodi chim nude) vdi 70 lodi, ttong do ed 34 lodi cfaim tji cu, 36 lodi cfaim dinh cu, 28 logi ed gia t i kinh tfi cao, dgc bipt co 21 loai dugc ghi trong
Kyyiu Hdi nghf Khoa hgc Dfa lp todn qudc ldn tha 7 — —
H8i Dia ly Viet Nam Dgi hgc ThdrNg^y^"
Danh luc chim bao ve nghiem ngdt cua Cdng dong Chdu Au vd 1 lodi trong Sdch dd Viet Nam.
Vao Dong Xuan sfi lugng chun len tdi 20.000 con. Cd luc dan ngong trdi tren 500 con, ddn vjt tidi, tren 1.000 con va dan sdm cam tdi 2 000 -3.000 con [13].
3.2. Cdc qud trinh tir nfaien dnh hirdng dfin hg sinh thdi dim phd Tam Giang - Cdu Hai \ a Hiin tugng phdn tdng nude
Hien tagng phan ting manh, the hien sy trao doi nude kem la mgt dgc thii cua dam pha^ Tinh chat phan ting thfi hien rd d moi difim trong dam phd vdo ea hai miia va thfi hipn d cdc yeu to thiiy
hda (S%o, pH, nhiet do) vd d ca su phan bo cua smh vat noi, ! Hien tugng phan ting manh do cau tnic he dam phd tuang doi kin vd nang lugng trieu yfiu,
Hien tagng phdn ting ngugc cd the do cung nhifiu nguyen nhan la su don ep khoi nuac trieu ttong dam pha ta phia cua Tu Hien ve phia ciia Thugn An, sy cung cap nude ngim^nhgt ta day (lien quan dfin hogt dgng dut gay hien dai, nen cat tru nude nhgt) vd cd the mgt pfain bfic hoi ve miia khd ciia ldp nude mat [8].
Sy phdn tang nude anh hudng den su phan bfi cae lodi dgng thyc vgt phii du, day Id nguon tinic an chu yfiu cfao cdc lodi dgng vdt khde. Do dd, sy phdn bo dpng thyc vgt phii du khong deu dan dfin su tgp trung cdc loai kfaac mot cacfa qua mirc gay nen sy tfaay doi vfi m^t dg lodi dnh hudng den chu trmh dinh duong vd chuoi tiiiic an trong dim. Chinh nhiing tdc dgng ndy se lam anh hudng den he sinh thai trong dim.
b. Qud trinh lap caa, chuyen caa ddm phd
Dim pha TG - CH tidi qua 3 hinh thai khde nhau theo thoi gian, mgt ciia (khi cua Tu Hien bj l ^ ) , hai ciia (khi ciia Tu Hien md) vd nhieu cua khi can lu lich sii tgi Thiia Thien Hue thang 11/1999 xdy ra Ba hinfa tfadi nay luan doi, ttang thdi hai cua thudng ddi lau nhit, dugc coi la ti^g thai binh on. Hai trgng thai kia la nhiing tai bifin. Lap cua, chuyfin md cd:a dam pha dgt ngpt la nhung tai bifin ndng nfi gay nhifiu hgu qud tieu cyc ve mdi trudng, sinh thai [10, 11],
Viec ddng cita vd dich chuyen eae eua bifin Tu Hifin vd Thugn An ldm anh hudng dfin van de giao thdng ra vao bien, tdng miic do n g ^ lyt, xao ttgn sy trao doi nude bifin va dam, gia tang nguy ca nggt hda. Sy thay doi vfi do man cd thfi ldm thay dfii difiu ki^n sfing mgt so loai (quen song trong mdi tradng cd do man cao) dan dfin suy gidm so luong, Ngoai ra, sy bifin dgng dg mgn trong dam cung se dnh faudng nhieu vd gay ra nhirng xao dgng den co cau danfa bat, suy giam hipu qua nudi ttong va khai tfaac thuy san Ben cgch dd, viec 1 ^ vd dicfa chuyen cac cira bien se lam suy giam sy luu thdng nude gay nen sy suy giam chit lugng moi trudng nude ddc bifit Id is cac khu vye nudi ttong thuy sdn, ldm tdng khd ndng sa boi, nong hda vuc nude.
c. Ndng hda vuc nude
Cdc qua trinh neu tren gop phin ldm tang nhanh qua trinh ddng kin va nong hoa, nggt hda vyc nude. Sy nong hoa cung dan dfin luu thdng nuoc giiia cdc khu khac nhau cua vyc nude. Toe dp ldng dgng tram tich tgi Ciu Hai da dugc xdc dinh l-l,4mm/ndm, la tfic dg nho nhit ttong dam phd.
Nfiu toe dg boi cao khoang Imm/nam, do sau tnmg binh cua dim pha la 1,5m tfai 1.500 nam sau dam phd se hi I ^ cgn [10].
d. Qud trinh nggt hoa, man hda ddm
^ Hien nay mgt so eac cdng trinh thuy dien vd ho chua dd dugc xdy dyng tren thugng luu hp tiiong song Huang. Trong do 2 nhd mdy tfauy dipn Binfa Difin (nhdnh Hihi Trach) vd Huong Dien (song Bfi) da dl vad hoat dpng vd theo dy kien, cuoi ndm 2013 ho Td Tracfa (nhdnh Td Trgch) se hoan thanh.
Luu lugng ttung bmh vdo cdc tiiang mua kipt ta thang I - IX cua nhanh Hiiu Tigcfa (Binfa Difin) la 21,7 mVs, nhanh Td Trgch (Thugng Nhgt) Id 8,2 mVs va nhanh song Bo (Cfi Bi) la 32 8 mVs, nhu vgy tong luu lugng trung binh cua hp thfing song Huang do vdo phd TG - CH khodrig 62,7 m /s [10,13]. Tuy nhien kfai co su hogt dgng eua cdc nha mdy thdy di§n vd ho chira d thugng luu, neu tich dii nude trong mua mua vd hogt dgng dung eong suit thiet ke tfai trong miia kiet luu
Kpyeu H$i nghf Khoa hgc Dia lp todn'^iJd^dn tha 7 ~
I
Hfli Bja '^ ^'^* '^^^ ®^' *'°*^ ^*'^' '^8"y^"
iuong qua nhd may thuy dipn Binh Difin tren nhanh Huu Trgch la 72 mVs, qua ho Ta Trgch tren nfaanfa Td Tracfa (udc tinh cfao luu luong thuy dipn) Id 60 mVs va nha may thiiy dien Huang Dien tren sdng Bd la 196,2 mVs Nhu vay tong luu lugng he thong song Huang dfi vao pha Tam Giang trong miia khd len dfin 328,2 mVs gip 5 lan so vdi ddng chay tu nhien. Ngufin nude nggt nay cd kha nang Idm ngpt hda khu vye nude lo trong pha TG-CH, anh hudng dfin vipc nu6i trong tiuiy san nude Ig cua viing dim phd nay [9].
3.3. Hi|n trang chit lirgng m5i trudng ntrdc
Trong nghien cuu ve mdi tmdng nude dim phd [1], dd xac djnh dugc 12 mgt cdt phan bfi tir phia Nam dfin phia Bac cua dam phd TG-CH vdi 41 fiem quan trac trong do 9 diem tfaugc dim C^u Hai; 9 diem tfaugc dim Tfauy Tii - Ha Tnmg; 7 difim thugc dim Sam - Chudn; 16 difim thugc pha Tam Giang.
a. Gid tri pH: Khu vye phd Dam Thuy Tii - fid Trung, Sam - Chufin, gid tri pH fin dinh ttong khoang 7,9 - 8,3 (trung binh dgt pH = 8,1). Khu vuc pha Tam Giang cd gia tri pH thip hon vd dao dpng trong khoang 7,5 - 7,9. Tat ed cdc vj tri do pH tren vung dim pfad deu nam ttong gidi hgn cho phep tiieo QCVN 10:2008/BTNMT vfi chit lugng nude bifin ven bd (pH = 6,5 - 8,5) cho muc dich nudi trfing thuy san (NTTS) [I].
b. Hdm lirgng oxy hoa tan (DO): Ham luong DO ttong nude deu dao dpng ttong khoang 5,6 - 6,8. Ham lugng DO trong nude d dim phd TG - CH deu thda man yeu cau cho myc dich NTTS da dugc quy djnfa trong QCVN I0:2008/BTNMTva tieu chuan ngdnh 28 TCN 171:2001 cho myc dich nudi tdm sit [I]
c. Dd mdn- Dg mgn Id mgt trong nfaung thdng so quan ttong ciia chat lugng nude dam phd, no anh hudng den nhiing thong so khde vd quyfit djnh tinh da dang sinh hgc cua dam pha Tam Giang - Cau Hai. Trong thdi gian nghien ciiu (2009 - 2010) do man tnmg binfa cua dim phd giao dpng til 2,4 - 14,6 °/oo; dp mgn dim phd TG-CH thudng cao vdo cdc thdng giua vd cufii miia khd (thang 3 den tfadng 8), t h ^ vao mua mua (thang 9 den thang 12, dg mgn < 5%o) vd trong nhiing tfiang day mua kfao (thang 1 va 2, dg mgn < 10%o).
d. Hdm lugng chdt hOu ca trong nude ddm phd: Gid tri COD trung binh trong thdi gian lay mau khd cao, dao dgng ta 10 - 21,7 mg/L, cao faon gidi fagn cho phep trong QCVN 10:2008/BTNMT cfao myc dich NTTS rat nhieu (3mg/L). Dieu nay chiing td rang hoat dgng nuoi trong thuy san tten dam phd da ldm gid tri COD tdng, tire Id tdng d nhiem chit hiiu co [1].
e. Hdm lugng chdt dinh du&ng:
+ Hdm lugng photphat trong nude dam pfad t h ^ (gid tri trung binh do duoc trong nam 2009 vd 2010) < 0,01 mg/L. Theo WHO (1992), kfai photpho la yeu tfi gidi hgn tiii ham lugng pho^hat d miic < 0,01 mg/L sg duy tri su phat trifin binh thudng cua sinh vgt phu du, nhung khi hdm lugng photphat tir 0,03 dfin 0,1 mg/L faogc ldn ban thi sinfa vdt phii du se phdt trien bung no, hie la sy phii duang xdy ra. Ket qud pfadn ticfa cho thiy ham lugng photphat vdo mua mua hau het d
— muu noug-dg-<-^0Hngflb, difiu nay chiing td viing dim pfad TG - CH chua cd nguy co xdy ra hien tiigng phu duong [1],
+ Hdm lugng nitrat trung binh tgi eac vi tri lay mau tren vimg dam phd TG - CH dao dgng trong kfaodng 0,15 - 1,05 mg/l. Cdc gid tri do duge vao mua mua cao ban vao miia kho, co the do sy cuon ttdi nitrat ta cac khu vyc dan cu, ngng ngfaipp, do tfai dgc tfaeo dam pha.
Kyyiu Hdi nghf Khoa hgc Dia lp tadn qudc ldnth^7
Hoi Dia ly Viet Nam Dai hgc ThdiNguy^" , 3.4. Vai trd ciia he sinh thai dam pha Tam Giang - CSu Hai doi vdi kinh te - xa hyi |
fl. Cung cdp nguyen, nhien lieu ; He dam phd TG - CH la ngufin cung cap rat nhifiu logi nguyen lieu quy cho cdc Iinh vyc y I
dugc, cong nghiep thyc pham, cdng nghiep det, san xuit fada efait, thuoc nfi, chat each dm cdch nhiet, cdng nghiep giiy, han dien vd nong nghiep nhu rong mo (Sargassum) [8], rong mai cheo, . rong den Id vdng,... Rong cdu mdnh {Gracilaria tenuispitata) \a ngudn nguyen lieu chinh de sdn xuat thgch agar Cdc loai rong it cd gia tri han nhu rong dot, rong dudi chd,.., dugc sii dyng lam j tiiiic an gia siic va phdn bdn. Cdc logi cd fafin, cd ldc,.. dugc khai tiiac va su dyng true tiep lam cac sdn phim thu cdng my nghe, hipn cac san pham nay da cd mat tten thj traang trong nude.
Vung dem cua he tiiong dam pha TG - CH, phan bo tii Phong Difin d phia Bdc dfin Phu Loc d phia Nam cd cdc md kfaodng sdn nhien lieu chu yfiu la than bun, cat thuy tinh vdi trir lugng ldn nhu d khu vyc xa Phong Chuong, huypn Phong Difin Trii lugng cdc md tiian biin d khu vyc cac trim, hdu tgi viuig dit eat ngi dong Phong Difin - Qudng Difin dugc ddnh gia len tdi 5 tripu met khoi. Hien tai than biin d day dang dugc khai thac dfi che bien phan huu co vi smh [12].
b. Cung c6.p thuc phdm
Voi sy da dang vd phong phii cda hp dpng - thuc vat trSn dim pfad, day la nguon thuc pham doi ddo cho todn bp ngudi ddn ttong tinfa. Them vdo dd, dieu kipn tu nhien tfaicfa fagp vd dipn tich mgt nude ldn Id nhiing difiu kipn thuan Igi cho vipc nudi trong thuy san, lam tang sdn lugng thiiy sdn he dim pha ldn ndy. So vai luong thyc, san lugng danh bit va nudi ttong thuy sdn tr6n fap tiiong dam phd chiem ti ttgng dang kfi ttong co ciu kinh tfi ciia tinfa, Chinh vi ly do do ma thiiy s ^ da ttd thanh nganh kmh te mui nhgn thii hai sau dich vy - du ljch ciia tinh Thiia Thien Hue.
c. Bao Vf moi trudng, con ngudi vd kiin tgo cdnh quan
He dim pha TG - CH cd vai trd giir nude, ban chfi xam nhgp mgn cua bifin vao done bang ben ttong vd bdo ve nude ngim: he dim phd la mgt vye nuoc ldn cd tdc dyng giii nude ta bien vdo vd hda tign vdi nude ta sdng do lam giam dang ke do man ttong nuac. Vdo miia kho, he dam pha lai Id noi chua vd trii nude ta song dfi ra, duy tri lugng nude ngam vung dong bdi^ ven ria, co tac dyng tot vdi he sinh thai dong ragng va duy tri nguon nude ngam sinh hoat cho nhan dan. Vao miia mua, hg dam pha da han cfafi rat nfaifiu kfad ndng gay n g ^ lyt khu vuc vd nhiing tdc hai ciia nude dang ttong bao.
- Vai trd bdo ve: Cung do Id mgt vyc nude kin ed 02 ciia thong ra bifin, phia ngoai con cd day con dun cat ven bifin vdi chifiu cao ta 10 -^ 30 m, rgng tir 0,3 dfin 5 km, ngdn cdch dam pha vdi bifin Ddng [13]. Cd vai tro nhu hire tadng kien eo bdo vp vuc nude phia ttong vd vung ^ n g bdng, moi khi cd bao hay gidng to lam dgng bien, dam pfad la nai cu tni, neo dgu an toan cho hang tram thdm ehi hang ngdn tdu thuyen nhd, tranh dugc nfaifiu thiet hgi ve tdi sdn cho con nguoi.
- Dieu hda khi hgu, tich ty cacbon: Vdi difiu kipn ty nhien thuan lgi, ehiia ttong mmh ham lugng phu sa Idn, he thyc vat ttong khu vyc dam phd phong phu vdi cac quan xd cd nuac, c6 thiiy smh, rong bien, rimg nggp mgn, ... la mgt ttong nhiing tdc nhan quan trgng lam cho khi hgu diu mat han, gidm nhipt dg tfii da va g i ^ bien do nhipt ttong vimg. Hp tfiuc vgt da thyc hipn tfit vai tro can bing Oz vd CO2 ttong khi quyen, fifiu fada kfai hgu dia phuong (nhipt dg, lugng mua) vd gidm thieu khi nfaa kinfa, dgc bipt la riing n g ^ mgn.
- Dfii vdi vimg bifin ven bd, vimg dim pha cdn cd chuc ndng lam sgch moi trudng, lgc vd xii ly nude thdi Bim c a t h b ^ ede chat gay 6 nhiem trong nude chdy ra tii lyc dia phan ldn roi ling va dugc luu giu trong dam phd hoac dugc xii ly bdi he thyc vat ttong dam phd trade khi chay ra bien.
Day la nai tich ty, cfadn vui cac vdt chit tiidi, de hi ton hgi do 6 nfaiem tir lyc dia, nfaung chinh nhd do ma bao.ve cho moi tradng bifin phia ngodi. Trong do, phai kfi dfin vai ttd cua c6 bien, tit cd cac loai cd bien deu ddng vai ttd Id mgt he tiiong lgc nude, ldm sgch nude, h ^ thy cde chat ban ttong moi tradng dim phd.
Kyyiu Hgi nghi Khoa hgc Dia lp todn qudc ldn tha 7
Hoi Dia I^ Vift Nam Bai hoc Thai Nguygn
^Giam tac hai cua nude bien dang: Thuc vat bgc cao xung quanh he dam pha cd dien tich I x?8 ha bao gom 6 logi cay nggp man va 24 Ioai cdc lodi thuc vat bac cao khac (khi lao, keo, .,).
Trons dd cdy rimg ngap co vai trd quan ttong nhat trong vigc phdng chong bao va nude bifin dang.
Theo khao sat cua GS TSKH Phan Nguyen Hong va cs (2007) [5], dp cao sdng bien gidm manh khi di qua dai RNM vdi miic bien ddi tit 75% dfin 85% (ta 1,3 m xudng cdn 0,2-0,3 m). Vdi 28,98 ha rime ngap mgn hien cd, toan bg dai rirng nay ttd thdnh mdt biic tudng thanh ngan can, gidm thifiu tac dgng ciia nude bien dang, bao ve de bien, lam cham ddng chay va Iam gidm dd cao cua sons khi trifiu cudng. Tuy nhien, hien nay limg ngap man d day chi tap trung d 2 khu vuc chinh:
Rii Cha Tan My. Chinh vi vgy, vai ttd ciia rimg ngap man chua dugc phat huy triet de - Bao ve ngufin lgi thuy sinh: rimg ngap mdn, cd bifin la noi bdo vp cac dgng vgt thiiy sinh khi nude trieu dang va sdng Idn Nhifiu Ioai dong vgt day sdng ttong hang hoac tren mat bun, khi thdi tiet bat lgi, nude trifiu cao, sdng lan da treo Ien cay dfi ttanh sdng nhu ca lac, cac loai edng, cay, OC. Khi lang gid vd trieu xuong thip, chiing trd Iai noi sfing eu. Do do, tinh da dang sinh hpc ttong he sinh thai dim pha taong doi on djnh.
- Dam pha TG-CH cdn la mdt khu du hch, gidi tri ly tadng. He dim pha c6 canh quan dep vdi viing nude yen tinh, cd hp con cat hung vT d phia bien, c6 cac dam lay cda song hoang da vdi cac dan chim nude cu tni day dae
3.5. Anh hudng cua rui ro thiSn tai l£n fa$ sinfa tfadi dam pfaa Tam Giang - Cau Hai Cac rui ro thien tai nhu lii lyt, hgn ban, anh hudng cua thuy luu, tac ddng ciia bien doi khi hau va d nhiem mdi trudng . se tac dgng len cac nguon tai nguyen thien nhien, ndng suat Iao dgng va se dnh hudng dfin toe dd tang trudng kinfa tfi va gia tang ddi ngheo. Riu ro thi8n tai va sy suy giam da dang sinh hgc dong thai cung anh hudng tieu cyc tdi sinh ke eiia ngudi dan va can ttd tdi vi?c hoan thanh muc tieu thien nien ky.
Suy thoai he sinh thai ldm gia tang cac thien tai vd lam giam khd ndng chju dyng ciia tu nhien vd eon ngudi trade tac dpng ciia cac riii ro thien tai. Suy thoai he sinh thdi Id mgt qua trinh se dan den viec buy dipt he sinfa thdi Mat da dang sinh fagc do suy thodi he smh thai co the lam gay chuoi thiic dn va anh faudng xiu dfin fae sinfa tiidi, dan den cdc tiitoi hga sinh hoe nhu sy xam nhgp cac loai mdi. Do do, suy thoai he sinh thai cung lam tang tinh de bi ton thuang cua cac he thong ta nhien va con ngudi trade tac dgng cua thien tai nhu lii lyt, traot Id dat va bao. Trong trudng hgp xau nhat, sy suy thoai he sinh thai cd thfi dan den viee buy hogi he sinh thai lam mit hfit kha nang chiu dyng vd cdc dich vu khac doi vdi con ngudi.
Cac hien tagng thoi tifit cyc doan nhu lii lut Idn, bao, sdng bdo ldn lam cho he dam pfaa TG - CH bi nggt hod vd man hod ciing nhu lam ndng hda cac vuc nude cua h% dam pha. Cde qua trinh nay cd thfi se tgo nen difiu kien khac nghiet, bit lgi vfi mdi tradng song cho smh vgt vd cdc dien bien cua he smh thai trong dim; lam thay dfii ciu tnic, anh hudng tieu cue dfin nguon gen vd da dang sinh hgc cua he, Difiu nay da gian tiep vd tryc tifip anh hudng dfin cdc loai hinh sinh kfi ciing nhu ddi sfing sdn xuat cua ngudi dan ven dam vd nhung ngudi dan tren dia ban nghien ciiu.
Hien nay sdn lugng khai thac thuy sdn vung dim pha ngdy cdng suy g i ^ do tdc dgng cua con ngudi vd cae yfiu tfi riii ro thien tai, Cac bieu hien cua nii ro thien tai nhu lu lut, han han, ngpt hod, ndng hod, xam nhap man, trieu cudng.,. deu gay anh hudng len sinh vgt thuy sinh va nguon lgi thuy san vung dam pha. Truac nam 1975, sdn lugng danh bat thuy san tren cac dim phd dgt khodng 4500 tan/nam, hipn san lugng nuoi^rong thuy san ehi edn khoang 3.800 - 4.000 tin/ndm.
Kpyiu Hdi nghi Khoa hgcDia lp todn qudc ldn tha 7
Hgi Dia ly Viet Nam Dai hoc Thai Nguyen Bang J
Cac gia tri Di^ntich (ha) Tong san lupng (tan)
Diin tich va sdn lixgng nuoi trdng thity son nu&c la [2]
Nam 2005 3.883,5
3.970
Nam 2009 3,883,2
5 813
Nim 2010 3 844,6
5 433
Nim 2011 3.875,4
5.950
Niim 2012 4.191,6
6.478 Do nam 6 vi tri taong tdc giiia cdc qua trinh ciia bien vd lyc dja, nen ngufin lgi thuy sdn ciia khu vue dam phd thuang bj tac dgng manh bdi cac hien tugng lu lyt bat thudng do tac dpng len da dang sinh hgc va ngudn Igi cua dim phd. Nghien curu cua Tran Dire Thanh vd cs nam 1995 duoc thuc hien d khu vyc pfaa TG - CH trudc va sau tran lyt ldn tfadng 11/1993 vd tfadng 11/1996 da cho thiy su bifin dgng mgnfa ciia nguon lgi tfauy sinh vd nguon led cd d khu vyc dam nay [7, 10].
Thyc vgt phii du: trade tfaang 11/1993, cdc lodi cd ngufin gfic bien pfao bifin, thdnfa pfaan loai len tdi 232 lodi, nhung kfit qud difiu tra ndm 1995 chi ghi nhgn 144 Ioai. Tgi Vinh Xuan, trade khi lap ciia Tu Hien khdng cd loai cd nguon goc nude nggt nao, nhung sau khi lap ciira, 48 lodi nude nggt dd dugc ghi nhgn. Ciu tnic khu he cung thay doi, cdc lodi nude mgn xuit hipn nam 1993 thi sang ndm 1995 lgi kfadng tfaay [2,7].
Ddng vat phu du: trade thang 11/1993, ttong so 34 loai co mat, cd cdc lodi nude mgn ttong cac giong Acartia, Paracalanus, Labidocera. Sau khi ciia Tu Hien bj ddng, cdc lodi nude man tren khong cdn, trong kfai so loai nude nggt tang len [2,7,14].,. Mgt khde, ciu tnic thdnh phin lodi khu he cung tfaay doi, so lugng cde lodi thudc nfadm Calanoida giam di, trong khi cde lodi thugc nhdm Cyclopoida tdng I8n. Mgt dp dgng vat phu du d phia Nam cua Thudn An tang len 2-3 lin, trong khi dd d phia bac lgi g i ^ di
Rieng doi vdi tham cd bien, ngufin lgi ca vd nguon lgi tom, cua Iai cd xu hudfng tang len trong pha TG - CH sau lii. Vi du sinfa lugng c6 bien tang I6n tir 1,75 kg/m^ (tiudc lii 10/1999) ten 2,27 kg/m^ ndm 2000 (sau lii), so lodi cd ciing tang len ta 7-19 lodi len 10-30 lodi tay theo thdng, chu yfiu Id cac lodi nude man. So lugng cd tfafi cd ciing tang len r5 rpt ta 1.256 catfafi/m' I8n 13.020 ca the/m , s ^ luong cdc loai cd kinh te trong phd tdng len nhu ca Doi, cd Dia, ca Mii, tdng len khodig 3-10 lan, nfaung san luong cd Diy lgi gidm di 2 lan. Tuong ta nfau vgy voi san lugng torn, tdm He va tdm Riu ting mat trude lu kfadng co (1999), nhung sau lu (2000) da xuat hipn, Tom He vd tom Riu tang ddy cung tdng mat dg khodng 11 lin vd 50 lan, ta 14 con/m' len 155 con/m' vd 134 con/m^ Ien 6.720 con/m^ [2, 7,14].
KETLUAN
^ Dam pha TG - CH la thuy vyc nude lg dpc ddo, ldn nhit ViSt Nam eung nhu Dong Nam A.
He dam phd ndy phan bo tten chifiu ddi gin 70km, co dien tich khodng 22.000 ha, ndm b vung ven bo thih Thua Thien Hue. Dam pha TG - CH nguon tai nguydn smh hgc phong pfaii vd dong vai tid rat quan trgng doi vdi pfadt trien kinfa te - xa hgi cua tinh, ngodi ra ^ pha TG-CH c6 dgc difim moi tradng ty nfaien nhgy cdm, phiic tgp va dfi thay doi, dong thdi cimg la vimg cd nhieu y nghia vfi gid tri kinh te vd mdi tradng.
He sinh tiidi cua dam pfad TG - CH dang cd cfaifiu faudng suy tiioai duoi tae dong cua tiuen tai vd d nfaiem mdi ttudng nude. Cae hien tagng tiiai tifit cyc doan nfau lii lyt ldn, bdo, song bao ldn lam cfao he dam pfad TG - CH bj nggt hod vd man faoa tao nen difiu kien khde ngfaiet, bit lgi vfi mdi ttudng song cho sinh vgt vd cac dien bifin eiia hfi smfa tiidi trong dam; ldm tiiay doi eau ttiic dnfa faudng tieu cue den nguon gen va da dgng sinfa hpc Dong tiioi gian tifip dnh huong dfin sinh kfi cua nguoi dan song xung quanh dam phd.
Kp yiu Hdi nghf Khoa hgc Dia lp todn quoc ldn tha 7
Hfli Bja 'y ^'^* ' ^ " " Dai hoc Thai Nguyen T A I LIEU THAM K H A O
1 Nguyen Huy Anh, Nghien cuu xdy dung mang ludn quan trdc mdi trudng nude a ddm phd Tam Giang - Cdu Hai. tinh Thaa Thiin Hue. Bao cao tdng kfit de tai khoa hpc cong nghe cap Bg, Hufi,20Il.
2 Cue Thong ke Thira Thien Hue, Nien gidm thdng ki ndm 2072, Hue, 2013
3. Nguyen Huu Cii va nnk, Tdc ddng cda con ngudi din mdi truang dia chdt hi ddm phd Tam Giang - Cdu Giang. tap IX - Tdi nguyen vd Mdi tiudng bifin, trang 103-120. Nxb KH & KT Ha Npi, 2002
4 Nguyen Chu Hoi va nnk, Nghien cuu su dung hgp lp cdc hi smh thdi ddm phd ven bd miin Trung. Bao cao chuyen de thudc dfi tdi KT, 03 - ll,HaNgi, 1995.
5, Phan Nguyen Hong, Le Xuan Tuan va Vii Thuc Hien, Vai trd ciia he smh thdi rung nggp mdn vd RSH trong viic gidm nhe thiin tai vd cdi thiin cugc sdng a vitng ven biin Nxb Nong nghiep. Ha Ngi, 2007,
6. Do Nam, Nguyen Vdn Tien, Ddnh gjd kinh te thdm cd biin ddm phd Tam Giang - Cdu Hat. Ky yeu hgi thao Qufic gia vfi dim phd Thira Thien Hue, trang 412 - 422, Hufi, 2005.
7 Cao Lp Quyen, Biin ddi khi hdu gdy dnh hirang ldn din nghi cd tgi cdc vitng ddm phd ven biin, tgi website: www.agroviet.gov.vn, cap nhat ngay 12/5/2010
8. Vo Van Phii vd nnk, Tdng quan mdt sd yeu td mdi trudmg vd da dgng smh hoc ddm phd Tam Giang - Cdu Hai. Kp yeu hpi thao Quoe gia ve dam phd Thua Thien Hue, trang 381 - 399, Hue, 2005
9. Nguyen Van Tifin, Di xudt cdc gidi phdp bdo vi ngudn lgi cd biin ddm phd Tam Giang - Cdu Hai. Ky yeu hgi thao Quoc gia ve dam pfaa Tfaira Tfaien Hue, trang 478 - 491, Hue, 2005,
10. Tran Diic Thanh, Nguyen Vdn Tien, Nguyen Huu Cii, Do Nam, Nhiing ddc trung ca bdn cua ddm phd Tam Giang - Cdu Hat. Ky yfiu hgi tfaao Quoc gia vfi dam pha Thira Thien Hufi, trang 44-64, Hufi, 2005
11. Hoang Cdng Tin, Mai Vdn Phd. Thdnh phdn lodi vd ddc diim phdn bd thuc vgt ngdp mdn a ThOa Thien Hui. Tgp chi Khoa hgc Lam nghiep. So 1, ttang 2085 - 2094, nam 2012.
12. UBND tinh Thiia Thien Hufi, Dia chi Thaa Thien Hui, Phan Ty nhien, Nxb Khoa hpc xd hpi, Hd Ngi, 2005,
13 UBND tinh Thiia Tfaien Hufi, Du an nord pas de calais, Hiiu biit di phdt tnin bin viing.
thugc du dn "Ngfaien ciiu phdt trifin bfin viing dam pha Thua Thien Hufi, Hue, 2003.
14, Vien Tdi nguyen vd Moi tradng Bien, Tdi nguyin vd Mdi trudng ddm phd Tam Giang - Cdu Hat, Bdo cdo kfit qud thyc hipn dy an IMOLA, Hue, 2006.
Kyyiu Hgi nghi Khoa hgc Dfa lp todn qudc ldn tha 7
