Tgp chi Khoa hgc Tnrang Dgi hgc Cdn Tba Phdn A Khoa hgc Tv nhien, Cdngnghfvd Moi tru&ng 31 (2014) 90 98 , ^ K % ^ Tap chi Khoa hpc Tru''''dng Oai hpc Can Thtf ^ ^ j ^ P ^ website sj ctu edu vn 1 uaoAspc[.]
Tgp chi Khoa hgc Tnrang Dgi hgc Cdn Tba Phdn A: Khoa hgc Tv nhien, Cdngnghfvd Moi tru&ng- 31 (2014 uaoAspc ,^K%^ ^^j^P^ Tap chi Khoa hpc Tru'dng Oai hpc Can Thtf website: sj.ctu.edu.vn DANH GIA Sir THAY DOI HE T H N G CANH TAC TREN CO S d TAX NGUYEN Nir6C M^T VIJNG DONG BANG S N G ClJtJ LONG: NGHIEN CUtJ CU THE TRONG DIEU KIEN HUYf N NGA NAJW, TiNH SOC TRANG Mai Thi Ha', Van Pham Dang Tri' va Nguyin Hieu Trung" ' Khoa Mdi trudng & Tdi nguyen Thien nhiin, Trudng Dgi hgc Cdn Tha Thdng tin chung: Ngdy nhgn: 22/10/2013 Ngdy chdp nhgn: 28/04/2014 Title: Assessing farming system changes based on (surface) water resources dynamics in in the Vietnamese Mekong Delta - a case study oflhe Nga Nam district Soc Trang province Tir khda: Hi thdng canh tdc dgng thdi ngudn tdi nguyin nuac mat, ddnh gid nhanh nong thdn cd su tham gia Ddng bang sdng Ciru Long Keywords: Farming system, water resources dynamics, participation, and Vietnamese Mekong Delta ABSTRACT This study is to assess possible changes of farming systems in the low coastal plain of the Vietnamese Mekong Delta according to changes oj (surface) water resources from 2005 to 2013 with the case study oflhe Nga Nam district, Soc Trang province Individual interviews with local staffs of relevant departments, group-interviews with representatives oj local farmers (via the Participatory Rural Appraisal approach) and household surveys with individual famers were main approaches to collect information and data about past farming systems and possible causes oj changes The obtained results showed that surface water resources and farming systems changed significantly both in terms of space and time and the surface water resources changes were amongst the main causes leading to farming system changes Moreover, agricultural policies and productivity, and land and labour availability also contributed to farming systeme' Nghien ciru dugc thi^c hiin nhdm ddnh ^d su thay ddi cua hi thdng canh tdc a vimg ddng bdng ven biin thdp, Ddng bdng sdng Cuu Long dua tren su thay ddi dgng thdi ngudn tdi nguyen nudc mgt chudi thdi gian lir 2005 din 2013; trudng hgp nghien ciru tgi huyin Ngd Ndm, tinh Sdc Trdng Phuang phdp phdng vdn cdc nhd qudn li, ddnh gid nhanh ndng thdn cd sir tham gia ciia ngirdi ddn dia phuang vd phdng vdn ndng hg dugc thttc hiin nhdm thu thgp cdc thdng tin dir liiu ve su thay ddi hi thdng canh tdc vd cdc nguyin nhdn dnh hudng Kit qua nghien ciru cho thdy ngudn nudc mat vd hi thdn^ canh tdc cd nhiiu biin dgng cd vi khdng gian vd thdi gian Thay ddi cita ngudn tdi nguyen nudc mat Id nguyen nhdn chinh ddn din thay ddi vi M thdng canh tdc Ngodi ra, cdc yeu Id ve chinh sdch nong nghiip, "Ong sudt khd nang tgn dirng ngudn tdi nguyen ddt vd lao dgng cSng dnh hudng din thay ddi hi thdng canh tdc d viing nghien ciru GlOfI THIfU Ding bdng sdng Cuu Long (DBSCL) - viing luu sdng Mekong; ddng thai, diy ciing li vung sin xuit ndng nghiep chii yiu ciia Viet Nam vdi diln tich dit ndng nghiip chiim 81% tdng diln tich dit ty nhiin, sdn lugng gao xudt khdu chiem khoang 80% san lugng ciia cd nudc (Ll Anh Tuin et al., 2007; Tdng cue Thing kl, 2012) Mat khac, vi|c canh tic liia d DBSCL dang diing trudc nfaiiu tfadcfa tinic vdi viec canfa tdc phu thudc vao ngudn tii nguyin nudc mat hi sdng Mekong (Lenton, MuUer, 2009) Viec tiiay ddi lugng mua, xira nhgp Tgp chi Khoa figc Tru&ng Dgi hgc Cdn Tho Phdn A: Khoa bgc Tv nhiin, Cdng nghf vd Mdi Iruang: 31 (2014): 90-98 ni§n nghiim frpng hon (do biin ddi kbifadu)vd sy suy giim luu lugng nudc tfaugng ngudn da, dang vd sl lira thay ddi d^ng thii ngudn tdi nguyen nudc radt vd siic sdn xuit ndng nghiip eiia DBSCL (Chu Thdi Hodnfa et ai, 2003; Ding Kiiu Nfadn et al., 2007; Le Anh Tuin et al., 2007; Ll Sira, 2006; Nguyin Hiiu Trung et al., 2012) Vi vdy, ngudn nudc tudi cho fa| tfadng canfa tic liia (thdra canh) Id mgt nhirng vdn de cdn dugc quan tam va viec xem xet ddng thii ngudn tii nguyin nudc mat frong cdc viing sinfa thdi ndng nghiep cd y nghia quan frgng frong vile ddm bio ngudn tdi nguyin nudc mat cho sdn xudt liia cung nhu ddm bio an ninh luong thyc frong tuong lai d DBSCL Vdi nfaiing thdch thirc frln, viec dua yiu td tdi nguyin nudc vio frong phdn viing sinfa thai ndng n ^ i l p (PVSTNN) la cdn thiit vd da dugc thyc failn nghiin ciiu eiia Nguyin Hieu Trung et al., (2012b) (Phdn viing sinh thdi nong nghiep Id sy pfadn chia mdt vimg cdc don vi nfad hon dya fren cdc yeu td khifadu,dia hinh vd dit cd lien quan den (FAO, 1996)) Trong ngfaien eiiu ndy, DBSCL dugc chia thdnh viing chinh dua frln bin dd phin viing cua Vo-Tdng Xuin, Matsui (1998) (Hinh I A); frong dd, mdi vimg dugc phdn chia thdnfa cdc tllu viing dya vao cic chi sd ngudn tdi nguyin nudc mdt (d^ sdu ngdp vi dO man) (xem them chi tilt cdc tiiu viing frong nghiin ciiu cua (Nguyen Hieu Tnmg et ai, 2012)) Mat khdc, xem xet d quy md ldn (toin viing ddng ban^) nin cic nghiin ciiu trudc chua md ta chi tilt mdi liln he giiia fai tfadng canfa tdc vd ngudn tdi nguyen nudc mil Vile ngfailn ciru mdi quan he giiia ngudn tdi nguyin nudc mdt v i cac hi thdng canh tic dd dugc thyc hiln bdi Nguyen Thi My Linh et al, (Gui ddng.) tien faanh pfaan vimg sinfa tfadi ndng nghiip d cip nhd hon (cdp tinh).Cu the, cdc yiu td vi thdi gian ngdp vd thdi gian man dugc xem xet chi tilt faon frong viec phan vimg sinfa tfadi cdp tinli Dya vio dpng tfadi ngudn tdi nguyin nude mat, tinfa Sdc Trdng dugc cfaia thinh vimg sinh thai ndng i ^ i l p chinh; frong do, 49 tiiu viing sinh thdi dviqc pfadn chia dya frln cac ylu td ve ngudn tdi nguyen dit, nudc vd sii dung dit dai (xem them ngfailn ciiu ciia (Nguyen Thj My Linh et al Gin ddng) Do pham vi nghiin ciru rdng nen cdc nghien ciiu frln chua md li r6 radi quan he giua thay ddi dOng thdi ngudn lai nguyin nudc ragt vd tiiay ddi ciia cic he thong canh tic liiln c6 d tirng phan vimg sinh thai ndng nghiip cu tfal Thim vio do, tic ddng cua dgng thii tai nguyen nudc mat lln cdcfaetfadng canh tic khic giiia cdc khu vyc dia ly khac (vi dy: ven biln vi ndi dia) (Van Phgra Ddng Tri et al., 2013) Do dd, di hiiu rd hon tac ddng ciia ddng thai ngudn tai nguyin nudc mat lln he thong canh tdc, ngltiln ciiu cdn dugc thyc hien frong pham vi nhd hon Ngltiln eiiu niy dugc tfayc hiln d phgm vi nJid hon (cap huy|n) dya fren sy kl thira tir nhiing nghien ciiu frudc nhdm lim rd nliiing thay doi dang diln he thong canh tdc hiln tgi vd mdi quan fae giiia ngudn tdi nguyen nudc radt vdi sy thay ddi ciia eac he tiidng canli tic Muc lilu cu thi bao gdm: - Xem xet dgng tfadi ngudn tdi nguyin nudc mdt va sy thay ddi ciia cic he thong canh tdc; - Xic dinli mdi quan hi glfla sy thay ddi ciia cdc he thdng canfa tic vi ddng tfaii ngudn tai nguyin nudc mit; - Xic dinh mdt sd bat cgp cdng tac qudn li ngudn tii nguyin nudc mil phyc vu cho cdc fae thdng canfa tdcfronghien tai; vi Xie dinh sy thay doi hi thdng canh tic frong tuong Iai Hinh 1: Phan vbng sinh thii ndng nghiep Dong bdng sdng Ciru Long (A) vd ban d i don vi hanh chanh tinh Sdc Trdng (Nguon: V6-Tdng Xuan, Matsui, 1998) Tgp chi Khoa hgc Tru&ng Dgi hgc Can Tho Pbdn A Kboa hgc Tv nhien, Cdng nghf vd Mdi iruang: 31 (2014): 90-98 PHU'ONG PHAP NGHIEN c t r u 2.1 Pbinmg pbap tfau thap so ii^n Cic sd lilu so cip vd thii c%i dugc thu thgp chu yiu tir Phdng Tai nguyen vd Mdi trudng, Phdng Ndng nghiep vi Phdt friin Ndng ttidn huyen Ngd Ndm vd ndng ddn dja pfauong Cdc sd lieu vl hiln frang thiiy Igi (myc nudc, man vi he thong cic cdng tiinfa tiiiiy Igi), tiiiiy vin (lugng mua) va sir dung dit (Bang I) dugc tfau thap tir Trung Tim Khi Tugng Thuy Vdn Sdc Tring, Sd Ndng nghi|p vi Phdt trien Ndng tfadn vd Cfai cue Quan li Thiiy ndng huyin Ngd Nam Mgt cuOc ddnh gii nhanh ndng thdn cd sy tham gia dugc tiin hdnh nhdra kiem chiing cic sd li|u dd thu thdp dugc va xic dinh Ijcfa thdi vy tgi tiing kfau vyc trongfauypn.Hai ndng ddn tryc tiip canh tac Ilia liu ndm (>5 ndm) tai moi xa / tfaj frin dugc mdi tham dy di thu thgp thdng tui DQ lieu dugc tiiu thgp (tiidng qua nien giim tfadng kl c ^ tinfa vd huyen tii ndm 2006 din nam 2010) kit hgp vdi kit qua tir dinh gii nhanh ndng thdn CO sy thara gia ciia ngudi din dia phuong (PRA) vi phdng vin tryc tilp cdn bd dia phuong cho thay frln dja bdn huyen cd hp thing canh tac chu yiu (h| tbdng canh tdc lua vy (DX-XH-HT) vi canh tdc liia vu (DX-HT)); dd, di tdi thyc hi|n phdng van 43 fap din dai di|n cho raoi he thing canh tdc dya frln die tinfa ngudn tdi nguyen nudc mdt vd sy tfaay ddi he thing canh tic frong kfaodng tiidi gian tir nim 2006 din ndm 2010 Ddi tugng cu Ihl ciia dilu tra ndng hp Id ndng din canh tac lua liu nim (>5 ndm) tai dia phuong yi cd vai frd quyit dinh vile lya chpn fae thong canh tic frong gia dinh Bdng 1: Cdc s6 lieu thu thap So li|u Tfadi gian Lugng raua Sd lieufadngngay (2005-2011) He thong oong jjj^jpij frinh thiiy lgi Sd li|u faing ngdy cac tiidng 2-7 (2007-2013) Muc nuoc Sd lieu hdng gid (2005-2011) Sir dung dat Ndm 2006 va 2010 2.2 Pfauung phap xtr li so li|u Dpm^ Phin ralm thdng ke vdi mpt sd cdng cy cy tfal nhu phuong pfadp: Dim tin sudt (Frequences), thing kl md id (Descriptives), so sinh cic nhdm ddi tugng (Crosstabs) vd kilm dinh frung binh mdu (Independent-Sample T-Test) dugc sir dyng dk: (i) Phdn tich sy tfaay ddi cua diiu kiln thiiy van (lugng mua, nfaiet do, myc nudc, vi dg mdn) theo thdi gian; vi (11) Phdn ticfa sy thay ddi he thoi^ canfa tdc, cdc tdc dpng cua n ^ d n tdi nguyin nudc mil len he thdng canh tdc vd sy tfaay ddifapthong canh tdc tir sd li|u dieu tra ndng h^ Ngodi ra, cdn^ cy GIS ciuig dugc sii dyng dl so hda cdc bdn nin cung nfau phdnfr'chkhdng gian nhdm xdc dinh ddng thii ngudn tdi nguyin nudc mat tai vung nghien ciiu theo kfadng gian KET QUA 3.1 Thay doi h | tfaing canh tdc 3.1 I Thay ddi dieu kiin tu nhien u Thay ddi lugng mua Huyin Ngd Nim - ndm frong viing kfai hiu cua vung DBSCL, cd raiia khd vd raua r5 ret; miia mua dugc xic dinfa tii tfadng din tfadng 11 hdng nim, cic tfaing cdn Igi faiu nfau khdng cd mua (Vfi Thi Phucmg Linh et al, 2013) Kit qui pfain ticfa chuoi sd lieu lugng mua thyc theo ngiy giai dogn 2005-2011 tgi fram mua MJ Tii (Hinh IB) (trgm mua gin nhit vdi fauyen Ngd Nim) cho tfaiy; (i) Lugng mua trung binh ndm vdo khodng 1.692 ± 400 mra nhung phdn bd kfadng deu theo thdi gian; (ii) Cd tdi kfaoang 90% lugng raua dugc pfadn bo frong miia mua (thdng 4-12) vi cic thing 1, 2, v i 3faiunfau khdng cd mua (Hinh 2) Kit qud phin U'ch sd li|u mua ket hgp vdi kit qui tir diiu tra PRA vi phdng van ndng hp cfao tfaiy khoing thdi gian nghien ciiu, lugng mua cd sy biln dpng kfad Idn tfaeo nim; nfaflng nam gdn day, miia mua bdt diu vd kit tfaiicfrifaon, lugng mua tgp trung vio cdc tfadng cudi ndra (9, 10, vd 11) Trong tfadi gian mua t^p trung, cic mua Idn klo ddi gay ngdp ting vd ldm dnh hudng din tiin dp xuong gidng cua vu Ddng Xudn d cdc viing triing trin dia ban n^ien cihi Theo Chivanno et al (2005), sy chuyin dicfa vd tiiay dii cua lugng mua co tic d^ng ddng ki din ndng suit Ilia; riing ddi vol vung DBSCL till tic dpng nghiim trpng hon vao vu He Thu Kit qui phdn tich lugng mua ngdy cao nhit theo thdng frong chudi thdi gian nghiin ciiu cho thay, lugng mua cao rUiit cd the vugt qua ngudng tdn faai cua cay lua (Hinh 2) (CIA, 2010) Nhu vgy, nang suit liia sl hi dnh hudng neu nfau mua ldn (> 100 mra/ngdy) vd keo ddi trin ngiy Tgp chi Khoa hgc Tnt&ng Dm hgc Cdn Tho ^ Phdn A: Khoa hgc Tu nhien Cdng nghf vd Moi trudng: 31 (2014): 90-98 f- Hinh 2: Dien biin tong lirgng mua tfaeo cac thing tir 2005 din 2011 t^i tram MJ Tu tii ndra 2007 den ndm 2013 cfao thdy; frong khoang then gian tir giua thdng din cuii thing 6, nhimg dgt man keo ddi thudng xuyln, ndng dd radn fren tuyin kinh Qudn Lg - Phung Hiep tfaudng xuyln vugt qua 496o Trong kfaoing thdi gian man, cdc khu vyc frgm bom dgc tuyln kinfa Quan Ld Pfaung Hiip canfa tic liia vu b) thiiu nudc tudi cac khu vue triing thugc kfau vyc phia Bdc vd Tdy Bdc cua tuyen kenh ndy, vin dl ngudn nudc tudi khong dang ngai Ngudn- Tmng ldm lugng thity vdn linh Soc Trdng ndm 2006-2011 b Thay ddi dgng thdi ngudn tdi nguyen nudc Kinh Qudn Lg - Phyng Hiep (Hinfa 4) dan nudc tir sdng Hgu tfadng qua mgng ludi kinh cip vd kinh npi dong la ngudn nudc chinh cho cdc hogt dgng canh tic d dia pfauong Trong khoang thdi gian nghien ciiu, myc nudc cd sy bien dpng ddng kl giiia cic nim; frong dd, sy kfadc bi|t ldn nhit dugc xic dinfa vdo thing 11 md myc nudc cao nhdt vd thip nhdt giiia cic ndm chenh l?ch nfaau den 41 cm Ngoai ra, kit qud phdn fr'ch cfauSi sd li?u myc nudc thyc hdng gid tai fram Dai Ngii cho thdy gii tri myc nudc cd su biln d$ng ding ki theo thdi gian (Hinfa 3) Cy thi: - Ci cic thing 10 vd 11, mua nhilu kit fagp vdi nudc lii tir sdng Mekong dd ve nen myc nudc dang cao ldm dnfa hudng din tiln dg xudng gidng vy Ddng Xuin ciia cic vimg friing (bdn dd cao frinfa dugc trinfa bay (Hinh 4B)) Vi vay, cic vung niy tiiudng xudng giong fri hon khodng I thing so vdi cdc viing cd cao trinh rail ddt cao hon (viing gd) cdc thing 5, va - thdi diim myc nudc fren sdng kilt nhit - dim bdo nudc tudi cho cdc vimg gd frong vu HI Thu dugc xem Id mgt frong nhiing vin di kfad khdn cho sdn xuit can dugc quan tdm Trong nhiing tiidng cudi mua khd (tiidng 4) luu lugng nudc tir thugng ngudn dd vl it nin xdm nfagp tiiudng xdy d cdc viing pfaia Nam viing nghiin ciiu (khu vyc gin kinh Ndng Rin) (Hinh 4A) Chuoi gia frj mdn t^ diim Ndm Kipu vi Vmh Biln (Hinh 5) (tuong ung vdi diira sd I vi sd frln Hinh 4) frong khoing thai gian S 10 11 12 Thang MiKuui>v [niasbinli Hinh 3: Myc nudc trung binh hang thing tai tram Dai Ngdi chuoi thdi gian 2006-2011 Ngudn - Trung tdm tugng thuy vdn linh Soc Trdng ndm 2007-2011 Tinfa fainh xdm nfaap mdn d Ngi Nim nfain chung cd liln quan ragt thilt tdi chl dp vgn hinh cdng ciia tinh Bac Lilu Vile liy nudc mdn phyc vy cfao nudi frdng thiiy sin dpe myln kinh Quin Lp - Phyng Hiep d tinli Bac Lilu frong kfaodng thdi gian nudc ngpt trin kinfa it (thdng 4-7) lim nudc m$n xim nfaip siu vio ndi ddng ciia cdc kfau vyc canfa tie dgc kinfa Qudn Lg - Pfaui^ Hiep d Ngi Ndra Be ngin nudc man vd bdo ve sdn xuat liia, ra^t fae tfadng cdng ngan mgn cfao cic kinfa dpe tuyln kenh Quin Lg - Pfaung Hi|p (gdm cdng) dugc xdy dyng (va dua vio vgn hinh nira 2011) Tuy nhien, theo cin bd Phdng Ndng nghiep vd Phdt frien Ndng thdn (huy|n Nga Nim), vile ddng cic cdng da lira thay ddi ddng thai ngudn nudc mit theo chilu hudng bat lgi cho sin xuat ndng nghiep; viec ddng cdc cdng ldm cho nudc man theo myin sdng chinh ngugc lln faudng Ddng Bac rdi dd xuong theo kinh 26/3 (Hinh 4A) vd vdy, cic kfau vuc dpe kinh 26/3 bi xam nhap ra§n din den tinh trang tfailu nudc nggt cfao cic faogt dgng sdn xudt ndng nghiep Tap chi Khoa hgc Tru&ng Dai hgc Cdn Tho Phdn A: Khoa bgc Tv nhiin Cdng nghf vd Mdi truang: 31 (2014): 9t>-98 (B) c£? ^•| - - iM^ •0 ô CietnelHRaa MMf tutt k^nb dp I â ããã I m^ Viai bl mta vto tai* Lb>> i i m Viisf tnm bom Vuny BUM n;io Hinh 4: H^ thong thiiy Igi va cdc diem ndng dp man (A) vd ban cao trinh (B) Nguon • Bdn thity lgi dugc tbtel Igp dua iren ngudn sd Mu tir Chi cue Thiiy lgi Soc Trdng vd Trgm Qudn li Thuy nong huyen NgS Nam bdn cao trinh dugc pban lich dua vdo bdn dd cao trinh sd Shuttle Radar Topography Mission-SRTM ; ^'''' "r^/WTOf' •• "^::.(B) ^T'fi^