KHOA HOC CONG NGHE
DIEIXI BIEIXI T H U C P H U DOIMG BAIXIG 5 0 M G CLIU LOIXIG GIAI D 0 A [ \ 1 1 9 9 0 - 2 0 1 8 : P H A I M T I C H TIJ DLT LIEU
VE TIIMH LAIMDSAT
Pham Bach Yi^t\ LSm D^o Nguy€n^
Nguyin Van Anh Vu', ChSu Nguy^ Xuan Quang^
T6MTAT
Nghien ciiu v4 bi^n dOng thuc phu/sii dung dat b d6ng bang s6ng Cuu Long tir nSrn 1990 d^n nSni 2018 vm cich tiefp can bang viln thim va he thong tin dia ly la muc tifeu chinh cua nghien ciiu niy. Bang cac ky thuat phan tich anh v$ tinh Landsat tr^n toan vung, phan tich ket qua giai doan tu nam 1990 d^n nam 2018 cho thay CO nhimg thay doi dang k& ve thuc phii. Dira tren khao sat thuc dia thu thap mSu khoa, phuong phap phan loai c6 giam sat theo cac miu khoa nay, ket qua phan loai thdi diem 2018 c6 dO chinh xie toan cue la 90.0%, chi so Kappa la 0,87. Phan tich di^n bien theo khong gian va thoi ^an bing cac phan tich chong lop trong GIS cho thay difin bien thay doi thuc phu b timg giai doan. Giai doan 1990-2000 co tm 4296 di^n tich loan vung c6 thay d6i v^ cac loai thuc phu. Tii nam 1990 toi nam 2018, co toi hon 52% di^n tich cua ca d6ng bang song CCru Long thay doi ve phan bd khong gian va dien tich. Liia la loai c6 nhi^u thay doi v6 phan bci khong gian nh^t, thuy san tang hon bay lan va rung giam gan mpt nCra v€ dien d'ch.
Tir khda: Didn bidn thuc phu, ddng bing sdng Cuu Long, Landsat, vidn tham.
1.DAT VANH
D6ng bSng s6ng Cuu Long thuoc vung ha liru cua luu vuc song M6 K6ng, co dien tich 4,08 tri^u ha, nam 2017 dan sd 17,719 trieu nguoi [1], xap xi 20%
dan s6 ca nuoc, mat dp dan so 433 nguoi/km^, trong d6 Ca Mau va KiSn Giang la hai tinh co dien tich lon nhat [2]. D6ng bang song Cuu Long ff)BSCL) co vi tri dac biet quan trong trong phat trien kinh te - xa hOi, la vung san xu^t nong nghiep, thuy san hang hoa lon, dong gop 18% cho GDP qudc gia [3], trong do san xuat Itia gao giir vai tro dac biet quan trong cho ca nuoc; xem xet tren goc do an ninh luong thuc, xuat khau va luc lupng lao dpng ndng thon chiem 67,9% cua ca nuoc (TTidng cao bao chi ve tinh hinh kinh te-xa hpi nam 2016 cua Tong cue Thdng ke) [2].
Xet rifeng vimg nay, co khoang 85% dan sd sinh sdng bang cac boat dpng ndng nghiep, san xuat va cung cap 90% Iirgng gao xuat khau cua ca nuoc va gan 60%
tupng xuat khau thuy san ca nude [3], San lupng liia ca viing Nam bp (NB) chiem 59,7% san lupng lua cua ca nude (26,9 tridu tan/ 45,1 trieu tan) [2], dien tich U-ong Ilia ca nam chiem 54% so vdi ca nude (sd lieu
Trang tSm LTng dung Cong nghe ViJ tru TP. HCM. Trung lam Vu try Viel Nam
" Nhom Nghien ciiu Thiiy van - Tai nguyen nude (HYDROWARE), Vi?n Moi tnicmg va Tai nguyen. Dai hoc Qu6c gia TP. HCM
Email: [email protected]
NONG NGHIEP VA PHAT TRIEN NONG THON
nam 2017-2018, dien tich trdng Itia ca nude la 7,70 trieu hecta) [2].
Dan sd cua viing ddng bang nSra 1995 U 15,5 trieu ngudi, tang len 17,8 tridu nam 2018, trong dd dan sd thanh thi tir 2,4 tang len 4,55 tridu va dan sd ndng thdn tir 13,09 tang I6n 13,25 tri6u dan cho cung thdi ky [2]. TTiay doi ty le dan sd thanh thi/ndng thon tir 18,6% tang len 34,2% la gan gap hai ldn tir nam 1995 tdi nam 2018, hen quan nhieu tdi cac hoat ddng san xuat va kinh te ciia viing, dSc biet la cac thay ddi vd sir dung dat va thuc phu. Cac thay doi nay dupe ghi nhan qua cac dij heu thdng k& hang nam cho timg dia phuong cua ca nuoc. Hieu biet vd didn bidn va dpng luc chuyen ddi sii dung dat/thuc phii la riit quan trpng trong viec quan ly tai nguyen dat ben viing d' cac nude dang phat trien, dac bidt d- cac viing ma sinh ke ngudi dan dia phuong phu thudc phan ldn vao ngudn tai nguyen thien nhien. Ben canh dd, qua trinh thay ddi su dung dat/thirc phu tac ddng true tiep den canh quan, da dang sinh hpc vd mat tu nhien va ca cac van d^ vd kinh te-xa hdi cua dia phuong dd [4]. Mdt each tdng quat, thay ddi sii dung dat lidn quan tdi md rpng dat ndng nghiep hoac la tang cudng tham canh, dd thi hda, mat rimg va chuyen doi dat ngap nude tu nhien thanh dat nong nghiep.
Ndi dung nghien cim nay sii dung each Uep can vidn tham, sir dung cac dii lieu quan sat U^ai dat tir ve tinh, phan tich cac dir lieu anh ve Unh de trich ra eac KYI -THANG 12/2019 73
•I K H O * HOC e 6 N O N 6 H »
lh6ng im ca %i- dmh Dnh Un djnh linjng cung nhu phan bo cua cac loji Ihgc phu. Thgc phu (land cover) la cac dm unTTii; che phu Wn mat dat. duoc xem xi-t ca v4 yf u lo vjt ly va sinh hoc. cac doi tuong bao gom mat (lal. mat nunc va thuc vat hi?n dien 6 cac trang thai hoac CHI doan khac nhau. bao gom tinh chat cua no la W nhitn hay nhan lao | 5 | . Ching han Wa la d6i tuong thuc vjl cay trong (nhan tao), ngan ngay. hoac rimg la cay go lon, tu nhien hoac nhan tao (rung U-ong). \ uc sii dung anh ve tinh cho cac nghitn cuu litn quan thuc phu/su dung dat co the ap dung cho qui m6 loan cau cho toi dm phmmg cr nhieu noi tren the gioi. Tai khu nrc DBSCL da co nhieu nghien cmi ve thuc phii sii dung du lieu anh ve tinh CO do phan giai khong gian thip (MODIS) toi ming binh a.andsat, SPOT). Cac nghien ciiu nay sir dung dii li?u do phan giai thap it chi Uet cho toan viing dong bang 16-91, hoac dp phan giai cao hon nhung chi trong pham vi mpt phan nho hoac mpt phan oia ding bang 1101, (111, ca hai loai thuong ngan ve chu6i thoi gian ph4n tich diJn biOn. Trong nhimg nam vita qua, da co nhifa nghifin ohi sii dung chu6i anh vf Unh radar Sentinel-1 dp phan giai trung binh (20 m) cho toan vimg nhung thuong chi thanh lap ban dA thijc phu cho mpt dot tm^ng, chang ban liia [121.
B a n g ! Dii li$u
Bi phan tich thay d6i fltuc phu/ su dung « • ^^^^
DBSCU du ueu anh vi tinh I ^ ^ s a l d a ^ nhan tu khoang dvoc nam 1990 cho d^n r,^-^^^
2018 v*i s.,1 thoi <Si(m anh dupe- su dung " l " « V ^ ^ dch xac dinh diin bi^n thay doi ve * v c Phu ^ DBSCL Ket qiia xac dinh cac loai Dm' phu theo cac tho, diem anh dupe phan tich thay do, I ' - 1*«"8 gian va thoi gian va la co so Ai phan tich jn"^-''^ * f doi cua timg loai. h6 trp xac dinh quan ly phat tnen cho vung ding bang trong tuong la,.
Z.I01BIVA PHUDNG PHAP 2.1. DOli$u
Du UOu anh Undsat thu nhan hi nam 1988 dfe nam 2018 theo cac khoang thM gian, chi ait trong bang 1, la da liSu miSn phi, dupe thu thap Hue tuy^n tai trang web https://earthexplorer.usgs.gov cia Hoa ky. DO lieu da xu ly a muc LITP (mtic 1) da hi?u chinh dia hinh va khi quyln a mtic toan cfc [131. Cac anh ve tinh Landsat 4 TM, Landsat 5 TM va Landsat 8 OLl (chu ly lap lai la 16 ngay) su dung trong nghien cim nay thupc nhom dii lieu anh quang hpc, diu CO chung dp phan giai khong gian la 30 m. Di phu het toan vting DBSCL can su dung sau canh anh (Bang 1) va do khu vuc thuong bi may nin c6 nhiing thoi diim can phai thu nhan nhieu hon mpt canh anh (trpng cung khoang thoi diem) de xu ly loai bo mSy.
Landsat sudung
SIT Path Row Thai dicm anh thu nhan (ngay/thang/nam)
Tru6cl990 I 1990-20(X) 2000-2005 2005-2010 2010-2015 2017-2018 052 I 30/01/1988 i 30/03/1998 • 11/12/2004
I _ " 21/llli/19il9.
09/12/2009 04/03/2006 09/12/2009 06/04/1989,
i 1S/12/19S9
\ 09/12/UWl.
17, 12/19,'i9
1-1/03/1'W 11.112/2004 09/12/2009 23/12/21H 19/1/2005, 20/04/2009
jmrnm 30/11/2009
18/09/2014,
09/02/2015 14/02/2017 22/02/2014,
24/01/2015
14/02/2017, 29/01/2017 09/02/2015 14/02/2017 21/04/2015 24/02/2018 12'0;',/19SM 10/03/20011 I'.i.'1/2011:,
126 054
<aimn'm_l21 wi/ans
24/ IZ/2!»)l3
24/02/2018 i / " i / a « 9 'US/ 12/03/2018 21/03/19i),«.
31/01/1989 18/12/1998. 15/l*/2un
^J]_K;_U'IU _ _
2.2. Phuong phip nghita oiu phan cho phim 1,.., , 1, han chTdanh gia do' chmh xac giai (loan anl ,,h Car 5 1, - * 1, A- Cong vi?c g,.i, doan va phan loa, cac yiu to thut duoc thuc hii^n Uen x ly di; inyinA^ '^ • , phu/su iliiii.i: dm (la sii dung cac miu khoa g,ai doan g.j ,„ pl,i„ xa, hieu chinh phan xa u ^ ' " ^ ^° "^
va phSn loai. dmn- thu thap th6ng qua cac dot khao ,.mmg phan xa va giam nliiiu kh " " "^ ^^
sal thuc dia. Cac miu khoa nay dmn: sir dung mot pir,mmK phap Tru doi tmmg l.ii DO^ /S"^™ ^^^
^ (Dark Object 74 NONG NGHIEP VA PHAT TRIEN NONG THON - KY 1 T H i . ,
"ANG ,2/2019
KHOA HOC CONG NGHE
Subtraction) [14, 15]. DOS la mot trong nhimg phucmg phap hieu chinh khi quyen don gian va pho bi^n; phuong phap gia dinh la phan xa tir cac ddi tirgng tdi lidn quan tcri buc xa khuech tan ciia bau khi quyen, giy nhidu khi quyen nhu suong mil anh hudng ddn chat lugng anh va cd thd loai bd. Gia tri ciia cac ddi tugng tdi dugc xac dmh, sau dd gia tri biic xa tai bg cam Uir cac gia tri nay theo cdng thiic tdng quat Gii tri phan xa (mdi) = Gii tri phan xa tai diu b0 cim - Gii tri phin xa cua ddi tirong tdi. Sau khi anh duge tidn xii ly, chi sd phan bidt thuc vat NDVl (Normalized Diffemce Vegetation Index) va chi so phan bidt nude MDWI (Modified Normalized Difference Water Index) [16] duge phan tich de ttng cudng nhan biet ddi tuong khi giai doan va phan loai ddi tuong tr&n anh ve tmh. NDVT duoc tinh tir cac k^nh pho man dd va hong ngoai gdn: (Hdng ngoai gin - Do)/(Hdng ngoai gin + Do); MDWI dugc tinh tir cac kdnh phd mau xanh luc va hdng ngoai giiia:
(Xanh lijiC - Hdng ngoai giua)/(Xanh luc + Hdng ngoaigida).
Cdc logi thuc phii/ sii dung dat dugc xac dinh theo bSy nhdm chinh, bao gdm: (y Trdng lua (khong phan bidt vu miia), (li) Cay an trai, (Hi) Rimg, (iv) Nuoi trdng thiiy san (NTTS), (v) Nudi trong thuy san xen Iin rimg ngiip man, (vi) Dat d (dat xay dung do thi v^ 6.it b rai rac) va (vii) Cac loai khac (bao gdm ca cac logi dat nong nghiep trdng cay ngan ngay - khdng phai lua, cay lau nSm khac - khdng phai cay an ti'ai, va cac loai thirc phii khae khong xac dinh duoe (mdt sd khu vue rimg trdng).
Cac ddi tugng tren anh duge phan loai dua tren cSc mSu khda phan loai theo bay nhdm chinh nay.
Phuong phap phan loai duoc sii dung la phan loai cd giam sat (sii dung mau khda phan loai), ky thuat phan logi Maximum Likelihood (MLC) ket hgp vdi Support Vector Machine (SVM). Thuat toan phan logi MLC dua tren ham mat do xac xuat, tinh toan Ihdng kd dua tren mau khda phan loai de phan nhdm cic phdn Ui anh cd cac gia tri gan nhat vao mdt nhdm; ky thuat phan loai SVM dua ti'en bd miu phan logi, mdi ldp phan loai la mot nen vector duge phan chia theo cac vector hd trg' (support vector) va phan nhdm theo ham tuyen tinh cua khong gian n chidu theo sd lugng kenh phd sir dung, ket qua phan ehia dtra tren cac mat phang vector n chieu.
Ket qua phan loai duoc danh gia do chinh xac va hidu chinh ket qua. Do ehinh xac phan loai thuc hien tr&n ket qua phan loai anh nam 2018, vdi tdng
NONG NGHIEP VA PHAT TRIEN NONG THON - KY 1 -THANG 12/2019
sd mau/vi tri khao sat la 556 vi tri. Bd miu danh gia nay bao gdm mau da thu thap tir khao sat thuc dia, ket hop vdi cac mau xac dinh trdn cac anh ve tinh cd dd phan giai khdng gian cao (cd the nhan dang ddi tugng bang mat) thu nhan trong khoang thdi gian 2016-2018, cd fren Google Earth. Tai mdi vi ti'i tren anh, miu danh gia duge lay 4 - 6 phan tir anh, sau dd sir dung ma trgn danh gia dg chinh xac vdi hai chi so, la do chinh xac toan cue va chi sd Kappa theo each tinh cua Congalton [18]. Kdt qua sau khi danh gia dat yeu cau duoc chuyen sang dinh dang GIS de bien tap, ghep kdt qua giai doan cho toan DBSCL va phan tich ket qua bang phuong phap phan tich sau phan loai, phan tich chdng ldp de phan ti'ch di&n bidn.
3 . KET QUA VA THAO L U A N
3.1. TTiiic phu/sir dung d^t DBSCL theo cic thdi di^m anh
Do chinh xac toan cue cho anh phan logi nam 2018 la 90,0%, chi sd Kappa la 0,87. Trong dd, phan loai nham cao d ba loai: Cay an trai 16,9%, cac loai khac 28,6% va thiiy san + rimg ngSp m$n 13,8%; phan loai bd sdt cao b cac logi khac 30,2% va rimg 10,0%.
Day la cac loai thuc phii dd bi lin qua nhau: Cay an trai va cac loai khac, cac loai khac vi rimg. Vdi mirc dg toan vimg, do chinh xac niy cd thd sii dung dugc cho cae phan tich tiep theo.
Ket qua phan loai cac thdi didm (Hinh 1) vi phan bd cac loai va bang 2 cho thay qui mo didn tich cua cac loai thuc phii theo cac thdi didm tuong ling li cac nam 1990, 2000, 2005, 2010, 2015 va 2018. Trong dd Ilia chidm ty le thap nhit vio thdi diem nam 2015 chi cd 39,4%, cao nhat li thdi diem nam 2000, chiem 49,5%. Tgi thdi diem nam 2018, lua chiem ty le 41,7%
so vdi tdng dien tich cua DBSCL va thuy san chidm qui md dien tich thii hai so vdi cac loai thuc phii khac.
Hinh 1 cho thay phan bd lua va cay an trii tap tnmg vimg trung tam ciia ddng bing, dgc luu vuc sdng Tidn va sdng Hau. Thiiy san tap trung phat trien viing ven bien, vimg trung phia Nam, chiu inh hudng true tidp ciia thiiy trieu bien.
3.2. Didn bi& thay ddi
Tir nam 1990 tdi nam 2018 cd tdi 52% dien Uch cua viing dong bing cd thay ddi, chiem 20.650 km-, cac thay ddi niy tap Unng tgi cac tinh Kien Giang (viing Tu giac Long Xuyen), Hau Giang, Ca Mau, Long An va cac tinh ven bien la Bac Lieu, Ben Tre, 75
Tra Vinh. Xi l v* qu, m6 thay d6i ve d , ^ uch trong gia, doa,i 1990-2018 (Bang 2) co Ihi phan chta thanh hai nhom nhu sau: Mmni 1 bao t:>im thuy san, cac Io9i khac va rimg vo, dien uch thay d6i theo thu tu la
»ii-2.'*l km-, -5.375 km-. -1..SJ.T km^ nhdm 2. vo, cay an tra,. thuy san * rimg ng^p man. dan cu en mUc do thay d6, v* d,^n nch 4«5] km=, »7.^ km- va 396 km-.
Xem xet v^ tang di^n tich co thiJy san. thuy san -t- rimg ngap man, cdy an trai va dan c-ir: xet vi giam d,f n tich CO cac loa, khac, rtmg va lua.
Trong tung giai doan thi thuc phu cci thay doi khac nhau nhu sau:
1990.2000: liia, thiiy san tang di?n Och, trong khi do cac loai khac va nmg giam di^n tich.
Bang 2. Dign tich c&c toai IhMC phu d ddng bang
2000-2005: thuy *.iii- cay an trai va rimg ••'">>
diin uch. irong kh'l 66 liia lai giam manh. cac I091 khac Uep mc giam, dien dch m(lt niroc nu6, ircng thuy san xen Idn rimg ngap man giam.
2005-2010: lua va cay an Uai tang dien uch: cac loai khac vki giam dien tich cung viii rimg va thuy san, Iluiy san xen rimg ngap man.
20102015: thiiy san tang manh cting vol cac loai khac va dan cu. Rimg van ti^p toe g,a,n dien tich cung vin cay an trai, ilia chi giam nhe vi dii^-n tich.
2015-2018: giai doan nay chi trir liia giam manh (giam tren 1,7 ngan km^ cac loai con lai d^u tang dien tich, riSng rung khong co thay doi.
sdng Cuu Long theo cac tfadi di^m aidi (km^
2010 2015
19.517 18.186
5.790
6.382 6080 7.293
742 717 758
1.339 1.226 1.229 1.195
Hinh 1. Thvc phu dfing bang s6ng Ciiu Long theo cdc thdi d , ^ anh
+ Dit^n bien thay doi thuc phii vc khong gian (llmliJ)
Khu vuc ven hai ben song Ti^n va song Hau co it thay doi nhat, day la khu vuc canh tac nong nghidp lau nam cr dong bang song Cuu Long. Cac khu vuc ven bien thuoc tinh Ca Mau, Kien Giang va cac viing trung thupc Tii giac Long Xuyen (dnh Kien Giang), Bong Thap MuiM (thugc dnh Dong Thap va dnh Long An) la cac khu vuc co thay doi nhieu tinh tii tnroc nam 1990.
Cac Ihay d«i vt thuc phu/su dung dat bao g6m hai dang la (/) thay Sm sans I. -. khac va OV loai khac chuyen sang l„., ihuc ,,1™ njy. Hinh 2 cho thiy muc do chuyen „„i ,.„a mot loai thuc phu nay sang loai khac ve phan i » r . , , n „ „ i a _ t , , • ..
viiar „i, -r ' '"^o cac giai doan khac nhau. Irons; cac nghien oiu khac cung nhu trong kel qua cua phan uch nay cho T ^ J 2010 lua c6 thay dCii 1™ „ h j f p™ ^ ^ ^ ^^o toi nam dien tich canh lac do khai - ™ '* " * ^ ^ •Tit kho vitng dim
il Dong Thap
Hinh 2. Phan b6 khdng gian cac vimg co n h i ^ thay d6i vi tfavc phii tfaeo timg giai doan
76 NONG NGHIEP VA PHAT TRIEN NONG THON
lay, xay dm,g he thdng kenh thoyta M u . n , T u G , a c U n g X u v e „ p ^ i , ' f , - - lua/nam sang hai va ba vu Wa/ * " * ' ™ thong thuy l.n va sau do la nhoht'th^ °*'°' ™° ***
vao mua mua 1111. Nu„i u-i,„g |}i„ "* ^'^ * ™ •"
"^ '*! nuiic man ' " ' ^ ^ ^ ^ ' ^ 1 2 / 2 0 , 9
KHOA HOC CONG NGHE
ven bi&i va dan cu ed xu hudng tang ddu cho thay l i ^ quan ddn gia tang nhu cau tieu thu (ca trong nuoc va xuat khau) ciing vdi gia tang dan sd va do thi hoa ti-ong viing.
Bang 3 cho thay miic dp thay doi theo phin tram ciia timg logi thuc phu va bidn ddng khac nhau theo timg giai doan cua cac ddi tugng, phan tram thay ddi cang eao thi muc dp bidn dgng cang ldn, cho thay miie do ciia loai thuc phii niy chuyen ddi sang dang khac. Xem xet trdn toan giai doan 1990-2018 ket qua phan tieh eho thay cae loai thuc phii thuoc nhdm cay BJing 3. Phdn fram thiy ddi theo timg giai
trdng cd nhidu thay ddi nhat Chi xem xel rieng liia va cay an trai thi ca hai cd thay ddi xaip xi 41% so vdi tdng dien tich thay ddi. Neu xem xet ludn ca nhdm tiiuc phu khac thi muc tiiay ddi tren 70%. Trong khi dd loai dan cu (do thi vi dan cu rai rac) chi chiem 0,07% so voi tdng thay ddi. Dang chii y la eo loai bien dpng manh vira tang dien tich, vira chuyen ddi qua loai khac trong cimg thdi ky nhu loai liia. Trong giai doan 1990-2000, liia da tang thuin tdng cpng 2 ngan km- nhung ddng thdi ciing chuyen ddi qua logi khac gan 4,3 ngin km-.
doan cua tung loai so vdi ^ n g thay d6i Qd) Loai
Liia cay an trai Khac Dancu Rimg Thiiy san Thuy san-i-RNM Mat nuiic
Tdng diin d'ch thay ddi (knf) Phdn tiSm Ihay ddi so vdi tdng DT
1990-2000 25,89 13,08 42,27 0,11 12,83 3,97 1,85 16.587,91
42,08
200(^2010 36,42
3,89 48,97
0,47 3,55 1,93 3,46 1,31 14.040,11
35,26
2010-2018 41,75 14,14 26,82 0,44 9,35 4,77 1,34 1,40 9.486,84
24,07
1990-2018 33,80
7,66 43,57 0,07 11,03 1,96 0,00 1,92 20.650,42
52,39 + Didn bidn thay ddi vd didn Uch trong timg giai
dogn nhu sau;
1990-2000: tong didn tich Oiay ddi 16.587 km^
chidm 42% tdng didn tich. Day la giai doan cd nhieu bidn dgng nhat ve thuc phii. Trong mgt loai vira tang didn ti'ch vira chuydn doi sang loai khac.
2000-2010: Thay ddi 14.040 km^ chidm 35% so vdi tdng didn ti'ch. Miic dg bien dgng giam so vdi giai doan trudc.
2010-2018: Thay doi 9.846 km^ chiem 24% so vdi tdng didn Uch. Muc dd bien ddng giam nhidu. Loai thuc phii Ilia la loai bien ddng chii yeu trong giai doan nay, so vdi hai giai doan trudc thi li loai khac.
Ty Id bidn ddng cua Iiia va ciy an trai la tren 45%, chii yeu la giam didn tich, chuyen ddi sang dang khac.
Nhu vgy giai doan 1990-2000 thay ddi vd phan bd khdng gian la ldn nhat, giam dan b hai giai doan kd tidp. Giai doan 1990 - 2000 cac thay doi tap trung ve thay ddi cac loai thuc phu lien quan den sin xuat ndng nghiep. Chinh trong giai doan niy hen quan ddn nhidu thay ddi ve chinh sach ndng nghiep, khai hoang mdf rgng dien tich, tham canh va ding ke nhit la didn tich trdng 2, 3 vu liia/nam da tang len nhidu hon (Bang 4) [18,19].
Banf
Giai doan 1975- 1980 1981- 1985 1986- 1990 1991- 1995
' 4. Tltay d6i ca c^u miia vu ilia 6 DBSCL Phan tram dien dch (%) so voi tong di^n
tich trong liia 1 vu-
gidng dia phucmg
75 74 59 43
1 vu- giong cao san
7 6 4 4
2vu- giong cao san
19 20 34 50
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0 0 1 3 Ngudn: Kono Yasuyuki. 2001(191 Trong khi do, thay doi aia loai dan cu ehu yen la tang trudng dien tich, chuyen ddi qua loai khac cr muc rat thap. Loai thuc phii mat nude nudi trong thuy sin tuy cd mire do thay ddi thap cr eac giai doan (chuyen ddi sang loai khic) nhung la loai ed muc do tang trudng dien tich manh nhat. Thdi diem nam 1990 chi cd khoang 1 ngan km^ (100 ngan ha) thi tdi thin diem cudi la nam 2018 didn tich mat nude nuoi trdng thuy sin tang len gin 7,3 ngan km- tire tang 7,3 NONG NGHIEP VA PHAT TRIEN NONG THON - KY 1 - THANG 12/2019 77
r. da id I4n Irong vong gin 30 nam. Dien (ich nay con chua tham radar vi quang hgc da thoi gian. ^^
bao glim i-ac mjl nuoc nuoi Bong thuy san xen lan giii de theo ddi diin bidn dien nch ra ^ ^
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trong nmg ngap man (khoang 75 ngan ha) va cac mat nuw v r r s mot ra, rac ven song ij phu trong DBSCL Chu y la mat nuoc nuo, trong thuy san a day chu yeu xac djnh cac vung tap trung a%'en bien.
NiHi xet vi- s6' dien tich chung. lua c6 thay doi kh6ng Ion nhung lai la loa, co t>- le chie'm di^n tich 1cm nhat so vm t6ng di$n ti'ch, ben carJi do liia lai co ki^u thay diSi vira giam di a mQt noi nay nhung Iai mii rong di^n Uch a mot no, khac d giai doan dau 1990- 2000 va u^p lyc cho den nam 2005. do vay n^u chi phan tich so li^u thong ke don diuan se chi thay la lua it thay doi (hoac tham chi la luong do, dn dinh ve difn ti'ch). Trong khi do mat nude nudi ti-dng thuy san tuy chifim di^n tich khdng Idn so vdi tdng d,dn tich, nhung iai la loai thuc phii cd miic dii thay ddi ldn nhat. Thuy san da lang didn ti'ch hon 7 lan tir nam 1990 den nam 2018 (xap xi mgt ngan km- thdi didm nam 1990, tang ldn gan 7,3 ngan km- thdi diem nam 2(11.S)
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Vdi each tidp can vidn tham tiong xac dinh cac loai tliuc phd cho DBSCL d cac thdi diem, dp chinh xac phan loai la 90,0%, chi sd Kappa la 0,87 la cd the sir dung dinjc cho cac phan tich. Kdt qua phan tich anh vd tinh Landsat cac Ihoi didm anh cac nam 1990.
2000. 2005,2010,2015 va 2018 cho thay thuc phii cua HKSCl thay dm manh lu nam 1990 tdi nay. So sanh vin giai doan tivdc dd thi nhung thay ddi nay tiimg hop vol cac chinh sdch ddi mdi bat dau nam 1986;
giai doan 5 nam 1986-1990 moi chi bat dau chuydn ddi CO ban va giai doan 5 nam tiep theo 1991-1995 da dat duoi- nhung ket qua quan tipng. Quy mo thay ddi thuc phu theo tung giai doan xap xi 10 nam 1990- 21HXI. .'1KKV211UI va 201O201,s cho thay gia, doan dau CO thay ddi manh nhSt, 121, di^n tich co tiiay doi so vin tdng dien tich loan vung; hai giai doan ke tidp niuv dd thay ddi giam xudng chi cdn 35% va sau do la 24%. Hal loai thuc phu co tliay ddi manh. gdp phan la,u thay iliii canh quan \-ung DBSCL la thuy san va lua. Trong khi dd vd muc dp thay ddi dien tich thi dat dan cu tang 121^, tuy didn tich khdng ldn so vdi cac lo9i khac nhung il.i> la muc tang dang ke lien quan ddn gia tang dan so va dd thi hoa.
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ning suit, san luong Ida vdng ddng / ri K/17 Long 13 ddng bang .<,>ng Hdng'. (IT-l !>•''-^^ "
201. thudc Chuong tiinh AHS-CX cap <Juoc gia ve cong nghi ni tin GB 20162020 va di ^ 'Nghien cmi sv biin ddi mdi tiirdng smh thai '-ung ha luu .',ing Mekong thude lanh thd I iii Nam vi dinh gii lac hai cua cic ho^t ddng kmh te khong duac kiSm soil tai vung thutmg luu song Mekong"
Cr,SB.BT/U-19/Cll).
TAI UEU n U M KHAO
1. Tdng cue Thdng ke. 2018. Kdt qua chu ydu dieu ti-a bidn dpng dan sd va kd hoach hda gia dinh thdi diem 1/4/2017.
2. Tdng cue Thdng ke: https://www.gso.gov. vn.
3. Huu Ninh Nguyen, Trung V. K., Niem N. X., 2007. Flood in Mekong nver delta, "Vietnam. Human development report 2007/2008 - UNDP.
4. Nangware Kajia Msofe, Lianxi Sheng and James Lyimo (2019). Land Use Change Trends and Their Dnving Forces in the Kilombero Valley Floodplain, Southeastern Tanzania, Sustainability 2019,11, 505; doi:10.3390/sull020505.
5. Antonio Di Gregorio and Louisa J. M. Jansen (2000). Land cover classification system (LCCS):
Classification concepts and user manual. FAO Land and Water Development Division. FAO, 2000.
6. Fah-ick Leinenkugel, Natascha Oppelt, Claudia Kuenzer (2014). A new land cover map for the Mekong: Southeast Asia's largest transboundary river basin. PaciSc Geographies No. 41, January/February 2014.
7- Dan, Tran & Ogawa, Susumu (2016). Land Cover Changes in the Mekong delta with MODIS Data. Remote Sensmg Society of Japan. Vol. 36.48.
8. Kithsiri Perera, Snkantha Herath, Armando
^ a n , UI Samarakoon (2010). AppUcatton of MODIS without in siU, observations for
nver basin land cover, of the Photogrammetry, 250ni images
mapping Mekong hitemational Archives Remote Sensing Volume XXXVIII, Part 8, Ky,
9. Killivin - Ryutaro Talenh Mekong B„sii Imagen -,?(ti \ , . „ ^ . Scnsini; S.-, 1. ty „i j ^ ^
andSpalial Information Science,
"In Japan 2010.
''•'lanfha Herath and
^''l^^'^d Use of Lower '''^niporal MODIS
!'i rera,
^1111 .-.,
•'cnce
"' the Remoti!
NONG NGHIEP VA PHAT TRIEN NONG THON • ^'»^>.W,„,2014, - M N ( 3
12/2019
KHOA HOC CONG NGHE Kyoto. Japan, https://eprints.usq.edu.au/ 27182/5/
PereraKithsiri_Kyoto_2014.pdf
10. Hanh Tran, Thuc Tran and Matthieu Kervyn, Dynamics of Land Cover/Land Use Changes in the Mekong delta, 1973-2011: A Remote Sensing Analysis of the Tran Van Thoi District, Ca Mau Province, Vietaam. Remote Sens. 2015, 7, 2899-2925;
doi:10.3390/rs70302899.
11. P. S. J. Minderhoud, L. Coumou, L. E.
Erban, H. Middelkoop, E. Stouthamer, E. A. Addink (2018). The relation between land use and subsidence in the Vietnamese Mekong delta. Science oftiie TotalEnvh-onment 634 {2018) 715-726.
12. Kersten Clauss, Marco Ottinger, Patrick Leinenkugel and Claudia Kuenzer (2018). Land Cover / Land Use Mapping in the Mekong delta, Vietnam, with focus on pond aquaculture and paddy rice utilizing time series of Copernicus Sentinel data.
Geophysical Research Abstiacts Vol. 20, EGU2018- 7929-1,2018.
scattering correction of multispectral data. Remote Sensmg o/Environment24{Z): 459479.
15. Z. Zhang, G. He & X. Wang., 2010. A practical DOS model-based atmospheric correction algorithm, International Journal of Remote Sensing, 31(11): 2837-2852, DOI: 10.1080/01431160903124682.
16. Hanqiu Xu., 2006. Modification of normaliased water index (NDWI) to enhance open water features in remotely sensed imagery. Int'l Journal of Remote sensing, 27(14): 3025-3033.17.
Congalton R. G., Green K. Assessing the accuracy of remotedly sensed data. Remote sensing of Environment 1991; 37:3&46.
18. Jean-Francois Le Coq, Marc Dufiimier, Guy Trebuil (2001). Histoiy of rice production in the Mekong delta. TTie third Euroseas Conference - London, September the 6th - 8 th 2001.
19. Kono Yasuyuki, 2001. Canal development and intensification of rice cultivation in the Mekong delta: a case study in Can Tho province, Vietnam - Land use development in the Mekong delta in the twentieth Centuary. Kyoto University.
https://pdfs.semanticscholar.org/0ca5/2ce4518bfl3 31f34c81a069e38d2cc9e3598.pdf
13. USGS, Landsat levels of processing https://www.usgs.gov/land-resources/nli/landsat/
landsat-levels-processmg.
14. Chavez Jr, P. S., 1988. An improved dark- object subtraction technique for atmospheric
LAND COVER CHANGE IN THE MEKONG DELTA 1990 - 2018: ANALYSIS FROM LANDSAT DATA Pham Bach VietS Lam Dao Nguyen^
Nguyen Van Anh Vu^, Chau Nguyen Xuan Quang^
'HCMC Space Technology Application Center- Vietnam National Space Center- VAST
^Institute for Environment and Resources - VNUHCM Summary
Studying on changes of land cover/ land use in the Vietnamese Mekong delta from 1990 to 2018 with remote sensing approach and geographic informaUon system is the main objective of this research. Using analysis techniques of Landsat satellite images, interpretation results of satellite images from 1990 to 2018 reveals significant changes in the land cover. Based on the field survey to collect key samples, supervised classification methods according to these key samples, the classification results in 2018 had a total accuracy of 90.0%, Kappa was 0.87. Analyzing changes in space and time by overlaying analysis in GIS shows changes in land cover in each penod. In the 1990-2000 penod, up to 42% of the whole area had different types of vegetation cover. From 1990 to 2018, more than 52% ol the total area of the Mekong Delta changes in spatial and area distnbution. Rice is the type with the most changes m spatial distribution, fisheries increase more than seven times and forests decrease by nearly half in area.
Keywords: Land cover change, Mekongdelta. Landsat, Remote sensing.
Ngu6i phin bifin: PGS.TS. Nguyen Van T u ^ Ngdy nhan bai: 30/9/2019
Ng4y thdng qua phan bi§n: 30/10/2019 Ng^y duy^t dSng: 6/11/2019
NONG NGHIEP VA PHAT TRIEN NONG THON - KY 1 - THANG 12/2019
