KHOA HOC CONG NGHE
tnVG DUIVG DLT LIEU VltlV THAM DE DAIVH GIA MIJC O d K H d HAIM TAI HLJY£I\I LOC HA, TilXIH HA TilXIH
Doan Thanh ThuyS "Mn Trgng Phuong^ Nguy&i Khac Ti^t Ba^
T6MTAT
Nghien cmi su diing dii lieu anh Landsat 8 de tinh toan chi so kho han nhiet do thuc vgt TVDI tren dia ban huyen Loc Ha, tinh Ha Tinh. Tir chi sd nay, nghi&n cmi xay dung ban do phan vimg miic do han ban cho toan huyen vao thdi diem thang 7 nam 2018. Ket qua cho thay dien tich khu vuc co kho han rat nang la 901 ha, dien tich khu virc kho han nang la 2688 ha, di^n tich khu vuc kho han trung binh la 2953 ha, di^n tich khu vuc kho ban nhe 3347 ha, dien tich khu vuc khong kho han la 1964 ha. Trong do, di^n tich dat trdng liia nam tiong viing kho hgn n$ng la cao nhat 212,37 ha, tiep d^n la difen tich cay hang nSm 60,07 ha va cuoi cimg la dien tich cay lau nam la 3.63 ha. Ket qua nay cho thay, kho han vao thang 7 nam 2018 a huyen Loc Ha anh hudng tnrc tidp den dien tich trong lua nuoc d huyen, de doa ddn an ninh luong thuc va san xu^t nong nghidp cila Loc Ha. Ket qua cua nghien cmi co the lam co so d^ cac nha quan ly c6 nhiimg bi?n phap sir dung dat ling phd vdi tinh hinh kho han duoc xem la cap bach trong bdi canh bien ddi khi hau dang di^n ra ngay cang nghiSm tiong khong chi d Vi?t Nam ma tren toan the' gidi.
Tii khda: M?t7, TVDI, Landsat 8, kho ban. sudung dat
1 . BAT VAN BE
Han han (khd han) la mdt hien tugng tu nhifin dupc coi la thien tai, tao thanh bdi su thidu hut [ nghifim trgng lirong mua trong thdi gian keo dai, lam
giam ham lugng am trong khdng khi va ham lugng nude trong d^t, lam giam suy kifit ddng chay sdng sudi, ha thap muc nude ao hd, muc nude trong cac tang chiia nude dudi dat gay anh hudng xau den su sinh trudng cua cay trdng. Mm mdi trudng suy thoai gay ddi ngheo dich bfinh [ 1 ].
Nhirng nam gan day, dudi bdi canh bien doi khi h^u tren toan cau thi miic dp va tin suat han ban ngay cang trd nen nghifim trpng hon. Nguyen nhan chii ydu la bien ddi khi hau gay ra nhirng bien ddi ldn ve nhiet dp, gid, do im, tan suat va cudng dd ciia mua [2], O Viet Nam, tinh hinh khd han d mrdc ta ngay cang gay gat hon ve cudng dp va md rdng ve pham vi vdi tan suat ngay cang tang, anh hudng nghifim trgng tdi san xuat ndng, lam, ngu nghiep va ddi song nhan dan, dac biet la cac vimg ddng bang.
Udc tinh trong giai doan 1995-2006, tdng thifit hai hi cac tran bao, lii lut va ban han da gay thifit hai cho Viet Nam 61.479 ty ddng, chua ke mat mat ldn vd sinh mang, hu hdng ca sd ha tang va ton that sinh ke [3]. Huyfin Ldc Ha, tinh Ha Tinh cd dien tich 11853,06 ha, dan sd hon 8,7 van ngudi. kinh te tap
tnmg chii yeu dua vao ndng nghidp nhu trdng hgt chan nudi, nudi trdng thuy san, lam mudi... Vi kinh td tap trung chii yeu vao ndng nghiep nen huyfin chiu anh hirdng boi yeu td thdi tiet, mdi tnrdng nhu mua bao, lu lut dac biet la han ban.
Vdi su phat trien cdng nghe thdng tin va cac ling dung cua nd trong quan ly tai nguyen thi vific su dung vifin tiiam trong phan tich, danh gia dp am dat.
miic dp khd han ciing nhu tac ddng ciia khd han ddn thuc vat la mdt phirong phap hieu qua do su thay ddi miic dd khd-am ciia tham thuc vat ludn dtrgc thd hi^n rd rang ti-fin kenh hdng ngoai nhifit ctia anh viln tham nhu Modis, Landsat... Nhi^t dp be m§t thu nhan dugc tii dai phd hdng ngoai nhifit anh LANDSAT la mdt chi tiii tdt cho ddng an nhifit [4, 5|.
nhifit do be mat cd tiie tang len rat nhanh ti-ong trudng hop thuc vat thieu mrdc. Vide su dung du li§u vifin tham trong xay dung ban dd khd han chii ydu dua vao vific tinh toan cac chi sd phan anh mdi quan he giiia cay trdng va dd am dat. Kogan (1995) da de xuat Chi sd dieu kifin thuc vat - VCI de theo ddi ban han va tiiu dugc nhiing ket qua kha quan [6]. Moran va cdng su (1994) da thiet ke Chi sd thidu nude - WDI nam 1994, Peter va cgng su nam (2002) gidi thieu chi sd Thuc vat chuan hda - SVI, Wang va cpng su (2015) da phat tnen mdt phucmg phap theo ddi han han cd ten la Chi sd dieu kien nhifit dp thuc vat - VTCI va xac nhan rang VTCI la phuong phap tiieo ddi han ban gan thdi gian thuc cd hen quan den Chl ' Khoa Quan ly dit dai. Hoc vi?n Nong nghiep Viet Nam
,24 NONG NGHIEP VA PHAT TRIEN NONG THON - KY 1 - THANG 5/2020
KHOA HOC CONG NGHE
so tiiuc vat NDVI va sir thay ddi nhidt dd be mat dat [7,91- Nam 2002, Sandholt va cgng su da de xuat Chi sd khd han nhi^t dg thuc vat- TVDI de danh gia miic do han han cua cay trdng dua trfin mdt luong ldn du lieu vifin tham [10]. Tir dd, TVDI dupc su dung rdng rai trong rat nhieu cac nghidn ciiu tren thd gidi vd danh gia do am d^t cua Mallick va cdng su (2(X)9) [11], Patel va cdng su (2009) [5]. Chen va cdng su (2015) da tinh toan TVDI tii dii lieu anh Landsat 5 TM de udc tinh dp am dat va dua ra kdt luan rang TVDI la mdt chi bao hiru hidu dd danh gia tinh trang dp am trong dat dudi mdt sd loai cay trong khac nhau [12]. Tai Viet Nam, nghien ctiu ciia Trinh LeHimgva cdng SIT (2015) da su dung TVDI de danh gia nguy ca han han d huyen Bac Binh, tinh Binh Thuan va cho kdt qua tdt [131.
Miic tieu ciia nghifin ciiu nay nham tinh toan chi sd TVDI tir dii lifiu anh Landsat 8 dugc thu tiiap tir ngudn dir lieu mifin phi cua Cue Khao sat Dia chat Hoa Kf va xay dimg ban dd nguy ca khd han tai huyfin Ldc Ha, tinh Ha TTnh. Ban dd phan vung miic dp han han se la mdt tai Ufiu quan trgng de danh gia anh hudng ciia khd han ddi vdi nhidu linh vuc khac nhau cung nhu giiip cho cac nha quan ly xay dung ke hoach ling phd va giam thieu miic do nghifim trgng cua han ban trong bdi canh bien ddi khi hau.
2. PHUDNG PHAP NGHIEN CUU 2.1. Dta ban nghifin ciiu
Huyfin Lgc Ha nam o Ddng Bac iinh Ha Tinh, cd vi tin dia ly quan trgng vdi tiem nang trd thanh cau ndi phat trien du lich sinh thai bien, du lich cac danh lam thang canh va di tich lich su. Dia hinh huyfin tirong ddi bang phang, thugc tieu vung khi hau Bac mien Trung, nam trong khu vuc khi hau nhiet ddi gid miia. Nhifit dg trung binh hang nam la 28''C, vfi mua khd do anh hudng true tidp ctia gid Lao, nhiet do cd Itic ti-en 35''C; dp am trung binh hang nam la 80%.
Lugng mua hang nam vao loai trung binh. phan bd khdng ddu miia khd (tiiang 4 - 8) thieu nude, cdn miia mua Iai thira nude (trfin 2000 mm) gay khd khan cho san xuat va ddi sdng.
2.2. Dir li^uviSn tham
Du lieu vifin tham sir dung trong nghifin ciiu la 01 canh anh ve tinh Landsat 8 chup ngay 02/7/2018 vdi path 126, row 47, cd dp che phu may la 0%.
LANDSAT 8 la the hfi vfi tinh tiiu 8 cua chuang trinh LANDSAT (NASA, My), sir dung 2 bg cam bien: bd
cam quang hpc OLI - Operational Land Imager va bg cam hdng ngoai nhiet TIRS - Theimal hifraRed Sensor. LANDSAT 8 dugc phdng Ifin quy dao vao 11 tiiang 02 nam 2013. LANDSAT 8 cung cap anh d 11 dai phd, trong dd cd 9 kenh da phd vdi do phan giai khdng gian 30 m, 1 kfinh toan sac vdi do phan giai 15 m va 2 kenh hdng ngoai nhiet d dd phan giai 100 m [14].
2.3. Phan tich, xii ly dti lifiu anh vi^n tii^m Hinh 1 the hifin quy trinh xu ly dur lieu anh Landsat 8 dd xay dung ban do phan cap miic do khd han ctia huyen Ldc Ha, tinh Ha Tmh. Dd xac dmh nhiet do thuc be mat cdn cd 2 yeu td chinh la chi sd NDVI va dp phat xa (e) ctta Idp phu daL Dp phat xa cua cac be mat tii nhien cd the thay doi dang ke do cd su khac biet trong dac tinh lop phu dat va thuc vat. Vi vay hieu chinh dp phat xa can phai thuc hifin, dd phat xa ciia cac be mat ttr nhifin se dugc sir dung de hifiu chinh nhifit dd sang (TQ) nham xac dinh nhiet dd thuc bd mat. Nhiet do thuc be mat la biic xa nhifit dp tnmg binh cua be mat dat tai mdt khu vuc.
Trong vidn tham, nd la ham sd ciia su thay ddi Idp phu thuc vat va ham lugng nude trong dat trfin pham vi mdi diem anh (pixel). Cac nghifin ciiu trudc day da chi ra mdi tuong quan vd khdng gian cua chi sd thuc vat (NDVI) va nhiet do be mat dat (LST) theo khai mem cua su bay hoi, su thoat nude va hgp phan Idp phu thuc vat (Hinh 2). Theo dd, cac thay doi ve nhiet do be mat cd mdi tuong quan kha chat che vdi nhimg thay ddi lop phu thuc vat va ham lugng nude trfin be mat dat trdng. Dat trdng khd - chi sd thuc vat thap, nhiet dp cao; dat trdng am - chi sd thuc vat thap, nhiet dp thap. Ben canh dd, khi phan Idp phii thuc vat tang, nhifit dp bd mat giam.
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Hinh 1. Quy trinh xii ly dii hfiu anh Landsat xay d^ng ban dd phan c ^ miic dO khd ban
KHOA HOC C O N G NGHE
Mdt sd nghien ciiu trudc day da cho thay mdi quan he nghich giiia LST va NDVI phan ldn la do nhirng thay ddi ve do che phii tham thuc vat va dp am cua dat va chi ra rang nhiet do bd mat cd thd tang len nhanh chdng theo mtic dp thidu nude. Mdi quan hfi LST - NDVI cho thay nhieu thdng tin hon so vdi timg chudi sd Ueu NDVI hay LST rieng biet vi cac nha nghien cim da chi ra rang, NDVI khdng nhay lam vdi su thieu nude cua thuc vat vi thuc vat vln xanh d giai doan dau han han. Ma nhifit dp be mat trai dat thu dugc tir cac kenh nhifit tii anh ve tinh la mdt chi thi tdt cho ddng nhiet an. Nhiet dp be mat cd the tang len rat nhanh khi thuc vat thieu nude va Idp phu Ihuc vat cd tac ddng dang ke den vific xac dinh nhifit do be mat. Nhu vay, LST va NDVI ket hgp vdi nhau cd the cung cap thdng tin vd didu kien siic khde thuc vat va do am trdn bd mat trai dat. Ndi each khac, phan tich mdi tuong quan giua chi sd thuc vat va nhifit dp be mat se la mdt chi thj cho danh gia miic dp khd han.
BSng 1. Miic dd c ^ h bao khd h ^ tuong img vdi cdc ngudng gia tai TVDI
S I T 1 2 3 4 5
Gia tri TVDI 0-0,2 0,2-0,4 0,4-0,6 0,6-0,8 0,8-1
Muc do kho han Khong kho han Kho han nhe Kho han trung binh
Kho han nang Khd han rat nang
KhoDg bfichoi
1
Boc hoi cue dai
TOltrong y S . %,,
raucvatthiiaN X ^
^ * ' * — ' T O K vat diy y S w Kliong thoat hoi
-»*NDVI
TVDI nhd hon 0,2 tiiang ting vdi cac vung khdng cd nguy CO han han (bd mat nude, tiiuc vat tuai tdt, dat ndng nghiep ngap nude). Neu chi so TVDI trong khoang tii 0,2 d^n 0,4 tirang ling vdi viing cd nguy co khd ban, chi sd TVDI ti-ong khoang hr 0,4 ddn 0,6 tuong ling vdi vung khd ban tiling binh, ti-ong khoang tii 0,6 den 0,8 tirang img vdi vimg khd han nang va trong khoang tii 0.8 den 1 tuong img vdi vimg khd han rlit nang [13],
2.4. Chdng x ^ dG U ^ trong ArcGIS Phuang phap chong xep dii Ufiu khdng gian trong phan mdm ArcGIS dugc su dung de chdng xep ban do phan muc khd ban va ban dd hien trang sii dung dat cua huyfin Ldc Ha dd xac dinh didn tich timg loai dat ndng nghiep nam trong vimg bi khd ban, tir do danh gia miic do anh hudng cua khd hiin den san xuat ndng nghifip va str dung dat cua dia phuong.
3. K ^ QUA VA THAO LUAN
3.1. I i n h chi sd khd h?n nhi^t dO tiiuc v^tTVDI Anh ve tinh Landsat 8 thu thap da duac xii ly 6 miic IT ( Level IT - Terrain Corected) nghia la da hifiu chinh vd btic xa, khi quydn, hinh hgc va khac phuc sai sd do dia hinh gay ra. Tir file ranh gidi hanh chinh huyfin Ldc Ha da thu nhap dupc vdi hd tga dO qudc te WGS 84, phep chieu UTM va miii chidu 48 cd dinh dang la *.shp tien hanh su dung cdng cti Extract by mask trong hop cdng cu Arctoolbox ti-fin phan mem ArcGis dd tidn hanh cat theo ranh gidi.
3.1.1. Tinh nhiet dp sing (TB)
Gia ti-i pbcel tir dang sd (DN) sang gia tri nang lugng biic xa phd (U) - gia tri nang lugng ma cdc ddi tirong trfin bd mat dat hap thu sau dd biic xa vao khi quyen. Nhiet dd chieu sang (TB) cdn gpi la nhifit dp vat den cd the duac tinh bang cdng thiic:
m^+n 1141 Hinh 2. M6i biaag quan gifla chi s6 NDVI va
nhi^t do thvrc hi mat
Voi nhi6t do be mat thuc, k^t hop voi chi so NDVI CO de tinh chi so kho han nhiet do thuc vat TVDI (Temperature Vegetation Dryness Index) [5]
tao ra ban do phan cjip kho han hi mJt huyen Loc Ha. Phan cap miic do kho han be mat ddi voi chi so TVDI duoc trinh bay trong bang 1. Trong do gia tn
k
Trong do: U - gia tri biic xa phd.
K , . 77,8853 , K, - 1321,0789 la hang so doi voi anh hong ngoai nhiet duoc cung cap trong file metadata anh Landsat ( don vi W/(m'.sr.iim) va K).
Ket qua tinh Tg theo don vi Kelvin (K) ddi vol kenh hong ngo^i nhiet co gia tn tu 297,064 din 309,634 va duoc the hi$n chi dft qua hmh 3.
NONG NGHIEP VA PHAT TRIEN NONG THON - KY 1 - THANG 5/2O20
KHOA HOC CONG NGH|
Hinh 3. Bdn dd gid tri nhi^t dd sang ctia huySn LOc Ha
Hinh 4. Bdn d6 g i i til NDVI cua huyfin Ldc Ha 3.1.2 Tmh chisd tiiuc vat NDVI
NDVI (Normalized Difference Vegetation Index) dugc gpi la chi sd thuc vat, nd dugc hieu la he sd lop phu thuc vat chenh lech chuan hda giiia he sd phan xa mat d dai sdng thi phd va hdng ngoai. Chi sd NDVI cho ta danh gia chung ve dd phat trien xanh ciia thuc vat, qua dd cd the theo ddi va giam sat nhirng tiiay ddi ctia thtrc vat theo thdi gian. Chi sd thirc vat (NDVI) duoc tinh bang cdng thtic;
NIR -I- RED [8]
Trong dd: NIR: Kenh can hong ngoai, RED:
Kfinh dd.
Ddi vdi Landsat 8 kfinh can hong ngoai tiiang ling vdi kenh 5, kfinh dd tuong ting vdi kenh 4. Chi sd NDVI nhan gia tri tii -1 den 1, trong dd thuc vat cd gia tri n4m trong khoang 0,2 -1,0. Trong trudng hop NDVI > 0,5 khu vuc dugc xem la phii kin thuc vat (sdng dien tir khdng tdi dupc Idp dat). Ddi vdi dat trdng khdng cd thuc vat bao phu thi NDVI < 0,2. Ddi vdi nude va dat am, NDVI nhan gia tri am. Ket qua tinh NDVI cua huyfin Ldc Ha cd gia tin tii -0.261638 den 0,591997 the hifin qua hinh 4.
3.1.3. Tmh nhiet dp thuc be mat (I) vi xay dung ban dd nhiet
Trong vifin tham hdng ngoai nhifit, nhifit dd biic xa hay nhifit dd sang (TB) ^^^ ^Pih nghia nhu la nhifit dd tuang duong ciia vat den truyen h-ong cimg mgt luprng biic xa thu dugc ttr mdt vat thuc td va phu thudc vao nhiet dd ddng Iuc hi be mat va do phat xa (e). Khi dd nhiet dp be mat da dugc hifiu chinh do phan xa (X) hay cdn ggi la nhifit dp thuc be mat cd the dupc tinh theo cdng thiic:
'^--^
Kdt qua tinh T(°K) cd gia tii hi 303,686''K den 316,367"^ Ban dd nhiet dp thuc be mat huyen Ldc Ha, tinh Ha Tinh thang 7 nam 2018 dupc th^ hifin d hinh 6.
3.1.4. Tinh chl sd kho han nhiet dp thuc vit TVDI
De danh gia mirc dp khd ban bd mat, trong nghifin ciiu nay sii dung chi sd khd ban nhifit dp thuc vat (Temperature Vegetation Dryness Index - TVDI), dugc Patel dua ra [5] trfin ca sd lugng hda mdi quan hfi giira nhifit do bfi mat va lap phti. Chi sd TVDI dugc xac dmh theo cdng thiic sau:
T-T^.„
TDVI--
Trong dd;
- T: nhiet do be mat.
[5]
- Tn,aj(, Tn,in la uhifit tip bd mat cue dai va cue tieu trong tam giac khdng gian nhifit dd/NDVI. T^ax duac xac dinh bang phuang phap hdi quy tuyen tinh cac gia tri nhifit dp ctrc dai tai cae khoang gia tri NDVI.
Gia tn chi sd TVDI cang cao tirong ling vdi nguy ca khd ban cang tang. Tai eanh khd, chi sd TVDI cd gia tri bang, trong khi dd tai canh udt gia tri TVDI la 0.
Huih 5. M6 hinh hdi quy tuydn tinh xie dinh Tn^
127
KHOA HOC CONG N G H £
Dd tinh gia til canh khd T^^ h-ong khdng gian nhiet dp/NDVI, ti-ong nghifin ciiu ta chia chi sd tiiuc vat NDVI lam 25 khoang. Tai mdi gia tri NDVI cd nhidu gia tri nhidt do, ta lay gia tri nhiet dp ldn nhat, canh udt T^^ dugc lay bang gia tri nhifit dd be mat thap nhat Tir ket qua hdi quy tuyen tinh cac gia tri nhifit do be mat cue dai tai cac khoang gia tri NDVI,
"canh khd" T^^ dugc the hien qua md hinh hdi quy tuyen tinh (Hinh 5):
T^^= -13,978 X NDVI -H 318,31 ("K) Md hinh nay cd hd so tuong quan R^ = 0,9557, hfi sd nay cang gan 1 phuong trinh hdi quy tuyen tinh duoc lap cang chinh xac. Vay ket qua dat dugc cd dp chinh xac tdt
Tir gia tri T„^ cd duac, xac dinh chi sd TVDI dua theo cdng thiic tren. Chi so TVDI se cd khoang gia tri tir-1 den 1.
3.2. xay dung ban do phan miic khd h ^ Bang 2. Di$n tich miic dO khd h ^ huyfin LOc Ha STT
1 2 3 4 5
Miic do kh6 han Khong kho han Kho han nhe Khd han trung binh Kho han nang Kho han rat nang
Dien tich Cha) 1964 3347 2953 2688 901
> K
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- :::.:- ,
1
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... ^- r'
Hinh 6. Ban d6 nhi^t dO thuc bd m^t huy^n Lgc Ha ngiy 02/7/2018
Trong nghifin ciiu nay, miic dd canh bao khd ban duoc phan cap tuong ling vdi cac ngudng gia tri nhu bang 1. Trong dd gia tri TVDI nhd hon 0,2 tuang ling vdi cac vimg khdng cd nguy ca ban ban (be mat nude, thuc vat tuoi tdt, dat ndng nghifip ngap nude).
Neu ehi sd TVDI trong khoang tii 0,2 den 0,4 tiiong ling vdi vimg cd nguy ca khd han, chi sd TVDI trong khoang tii 0,4 den 0.6 tirong ting vdi viing khd ban trung binh, trong khoang tii 0,6 ddn 0,8 tuong img
vdi vimg khd ban nang va trong khoang lu 0,8 dfin 1 tiicmg ling vdi vimg khd ban rat nang- Kfit qua phan cap khd ban dugc tiie hien d hinh 7 va dien tich dugc tild hifin h-ong bang 2. Phan ldn difin tich huyfin Ldc Ha cd miic dd khd ban nhe va khd ban tmng binh la chii ydu rai deu trfin toan huyen.
Hinh 7. Ban do phan c^p miic dO khd ban huyen LOc Ha ngiy 02/7/2018 3.3. Danh gia Snh hudng ctia khd h ^ d^n co c^u su dung d^t huyfin LOc Ha
Tir ban dd phan cap mtic dp khd han ciia huydn Ldc Ha, tien hanh chdng xdp vdi ban dd hifin trang su dung dat cua huyfin Ldc Ha bang chiic nang Intersect trong phan mdm ArcGIS d^ xac dinh di§n tich dat ndng nghiep nam trong vimg bi han theo cic miic. Bang 3 thd hidn difin tich timg loai d^t ndng nghifip cua huyfin Ldc Ha theo timg miic phan viing khd han.
Ket qua d bang 3 cho thay, dien tich dat trong lua d miic khd ban nang la cao nhat 212,37 ha, tidp ddn la didn tich dat trdng cay hang nam 60,07 ha va cudi cung la dien tich dat cay lau nam la 3,63 ha. Cd 19,2% dien tich dat trong liia nam trong vung hi khd ban nang va khd han rat nang, dieu nay true tidp anh huong ddn san xuat ndng nghifip va c a cau kinh te nam 2018 ctia huyen Ldc Ha, vi dien tich dat trdng Ilia chifi'm 27,82% dien tich dat tu nhien va cay Itia la cay trong chu Iuc d dia phuang. Dien tich cay hang nam nam trong vimg d miic khdng khd ban ddn khd ban trung binh la 94,84%, tirong tii vdi didn tich dat cay lau nam la 98,91%. Ket qua nay cho thay, khd h?n vao thang 7 nam 2018 d huyfin Ldc Ha anh hudng true tiep den didn tich trdng lua nude d huyfin, de dpa den an ninh Iuong thuc va san xuai nong nghi$p cua l/)c Ha.
128 NONG NGHIEP VA PHAT TRIEN NONG THON - KY 1 - THANG 5/2020
KHOA HOC CONG NGHE
B&ig 3. Dien tich cdc loai dit nong nghiep cua huy$n L6c H4 theo timg miic phta vimg khd hta Don vi:ha Loai cay trong
Lua nuoc Cay hang nam
Cay lau nam
Khong kho han 606,51
14,62 475,16
Khd han nhe 1548,94
105,31 256,11
Kho han trung binh
508,99 115,67 42,92
Kho han nang 421,07 110,08 32,25
Khd han rat nang 212,37
60,07 3,63
Tdng 3297,89 405,74 810,08 4.i(ETLUllN
Nghien ctiu da su dimg dti Ufiu anh vidn tham Landsat 8, la dii Heu hoan toan mifin phi va cd chu ky thu thap anh ngdn de xay dtmg ban do phan vimg muc dd khd ban ctia huyen Lde Ha, tinh Ha Tmh vao thdi diem thang 7 nam 2018. Tren ca sd xu ly anh vfi tinh Landsat 8, da xac dmh nhifit dp thtrc bd mat huydn Ldc Ha nam trong khoang 303,686''K 316,367°K. Tir ca sd dd, su dung md hinh hoi quy tuyen tinh da tim ra mdi tuong quan giiia nhiet do thuc bd mat va chi sd TVDI, qua dd phan cap dugc 5 miic dp han han tai huyfin Lpc Ha: difin tich khu virc cd khd ban rat nang la 901 ha, dien tich khu vuc khd han nang la 2688 ha, dien tich khu vuc khd han trung binh la 2953 ha, dien tich khu vuc khd han nhe 3347 ha, dien tich khu vuc khdng khd ban la 1964 ha.
Trong dd, difin tieh dat trong lua nam trong viing khd han nang la cao nhat 212,37 ha, hep den la dien tich cay hang nam 60,07 ha va cudi ciing la difin tich cay lau nam la 3,63 ha.
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11401-11417,2015. , . , , „ „ rr • Hmdbook 14. Landsat-S Science Dam Users HMUOOOK.
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Bac Binh district, Binh Thuan province. Joumal of
APPLYING LANDSAT 8 DATA TO EVALUATE DROUGHTS IN LOG HA DISTRICT, HA TINH PROVINCE Doan Thanh Thuy', Tran Trong Phuong', Nguyen Khac Viet Ba' 'Faculty of Land Management Vietnam National University of Agnculture
Summaiy
The research used Landsat 8 image data to calculate the Drought Vegetation Dryness Index - TVDI in Loc Ha distnct. Ha Tmh province. Based on this index, the map of droughts for such district m July, 2018 was constructed to evaluate the effects of droughts to agricultural production. The results show that the area of very dry zone is 708 ha, dry zone is 2688 ha, the intermediate dry zone is 2953 ha, the light dry zone is 3347 ha, the non-dry zone is 1964 ha. In particular, the land area for rice cultivahon in the very dry zone is the highest 212.37 hectares, followed by the annual crop area of 60.07 hectares and finally the perennial crop area is 3.63 hectares. This result shows that the drought in July 2018 in Loc Ha district duecdy affected the area of paddy nee cultivation in the district, therefore threatening food secunty and agricultural production of Loc Ha. Results of this study can sopport the stakeholders to apply appropriate land managements to cope with drought situation which is considered to be urgent in the context of climate change.
Keywords: NDVI, TVDI, Droughts, Landsat 8, Landuse.
NguM phan bi$n:TS.Hc4ngTuSn Hiep Ngay nhtobM: 3/3/2020
Ngiy thdng qua phan bien: 3/4/2020 Ngay duy$t dSng: 10/4/2020
130 NONG NGHIEP VA PHAT TRIEN NONG THON - KY 1 - THANG 5/2O20
