NGHIEN CUU U*NG DUNG N £ N TANG GOOGLE EARTH ENGINE
T H A N H L A P B A N B6 G I A M S A T H A N H A N LlTU VUCSONG DONG NAI VUNG DONG NAIM BO
Nguyin Van Hoang, Huynh Thi Kim Nhan, NguySn Dinh Vugng Vien Khoa hgc Thuy hi mien Nam Tom tat: Nghiin ciru sie dung nin tdng xir ly dua trin ddm mdy Google Earth Engine (GEE) di xdy dung bdn dd phdn vung mire dp hgn hdn luu virc sdng Ddng Nai tir 2014 den 2019, dua trin linh todn chi sd khdc biit hgn hdn (NDBI - Normalized Bifferenee Drought Index). Kit qud nghien cuu cho thdy ty li diin tich hgn ndng vd rdt ndng vung nghien aim ndm 2016 chiem ty li cao nhdt trong th&i dogn nghiin ciru v&i 78,1%. Ddnh gid dp chinh xde dua trin xem xet su phii hap gida kit qud phdn logi chl so khdc biet thuc vdt (ND VI) vd chl sd khdc biit nu&c (ND WI) vai kit qud quan sdt true quan tir Google Earth dgt duae la 100.0%. cho thdy tiem ndng ldn trong viic img dung nin tdng Google Earth Engine trong gidm sdt hgn hdn a LVS Ddng Nai.
Tir khoa; Bdng Nam Bd. GEE. hgn hdn. Landsat 8. L VS Dong Nai 1. DAT VAN DE
Luu virc sdng Ddng Nai dugc xem la ngudn nude CO ban va quan trpng nbat trong pbat trign kinh te - xa hgi vimg Ddng Nam Bg, nam tren dia pban eae tinh Lam Ddng, Dak Ndng, Binh Phudc, Binh Duong, Binh Thuan, Ddng Nai, Ba Rja - Vung Tau, Tay Ninh, Thanh pho Hd Chi Minb, Ninh Thuan va mpt phan cua 2 tinh Ddk Nong va Long An vdi ldng dien tich luu vuc khoang 44.100 km^. Do ndm d vi tri cbuyen tiep giQa cao nguyen Nam Trung Bd va Ddng bang sdng Cim Long, lai tigp giap vdi thgm luc dia bien Ddng nen dia hinh luu vuc sdng Ddng Nai nghieng dan tir Ddng Bae xudng Tay Nam vdi dp ddc trung binb loan luu vuc la 4,6%, ngn tai day thudng xuyen bi thigu nude vao miia khd gay ban han xay ra cue bp tai cac dia phuong.
Da cd nhieu du an dua ra nham danh gia anh hudng ban ban tai luu vuc sdng Ddng Nai dg dua ra eac giai phap giam thieu thiet bai bang phuong pbap md hinh loan, cac nguy eo ban do Ngay nhan bai: 09/01/2020
Ngay tbong qua pban bien: 06/02/2020 Ngay duyet dang: 12/02/2020
suy giam ddng ehay, luu lugng mua da dugc danh gia cu the thdng qua cac con sd ve dien tieb ban. Tuy nhign de dat dupe bieu qua tdi uu trong viec giam thieu den mii'c tdi da tac ddng eiia han ban can nghign cim mpt each tdng hpp, da chieu, bdi vi viee thuc bien cae chinb sach tang cudng quan tri nii ro tbign tai dugc thuc hanh dua tren cac bang ehiing ve pbam vi anh hudng, nguygn nhan va miic dp tac ddng.
Vidn tham ii'ng dung trong quan Iy rui ro thien tai, lap ban dd va giam sat ban han la mdt phan thigt ydu dg chinh quygn va cac bgn lien quan c6 thd thuc bien cac boat ddng iing pbo va giam thigu pbii hpp. Gan day, cdng ngbe vien tbam da dupe phat trien nbanb chdng vdi dir lieu ldn va cdng ngbe dien loan dam may.
Google Earth Engine (GEE) la mdt ndn tang xir ly kbdng gian dia Iy dua trdn dam may tien tidn sir dung dil lieu Idn, ngudn md co san bao gom cac hinh anh va dil lieu khdng gian dja ly quy md petabyte trdn toan cau. De cung cap thdng tin chinb xac vg pbam vi va miic do anh hudng, dii' lieu quan sat trai ddt theo chudi thdi gian la mdt cdng cu manh me trong viee chuan bi tbudng xuygn va irng phd cac tac ddng bat lgi trgn cac khu vuc rdng ldn.
TAP CHf KHOA HOC VA CONG NGH^ THUY LOI SO 58 - 2020 47
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Xuat pbat tir nhirng thuc trang va nguyen nhan dung web dd kham pba danb muc dir lie^' ^^
nhu trgn, viec nghign etiu irng dung ngn tang chay cae phan tieb don gian va thu \ ien tai lieu Google Earth Engine Ihanh lap ban dd giam cung cdp cac Python va JavaScript, sal ban han luu vyc sdng Ddng Nai vimg Ddng
Nam Bp dugc thuc hien la rat can thigt.
2. PHU'OfNG P H A P NGHIEN CLTU 2.1 Khu vuc nghien cuu
Khu vuc nghien ciiu la loan bd dien tich luu vuc sdng Ddng Nai lidn quan den cac tinb Ddng Nai, Binh Phudc, Bmh Duong, Ba Ria Vung Tau va TP. Hd Chi Minb (TPHCM) vdi tdng dien tich la 9.179,73 k m l
Hinh 2; Giao diin Code Editor trong GEE 2.3 P h u o n g p h a p giai doan a n h vien tham d u a tren nen tang G E E
Sir dung cac thuat toan lap trinh ngdn ngii JavaScript tren giao dien Code Editor de dua do lieu anh vao nen tang va tien hanb eac bude xu ly, phan tieh, hien tbi va xuat ket qua.
Bp suu tap hinh anb Landsat 8 ed ten "USGS Landsat 8 Collection 1 Tier 1 TOA Reflectance", ed tdn ID '"LANDS AT/LCOS/CO1 /T 1_T0A"', dugc Google Earth Engine hieu cbinh khi quyen dupe sir dung trong de tai nay. Dil lieu anb sau do duge lpc theo vimg va thdi gian nghign cim de giam bdt thdi gian xir ly, sir dung doan code khai bao sau:
-'
I , 4
-0
M
i
Hinh 1: Khu vuc nghiin cim 2.2 Tong quan ve nen tang E a r t h Engine Google Earth Engme la mdt ngn tang dien loan dam may cho phep ngudi dimg chay cac phan tieh khdng gian dia ly trgn co sd ndn tang ciia Google. Cd mpt sd each de tuong tae vdi nen tang. Code Editor la mot IDE (Interactive Development Environment) dua tren web dg vigt va chay cac lap lenh, Explorer la mpl iing // Lpc anh theo thdi gian nghign ciiu
var collection - ee.ImageCoIIection('LANDSAT/LC08/C01/Tl_TOA') .filterDale('2016-03-01', '2016-03-30');
// Lpc anh theo viing ngbien ciru
var studyarea-ee.Geometry.PoIygon([[[l06.87036800694693,10.050601310799461], [107.89758968663443,10.574828473127113],[107.40075269051226,12.112098864151134], [105.99519293772471,11.467098807165632],[106.87036S00694693,10.05060!310799461]]]);
var L8_studyarea ^ coIIection.fiIterBounds(studyarea);
Chudi thdi gian ciia bd suu lap binh anb eac chi sd bao gdm cbi sd khac biet thirc vat Landsat TOA da dugc sir dung de tinh loan (NDVI - Normalized Difference Vegetation
48 TAP CHi KHOA HOC VA CONG NGHE THUY LOl Sd 58 - 2020
Index) (Tucker, 1979), chi so khac biet nuac (NDWI -Normalized Difference Water Index) (Rahimi et al., 2014) va chi so khac biet ban han (NDDI - Normalized Difference Drought Index), CO the xac dinh cac muc dp han han trong khoang thai gian quan tam dua tren nguong han ban tu pham vi gia tri NDDI, pham vi NDDI cao hon cho tbay han han nghiem trgng ban (Charat et al., 2009). Cac chi so dugc tinh bang cac phuong trinh sau:
NIR - RED NDVI =
NDWI JVIR - SW/R
NDDI =
NIR + RED (1)
NIR + SWIR (2) WOVI - NDWI
NDVI + NDWI (3) Trong do, NIR la pho phan xa cua d6i tugng tren kenh h6ng ngoai gSn, RED la ph6 phan xa cua d6i tugng tren kenh do, SWIR la ph6 phan xa cua doi tugng tren kenh hdng ngoai song ngan trong cam bien Landsat 8. Phan tich chi s6 NDVI, NDWI, NDDI cho tap dii lieu anh theo doan code dual day:
var L8_collection = collection.select(["B6","B5","B4"]);
var median_L8_2016 = L8_coIlection.median();
// Tinh toan va hien thi chi so NDVI
var ndvi = L8_collection.normalizedDifference(['B5', 'B4']);
var vis = {min: 0, max: 1, palette: [TFFFFF', 'CE7E45', TCD163', '66A000', '207401', '056201', '004C00','023B01','012E01','011301']};
Map.addLayer(ndvi.clip(studyarea), vis, "NDVI");
// Tinh toan va hiSn thi chi s6 NDWI
var ndwi = L8_collection.normalizedDiffcrence(['B5', 'B6']);
var VIS = {min: 0, max: I, palette: ['OOOOff, 'OOffff, 'ffffOO', 'ffOOOO', 'ffffff]};
Map.addLayer(ndwi.clip(studyarea), vis, "NDWI");
// Tinh toan va hiSn thi chi s6 NDDI
var nddi = ndvi.subtract(ndwi).divide(ndvi.add(ndwi)).rename('NDDr);
var vis = {min: 0, max: I, palette: ['OOOOfP, 'OOffff, 'ffffflO', 'ffOOOO', 'ffffff]};
Map.addLayer(nddi.clip(studyarea), vis, "NDDI");
Go^gte Earth Engine
Hinh 3; The hien chi sd ND VI khu vuc nghien ciru
Kgt qua giai doan tir GEE se dugc xuat sang Google Drive dg thuan lien bign lap ban dd trong GIS, trong qua trinh xuat dii lieu anh, ed thg tiiy chpn he tga dp cua anh.
// Xuat kgt qua
Export.image.toDrive({image:nddi,descriplion :"NDD1_2016",maxPixels: 1 e 13,region:
studyarea, file Format: 'GeoTlFF',ers:
'EPSG:32648',scale: 30});
TAP CHi KHOA HOC VA CONG NGHE T H O Y LOI SO 58 - 2020
KHOA HOC
Ket qua tinh toan chi s6 NDDI tii GEE GIS, chi s6 kho han dugc chia thanh 5 cap, d u g c bien tap, thanh lap ban d6 phan viing tuong ling vai 5 mile do kho han khac nhau ban ban LVS Ddng Nai tren pban mSm (Bang 1).
Bang 1: Phan Ioai muc do ban han dua tren gia tri NDDI Gia tri NDDI
<0
0-0,2
0,2 - 0,4 0,4 - 0,6>0,6
Phan loai Khong han ban Han han nhe Han ban trung blnh Han ban nang Han ban rat nang
Hiin thi
^^m
^^M ^^M
I USGSLaiid ] T O A Rctlcclance
I L g c a n
[ ^ ^ i h N D V r . N D W I 1 [ N D V I [
[ r h u a t loan xac Jiiib NDDI |- — • ! Ban da hgn hin LVS Dong |
Hinh 4; Sa do thuc hien
3. KET QUA VA THAO LUAN 3.1 Tinh toan chi s6 NDVI, NDWI cho tap hgp anh khu vuc nghien cuu
Nhiing noi cd mau xanh cang dam, thi kha nang tap trung thue vat cang cao nbu dat ndng nghiep.
lam nghiep. Nhirng noi cd rat it mau xanh, the bien miic do tap trung tbuc vat thap, cd thg la dat d do thi, dat trdng. Nhirng noi khdng cd mau xanh, cho thdy kbdng ed su hien dien ciia tbuc vat, dign hinh nhu cac ddi tugng sdng ngdi, kenh rach, dat cbuygn nudi trdng thiiy san. Cu the, mau xanh dam pban bd d Vudn Qudc Gia Cat Tien, ven bign Thanb pbd Hd Cbi Minb noi cd rimg ngap man Can Gid va khu bao tdn thien nhien Chau Phudc tbugc Ba Rja Vung Tau.
Trong ngbien ciru nay, gia tri NDVI < 0,1 duge quan tam, noi dupe xem la bi anh hudng nang ne nhat khi ban ban keo dai. Ket qua ban dd ehi sd NDVI LVS Ddng Nai tir 2014 ddn 2019 dupe the hien trong Hinb 5.
Hinh 5: Phdn bd NDVI LVS Bdng Nai tir ndm 2014 din 2019
50 TAP CHi KHOA HOC VA CONG NGHE THUY LOl SO 58 - 2020
Sau khi xay dung ban dd phan bd cbi sd thuc vat NDVI, tac gia da xay dung cac ban do phan bd khdng gian cua NDWI trong khu vue ngbien ciiu tir nam 2014 dgn 2019 (Hinb 6).
Vg mat khdng gian, ket qua cbo thay su phan bd ciia cac gia tn NDWI thap (hidn tbi mau dd va vang) phan ldn tap trung d khu vue phia Nam tinh Ddng Nai, phia Bac Ba Ria Vung Tau va phan dien tieh luu vuc thudc dja phan tinh Binh Duong. Khu vuc cd ehi sd NDWI d
miic cao phan bd d nbiing noi cd he tbdng thiiy van luu vuc, dac biet la khu vuc Ckn Gid va noi tiep giap vdi hd Ihiiy dien Tri An, nhiing noi cd tbuc vat rung che pbii ciing cbo thay gia tri NDWI cao. Kgt qua cung cho thky, su suy giam lon nhat trong cac gia tri NDWI dugc quan sat thay vao nam 2014, 2015 va 2016, khi cae ldng mau ndng trong ban dd chiem nhieu hon cac nam cdn lai trong giai doan quan sat.
Hinh 6: Phdn bd NDWI LVS Ddng Nai tiendm 2014 din 2019
^ ^j^^rW^Tf^
Hinh 7; So sdnh l&p phii thuc vdt giua kit qud phdn logi vd dd lieu Google Earth
TAP CHi KHOA HOC VA C O N G NGHE T H O Y L O I 5 6 58 - 2020 51
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Tir kgt qua phan loai ehi sd NDVI, NDWI tir tap bgp anh vien tbam, tign hanh danb gia do chinh xac bang phuong phap so sanh kgt qua pban loai vdi ket qua quan sat Irue quan di ngn tang Google Earth. Kel qua danb gia do chinh xae pban ioai NDVI, NDWI nam 2019 dat dupe la 100,0%, do dd ket qua pban loai dii co sd dh lam dir lieu cho tbanb lap ban do han ban vimg nghidn ciiu.
3.2 Danh gia tinh hinh ban ban LVS Ddng Nai til' tap hgp anh vi6n tham
Ban dd pban bd gia In chi sd kbac biet ban ban NDDI khu vuc nghien ciiu dugc thg hien Irong Hinh 8. Kgt qua cho thky, khu vuc cd NDDI tir <
0 - 0,2, tap trung cbii yeu d khu vuc rimg ngap man Can Gid. Khu virc cd miie kbd ban nang va rat nang (vdi gia Iri NDDI d miie > 0,4) xukt hien phan ldn d khu vue dat san xuat ndng ngbiep thuge phia Bac va tmng tam viing nghien cuu.
Tbeo dd dien ticb kbu vuc cd miic dp ban ban nang (tuong irng vdi gia tri chi so NDDI lir 0,4 dgn 0,6) chiem ti le cao nhat vao nam 2016 vdi 40,2%, kbu vuc cd muc dp ban rat nang chiem cao nhat d eac nam 2019, 2016 vdi 44,4% va 37,9% trong Ihdi doan ngbien ciiu. Han ban nam 2016 nghiem trpng bon cac nam cdn Iai, dugc the hien tbdng qua dien tich miic dp ban nang va rat nang trong ban dd nam 2016 dat eao nhat, kdt qua nay phu hpp vdi cac bao cao ciia dia phuong, theo ghi nhan lim lupng nude sdng Ddng Nai dat tbap nbdt vao nam 2016 trong giai doan 2014 - 2017.
Dgn nam 2018, muc dp ban ban cd xu budng giam, ty le dien tich cd muc ban rkt nang chi chigm 14,8%, nbung cd xu hudng lang trd lai
d miic bao dpng vao nam 2019, cbo lii^y han ban kbu vuc ngbien ciiu dien bign pi';.:--' ^'-^P '^^
cd xu budng gia lang mirc dp. Ket qua nhan dupe ciing cbo thay vai trd quan trgng cua lop phil thuc vat trong giam nguy co ban ban, d nhirng vimg duge pbii xanb bdi dat rimg it cbiu anb hirdng bdi ban ban, ngoai ra ygu td dia hinb cung cd nhiing tac dpng it nhigu den mirc kbd ban, vimg ven bidn phia Ddng ed miic dp khd ban cao hon so vdi vimg niii cao.
Hinh 8; Phdn vung muc dp hgn hdn LVS Dong Nai tii- 2014 din 2019
Bang 2: Thong Nam
2014 2015 2016 2017 2018 2019
Khong han 8,3 8,3 7,4 8,3 10,8
6,8
te ty Ie dien tich (%) cac muc do han han khu vuc nghien cii'u Han nhe
8,6 9,4 3,2 9,8 16.2 3,5
Han trung binh 20,6 17,2 11,3 14,5 27,9 13,4
Han nang 34,1 30,0 40,2 31,4 30,3 31,9
Han rfit nang 28,4 35,1 37,9 36,0 14,8 44.4
TAP CHI KHOA HOC VA CONG NGHE THUY LOI SO 58 - 2020
KHOA HOC • » { . l } [ c r T a ! T M i
4. KET LUAN VA KIEN NGHI
Chidm gkn dai bd phan mign Ddng Nam Bp, LVS Ddng Nai cd mot vi tri kha quan trpng ve mat tai nguyen nude, ehinh vi tbg viec giam sal ban ban viing nghign ciiu la eo sd quan trgng cho cae quy boach tdng tbg nguon nude luu vuc.
Ket qua phan loai cho thay, dign tien ban ban khu vuc nghien ciiu kha phiic tap va cd xu hudng gia tang cimg vdi su thay ddi ciia khi hau, ban nam 2016 dupe danh gia la nang ne nhat trong thai doan quan sat tir 2014 dgn 2019. Theo dd yeu td dia hinh, ldp pbii thue vat ed tac dgng rat ldn ddn miic dp ban ban nang, nhe.
Kgt qua nghien da ehirng minb ndn lang GEE la mdt cdng cu bieu qua va nbanb ehdng dg giam sat han ban LVS Ddng Nai, dua tren ket qua danh gia su phii bgp giua kdt qua pban loai eac chi sd han ban Iren GEE vdi kel qua quan sal true quan lir Google Earth dat dugc la 100,0%. Trong tuong lai, c^n thidt ling dung cbo giam sal ban d quy md kbu vuc rdng ban, ke ca d t§in qudc gia nham cd cai nhin toan dien vd dien lidn thien tai ban ban trudc thach thiic ciia bidn ddi khi bau, tir do c6 nbOng bien pbii bgp iing vdi tirng vimg, dia phuong.
TAI LIEU THAM KHAO
[1] Charat, M., Wattanakij, N., Kamcbai, T., Mongkolsawat, K, Chuyakbai, D. (2009).
Exploration of Spalio-Tenporal Drought Patterns using Satellite-Derived Indice for Crop Management in Northeastem Thailand. Asian association on remote sensmg. Beijing, China.
[2] Google Earth Engine API, 2016. Introduction, ngay truy cap 22/07/2019. Dja chi https;//developers, goo gle.com/earth-engine.
[3] Rahimi, L., Sharifian, H. (2014). Monitoring drought based on SPI, deciles, and normal. In proceeding of the first national congress on challenges of water resources and agriculture.
Khorasgan Azad University, Isfahan, 25-31.
[4] Td Van Tudng (2009). Quy hoach tai nguygn nuac luu vue sdng Ddng Nai. Du an cap Bd - Vien Quy hoach Tbiiy Ipi mign Nam.
[5] Vien Quy boach Thuy Igi mign Nam (2013). Quy hoach long the thuy lpi viing Ddng Nam Bp thich ling vdi bien ddi kbi hau, nude bien dang. Du an quy hoach cap Bd.
[6] Vien Khoa hpc Tbuy lgi miln Nam (2015). Ra soat quy hoaeh tbiiy lgi viing Ddng Nam Bd pbuc vu tai eau triic nganh ndng nghiep. Du an quy boach cap Bp.
TAP CHf KHOA HOC VA C O N G NGHE T H O Y L O I S 6 58 - 2020 53
