Land use change and rice crop monitoring in the Mekong Delta, Vietnam

International Meeting on Land Use and Emissions in South/Southeast Asia Ho Chi Minh City, 17-19 October 2016 Land use change and rice crop monitoring in the Mekong Delta, Vietnam Nguyen Lam-Dao, Phung Hoang-Phi VN Southern Satellite Technology Application Center (STAC) VNSC VAST Thuy Le-Toan Centre d'etudes Spatiales de la BIOsphère (CESBIO), France Viet Pham-Bach, Mai Thy Pham-Thi GIS and Remote Sensing Research Center (GIRS) HCMIRG VAST

Contents 1. Introduction 2. Land use change in the Mekong Delta, Vietnam 3. Rice crop monitoring 4. Discussion 2

INTRODUCTION Source: Parry, M.L. et al., 2007 Mekong Delta (Source: GSO, 2015): Area: 40,576 Km 2 (1/8) Population: 17.590 M (~1/5) MD accounts for more than half (25.7 / 45.2 Mt) of the country s rice production (>1/2) 2012 3 The Mekong Delta, South of Vietnam is one of the most affected regions in the world by global warming.

LAND USE CHANGE - Introduction State-level project (2013-2016): Utilisation of satellite imagery VNREDSat-1 and equivalent for monitoring agricultural land cover/land use of the Mekong Delta, Vietnam in the context of socio-economic development and climate change. 4 VNREDSat-1 (7 scenes) and Landsat data used

LAND USE CHANGE - Introduction Landsat 5, 21/2/1996 Landsat 7, 20/01/2005 5 Landsat 8, 27/2/2014

LAND USE CHANGE - Introduction Field work: collecting 1.089 samples, 70% for training data; 30% for accuracy assessment. 6 1 st field trip (6-16/1/2014) 2 nd field trip (11-17/4/2014)

LAND USE CHANGE Results from Landsat 1996 2005 7 Overall Acc.: 80 % Kappa: 0,75 2014

LAND USE CHANGE - Results from Landsat 1996-2005 2005-2014 1996-2014 8

LAND USE CHANGE - Results from Landsat Agricultural land use was changed in the period of 1996 2005 2014; Rice and aquaculture land fast increased during the period of 1996 2005; 9

LAND USE CHANGE Results from VNREDSat-1 LU change Rice in Thoai Son, An Giang (1998-2015) LU change Fruit tree in Cai Be, Tien Giang (1995-2015) 10

LAND USE CHANGE - Results from VNREDSat-1 LU change Forest in Tram Chim, Dong thap (1995-2015) LU change Aquaculture in Vinh Chau, Soc Trang (1996-2015) 11

12 Wetland map of Lower Mekong basin (2015)

RICE CROP MONITORING - Introduction Previous projects 1. Rice & Mangrove monitoring in Southern Vietnam - RICEMAN TerraSAR-X & ENVISAT-ASAR data, 2010-2011 Rice mapping: Single-date mapping algorithm Yield estimation model: Statistical model. 2. Rice crop monitoring using new generation synthetic aperture radar (SAR) imagery ENVISAT-ASAR data, 2007-2008 Rice mapping: Single-date mapping algorithm Yield estimation model: Statistical model. 3. Utilisation of SAR data for rice crop monitoring ERS2-SAR data, 1997-1998 Rice mapping: Temporal change measurement Yield estimation model: Agro-meteorological model (AMM). 4. Other projects in the Mekong and Red River Delta Ongoing projects 1. SAFE/APRSAF (2013-2016) &Asia-RiCE 2. GeoRice (2015-2017) Data used: COSMO-SkyMed, RADARSAT-2, ALOS-2, Sentinel-1. 13

Introduction Rice cropping system Rice season Single rice crop Traditional rice (rain-fed) Sowing-transplanting period Vegetative stage Double rice crop SA AW (rain-fed) WS SA (irrigated) Triple rice crop WS SA - AW Main rice-based cropping systems in the MD Reproductive stage Ripening stage Pictures of rice growing stages Rice crop Planting Harvesting English name Local name Winter Spring (WS) Dong Xuan Nov./Dec. Mar./Apr. Summer Autumn (SA) He Thu Apr./May Jul./Aug. Rainy season Thu Dong (Autumn Winter-AW) Jul./Sep. Oct./Dec. Mua (Traditional rice) Jul./Sep. Nov./Jan. 14 Main rice seasons in An Giang province, Mekong Delta

Introduction Objectives: To evaluate the use of SAR data in rice mapping, monitoring and yield estimation, towards an operational system for rice crop inventory in the Mekong Delta, Vietnam. 24/03/07 17/02/2007 15

Ongoing research works Asia-RiCE&SAFE, GEORice Technical Demonstrator Site Mekong Delta, VN An Giang province, Mekong Delta, Vietnam Geographic coordinates: UL: 10 58'47.38"N, 104 44'39.51"E, UR:10 58'35.84"N, 105 40'12.84"E LR: 10 05'24.65"N, 105 40'15.36"E, LL: 10 05'45.13"N, 104 44'23.41"E 16

Methods SAR data Ground-truth data σ o of sampling fields Classification method Thresholding 24/03/07 In situ rice yield Regression analysis Regression equation Classification maps Asia-RiCE Target Agricultural Products Estimated rice yield distribution maps Accuracy assessment Reference data Ground data Estimated rice production (P5) Rice/Non-rice maps (P1) 17

Data set SAR data received: COSMO-SkyMed: Aug 2013 Feb 2014 RADARSAT-2: Aug 2013 Now Sentinel-1: Aug 2014 Now ALOS-2: Nov 2014 Now Rice crops monitored: 2013: AW; 2014-2016: WS, SA, AW. 18 COSMO-SkyMed data: - Band: X - Polarisation: HH&VV - Resolution: 20 m (StripMap PINGPONG) RADARSAT-2 data: - Band: C - Polarisation: VV&VH - Resolution: 10 m (Wide Fine) Sentinel-1 data: - Band: C - Polarisation: VV&VH - Resolution: 20 m (SW) ALOS-2 data: - Band: L - Polarisation: HH&HV - Resolution: 50 m (WS) & 12.5 m (Fine) Sentinel-1 6 October 2014

General parameters 19 Guidelines for ground data collection for rice monitoring experiments using radar data (Thuy Le Toan) Leaf parameters (optional) Panicle parameters Rice parameters Description Equipment Paddy variety Data set: CSK & RSAT-2, Ex.: IR 2013-2014 64 Method of planting direct sowing/ transplanting Sowing date Transplanting date (if transplanting) Date of harvesting Yield (kg/m 2 ) date of direct sowing or number of days after sowing date of transplantation or the number of days after transplantation if the rice has been harvested if the rice have been harvested Seeding, transplanting, tillering, Plant phenological stage heading, flowering, ripening, ready to harvest Water layer height (cm) if fields are flooded stick Plant height (cm) above water layer tape Wet weight per m 2 (g) Dry weight per m 2 (g) Number of leaves per stem Leaf length (cm) Leaf width (cm) Moist and dry biomass of panicles per m 2 above water biomass (moist weight by m 2 ) cut all plants from defined areas (min 50 x 50 cm) objective is to measure the dry Oven dry (105 biomass per m 2 during 24 hours) Few samples for each sortie -Photo -Xerox copy of leaves

15.0 Data set: CSK, 2013-2014 10.0 HH/VV (db) 5.0 0.0 CSK_PP_20130819 CSK_PP_20130904 CSK_PP_20130920 CSK_PP_20131006 CSK_PP_20131014 CSK_PP_20131030 HH/VV (db) 20 TSX (2010-11) -5.0 CSK_PP_20131107 CSK_PP_20131115 CSK (2013) -10.0 0 10 20 30 40 50 60 70 80 90 100 110 Days Ngày after sau sowing khi sạ 14.0 12.0 10.0 8.0 6.0 TĐ2010_CM 4.0 ĐX2011_CM 2.0 ĐX2011_TL 0.0-2.0-4.0-6.0 0 10 20 30 40 50 60 70 80 90 100 110 Số ngày sau sạ/cấy HH/VV (db) ASAR APP(2007) 10 8 6 4 2 0-2 -4 0 20 40 60 80 100 Days after sowing WS SA AW WS0 SA0 AW0

Data set: CSK, 2013-2014 AW 2013 crop from CSK PP (20 Sep and 14 Oct 2013) Overall acc.: 89% Kappa: 0.77 21 WS 2014 crop from CSK PP (11 Feb 2014)

Estimated area Agency data Percentage error Commune Name (ha) (ha) (%) An Bình 2,274 2,287-0.6 Bình Thành 2,313 2,325-0.5 Định Mỹ 3,178 2,965 7.2 Định Thành 2,613 2,454 6.5 Mỹ Phú Đông 2,676 2,740-2.3 Phú Thuận 1,131 835 35.4 Thoại Giang 2,203 2,248-2.0 Núi Sập 455 442 2.9 Óc Eo 522 592-11.8 Phú Hòa 294 310-5.2 Vĩnh Khánh 2,500 2,810-11.0 Vĩnh Phú 3,069 3,153-2.7 Vĩnh Trạch 1,269 1,424-10.9 Vĩnh Chánh 2,357 1,996 18.1 Vọng Đông 2,601 2,096 24.1 Total 29,455 28,677 2.7 22 Data set: CSK, 2013-2014 Agency data (ha) 3,500 3,000 2,500 2,000 1,500 1,000 500 Accuracy assessment of rice/non-rice mapping method for AW 2013 crop in Thoai Son district using two-date CSK data (20 Sep and 14 Oct) based on statistical data 0 y = 0.9639x + 18.956 R² = 0.9511 0 500 1,000 1,500 2,000 2,500 3,000 3,500 Estimated area (ha)

Data set: CSK, 2013-2014 23 AW 2007 crop from ASAR APP AW 2010 crop from ASAR APP AW 2013 crop from CSK PP

Data set: CSK, 2013-2014 Y Ra = 6.66696 0.483956*Ra 1 0.284715*Ra 2 + 0.641779*Ra 3 r 2 = 0.646, se y = 0.5 ton/ha Where: A distribution map of estimated rice yield in AW Y Ra : rice yield (ton/ha), 2013 crop at Chau Thanh and Thoai Son Ra 1 : polarisation ratio of first date image, districts using three-date polarisation ratios: Ra 2 : polarisation ratio of second date image, CSK 04 Sep 2013 Ra 3 : polarisation ratio of third date image, r 2 : the coefficient of determination, CSK 22 Oct 2013 se y : the standard error for the y estimate. CSK 07 Nov 2013 24

Commune name 25 Estimated production (ton) Agency data (ton) Percentage error (%) Vinh Thanh 11,655 11,382 2.4 Vinh Nhuan 19,097 18,640 2.5 Vinh Loi 12,620 13,229-4.6 Hoa Binh Thanh 13,539 14,797-8.5 TT. An Chau 2,744 3,472-21.0 Binh Hoa 7,076 6,852 3.3 Vinh Binh 14,220 12,565 13.2 Vinh Hanh 14,653 15,188-3.5 Can Dang 12,688 12,973-2.2 An Hoa 3,048 2,679 13.8 Binh Thanh 14,028 13,225 6.1 Dinh My 19,492 17,668 10.3 Dinh Thanh 14,951 14,157 5.6 My Phu Dong 15,114 18,056-16.3 Phu Thuan 4,961 5,684-12.7 Thoai Giang 13,865 13,025 6.4 TT. Nui Sap 2,905 2,495 16.4 TT. Oc Eo 3,390 3,297 2.8 TT. Phu Hoa 1,436 1,614-11.0 Vinh Khanh 14,432 16,357-11.8 Vinh Phu 18,541 19,735-6.1 Vinh Trach 7,404 8,975-17.5 Vinh Chanh 11,538 12,333-6.4 Vong Dong 16,158 12,551 28.7 Total 269,555 270,949-0.5 Estimated production (ton) 25000 20000 15000 10000 5000 0 Data set: CSK, 2013-2014 y = 0.9788x + 181.2 R² = 0.9429 0 5000 10000 15000 20000 25000 Agency data (ton) Chau Thanh Thoai Son Accuracy assessment of estimated production for AW 2013 crop at Chau Thanh and Thoai Son district using three-date polarisation ratios (HH/VV) of CSK (04 Sep, 22 Oct, 07 Nov 2013) based on statistical data

Data set: RADARSAT-2, 2013-2014 26 RADARSAT-2 data: - Band: C - Polarisation: VV&VH - Resolution: 10 m (Wide Fine)

Data set: RADARSAT-2, 2013-2014 AW 2013 crop from RADARSAT-2 (29 Aug & 09 Nov 2013) AW 2013 crop from CSK PP (20 Sep & 14 Oct 2013) 27

Data set: RADARSAT-2, 2013-2014 Accuracy assessment of rice/non-rice mapping method for AW 2013 crop in Thoai Son district using two-date RADARSAT-2 data (29 Aug & 9 Nov 2013) based on statistical data Commune name Estimated area (ha) Agency data (ha) Percentage error (%) RADARSAT-2, Thoai Son District - AW2013 An Binh 2,422 2,287 5.9 Binh Thanh 2,316 2,325-0.4 Đinh My 3,274 2,965 10.4 Đinh Thanh 2,743 2,454 11.8 My Phu Đong 2,828 2,740 3.2 Phu Thuan 326 835-61.0 Tay Phu 1,936 2,386-18.9 Thoai Giang 2,349 2,248 4.5 Nui Sap 481 442 8.8 Oc Eo 507 592-14.4 Phu Hoa 99 310-68.1 Vinh Khanh 2,545 2,810-9.4 Vinh Phu 3,213 3,153 1.9 Vĩnh Trach 1,303 1,424-8.5 Vinh Chanh 1,530 1,996-23.3 Vong Đong 2,620 2,096 25.0 Vong The 2,383 2,300 3.6 Total 32,875 33,363-1.5 28 Agency data (ha) 3,500 3,000 2,500 2,000 1,500 1,000 500 0 y = 0.8439x + 330.44 R² = 0.9324 0 500 1,000 1,500 2,000 2,500 3,000 3,500 Estimated area (ha)

Data set: RADARSAT-2, 2016 District Agency data (ha) Estimated area (ha) Difference percentage (%) An Phu 13,640 13,679 0.3 Cho Moi 13,304 14,784 11.1 Chau Phu 34,940 30,274-13.4 Chau Thanh 28,630 26,857-6.2 Phu Tan 22,151 23,382 5.6 Tinh Bien 16,288 21,000 28.9 Chau Doc 6,315 6,218-1.5 Long Xuyen 4,518 3,427-24.1 Thoai Son 38,882 37,236-4.2 Tri Ton 42,210 38,042-9.9 Tan Chau 9,321 9,874 5.9 Total 230,199 224,774-2.4 50,000 40,000 R² = 0.97 Estimated area (ha) 30,000 20,000 10,000 29 SA 2016 crop from RADARSAT-2 (15 Apr, 09 May, 02 Jun, 26Jun, 20 Jul & 13 Aug) 0 0 10,000 20,000 30,000 40,000 50,000 Agency data (ha)

Data set: RADARSAT-2, 2013-2014 A distribution map of estimated rice yield in AW 2013 crop at Chau Thanh and Thoai Son district using three-date VH polarisation: RADARSAT-2 29 Aug 2013 RADARSAT-2 16 Oct 2013 RADARSAT-2 09 Nov 2013 A distribution map of estimated rice yield in WS 2014 crop at Chau Thanh and Thoai Son district using three-date VH polarisation: RADARSAT-2 27 Dec 2013 RADARSAT-2 20 Jan 2014 RADARSAT-2 13 Feb 2014 30

Data set: RADARSAT-2, 2013-2014 31 A distribution map of estimated rice yield of An Giang in AW 2013 crop using RADARSAT-2 data

Data set: RADARSAT-2, 2016 250,000 R² = 0.97 A distribution map of estimated rice yield of An Giang in SA 2016 crop using RADARSAT-2 data Estimated production (ton) 200,000 150,000 100,000 50,000 0 0 50,000 100,000 150,000 200,000 250,000 Agency data (ton) District Agency data (ton) Estimated production (ton) Difference percentage (%) 32 An Phú 73,656 68,296-7.3 Chợ Mới 77,296 77,720 0.5 Châu Phú 201,254 166,581-17.2 Châu Thành 166,054 148,199-10.8 Phú Tân 134,457 132,012-1.8 Tịnh Biên 89,584 111,364 24.3 Châu Đốc 37,890 32,798-13.4 Long Xuyên 29,503 16,456-44.2 Thoại Sơn 233,292 202,704-13.1 Tri Tôn 229,200 204,518-10.8 Tân Châu 54,994 53,099-3.4 Total 1,325,946 1,213,746-8.5

Data set: ALOS-2, 2015 ALOS-2 data: - Band: L - Polarisation: HH&HV - Resolution: 50 m (WS) & 12.5 m (Fine) SA 2015 crop (using 4-date ALOS-2 HH image, 10/04, 22/05, 03/07 & 14/08/2015) 33

Data set: Sentinel-1, 2015 Sentinel-1 data: - Band: C - Polarisation: VV&VH - Resolution: 20 m (SW) Overall acc.: 93% Kappa: 0.97 WS 2015 crop (using 4-date S-1 image, 17/12/2014, 10/01, 27/02 & 04/04/2015) 34

Data set: Sentinel-1, 2016 District Agency data (ha) Estimated area (ha) Difference percentage (%) An Phu 13,640 10,208-25.2 Cho Moi 13,304 11,351-14.7 Chau Phu 34,940 32,294-7.6 Chau Thanh 28,630 25,465-11.1 Phu Tan 22,151 23,329 5.3 Tinh Bien 16,288 22,137 35.9 Chau Doc 6,315 6,834 8.2 Long Xuyen 4,518 3,819-15.5 Thoai Son 38,882 35,387-9.0 Tri Ton 42,210 41,661-1.3 Tan Chau 9,321 7,937-14.9 Total 230,199 224,774-2.4 50,000 40,000 R² = 0.9583 Estimated area (ha) 30,000 20,000 SA 2016 crop (using S-1 images) 10,000 35 0 0 10,000 20,000 30,000 40,000 50,000 Agency data (ha)

Data set: Sentinel-1, 2016 SA 2016 crop (using S-1 images) SA 2016 crop (using R-2 images) 36

Data set: Sentinel-1, 2015-2016 at regional scale Map of WS Rice 2015 Map of WS Rice 2016 37 Reduced area in 2016 caused by shortage of water and saline water intrusion

Data set: Sentinel-1, 2015-2016 at regional scale 38 Rice area of Mekong Delta (1000 ha) 1800 1600 1400 1200 1000 800 600 400 200 0 1990 1995 2000 2005 2010 2015 2020 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 Year WS Rice area (1000 ha) 1995 1035.7 1996 1152.2 1997 1254.0 1998 1349.0 1999 1448.5 2000 1520.6 2001 1537.6 2002 1513.7 2003 1498.9 2004 1467.1 2005 1478.7 2006 1500.3 2007 1506.5 2008 1526.5 2009 1548.8 2010 1564.6 2011 1567.5 2012 1580.2 2013 1564.4 2014 1562.7 2015 1562.3 2016 1383.3

Discussion Extend the target area and increase the observation frequency; Validation activities for the rice crop estimation; Number of fields: 100 rice fields and 30 non-rice points for each of the 3 regions Region 1: An Giang; Kien Giang; Can Tho Region 2: Dong Thap; Long An; Tien Giang Region 3: Soc Trang; Tra Vinh, Vinh Long Frequency: beginning, middle and end of season (3 times per rice season) Capacity building activities for end user. 39

VNREDSat-1 LOTUSAT-1 2013 2019 40