Multi-temporal and Multi-resolution Analysis of Normalized Differential Vegetation Index and Rainfall towards Global Irrigated Area Mapping 1. Introduction The main objective of this study is to use multi-temporal Normalized Difference Vegetation Index (NDVI) and rainfall data for improving the estimation of actual irrigated area in global scale. Firstly, this study started to focus on multi-temporal NDVI of irrigated and non-irrigated crops at local scale. Rice, the most important cereal crop, has been focused and analyzed as a pilot crop. Suphanburi province in Thailand is suitable to be the pilot area because the dominant of agriculture activities in this area is rice cultivation with and without irrigation system. The non-irrigated area observed here is located in Don Chedi district middle Suphanburi. The LANDSAT image (08 Jan 2002: False Color Composite) shown very large and dry area out of planting season (light brown color in the image, Figure 3). NDVI time series over 3 years ( ) were analyzed at various type of rice fields continuously. The fluctuation of NDVI value in time series of irrigated and non- irrigated rice cultivation that was defined based on field survey were discussed together with rainfall which has its peak at the beginning of September. Daroonwan Kamthonkiat 1, Dr.Honda Kiyoshi 2, Prof. Vilas Wuvongse 3 Dr. Nitin K. Tripathi 4, Dr.Turral Hugh 5 1,2,3,4 School of Advanced Technologies, Asian Institute of Technology, P.O. Box 4, Klongluang, Pathumthani 12120, Thailand International Water Management Institute (IWMI), Columbo, Sri Lanka. Figure 6 NDVI fluctuation over 3 years of non-irrigated rice (cultivated 1 times/year) Non-irrigated rice is planted only one time a year, starting around the middle to the end of August till the end of December to the middle of January. After harvested in January, farmers always leave their field blank or change to pasture and will cultivate rice again in the next August. Figure 4 and Figure 5 shown some changes in the same non-irrigated rice field; small grass appeared in the field after rainy season started at the end of May. NDVI Range: to 0.45 Number of peak per year: Irrigated Rice In irrigated area, farmers can start planting anytime because of water fertility. It is very difficult to define exactly crop calendar in this area. The observed sites of irrigated rice in this study have different planting patterns including with number of crops planting per year (two/three crops a year) and cultivation pattern (homogeneous/heterogeneous). The maximum cultivation in the areas shown in Figure 7-9 is 2 times a year, the second half-year crop always has lower density comparing to the planting in the first half of year. Figure 7 Irrigated rice, large continuous field. (Map: E, N) Figure 8 Irrigated rice, large continuous field (26 th April 2003) Figure 10 NDVI fluctuation over 3 years of irrigated rice, cultivated 2 times/year (Large continuous field) Figure 9 Irrigated rice, large continuous field (20 th June 2003) NDVI Range: to 0.82 Number of peak per year: 2 Note: PR = Peak of Rainfall. 4. Analysis Results 4.1 Rainfed Rice 2. Study Area Irrigated Zone (Green vector) Boundary of Suphanbri (Blue vector) Suphanburi is located 169 kilometers from Bangkok, occupying an area of 5,358 square kilometers (Figure 1). Suphanburi has low and flat terrain, 3-10 meters above mean sea level, except in the west where it approaches the mountains of Kanchanaburi and Uthai Thani. Figure 1 Suphanburi province: Boundary and Irrigation Zone Figure 3 Non-irrigated area (Map: E, N) Figure 4 Non-irrigated/Rainfed rice field, dry season (26 th April 2003) Figure 5 Non-irrigated/Rainfed rice field (20 th June 2003) 3. Analysis Steps LS Time series: SPOT VI (LMF Processed) Ground truth Data Masking Forest, Water body and Urban areas out of the images Transferring Classifying Map of Irrigated and Non-irrigated rice cultivation Accuracy checking Accepted Apply criteria to other areas Define Irrigated and Non- irrigated rice field, etc., Referencing NDVI fluctuation pattern in time series Statistic analyzing Not accepted Adjusting/Correcting Rainfall Data Relationship Identifying Criteria or patterns of Irrigated and Non-irrigated rice cultivation Criteria setting Figure 2 Analysis steps PR PR Figure 11 shown irrigated rice cultivation 3 times per year in northern Suphanburi where most of agriculture area is under irrigated. With a good irrigation system in this area, farmers can continue planting 3 times per year. However the planting unit is smaller than a pixel (around 1 square kilometer) of SPOT VI, one pixel contains many agriculture activities. Therefore the shape of the curve in Figure 14 is not a big wave like Figure 10 because cropping patterns is heterogeneous. Figure 11 Irrigate rice 3 crops per year, discontinuous/small patchy fields (Map: E, N). Figure 12 Irrigate rice 3 crops per year, ripening stages (26 th April 2003) Figure 13 Irrigate rice 3 crops per year, heading stage (20 th June 2003) PR Figure 14 NDVI fluctuation over 3 years of irrigated rice, cultivated 3 times/year PR NDVI Range:-0.26 to 0.57 Number of peak per year: 3 5. Summary  Irrigated rice is cultivated 2-3 crops per years with certain periods of sowing but difficult to indicate the exact date. Farmers can start planting anytime because of water fertility in this area.  The first crop of irrigated rice 2 crops per year is always higher peak of NDVI than the latter crops while the NDVI peak of 2 crops per year is higher as twice as 3 crops per year.  NDVI fluctuation of irrigated rice shown low correlation with peak of rainfall while non-irrigated shown much higher correlation. The pattern of NDVI fluctuation in time series at various type of rice cultivation and its relationship of rainfall will be summarized as a set of criteria. This developed criteria will be used for mapping actual irrigated area in the study area