Spatial and Temporal Distribution of Water Requirement by Major Crops in Chainat Province, Thailand

Water plays an important role in supporting agriculture. Accurate assessment of water requirements in terms of time, quantity, and space is critical for agriculture and food production sustainability. The objective of this study was to assess the spatial and temporal distribution of water requirements for major crops in Chainat Province, Thailand and identify the water shortage hotspots using a geographic information system (GIS). The spatial model was used to identify the crops plantation. Land use is divided into eight categories: rice, sugarcane, cassava, other agriculture, urban and built-up, forest, water bodies, and other lands. The result shows that the main land use in 2019 is for agriculture, accounting for about 85% of the total area. The main crops are rice, sugarcane, and cassava, accounting for 59%, 14%, and 8% of the total area, respectively. The model calculated the water requirements for those three main crops using the crop evapotranspiration, monthly climate data, and the existing water irrigation areas. The results were presented in a grid cell map of monthly crop water demand. The average water requirements of rice, sugarcane, and cassava are 9,675, 10,577 and 7,979 m³/ha, respectively. The water deficit areas for rice cultivation were Nong Mamong, Wat Sing, Hankha, and Wat Sing districts during February to March. In July, Noen Kham was found as the water deficit area for cassava and sugarcane cultivation. For the irrigation water requirement per year, rice requires around 5,612 m³/ha/two crop cycles, followed by sugarcane at about 4,322 m³/ha/crop cycle and cassava around 2,186 m³/ha/crop cycle. The substitution of rice cultivation by sugarcane or cassava in the water deficit areas could save water resources by about 1,289 and 3,426 m³/ha, respectively.