Soil Water Modeling for Making Decision in Cultivation Using Geographic Information System

摘要

This object of study was to modulate soil water content from water balance model by using GIS. The study area was cultivated area of Phitsanulok province, Thailand. The spatial resolution of grid data used in the analysis was 40~*40 meter and temporal resolution was weekly accounted for 52 weeks. The results showed that average annual rainfall, average annual evaporation pan, average annual runoff, and average annual deep percolation were 2,094,2,540, 516, and 150 m~3/rai, respectively. These variables were later calculated together to determine soil water content. The computation showed that average annual soil water content was 97 m~3/rai. Soil water content was accumulated starting from week 18th to week 3rd of the next year and maximized in week 37th (75.5m~3/rai). The soil water-based suitable week for cultivating 3 crop types; vegetable, field crop and rice; appeared from week 20th to week 47th (28 weeks), week 20th to week 45th (25 weeks), and week 23rd to week 42nd (19 weeks), respectively. However, the suitable areas were decreased when these areas were considered on a combination criteria between soil water content suitability and soil property suitability.