Impact of land-use development on the water balance and flow regime of the Chi River basin, Thailand

To analyze the relationships between land-use changes and water balance and flow regimes in the Chi River basin, Thailand, we used historical data of annual rainfall and seasonal and annual flow from 1951 to 2003, which corresponded to land-use changes derived from Landsat imagery acquired between 1973 and 2003. We found that during the past 52 years the forested area in the Chi River basin has declined by 20%, whereas agricultural areas, paddy fields, and urban areas have expanded rapidly. Upland agriculture (maize, cassava) fluctuated from more than 36% in 1973 to less than 20% in 2000, with a notable drop in cassava cultivation. In contrast, sugarcane cultivation increased during the past 5 years because of increased market demands, and rice fields were expanded from 20% to 42% in 2000. Although annual rainfall in the Chi River basin has tended to decrease, we found an insignificant relationship between land-use changes, in particular, the depletion of forested areas, and annual rainfall. We also found an insignificant relationship between the water budget component and land-use changes, with a rather small effect on seasonal and annual flows of the basin.