THAI FOREST ECOLOGICAL RESEARCH JOURNAL
The study on Hydrological Characteristics of Mae Klong Head Watershed in response to land use changes was conducted at Mae Klong watershed, Kanchanaburi province. The meteorological and hydrological data during 1994-2014 were identified and interpreted. The result found that average annual rainfall at Mae Klong watershed was 1,679.3 mm and it provided streamflow of 552ม512.50 m3/km2 or 552.5 mm. Potential streamflow of the watershed was 33.2% of rainfall amount; 73.5% was streamflow during wet period and 26.5 % was streamflow during dry period. The response of hydrological characteristics to land use change in the study period were divided in 3 phases; 1994-1999, 2000-2005 and 2006-2011. During this period, forest area of the watershed tended to increase. There was 4.25% of forest area in 1992 or the first phase, and increased to be 92.48% and 97.27% in 2000 and 2008, respectively. The annual streamflow and streamflow during wet period tended to decrease from the first to the third phase, while those of dry period trended to increase. According to flow characteristics, it was found that 50% flow intervals tended to increase; they were 72 days at the first phase, 95 and 96 days in the second phase and the third phase, respectively. Increased forest area led to decrements in 5% and 1% intervals of the streamflow. The succession watershed provided stream flow of 188,831.25 m3/km2 or at level height of 245.48 mm. Potential streamflow of the watershed was 15.22% of rainfall amount. It delivered suspended sediment 25,547.14 kg/yr or 7.13 kg/rai/yr. The approximated soil water storage capacity of a 1.5 m soil depth ranges from 259 mm to 343 mm with average of 289.97 mm. They were harmonious to those of the soil in the mixed deciduous forest which is the local forest in the area.
Keywords: streamflow, land use change, water balance, mixed deciduous forest, secondary forest, Mae Klong watershed, research station