Water Infiltration Into Soil and ITS Effect to Surface Runoff in Subdistrict of Kasihan, Bantul Regency

摘要

Water infiltration into the soil is one of the important processes in hydrology, because its effect on water quantity that could infiltrate into the soil. Decreasing of infiltration rate can make increasement of surface runoff and flood discharge in a region. In the other hand, decreasing of infiltration rate cause decreasement of groundwater input into aquifer. This study was conducted to (1) measure and analyze the behavior of water infiltration into the soil, (2) analyze the influencing factors to the quantity of surface runoff in the researched region, and (3) analyze the role of infiltration rate to the quantity of surface runoff in the researched region. In achieving them, it was conducted infiltration measurement using double ring infiltrometer and it was analyzed the results using Horton Model. Evapotranspiration estimation was determined using Thornthwaite Method and the quantity of surface runoff was determined using the equation of water balance. The study results showed that the highest rate of soil infiltration was occurred in land use of farm, and then rice field and residential. Viewed from the kinds of soil, the regosol had higher constant infiltration rate than grumusol, and so it was also with the initial infiltration rate. The volume of evapotranspiration in the researched region was 4,705,455.393 m~3/month and infiltration volume was 3,357,158.400 m~3/month. By having volume of rain of 5,997,747.4 m~3/month, the ground surface in the subdistrict of Kasihan could still absorb all of the rainfall. So, artificial recharge can be applied as groundwater conservation model.