Author : Generalao, Irvin C.

Summary : A study of modeling and spatial interpolation of potential evapotranspiration in Mindanao was conducted to: evaluate the reliability of using modified Penman to compute potential evapotranspiration (PET), develop a model on daily PET data in each station, evaluate different Geographic Information Systems (GIS) interpolation techniques in estimating dekadal PET, and generate monthly PET maps of Mindanao. Generation of monthly PET maps for different climatic types in Mindanao was done using GIS following inverse distance interpolation method. A summary of mean monthly PET averaged over ten years for each weather station was also generated. It was found out that on the average the lowest PET of 3.88 mm/day is estimated for the month of December. PET increases with time until it reaches its peak of 5.13 mm/day for the month of April. Monthly PET shows an increasing trend from December. During the month of December, low PET values (3.5-4.0 mm/day) were estimated for the whole of Mindanao except is some isolated regions in Davao and Zamboanga Cities. Estimated PET values tend to decrease as elevation increased, such as in Marawi and Malaybalay During the months of April and May, higher PET values (5-6 mm/day) were computed for the eastern part of Mindanao. The observed decreased in PET with decreasing longitude could possibly be due to trade winds from the Pacific Ocean. PET maps showed that there are four existing groupings, indicating that there are no pronounced wet and dry seasons in Mindanao.