Assessment of Water Budget and Demand for Agriculture in Ban Klang Subdistrict, Lom Sak District, Phetchabun Province

Abstract

The purpose of this study was to assess the water budget and demand for agricultural areas in Ban Klang subdistrict, Lom Sak district, Phetchabun province, and along with suggesting guidelines for adjusting the planting pattern in accordance with the amount of water budget. The methods of this study consist of estimated water budget from runoff volume (R) by equation R = PCA using 30-year average monthly rainfall data (P), runoff coefficient from land use data (C) and the study area size (A). Then, the plant water demand (ET) was analyzed from the equation ET = Kc * ETP consisted of the plant water use coefficient (Kc) and the evaporative potential of the plant or reference plant water use (ETP). Then, compare the cost of water budget with the amount of monthly water demand and to analyze the sufficiency or insufficiency of water for agriculture in the area.

The results showed that Ban Klang subdistrict has a total cost of water budget 116,867,68 m3 per year, while the total agricultural water demand is 328,532,06 m3 per year, accounted for approximately 211,664,38 m3 of water per year. When considering on a monthly basis, it found that only 2 months the amount of water budget was higher than the amount of water needed for agriculture was August and May with excess water at 4,230,614 and 3,766,929 m3, respectively. For the month when the amount of water budget less than the amount of water required for agriculture, accounted for the largest volumes were October, November, December and February. The results of this study can be used to plan planting according to the amount of water budget and to adjust the planting system to suit the limited amount of water available.