A thesis submitted in partial fulfilment of the requirements for the degree of Master of Engineering, School of Engineering and Technology

Thesis (M.Eng.) - Asian Institute of Technology, 1980

The study was intended to appraise the available groundwater resources in relation to the crop requirement of the Sukhothai project area zone II. In doing so, the long term average annual. groundwater recharge to the Yom basin is calculated from water balance computation - in which measured rainfall and estimated evapotranspiration and stream flow data are used. Modified Penman equation as well as class A pan evaporation data are used to predict potential evapotranspiration. Area proportion method is used to estimate local inflow to river and thus river flow at Yom basin outlet at Pho Thale. The amount of natural groundwater recharge is estimated to about 10 cm/ year for the whole basin. For full scale development of the area, induced recharge from the Nan and Yom river is computed by image well theory and is found to be about 40 percent of pumping rate in which the maximum pumpage is 5. 55 m3 / sec per 100 wells. In this computation the 100 multiple well system is replaced by an equivalent single well. Four alternative cropping patterns are tried to compute monthly and annual project supply requirement - out of which one is selected on the basis of maximum productivity and minimum water requirement. For this cropping pattern, the annual project requirement is about 42 cm per year. The results are interpreted in terms of the available water resources - the natural and induced recharge.