Presents methods of studying evapotranspiration or consumptive use of water by crop plants, and desirability of knowing the water balance of a specific place. Graphs are included charting the factors in water balance (rainfall potential evapotranspiration, actual evapotranspiration, water deficit, soil moisture rechange, water surplus, and soil moisture utilization). Describes four sites in the Philippines used in the study. Explains instruments used and methods of calculation. Contains findings for each site. [TAIC]