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- Climatology of the Mabacan River Watershed: I, Evapotranspiration
Climatology of the Mabacan River Watershed: I, Evapotranspiration
Thesis Abstract:
The study was designed to determine the applicability of the evapotranspiration climatonomy model as conceived by H. Lettau, to the 46sq. km. Mabacan River watershed at Calauan, Laguna ,Philipphines. This study was specially concerned with the development of a scheme for making more realistic estimate of immediate and delayed runoff for this watershed.
The Numerical model required input of mass (precipitation and solar energy (global radiation) to estimate runoff, evapotranspiration and soil moisture storage. The computed mothly runoff, based on the multiannual means was within -4.0 and +0.7 mm of the observed streamflow. The observed runoff had a root mean square value of month-to-month variation from its annual average of 19.2 mm/mo, while the computed runoff had a corresponding R-M-S value of 18.8 mm/mo, with a linear correlation coefficient of 0.99.
The computed monthly evapotranspanspirations for the individual years were comparable with the empirical data obtained at the International rice research Institute (IRRI), about 10 kg northeast of the watershed. How ever the computed monthly runoff differed from the observed runoff, the difference ranging from -191.6 to +233.4 mm/mo Possible causes of the discrepancies were noted, such as variations in rainfall due to the difference in elevation.
Results of the study show that climatonomy is a usefull indication of climate trends for average years. However, the model still needs further modification and refinement if it is to be used for short-period processes.