Numerical modelling of potential evapotranspiration in different regions of the Philippines

Date

1977

Abstract

Numerical Modelling of Potential Evapotranspiration in Different Regions of the Philippines. Major Professor: Dr. Danielito T. Franco. Computerization¹ was employed in the analyses using stepwise multiple regression and general linear models² for developing the empirical formulas. The Penman equation was modified and computerized for Philippine conditions to estimate potential evapotranspiration. Several regression equations in the form: Eti = A + bx₁ , a + b₁x₁ + b₂x₂; ??.. ; a + b₁x₁ + b2x₁ + b₃x₃ + ??? + b₆x₆ where i = station 1 - 35; x's were the meterological variables considered in the regression. The present study proved the significance of the heat budget or global radiation to evapotranspiration at the UPLB; (b) twenty-seven (27) out of thirty-five (35) stations showed that global radiation is the most important meterological factor in potential evapotranspiration (Et) and indicated that, an average, about 80% of the variations of Et was attributed to the variations of global radiation. ¹ At the Agricultural Resource Center, UPLB, College, Laguna, employing an IBM System/370 Model 135 computer with 512 K storage capacity. ² Batch jobs or package programs in the computer library. The influence of global radiation or Et appeard to be decreased by rainfall or cloudiness as indicated by: (a) the decreasing slope b of the radiation equation from higher to lower latitudes and by the observation that the distribution of number of rainy days increases with decreasing latitude in the Philippines; (b) the decreasing R² between global radiation and potential evapotranspiration from regions few of rainy days to regions with more rainy days; and (c) lower R² between Qt and Et during the wet season (rainy months) than during the dry months at the UPLB. Results of test for goodness to fit of the developed models showed that these models are comparable to the modified Penman model whose estimates we proven closely approximate lysimeter values by separate test. These results might be sufficient to state that, the developed models are capable of obtaining estimates comparable to observed values and are recommended for use.

Document Type

Master Thesis

Degree

Master of Science in in Agricultural Engineering

Language

English

LC Subject

Agricultural Engineering

Location

UPLB Main Library Special Collections Section (USCS)

Call Number

LG 995 1977 A2 T35

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