| Summary: | 碩士 === 國立臺灣大學 === 土木工程學研究所 === 83 === The goal of the reserch is to compute evaporation from bare soil , then the recharge from unsaturated siol zone to groundwater can be determined . Three conditions are necessary if the evaporation process from a given body is to persist . First , there must be a continuous supply of heat to meet latent heat requirement . Second , the va-por pressure in the atmosphere over the evaporation body must remain lower than the vapor pressure at the surface of the body , and the vapor must be transported away , by duffusion or convection , or both . The third condition is that there be a continual supply of water from or throught the interior of the body to the site of evapo-ration .
The research can be divided into three parts. First of all ,tensiometers are installed in the field to observed the unsaturated flow , and hydrometeorological data are collected . Secondly , soil water haracteristic curve parameters are analysised by pressure plate extracter and particle size distribution by specific gravity analysis . Finally , soil water flow in the unsaturation zone was modeled by a numerical model . In this way , parameter identification can be accomplished by using the siol water time series observed by tensiometers.
Because the numerical simulation model , VS2D , does not simulate the physical process of surface ponding ,some rainfall will be loset during simulation . Thus , simulation result during rainfall period does not match with the observed soil moisture data . However , the simulation at the sunny day , the matching is much better .
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