Study On The Influence Of Geotemperature On Phreatic Evaporation Under Non-stress Conditions

Phreatic evaporation is one of the major consumption of underground water sources, also the regional evapotranspiration’s main resources which results in the salinization of soil as well. Among the many factors of Phreatic evaporation, geotemperature has not been taken into consideration and lacks of relevant research. In terms of energy, geotemperature is the main source of energy of liquid water’s gasification in the process of Phreatic evaporation.This paper chooses sand as the research target and analyzes the physical nature and thermal property. Consequently an experimental equipment which can animate the geotemperature and do the stress phreatic evaporation which can both measure and analyze the changing law of the sand column of water and temporal-spatial temperature with the influence of geotemperature and without it. This contrastive experiment proves the big influence of geotemperature on soil moisture transfer and distribution.This paper was based on the hypothesis of the balance of TKE and calculate the different soil moisture diflusivity with and without the influence of geotemperature. And the water vapor flux change curve was obtained through the observation of the heated sand column and the normal temperature sand column which are both buried into the ground by 50 meters. The heated sand column’s water-vapor flux is positive in the experiment and plays a stimulating role in the soil moisture transfer. This shows that influence of geotemperature comes from water-vapor flux.The experiemnt designs the ways of calculating the evaporation discharge of phreatic water on the surface of sand column through Calcium chloride particles moisture absorption. The contrastive analysis shows that evaporation was influence by the daily environment. The change of heated sand column and normal temperature sand column is also the same. The maximum evaporation capacity of the heated sand column is 0.065mm, minimum is 0.030mm; while the maximum evaporation capacity of the normal temperature sand column is 0.052mm,minim is 0.021 mm。 The evaporaiton capacity of heated sand column is higher than the normal temperature one whose accumulated evaporation capacity is 1.235mm while the normal one is 0.924mm. So it’s obvious to see that influence of geotemperature is big from the fact that Phreatic water evaporation is 33.7% under the condition of taking the geotemperature into consideration.This paper adopts the PdV Model and establishes the migration model on the basis of hydrus-1D on considering about the sand pile’s sand, water and heat transfer. This also proves the reliability of this paper which calculate the Phreatic water evaporation.