Evapotranspiration (ET) from oasis and Gobi surfaces in the Heihe River region of China was estimated by Kotoda (1986) and Advection‐Aridity (Brutsaert and Stricker, 1979) models. The ET estimates were compared with eddy‐correlation ET estimates. The ET estimated by both models are in good agreement with ET obtained by means of eddy‐correlation method for the oasis surface while underestimating ET as compared to the eddy‐correlation method. For the Gobi surface, the models yielded obviously overestimates of evapotranspiration.
In order to estimate evapotranspiration from arid surfaces, the Kotoda model was modified by introducing the surface moisture availability parameter a from Barton (1979). The modified Kotoda model yielded ET estimates that were very close to that from the eddy‐correlation method for the Gobi surface. The modified Kotoda model was used to estimate evapotranspiration from the Heihe River watershed, an area with complicated topography and land use, and the results compared with those from a water balance method. A sensitivity analysis of the modified model was performed. The results show that the modified Kotoda model can reflect the relationship between the actual evapotranspiration and the main controlling factors on it for both wet and arid surfaces reasonably. From this study, it can be concluded that the modified Kotoda model is applicable fro the estimation of regional evapotranspiration from areas with complicated topography and land use.
Stable isotopes (deuterium and oxygen-18) were used for determining the origin of water and interactions between groundwater and river water, and clarifying the relationship between groundwater salinity and changes in the isotopic components of groundwater in the HEIFE area, northwestern China. An indication that active mixing of groundwater and river water occurred from October to March, was recognized from seasonal changes in their isotopic components. The relationship between electrical conductivity and isotopic components of groundwater shows that there are two groups of sites. Groundwater in one group has the characteristic of increasing 6D with increasing electrical conductivity (caused by evaporation), while the electrical conductivity of the groundwater in a second group does not change with changing isotope composition, and is identified as water of mountain origin.
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