Rough water budget analysis

The HEIFE project gathered river run-off data as well as other meteorological and hydrological data. Using the run-off data, the above mentioned evaporation/evapotranspiration estimation and precipitation data, the rough water budget analysis of monthly data were made in Kimura (2000)[11]. The following issues are assumed in the analysis:

• the precipitation and evapotranspiration over all oasis are same to those at the oasis station,
• same for desert,
• and the water budget can be closed between Gaoyao and Zhengyixia run-off stations.

The distance between Gaoyao and Zhengyixia are about 95km. The amount of the flow of Heihe river decreases as going to downstream in summer season, and increase in winter season. The value at Zhengyixia, which is the most downstream station, shows zero in summer.

The area of the oasis are counted from the Chinese hydrological map as 410km$^2$. The effective evaporation area of desert are determined to close annual water budget as 870km$^2$. This area corresponds to be about 5km bands outside of oasis along the river, which seems not to be unreasonable. The desert station, which shows a little larger evaporation than precipitation, locates about 10km north from the river. Using these area and the values in figure 7, the water budget in the area are shown in figure 8.

図 8: Rough water budget analysis of Heihe river between Gaoyao and Zhengyixia. The diamond and the triangle show the consumption of oasis and that of desert, respectively. The square shows the convergence of Heihe river flow.

And the remainder of the water budget are shown in figure 9.

図 9: The remainder of the monthly water budget of figure 8

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From figure 8 and 9, the following results are suggested.

• about the half of convergence of river flow was consumed by oasis evapotranspiration in summer,
• about 20% of the convergence was consumed by desert in summer,
• and the remainder seems to be ground water and come back to river in winter.

The last issue is consistent to the results of ground water quality observation (Taniguchi el. al. (1995). They concluded that ground water was mixed with the river water in winter.