tangqh@iis.u-tokyo.ac.jp
[cor1]Corresponding author. Tel.: +81-3-5452-6381; Fax: +81-3-5452-6383.
The effects of natural and anthropogenic heterogeneity on hydrological simulation were evaluated with a distributed biosphere hydrological model (DBHM) system. The DBHM embeds a biosphere model into distributed hydrological scheme, representing both topography and vegetation conditions in mesoscale hydrological simulation. An irrigation scheme has been included in the model system.
The effects on hydrological processes of two kinds of variability, precipitation variability and the variability on irrigation redistributing runoff, was investigated in this study, representing the natural and anthropogenic heterogeneity, respectively.
Runoff is underestimated if the rainfall is spatially uniformly put over large grid cell. And runoff simulation could be improved by taking into account the precipitation heterogeneity. However, the negative runoff contribution cannot be simulated by only considering the natural heterogeneity. This constructive model shortcoming can be eliminated by taking into account anthropogenic heterogeneity, irrigation water withdrawals. Irrigation leads to increased evapotranspiration and decreased runoff. Surface soil moisture in the irrigated area increases because of irrigation. Simulations performed for the Yellow River basin indicates that stream flow decrease of 41% by irrigation. The latent heat flux increase in peak irrigation season (JJA) is 3.3 Wm
-2 with a decrease in ground surface temperature of 0.1 K of the river basin. The maximum simulated increase in latent heat flux is 43 Wm
-2 and ground temperature decrease is 1.6 K in peak irrigation season.
