Runoff simulation considering the effects of hydraulic structures on agricultural water uses

Abstract

For the efficient management of water resources in the target basin, this study proposed a method to improve the reliability of a long-term hydrological simulation model by applying to the model agricultural water more approximate to actual water uses (than planned water demands) through their adjustment based on the effects of small-scale hydraulic structures. To verify agricultural water uses estimated using the proposed method, they were applied to a basin management model. And then, simulated runoff at main station points was compared with measured runoff. As a result, there occurred errors with large differences from measured data, mainly, at station points where their dependency on river water was high. To verify simulated return rate, return rate for a test zone was estimated, and then compared with the simulated return rate. Correlations between annual rainfall and runoff errors were analyzed. As a result, it was found that those errors were enlarged in dry years. Long-term runoff simulation analysis showed that simulated runoff came to be negative when a farming season began. This could be significantly improved using water uses adjusted to consider the effects of small-scale hydraulic structures. Also, correlation analysis quantitatively confirmed that simulated runoff after adjustment was more correlated with measured runoff than before adjustment. Finally, fitness tests for runoff simulations before and after adjustment were carried out through a residual analysis to analyze residual normality and independence. As a result, the fitness of runoff simulation after adjustment was significantly improved.