Impact of Climate Seasonality on Hydrological Partitioning by Using Stochastic Soil Moisture Model

Abstract:

As an index representing the hydrologic characteristics of the watershed, Horton index can be cited. This index is defined as the ratio of the amount of vaporization for the wetting amount and often used as a value of quantifying the water use efficiency of vegetation in the watershed. Since this index is relatively small annual fluctuations, this index is being evaluated as a good indicator of precipitation partitioning characteristics of the watershed. Thus, using this index, many studies on the relationship among the climate, terrain and vegetation of the watershed are being conducted in various ways. In this presentation, the seasonal effect of climate on the hydrologic partitioning of the watershed is analyzed using Horton index. The probability density of the soil moisture is stochastically simulated using the meteorologic date at Seoul, Daegu, Busan and Jeju observation site in the Korean peninsula and Horton index is calculated using the simulated probability density of the soil moisture. As a result of examining the relationship between Horton index and annual precipitation and annual potential evapotranspiration, annual precipitation is a strong negative correlation with Horton index, while annual potential evapotranspiration is found to have a very weak positive correlation. This means that the amount of water supplied to the watershed has a greater impact on Horton index rather than the energy fed to the watershed. In order to investigate the impact of the climate seasonality on the hydrologic partitioning, Horton index considering the climate seasonality and Horton index removing the climate seasonality are calculated, respectively. It can be seen that the seasonality has an effect in reducing Horton index. Considering Horton index is proportional to the water use efficiency of vegetation, seasonality can be thought to inhibit the vegetation water use efficiency. In addition, much more than usual precipitation in seoul with a wet climate and much less than usual precipitation in daegu with a dry climate tend to disappear to the influence of seasonality on Horton index

Acknowledgement

This subject is supported by Korea Ministry of Environment as "The Eco Innovation Project : Non-point source pollution control research group"