Stochastic parsimonious hydrologic partitioning model under east asia monsoon climate and its application to climate change

Abstract

A conceptual hydrologic partitioning model suitable for the East Asia monsoon climate region is constructed parsimoniously, and the variability of Horton index, which is the ratio of water vaporization and wetting in the watershed, is investigated. Numerical simulations in the study area show that the inter-annual variability of Horton index is reduced to around 60% of the inter-annual variability of annual precipitation, and there is a strong inverse correlation between Horton index and annual precipitation. Using cumulant expansion theory, the probability distribution function of soil water with various hydro-meteorological variables and watershed characteristics is derived. Using the steady-state soil water probability distribution function, the sensitivity of Horton index to hydro-meteorological variables such as precipitation occurrence probability, average rainfall depth at rainy days, and evapotranspiration rate and hydro-geophysical characteristics such as surface runoff coefficients, threshold soil water value to control vaporization, and exponent value to control groundwater recharge is analyzed. Looking at the future Horton index of the study area using a variety of future climate information ensemble, it is projected that the water stress of vegetation in the watershed is likely to increase due to fluctuations in precipitation patterns and increase in potential evapotranspiration even if annual precipitation increases.