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.
Highlights
Climate change affects the hydrological response of the surface through various paths
The purpose of this study is to develop a conceptual soil water balance model that simulates the hydrologic partitioning process at monthly or annual level in watershed units
The focus was on vertical one-dimensional water balance, which determines hydrologic partitioning such as precipitation, surface flow, wetting, vaporization, and groundwater recharge
Summary
Climate change affects the hydrological response of the surface through various paths. Since changes in the hydrological cycle, in the hydrologic partitioning process, result in changes in the ecological environment, climate change affects the structure and function of ecosystems [1]. Understanding and predicting the impact of climate change on the watershed’s water balance has emerged as an important issue in managing and conserving the natural environment [2]. Soil water near the surface plays an important role in hydrologic partitioning, including precipitation, surface flow, wetting, vaporization, and groundwater recharge processes [3,4]. It is known that the ability of the watershed to store soil water supplied to the soil layer by precipitation and to vaporize it back into the atmosphere is mainly controlled by vegetation [5,6].
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