Uncertainties of precipitation products and their impacts on runoff estimates through hydrological land surface simulation in Southeast Asia

Abstract

Precipitation is one of the most important climate variables for runoff simulation. The main objective of this study is to reveal uncertainties in precipitation products and demonstrate how those uncertainties affect runoff estimations in Southeast Asia. Through comparing precipitation products and performing hydrological simulations, the authors have reached the following main conclusions. In Southeast Asia, gauge-based precipitation products have similar monthly precipitation patterns and small differences in precipitation amount, except for Myanmar and Sumatra Island where few gauging stations are used for the precipitation products. Conversely, the uncertainties in seasonal and annual precipitation are large in Southeast Asia if few gauging stations are used for the precipitation products. Since most of the difference in precipitation translates to difference in runoff in wet region, small errors in precipitation can easily result in large errors in runoff in Southeast Asia. Even if located in wet Southeast Asia, impacts of precipitation errors on runoff estimates are different depending on precipitation amount and runoff ratio. In Chao Phraya Basin, relatively low precipitation and runoff ratio cause large percentage differences in simulated runoff. In Irrawaddy Basin, relatively high precipitation and runoff ratio cause large difference in simulated runoff volume.