Evaluation of corrected APHRODITE estimates for hydrological simulation in the Yarlung Tsangpo-Brahmaputra River Basin

Precipitation is one of the most important inputs for hydrological simulation because it controls water balance, and accurate representation of rainfall distribution is essential for hydrological simulation. In the Yarlung Tsangpo-Brahmaputra River Basin (YBRB), gauge-based gridded datasets have difficulties in representing complex orographic precipitation as the rainfall stations are too sparse to capture accurate precipitation patterns. This study used Asian Precipitation Highly Resolved Observational Data Integration Towards Evaluation of Water Resources (APHRODITE) estimates to drive the Soil and Water Assessment Tool (SWAT) model in the YBRB. Bias correction on APHRODITE estimates was achieved through linear scaling based on a denser network of gauges. In addition, the elevation bands method was implemented in SWAT to reproduce spatial precipitation by considering orographic effects. The results showed that original APHRODITE data tended to systematically underestimate rainy season precipitation with considerable underestimation on windward slopes of the Himalayas. Corrected APHRODITE data increased precipitation estimates and were able to better represent the spatial patterns of precipitation. During the calibration and validation periods, the mean monthly Nash-Sutcliffe efficiency (NSE) of the corrected APHRODITE-simulation were 0.86 and 0.82, respectively, which were much higher than those of the original APHRODITE-simulation (0.79 and 0.72), indicating the reliability of corrected APHRODITE estimates in driving hydrological model. In addition, although the elevation bands method has some limitations induced by the constant precipitation lapse rate, it was also found that this method could improve the accuracy of hydrological simulation. In large transboundary sparsely gauged river basins, implementation of bias correction and elevation bands can improve the representation of spatial precipitation of gridded gauge-based rainfall products, which may be beneficial for hydrological simulation and water resources management.