Historical and predicted variations of baseflow in China's Poyang Lake catchment

Baseflow availability and its contribution to streamflow are critical for planning and management of catchment hydrology and ecology. This study uses a digital filtering technique, statistical methods, and hydrological projection to investigate historical and future baseflow characteristics with respect to climate and land use impacts, exemplified by the large Poyang Lake catchment (China). Digital filtering results show that annual baseflow varied between 25 x 10(8) and 820 x 10(8) m(3)/year for the catchment rivers during 1953-2014. The results reveal that on average 62% of the long-term streamflow in the catchment is derived from baseflow contribution. Statistics show a generally increasing trend in the annual baseflow and baseflow index (BFI) for most of the rivers over the past 60 years, with the major frequencies varying between 5 and 20 years. Although the trends in baseflow and BFI are attributable to the combined effects of climate and land use change across the catchment, baseflow variations are expected to be more sensitive to climate than land use changes. In general, precipitation plays a dominant role in controlling baseflow and can be used as an indication of the variations in baseflow at the subcatchment scale. Hydrological projection shows that annual baseflow and BFI are likely to increase by up to 31% and 13% during 2018-2035, respectively, based on historical baseflow trends. Our results indicate that management approaches for the catchment that consider groundwater and surface water as a joint resource will be needed to effectively manage the current and future river regime, its water resources, and water quality.