Multi-methods to investigate the baseflow: Insight from watershed scale spatiotemporal variety perspective

Abstract

Baseflow is the stable part of streamflow meeting the ecological water requirement of the watershed in dry season. Baseflow separation plays a vital role in maintaining the biodiversity of watershed ecosystem. However, research systematically on spatiotemporal variety in watershed scale in baseflow separation is not well documented. In this study, we chose six hydrometric stations in the Yiluo River watershed and carried ten methods (in the group of HYSEP, UKIH and digital filter methods) to isolate the daily runoff data from 2002 to 2021. Two evaluation indicators (Nash-Sutcliffe efficiency coefficient and relative error) were applied to measure the accuracy of those methods. The results showed that the Yiluo River had the average annual baseflow of 10.73 × 108 m3 and average baseflow index (BFI) of 0.42. The UKIH and Eckhardt filtering method methods were fit for the Yiluo River watershed. Temporally, BFI in the wet season (average of 0.35) was smaller than the dry season (average of 0.49). As to the interannual scale, the baseflow in the wet year accounted for nearly a half (49 %) of whole twenty years. Spatially, the BFI of lower reaches (0.35 in Heishiguan) was higher than upper reaches (0.30 in Dongwan and 0.24 in Lushi) on the same river. Nearly half river runoff was from the groundwater recharge and suggests that the Yiluo River is a heavily “Groundwater-dependent River”. Those results of this study can enhance the understanding of spatiotemporal changes of baseflow separations in watershed scale and provide the important references to the international readers.