Mountainous areas provide important sources of fresh water for adjacent lowlands. However, hydrogeological and hydrometeorological complexities of mountainous catchments, make reliable seasonally estimation of catchment water balance components challenging, such as the evapotranspiration (ET), subsurface lateral flow (L) in the dry season and catchment water storage change of the wet season. In this study, an improved method based on storage-discharge relationship (SQL) is proposed to estimate seasonal catchment water balance for mountainous catchments. In comparison to the previous approach, the improved SQL method has incorporated the subsurface lateral flow.
The improved SQL method was applied over six catchments with various sizes, climatic and hydrogeological conditions in the Mount Lofty Ranges (MLR) of South Australia. ET estimate for the six catchments agrees well with that from the method based on surface reflectance from MODIS-Terra and interpolated climate data, suggesting that the improved SQL method can be an alternative approach for catchment water balance quantification in mountainous regions. The improved SQL method, only based on continuous streamflow data, provides estimation of inter-annual variation of ET and subsurface lateral flow in the dry season, and catchment water storage change of the wet season. For the dry season, it is critical to understand the contribution of the subsurface lateral flow to the region, which may be the main water sources to the adjacent catchments. For the wet season, it is of importance to know that how much water has been left in the catchment for sustainable water sources management.