Location, location, location – Considering relative catchment location to understand subsurface losses

The analysis of large samples of hydrologic catchments is regularly used to gain understanding of hydrologic variability and controlling processes. Several studies have pointed towards the problem that available catchment descriptors (such as mean topographic slope or average subsurface properties) are insufficient to capture hydrologically relevant properties. Here, we test the assumption that indicators of catchment location, i.e. the relative properties of catchments in relation to their surrounding neighbours, can provide additional information to reduce this problem. We test this idea in the context of Great Britain for a widely discussed problem, that of catchment water balance errors due to subsurface losses. We focus on three different locational aspects (i.e. location to coast, location within a wider basin and location to a neighboring catchment), utilizing only basic and widely available geological and topographical information to make the result useful for large sample hydrology. To achieve this, we introduce the Strahler Sequence Index to define catchment location within the wider river basin. Our results imply that location, geology and topography combine to define the differences of water balances of catchments in Great Britain compared to what we would expect from their climatic estimation alone. However, the given sample size limited our ability to derive robust conclusions.