Location, location, location – Considering local neighborhood when analyzing large samples of UK catchments

Studying large samples of catchments has been an effective means for comparative hydrology as it provides a wide range of hydrological conditions which can be used to learn similarities and differences between places. Such analyses typically include an attempt to organize catchments along some gradient (e.g. climate) or in clusters (e.g. geology) using catchment descriptors (e.g. an aridity index). Various past studies have pointed to the problem that available catchment descriptors are often not sufficient to capture hydrologically relevant catchment behaviours. It is further widely acknowledged that the water balance of many catchments is not closed. Several hypotheses for the causes of this lack of closed water balance are stated in literature.

If we assume that the dominant control on water balance is climate, then catchments’ water balances should change smoothly in space (since the climate varies smoothly). If they do not, then something else must be controlling this behaviour. We expect that size, location and geology might play important role in the water balances of UK catchments. We aim to study the differences in water balance between catchments to understand the role of catchment location. We test different hypotheses while considering the local neighborhood of 669 UK catchments from the CAMELS-GB dataset.