Climatic origin of hydrological response

Hydrological processes leading to flow in river channels are extremely complex, which is why hydrologists have not yet found any fundamental law to explain river flow dynamics at basin-scale. Hydrological models generally keep a set of free parameters that need to be calibrated using observed discharge time series data. The underlying assumption is that each catchment is unique and that each model parameter represents certain catchment characteristics. Thus, prediction in ungauged basins is a challenge. In this study, it is argued that we should focus on developing calibration-free hydrological models. In other words, we hypothesize that hydrological response is primarily determined by climatic inputs. We compared the dynamic Budyko (DB) rainfall-runoff model with the HBV model considering a global dataset. The two models showed very similar performance across geographical regions, supporting our hypothesis. We conclude that more efforts should be made to develop rainfall-runoff models that exploit climatic information for explaining streamflow variation.