Operational Rainfall/Snowmelt-runoff Model for Upper Narew River -- Multi-site Calibration and Validation of the Hydrological Component of SWAT in a large Lowland Catchment -- Automatic Calibration of the WetSpa Distributed Hydrological Model for small Lowland Catchments -- Modelling Hydrological Flow Paths during Snowmelt induced high flow event. Since climate and land use strongly affect the runoff pattern and intensity of solute export, it is likely that some observations and conclusions formulated on the basis of investigations carried out in forested catchment may not be fully adequate to describe controls on solute export from agricultural watersheds. The primary objective of the present research is to better understand the flow paths that affect the fluxes of dissolved compounds from a small agricultural catchment during snowmelt. This book focuses on spring snowmelt, because this is the dominant hydrological event in many moderate and high latitude catchments and, thus, is regarded as a prominent factor influencing the quality of surface waters