Assess understanding of hydrological and biogeochemical controls on nitrate fate in agricultural catchments, including nitrate sources, transport pathways (surface runoff, tile drains, vadose zone, groundwater), attenuation processes (nitrification, denitrification, plant uptake, sorption, dilution), temporal/spatial variability, diagnostic tools (concentration time series, isotopes, tracers) and common measurement and modelling approaches; evaluate implications for monitoring and mitigation strategies.