Pilot Study of Catchment-Scale Modeling in the UK
Accurate predictions of peak agrochemical concentrations in England and Wales watercourses were needed as input data to a larger project. The larger project sought to identify the most significant catchment pressures using eco-epidemiological techniques. The UK Environmental Agency was using CATCHIS to predict catchment-scale concentrations. We had concern that CATCHIS underestimated the peak agrochemical concentrations and underestimated the potential risk to aquatic organisms.
To be confident in the conclusions of the larger study, we needed to be confident that input data represented realistic worst-case information. Therefore, we undertook a pilot study for three catchments: Waveney, Yare and Wensum in the East Anglia region of England. The study compared predictions for nine agrochemicals made by two different models (SWAT and PRZM/RIVWQ) to measured data.
Both models predicted concentrations in the same order of magnitude as the observed bi-weekly data. However, both models failed to accurately predict peak concentrations. Lack of spatially refined agrochemical application data was identified as a major concern in the inaccurate concentration predictions.