Integrated lake and catchment phosphorus mode - A eutrophication management tool. I: Model theory

The paper describes an integrated lake and catchment model which was develo ped and tested against data from the Rutland Water catchment (River Nene an d Welland) in Eastern England. The model uses export coefficients to predic t annual diffuse losses of phosphorus from catchment land use, which are te mporally disaggregated using empirical relationships between phosphorus loa d and discharge in headwater streams. Dynamic inputs of phosphorus are inco rporated into a hydrologically based, multi-reach distributed catchment mod el which also simulates sewage discharges, abstractions and reservoirs/lake s. The model allows a comparison of simulated output with observed discharg e and water-quality data from various points within the river system.