Long-term prediction of water quality for three types of catchment

A simple dynamic model relating the temporal change of the total mass of ch emicals in a catchment to the chemical loading in the river provides high-a ccuracy predictions of absolute and time-integrated chemical loads. The dev eloped model is able to reproduce effectively and simultaneously for all co nsidered time scales the observed hysteresis in the relationship between ch emical concentration in stream water and river discharge. Three types of ca tchment have been examined for long-term modelling: a local urban streamwat er catchment, a transition urban-agricultural catchment and a large catchme nt with varied land use (urban, agricultural and protected forested areas). The long-period changes in model parameters and in water-quality variables are determined for each catchment.