This paper presents (1) general considerations related to the development of two mathematical models for non-conservative transport
of nitrate and ammonium under unsteady water flow conditions; (2) their application to predict the transport of pollutant in both
customary and accidental pollutant release circumstances; and (2) a discussion related to models use in water quality management.
The studied river stretch is part of the River Swale in England, where pollutants are discharged by multiple point sources and also by
tributaries. Experimental data was used for model development and verification. The models are useful to (i) assess the downstream
river distance affected by pollutant release; (ii) estimate environmental damage; (iii) support decisions on where and how to
counteract pollutant discharge; and (iv) also to support the further development of more refined water quality simulation tool