The dynamic nature of the interactions between wastewater discharges and receiving water quality can complicate the analysis of pollution abatement programs; a numerical example of ammonia toxicity is used to illustrate this. It shows the role that correlated variables, chemical transformations, and water quality criteria play in determining water quality responses and their environmental significance. Several methods of waste load allocation (the process of identifying discharge limits satisfying water quality criteria) that take these dynamic interactions into account are reviewed. Also reviewed are pollution control strategies based on variable effluent limits. These can lower treatment costs by allowing discharge levels to change by time of year or with conditions in the receiving water. A waste load allocation method for seasonal discharge limits is introduced that maintains an equal risk of water quality criteria violation with nonseasonal limits.