Transient pollution events occur in runoff from both agricultural and silvicultural environments. In agricultural runoff, transient pollution events may be associated with sediment, nutrients, and pesticides. Depending upon hydrological conditions, these events may be responsible for most of the yearly yield of sediment, nutrients, and pesticides, and may have a profound effect on the ecological health of streams and reservoirs, limiting seasonal primary productivity, changing the balance of functional groups, and altering reproductive cycles. Transient pollution events are most noticeable in surface runoff, but are also observable in shallow ground water. Such occurrences in both runoff and shallow ground water may be associated with natural seasonal events including the fall leaching of crop residues, or with cultural activities including the application of fertilizers and pesticides. In either case, rainfall distribution and intensity become important factors in the magnitude of the transient pollution event. Best management practices (BMPs) must be designed to remediate transient pollution in agricultural storm events. Not only must total storm agrichemical loading to aquatic ecosystems be reduced, but also the transient agrichemical concentration peaks occurring within the storm hydrograph.

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