A model for nitrate mass in runoff during single storm events

A model to predict the temporal distribution of nitrate mass in runoff during single storm events was developed using data measured at four Florida watersheds. The input influencing the mass of nitrate in rainfall was identified, and a model developed using these factors to predict the mass of nitrate in runoff. Validation showed successful results for 92% of the storms.; The goal of this research was to develop a model to predict the temporal loads of a nonpoint source contaminant during single storm events. Nitrate was chosen as the contaminant because of the availability of data and the significant impact of high nitrate loads on receiving waters. The data was collected by the U.S. Geological Survey from four sites in Dade and Broward counties, Florida from 1974 to 1978. The sites were chosen because there were no point contaminant sources. For the four sites, there was a total of 77 storms. The drainage areas varied from 15 to 58 acres, and the impervious cover varied from 36% to 98%.; Inspection of the measured data showed two patterns: as rainfall increases the mass of nitrate removed from the atmosphere increases, and during a storm with two occurrences of the same rainfall depth less nitrate is removed from the atmosphere for the later rainfall. To reflect the first pattern in the model, the mass of nitrate removed is directly related to the rainfall depth. To reflect the second pattern, the mass of nitrate is directly related to a factor representing the remaining atmospheric nitrate supply.; The model can be used alone or with an hydrologic model. If additional nitrate sources are known, the nitrate from those sources can be added to the contribution predicted by this model. This model was both developed and validated using the Florida data, and without any watershed or meteorological limits. Its applicability to other sites should be determined.