Main Issues for Gathering and Compiling Data Necessary for TMDL Modeling Efforts

Modeling efforts necessary for large-scale TMDLs goes beyond calibration and validation of models that relate pollutant sources to instream water quality. Gathering and compiling necessary data is as important as the modeling effort. Time series of point-source loads, stream temperature data, water quality calibration data, weather data and flow records are just a glimpse of the information needed to perform simulations. Some of the input data may not be available at all. It is not uncommon to develop sub-models in order to estimate the relevant input data for the hydrologic or water quality models used for the TMDL study. In some cases, large volumes of data would need to be gathered to run the hydrologic or water quality model for the TMDL. In these cases, databases to organize and sort the data according to different criteria are generally useful and should be employed. The various types of data necessary for nutrient TMDL studies in New Jersey, the processes undertaken to obtain the data, the development of sub-models to estimate some input data, and the compilation of water quality and hydrologic data in a database are discussed in this paper.