LDC: Load Duration Curves
There are two basic options for estimating existing and allowable loads in a stream or river: (1) applying a computer model to simulate conditions within the watershed; and (2) using the available water quality and flow data in a statistical analysis. Load duration curve is a statistical analysis that has been used for TMDL calculations.Challenges are often associated with effectively setting up and applying a computer model, however, including having the necessary time, expertise, data, and resources. Some watersheds are also difficult to model because the available tools do not fully address key environmental factors such as extensive hydromodifications (e.g., irrigation diversions or tiling) or complex geology (e.g., karst). Faced with these challenges, some TMDL developers have explored the possibility of using statistical techniques to estimate existing and allowable loads.
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