LDCurve is a tool for automatically creating bacterial load duration curves for water quality segments in the State of Texas. The tool uses web services and a webscraper to download U.S. Geological Survey (USGS) mean daily streamflow data and Texas Commission on Environmental Quality (TCEQ) water quality data over an internet connection. This data is imported to the LDCurve tool and manipulated through Visual Basic programming to create the flow duration curve, fecal coliform load duration curve, and E. coli load duration curve using the Texas non-tidal river single sample contact recreation standards. As a final step, the tool calculates a preliminary estimate of the overall load reductions needed to meet water quality standards in the modeled segment.

Outputs from this tool have numerous applications in the water resources field, including the preliminary analysis of bacterial total maximum daily loads (TMDLs). The tool is meant as a first step in water quality analysis, providing the user with a preliminary estimate of the overall (a combination of point and non-point source) load reductions needed to meet the single sample bacterial water quality standard. The LDCurve tool provides a methodical, reproducible procedure for performing these analyses in a matter of minutes, expediting a process that would normally take hours.