The Web-Based Load Duration Curve Tool
This web-based tool allows users to create flow and load duration curves in a few straightforward steps. Load duration curves (LDC) help to show
the percentage of time, or duration interval, for which a given value of a pollutant load is equaled
or exceeded with a particular watershed.
The tool provides several shortcuts to a Load Duration Curve, including an easy way to download USGS flow data used to construct these curves.
Use the Tool
1. Flow Duration Curve only
Upload you flow data to determine the cumulative frequency over a specified time period and to relate flow values to the percent of time those values have been equaled or exceeded
2. LDC from user-provided flow
Useful if you have flow and water quality values...
3. LDC from USGS flow
Useful if you have water quality data from a location near a USGS gage
4. LDC from USGS flow, for locations not at a gage (drainage area method)
Useful if you have water quality data from a location upstream or downstream from a USGS gage
5. LDC with surface runoff and load
Not really sure what this option is...Provides information about when more than 50% of the flow is estimated to come from surface flow???
About Load Duration Curves
LDCs can be used for watershed analysis and TMDL development, to analyze the relationship between exceedances of water quality targets and flow conditions.
Load duration curves are developed by multiplying stream flow rate with the numeric water quality target/criterion value and a conversion factor for the pollutant of concern.
USEPA has approved numerous Total Maximum Daily Loads (TMDLs) using Load Duration Curves and examples are contained in the documentation above. USEPA also provides information on meeting the 9 basic elements for itsClean Water Act Section 319 projects using Load Duration (LDC) Approach in its “Handbook for Developing Watershed Plans to Restore and Protect our Waters.”
About This Tool
This was developed by ...
For more information contact Dr. Indrajeet Chaubey...
