Flow monitoring technology and methodology assessment EPA region 7 grant: X7 97702501-0

Iowa Department of Natural Resources

Iowa Department of Natural Resources (IDNR) Total Maximum Daily Load (TMDL) watershed plans in Iowa focus on small (HUC 12) watersheds. These watersheds rarely contain U.S. Geological Survey (USGS) gaging stations, making flow one of the most difficult attributes to estimate for TMDL development. This lack of accurate flow data complicates the calibration of advanced models, such as SWAT, strains the ability to develop accurate and attainable TMDL targets, and limits the program’s ability to show improvements in water quality through monitoring.This study focused on assessing the accuracy and reliability of Area Velocity Flow Meters (AVFM) for use in TMDL development and subsequent water quality improvement monitoring in small (HUC 12) watersheds. The assessment of this flow collection technology and deployment methodology contributes to goal two of EPA’s 2010 Strategic Plan – clean and safe water. Specifically, this project contributes to the first four strategic targets identified in this Strategic Plan. The first three targets relate to measurable goals of improving water quality adequately to eliminate impairments in water bodies and/or across watershed and the fourth target relates to preventing the deterioration of water quality in wadeable streams.During this study, Isco 2150 AVFM units were co-located at existing USGS gage stations in three watersheds in eastern Iowa. The co-location with USGS gages allowed for an assessment of the accuracy of AVFM collected data. Two of the sites yielded positive results. Stage-discharge curves developed from Clear Creek and Rapid Creek had 95 and 98 percent (respectively) of discharge comparison points fell within an acceptable range of accuracy when compared to USGS generated data. Hoover Creek, the site with the smallest drainage area, did not perform well. Only 10 percent of all comparison points were acceptable when compared to USGS data. Site specific conditions were determined to be the primary cause of the errors found at this site.On the whole this study determined that the Isco 2150 AVFM and other similar flow technologies can provide a useful tool for obtaining more accurate and affordable continuous flow data. The use of this technology with appropriate deployment methodologies has the potential to provide resource managers with site specific data critical to the development of restoration plans and could be a key component in continued monitoring for water quality improvements.

Flow monitoring technology and methodology assessment EPA region 7 grant: X7 97702501-0

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