Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 10/15/2009
Publication Date: 2/21/2010
Citation: O'Donnell, T.K., Baffaut, C., Anderson, S. 2010. Evaluation of Water Quality Trends in Goodwater Creek Experimental Watershed, Missouri: Implications for Monitoring Strategies and Objective Setting [abstract]. 2010 Land Grant and Sea Grant National Water Conference Abstracts. Available: http://www.usawaterquality.org/conferences/2010/Conf_themes.html Interpretive Summary:
Technical Abstract: Continued public support for U.S. tax-payer funded programs aimed at reducing agricultural non-point source pollutants depends on clear demonstrations of water quality improvements. Effectiveness of structural BMPs, as well as watershed monitoring networks is an important information need to make future efforts more defensible. The objective of this research is to determine if significant linear trends exist between spring atrazine concentrations and loads at three locations in the Goodwater Creek Experimental Watershed (GCEW) and flow, precipitation, and structural BMP implementation chronology between 1993 and 2006. An additional objective is to determine the minimum detectable change in atrazine necessary to detect a statistically significant future change. The GCEW is a 73 km2 watershed located in north-central Missouri and currently included in the USDA Conservation Effects Assessment Project. Structural BMPs implemented in the GCEW included grass waterways, terraces, and establishment of permanent vegetation. Three stream gauges with automated water samplers and ten rainfall gauges provided sub-daily data at varying seasons and years between 1993 and 2006 for three nested watersheds (12, 31, 73 km2). Hydrologic events at each weir were determined by the Hewlett-Hibbert constant slope method. Atrazine flow-weighted concentrations and loads were determined for each hydrologic event by straight-line interpolation between chemical samples occurring during an event. Variables useful for predicting spring atrazine trends included time to peak discharge during an event and rainfall contributing to an identified event as well as prior to an event. Effects of BMPs were not shown (alpha=0.05) after 14% of the total watershed area was protected by structural BMPs. Minimum changes in atrazine necessary to statistically detect them following additional, future BMP implementation ranged from 45% to 80% depending on watershed location monitored. This evaluation provides information necessary for managers to adapt monitoring protocols and increase abilities to demonstrate future changes in water quality.