Study Finds Urbanization Plays a Large Role in Water Quality
Nutrient levels decreased 40 to 55 percent in Indian Creek following upgrades and changes to treatment processes at the Douglas L. Smith Middle Basin and Tomahawk Creek Wastewater Treatment Facilities (WWTFs) in Johnson County, Kansas, according to a new U.S. Geological Survey study.
High levels of nutrients, which are essential for plant growth, are not necessarily beneficial. Excessive nutrients can be harmful by degrading habitats and decreasing the amount of oxygen in the water. This can result in areas experiencing stress or death of near or bottom dwelling organisms. Johnson County Wastewater completed treatment upgrades at both wastewater treatment plants totaling approximately $37 million, and a significant part of the investment went directly to nutrient removal facilities.
While wastewater discharge has the most substantial effect on nutrient levels in Indian Creek, urban influences were also found to play a major role in affecting water quality. Indian Creek is one of the most urbanized drainage basins in Johnson County, and receives discharge from two WWTFs. After upgrades to the Indian Creek WWTFs in 2008–2009, nutrient levels decreased by about 40 to 55 percent in both wastewater discharges and water tested downstream of the plants from 2010-13.
However, increasing urban development contributes to the decline of water-quality and habitat, and aquatic plants and animals adapting to those declining conditions. The complete USGS study, done in cooperation with Johnson County Wastewater, can be found online.
“Johnson County Wastewater values the information provided in this USGS study,” said John O’Neil, general manager for Johnson County Wastewater. “In our role of providing wastewater treatment to a significant population and discharging to effluent-dominated streams, this information is critical in making sound decisions to further improve water-quality in the receiving streams while also minimizing the impact to our rate payers.”
Aquatic plants and animals that tolerate degraded water-quality conditions were more prevalent in Indian Creek than in less urbanized drainage basins in Johnson County.
“The Indian Creek study furthers our understanding of the relationship between urbanization, wastewater discharges and stream health,” said Mike Tate, Kansas Department of Health and Environment. “This study, and others like it, will assist policy makers in determining the most cost effective means of improving stream health in urban areas.”
Despite decreases in nutrient concentrations, effects of wastewater discharge on Indian Creek were still evident. When wastewater represented a substantial portion of total streamflow, nutrient concentrations were ten to 100 times larger downstream from the WWTFs than upstream from the WWTFs.
“This study was an excellent opportunity to learn more about the effects of wastewater discharge on an urban stream,” said Jennifer Graham, research hydrologist and lead USGS scientist on the study. “The high-resolution data collected by this study allowed us to document water-quality improvements following WWTF upgrades and differentiate between urban and wastewater influences on Indian Creek.”
More information about USGS studies in Johnson County can be found on the USGS Kansas Water Science Center website.