North Bosque: Evaluating Effectiveness of TMDL Implementation

Background

The North Bosque River (Segments 1226 and 1255) originates near Stephenville and flows southeast over a primarily rural landscape, eventually flowing into Lake Waco (Segment 1225). Portions of the North Bosque River have had nutrient and algal concentrations in excess of screening levels established by state water quality standards since 1996. Excessive algal growth can lead to taste and odor problems for drinking water and can cause low levels of dissolved oxygen within a stream, which could kill fish. Portions of the Upper North Bosque River (Segment 1255) have not met standards for fecal bacteria (E. coli) since 1996, nor dissolved oxygen since 2008. These bacteria are naturally found in the intestines of humans, livestock, wildlife, and pets and although they do not generally cause disease their presence in water indicate the potential presence of disease-causing microorganisms from fecal contamination. Therefore, higher levels of fecal bacteria in water mean a higher risk to humans of contracting diseases by ingesting contaminated water during swimming, wading, or kayaking — activities, called “contact recreation,” in the state’s standards for water quality. Low dissolved oxygen can negatively affect aquatic life.

In response to water quality concerns, TCEQ completed two Total Maximum Daily Loads (TMDLs) for phosphorus, the limiting nutrient of the watershed, in 2001. A subsequent TMDL Implementation Plan (I-Plan) was adopted in 2003. Dairy-waste application fields and municipal wastewater treatment plants were shown to be the major controllable sources of phosphorus in the watershed.

Since approval of the I-Plan, many projects and activities have been put in place to control and remove sources of nutrient loadings in the watershed. To assess the effectiveness of these activities in improving water quality, TCEQ installed many monitoring stations in the watershed.

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Project Description

This project, led by Texas Institute for Applied Environmental Research, continued water quality monitoring at eight monitoring stations and conducted storm-event sampling at seven stations. Five of these stations were designated by the I-Plan for assessing the plan's effectiveness. The monitoring results were compared with updated land use activities associated with Concentrated Animal Feed Operations and Animal Feeding Operations. This allows water quality assessments to correlate changes in water quality with land management practices. Data were also submitted to TCEQs Surface Water Quality Monitoring Information System and used in the Texas Water Quality Inventory and 303(d) List. The project ended in 2017.

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For More Information

To find out more about the NPS Program, call 512-239-6682 or e-mail us at nps@tceq.texas.gov.

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