TR-476 Basin Approach to Address Bacterial Impairments in the Navasota River Watershed

Authors: L. Gregory, A. Gitter, K. Lazar

The 2012 Texas Integrated Report – Texas 303(d) List identifies 11 impaired waterbody segments along the Navasota River due to Escherichia coli (E.coli) bacteria (Figure 1). The Clean Water Act (CWA) requires water bodies that are impaired for a specific parameter or condition, to be restored and their water quality maintained. Efforts to restore impaired waterbodies include additional monitoring, assessing the current standards and conditions of the waterbody, stakeholder outreach and education, and exploring opportunities for developing watershed restoration plans. Previous reports regarding the watershed have revealed E. coli levels to be elevated in specific tributaries since as early as 1999 (TCEQ 2013b; BRA 2011). The river’s elevated E.coli levels do not comply with the state’s recreational water quality criteria for primary contact recreation, which is established at 126 cfu/100 mL. Segment 1210A of the river, which lies above Lake Mexia, is an unclassified waterbody that has been named impaired by bacterial contamination since 2002. The Navasota River below Lake Mexia, segment 1253, is considered impaired for depressed dissolved oxygen (DO) because of frequent low water levels (BRA 2011). The project’s goals include: (1) characterize the current bacteria loading and sources for the watershed, (2) determine the necessary levels of loading reduction to restore the water body, (3) work with stakeholders to select and prioritize management measures necessary to restore the waterbody, and (4) develop a watershed protection plan for the Navasota River below Lake Limestone.

This report discusses the climatic, physical, demographic, and hydrological conditions as well the potential sources of pollution within the watershed. The report also includes an assessment of current and historical conditions within the Navasota River watershed and aims to begin the process of defining its current bacteria levels. Information is largely presented on a watershed-wide basis; however, where appropriate and possible, information is discussed on a more refined scale.