The impact of the comprehensive watersheds ordinance on stream health in Austin, Texas

While Austin is often considered a leader in water quality management, it still has streams which are impaired. As urban development occurred in Austin, there appears to have been a diminishing regard for these creeks. As Austin receives the majority of its drinking-water supply from the Colorado River (a surface water source), there is a critical need to increase our understanding of the relationship between development trends and water quality in order to continue the implementation of successful watershed planning strategies and regulations. Further, there is a need for the evaluation of watershed protection regulations that have already been established, in order to determine their success. This thesis presents data from an analysis of water quality of creeks in watersheds that were primarily developed prior to the passing of Austin’s first Comprehensive Watershed Ordinance (CWO) in 1986, compared to water quality of creeks in watersheds that were primarily developed after the Ordinance was adopted. This exploratory study investigated the following research questions: How does stream health differ between watersheds that were primarily developed prior to the passing of the CWO compared to those that were mostly developed after the CWO? How do impervious cover, watershed size, soil type and watershed development affect stream health outcomes (metals, nutrients, macroinvertebrate biodiversity and water temperature) in the creeks under study and what are their empirical relationships? A total of forty-eight creeks were studied. Analysis included both GIS mapping and statistical methods. Three of the primary best management practices established by the CWO included riparian buffers, impervious cover regulations, and density controls. The findings reveal that post-CWO creeks have better stream health outcomes for lead, chromium, and nitrate concentrations. Water temperatures are generally lower in post-CWO creeks. Additionally, these creeks have greater macroinvertebrate biodiversity. Therefore, this study confirms that Austin’s watershed regulations do matter as they have had a positive impact on stream health in the city. The city should continue to focus on best management practices that will result in living streams, including: increasing riparian canopy cover throughout the city, promoting the development of rain gardens, establishing incentives for the use of impervious surface alternatives such as permeable pavers, and finally continue to educate and engage with Austinites regarding the protection of the city’s water network.