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County tax appraisal district records and regional population projections are used as surrogates to track historical and future development in the Barton Springs Zone of the Edwards Aquifer. Wastewater disposal by either Texas Land Application Permit (TLAP) and by individual on-site sewage facility (OSSF) are identified spatially and temporally. There are 27 active TLAP permits in the Barton Springs Zone and as of 2010 there is 3.8 million gallons per day of permitted wastewater irrigation volume. There are at least 9,470 OSSF permits in the Barton Springs Zone, with the highest density of permits observed in the Bear Creek watershed. Williamson Creek is the most densely developed watershed in the Barton Springs Zone, although density of impervious structures increased 2.6 times from 2005 to 2010 in the Hays County portion of Bear Creek. The current population in the Barton Springs Zone is estimated to be 143,382 persons, and is projected to increase 1.6 times from 2010 to 2035 estimates with the largest increases near Dripping Springs and Bee Cave. Identifying and quantifying potential water quality impacts from effluent land application is key to improving existing design specifications and regulations to prevent groundwater contamination.

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City of Austin Watershed Protection Department Review, Vol. 11, no. 1 (2010).





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