1. Water Quality in the Edwards Aquifer Katrina E. Mabin CE 394K GIS in Water Resources Dr. D. R. Maidment

2. Counties of study  Williamson  Travis  Hays Data from TWDB

3. Edwards Aquifer Data from TWDB

4. Add well data…  Well data covers entire state  Need to select locations important to study  Qualifications for use

5. Select only wells with water quality data:

6.  Select objects by attributes (WATER_QUAL), then save selection as layer and export as a shapefile

7. Select only wells within study counties and Edwards aquifer:

8.   Select objects by location (those falling within the features of another layer)

9.  Obtained groundwater data for Travis County from Texas Water Development Board (TWDB) website – referenced by state well ID

10.  Convert.xls file to.dbf file to be included in geodatabase as object class

11.  Joined object class (travis_wq) to feature class (edwards_wells) Selected wells with water quality data from 1999 – only 12 wells within Travis Co.

12.  Interpolate points to raster: can Spatial Analyst depict chemical gradients in groundwater?  Calculate spline of TDS values associated with Travis Co wells in Edwards Aquifer (1999 data)  Very few points, so Spatial Analyst interpolates breach of Higher TDS water across aquifer  Drinking water standards <1000 ppm TDS, no evidence of “bad water line” in this analysis

13. Questions for further work  Would more point values improve spatial analysis of WQ data?  Can spatial water quality be associated with other spatial parameters (i.e. land use)?  Does WQ vary with time in a geospatial sense?  Can WQ changes be related to changes in water use?

14. Conclusions  Groundwater water quality can be presented spatially  Spatial interpolation of WQ is limited by available data  In order to employ useful spatial analysis of WQ, as well as integration with surface water and consumption practices, more complete data sets and easier data access must be made available

15. Thanks  Dr. Maidment  Texas Water Development Board