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Scientific Investigations Report 2011–5226

In cooperation with the U.S. Department of Agriculture Natural Resources Conservation Service, the Edwards Region Grazing Lands Conservation Initiative, the Texas State Soil and Water Conservation Board, the San Antonio River Authority, the Edwards Aquifer Authority, Texas Parks and Wildlife, the Guadalupe Blanco River Authority, and the San Antonio Water System

Effects of Brush Management on the Hydrologic Budget and Water Quality In and Adjacent to Honey Creek State Natural Area, Comal County, Texas, 2001–10

By J. Ryan Banta and Richard N. Slattery

Thumbnail of and link to report PDF (5.06 MB)Abstract

The U.S. Geological Survey, in cooperation with the U.S. Department of Agriculture Natural Resources Conservation Service, the Edwards Region Grazing Lands Conservation Initiative, the Texas State Soil and Water Conservation Board, the San Antonio River Authority, the Edwards Aquifer Authority, Texas Parks and Wildlife, the Guadalupe Blanco River Authority, and the San Antonio Water System, evaluated the hydrologic effects of ashe juniper (Juniperus ashei) removal as a brush management conservation practice in and adjacent to the Honey Creek State Natural Area in Comal County, Tex. By removing the ashe juniper and allowing native grasses to reestablish in the area as a brush management conservation practice, the hydrology in the watershed might change. Using a simplified mass balance approach of the hydrologic cycle, the incoming rainfall was distributed to surface water runoff, evapotranspiration, or groundwater recharge. After hydrologic data were collected in adjacent watersheds for 3 years, brush management occurred on the treatment watershed while the reference watershed was left in its original condition. Hydrologic data were collected for another 6 years. Hydrologic data include rainfall, streamflow, evapotranspiration, and water quality. Groundwater recharge was not directly measured but potential groundwater recharge was calculated using a simplified mass balance approach. The resulting hydrologic datasets were examined for differences between the watersheds and between pre- and post-treatment periods to assess the effects of brush management. The streamflow to rainfall relation (expressed as event unit runoff to event rainfall relation) did not change between the watersheds during pre- and post-treatment periods. The daily evapotranspiration rates at the reference watershed and treatment watershed sites exhibited a seasonal cycle during the pre- and post-treatment periods, with intra- and interannual variability. Statistical analyses indicate the mean difference in daily evapotranspiration rates between the two watershed sites is greater during the post-treatment than the pre-treatment period. Average annual rainfall, streamflow, evapotranspiration, and potential groundwater-recharge conditions were incorporated into a single hydrologic budget (expressed as a percentage of the average annual rainfall) applied to each watershed before and after treatment to evaluate the effects of brush management. During the post-treatment period, the percent average annual unit runoff in the reference watershed was similar to that in the treatment watershed, however, the difference in percentages of average annual evapotranspiration and potential groundwater recharge were more appreciable between the reference and treatment watersheds than during the pre-treatment period. Using graphical comparisons, no notable differences in major ion or nutrient concentrations were found between samples collected at the reference watershed (site 1C) and treatment watershed (site 2C) during pre- and post-treatment periods. Suspended-sediment loads were calculated from samples collected at sites 1C and 2T. The relation between suspended-sediment loads and streamflow calculated from samples collected from sites 1C and 2T did not exhibit a statistically significant difference during the pre-treatment period, whereas during the post-treatment period, relation between suspended-sediment loads and streamflow did exhibit a statistically significant difference. The suspended-sediment load to streamflow relations indicate that for the same streamflow, the suspended-sediment loads calculated from site 2T were generally less than suspended-sediment loads calculated from site 1C during the post-treatment period.

First posted January 6, 2011

For additional information contact:
Director, Texas Water Science Center
U.S. Geological Survey
1505 Ferguson Lane
Austin, Texas 78754-4501
http://tx.usgs.gov/

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Suggested citation:

Banta, J.R., and Slattery, R.N., 2011, Effects of brush management on the hydrologic budget and water quality in and adjacent to Honey Creek State Natural Area, Comal County, Texas, 2001–10: U.S. Geological Survey Scientific Investigations Report 2011–5226, 35 p. (Appendixes available online at http://pubs.usgs.gov/sir/2011/5226/.)



Contents

Abstract

Introduction

Data Collection Methods

Hydrologic Budget

Water Quality

Summary

References

Appendix 1. Average of daily rainfall totals from sites RG1, 1C, 1T and 2T during January 2001–December 2010, Honey Creek State Natural Area, Comal County, Texas

Appendix 2A.Daily mean streamflow during January 2001–December 2010 at site 1C (U.S. Geological Survey station 08167347 Unnamed tributary of Honey Creek site 1C near Spring Branch, Tex.), Honey Creek State Natural Area, Comal County, Texas

Appendix 2B.Daily mean streamflow during January 2001–December 2010 at site 1T (U.S. Geological Survey station 08167350 Unnamed tributary of Honey Creek site 1T near Spring Branch, Tex.), Honey Creek State Natural Area, Comal County, Texas

Appendix 2C.Daily mean streamflow during January 2001–December 2010 at site 2T (U.S. Geological Survey station 08167353 Unnamed tributary of Honey Creek site 2T near Spring Branch, Tex.), Honey Creek State Natural Area, Comal County, Texas

Appendix 3A. Daily total evapotranspiration during January 2002–December 2010 at site RWSET(U.S. Geological Survey station 295104098285900 Honey Creek reference evapotranspiration near Spring Branch, Tex.), Honey Creek State Natural Area, Comal County, Texas

Appendix 3B. Daily total evapotranspiration during January 2002–December 2010 at site TWSET(U.S. Geological Survey station 295102098283200 Honey Creek treatment evapotranspiration near Spring Branch, Tex.), Honey Creek State Natural Area, Comal County, Texas

Appendix 4A.Water-quality and isotope data in rainfall samples collected from site RQW (U.S. Geological Survey station 295108098283201 Honey Creek rainfall water quality near Spring Branch, Tex.), Honey Creek State Natural Area, Comal County, Texas

Appendix 4B.Water-quality and isotope data in samples collected from site 1C (U.S. Geological Survey station 08167347 Unnamed tributary of Honey Creek site 1C near Spring Branch, Tex.), Honey Creek State Natural Area, Comal County, Texas

Appendix 4C.Water-quality and isotope data in samples collected from site 1T (U.S. Geological Survey station 08167350 Unnamed tributary of Honey Creek site 1T near Spring Branch, Tex.), Honey Creek State Natural Area, Comal County, Texas

Appendix 4D.Water-quality and isotope data in samples collected from site 2T (U.S. Geological Survey station 08167353 Unnamed tributary of Honey Creek site 2T near Spring Branch, Tex.), Honey Creek State Natural Area, Comal County, Texas

Appendix 4E.Chemical data for quality-assurance equipment blank samples collected by the auto-sampler at water-quality collection sites in the Honey Creek State Natural Area, Comal County, Texas

Appendix 5A.Suspended-sediment concentration data for surface-water samples collected from site 1C (U.S. Geological Survey station 08167347 Unnamed tributary of Honey Creek site 1C near Spring Branch, Tex.), Honey Creek State Natural Area, Comal County, Texas

Appendix 5B.Suspended-sediment concentration data for surface-water samples collected from site 1T (U.S. Geological Survey station 08167350 Unnamed tributary of Honey Creek site 1T near Spring Branch, Tex.), Honey Creek State Natural Area, Comal County, Texas

Appendix 5C.Suspended-sediment concentration data for surface-water samples collected from site 2T (U.S. Geological Survey station 08167353 Unnamed tributary of Honey Creek site 2T near Spring Branch, Tex.), Honey Creek State Natural Area, Comal County, Texas

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