Urban Waters Federal Partnership - Edwards Aquifer Recharge Zone Monitoring Network

Science Center Objects

The USGS Texas Water Science Center is implementing a more complete and integrated monitoring network for the Edwards aquifer to improve the understanding of aquifer water quality and establish a baseline for measuring future water-quality changes.

    Data from this study can be used to address these primary objectives:

    1. Long-term trends in water quality, with particular emphasis on nutrients and organic contaminants including pesticides, pharmaceuticals, and wastewater compounds.
    2. How surface water - groundwater interaction affects water quality changes over a range of hydrologic conditions.

     

    Edwards Aquifer conceptual model

    Edwards Aquifer conceptual model

    The San Antonio segment of the Edwards aquifer (hereafter, the Edwards aquifer), located in south-central Texas is a karst groundwater system that provides important water resources to the region, provides habitat for endemic and endangered species, and supplies major spring systems such as Comal Springs and San Marcos Springs. 

    In the face of increasing pressures from urbanization, a better understanding of the sources, fate, and transport of anthropogenic contaminants in the aquifer is needed to improve water management decision-making capabilities. 

    Additionally, the role of surface water-groundwater interaction, and effects on water quality under a range of flow conditions, is needed to understand urbanization impacts to the aquifer.  Sources of anthropogenic constituents to the aquifer, such as nutrients, pesticides, pharmaceuticals, and other wastewater compounds and the influences of different land-cover types, are largely unknown.  

     

    Approach

    Rapid recharge to Edwards Aquifer

    Seco Creek sinkhole in Medina County provides direct recharge to the Edwards Aquifer.    

    An approach integrating  real-time data logging, discrete sample collection, and automated sampling is being used to obtain water-quality data on major ions, nutrients, organic contaminants, and selected isotopes (hydrogen, oxygen, nitrogen, and strontium) in rainfall, recharging surface water, unconfined groundwater, confined groundwater, and spring discharge.

    Continuous surface-water and groundwater measurements

    Selected sites will include:

    • Precipitation collection sites on the urbanized and rural portion of the Edwards aquifer recharge zone
    • Surface water sites, selected to represent urban and rural surface-water runoff
    • Groundwater sites with contrasting properties, including urban and rural settings and shallow unconfined and deeper confined groundwater wells
    • Comal spring #1 –a major discharge point of the aquifer and integrator of regional aquifer flowpaths

    Routine sampling

    Routine samples have been collected at regular intervals through multiple years with the objective of covering a range of aquifer flow conditions. 

    Event-based sampling

    Event-based samples have been collected in response to storm events from surface water sites, groundwater sites, and the spring discharge site.  Additionally, precipitation samples have been collected and characterized for water quality.

     

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