Subtask 3.3 Quantity and Fate of Water Salvaged as a Result of Saltcedar Control

Inflows to this reach of the Pecos River include precipitation, runoff, groundwater discharge and releases from Red Bluff Reservoir. Outflows from the river consist of seepage into aquifers, evaporation, transpiration, and irrigation diversion. This Subtask will evaluate flows between the river and the aquifer. It will explore the effects of saltcedar control on the fate of salvaged water and will determine the amount of water released to downstream riverine flow and groundwater recharge.

Texas AgriLife Extension Service and Texas AgriLife Research will:

  • Characterize the aquifer beneath treated and untreated sites with borehole exploration;
  • Install additional monitoring wells to configure subsurface flow patterns, and
  • Conduct flow measurements with designated releases from Red Bluff Reservoir.

First, a map of alluvial sediments will be developed to diagram subsurface flow patterns. The goal is to delineate the extent of the shallow aquifer by drilling additional boreholes at plots along the Pecos River. Soil and water samples will be collected and analyzed to determine spatial variation in hydrological properties.

Second, additional monitoring wells will be installed on both sides of the Pecos River to better understand flow patterns. This work will expand the existing well monitoring network. Data loggers will record hourly changes in the water level in these wells. Water level data will be processed to construct a flow net of the shallow aquifer. The flow net will be used to define the interaction between surface water and ground water, and will be used to assess volume and direction of flow.

Finally, designated releases of water from Red Bluff Reservoir will be scheduled to establish the relationship between surface water and ground water flows in the Basin. Multiple releases will be monitored for a period of several days during the project to detect whether saltcedar control causes any seasonal changes in the response of the shallow aquifer. Seepage losses and gains by the river will be calculated and the factors that influence seepage losses and gains will be assessed.

Deliverables for this Subtask

  • A well monitoring schedule will be developed
  • A map of soil physical properties within the study area will be created
  • A flow net, illustrating velocity and direction of subsurface flow, will be developed
  • A water balance analyses that includes the effects of seasonal seepage will be developed
  • Predictions will be developed about the extent to which saltcedar control may influence surface and ground water flows

Reports

  • TR-304: Quantity and Fate of Water Salvage as a Result of Saltcedar Control on the Pecos River in Texas
  • Will Hatler Thesis: Water Loss And Potential Salvage In Saltcedar (Tamarix spp.) Stands On The Pecos River In Texas