Tens of millions of dollars have been spent to control Tamarix (saltcedar)
trees along waterways in the Southwestern United States for the purpose of
increasing streamflow yet no increase in streamflow has been demonstrated.
The Pecos River Ecosystem Project (PREP) served as a case study to
characterize surface and groundwater interaction along the Pecos River in
Texas, assess the influence of saltcedar transpiration on stream stage and water
table fluctuations, and evaluate the impacts of large-scale saltcedar control on
baseflows. This is the first study that has investigated the influence of saltcedar
transpiration on surface and groundwater interaction and the first to provide a
mechanistic explanation for the lack of measurable increase in streamflow.
Neither saltcedar transpiration nor saltcedar removal influenced hydraulic
gradients, streambank seepage, or stream elevations. The results of the plot
scale studies indicate saltcedar transpiration along the Pecos River is lower than
reported elsewhere and therefore may not yield detectable increases in baseflow. To extend the study to a much larger scale, we analyzed annual
baseflows at the downstream end of 340 km river reach from 1999
(pretreatment) through 2009. Surprisingly, baseflows declined for four years
after the project began despite additional acreages of saltcedar treatment each
year. However, baseflow surged in 2005 and remained higher than the
pretreatment year (1999) through 2009. Additional detailed analyses of
reservoir release and delivery records and rainfall are needed to better
understand contributions of rainfall and flow regulation to this increase. Tracer
based studies to determine the relative contributions of releases and
groundwater would also enable a better interpretation of the change in
baseflows. We did not investigate any other reported benefits, such as
restoration of native plant species, or reduced soil salinity, of saltcedar control.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/ETD-TAMU-2010-12-8633 |
| Date | 2010 December 1900 |
| Creators | McDonald, Alyson Kay |
| Contributors | Hart, Charles R., Wilcox, Bradford P. |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | thesis, text |
| Format | application/pdf |
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