State Water Resources Research Institute Program

Project ID: 2003KS33B
Title: A Field Assessment of a Method for Estimation of Ground-Water Consumption By Phreatophytes
Project Type: Research
Start Date: 3/01/2003
End Date: 2/28/2008
Congressional District: 2nd District
Focus Categories: Groundwater, Water Use
Keywords: phreatophytes, ground water, evapotranspiration, water balance
Principal Investigators: Butler, James J. (Kansas Geological Survey); Kluitenberg, Gerard; Whittemore, Donald
Federal Funds: $ 19,490
Non-Federal Matching Funds: $ 46,151
Abstract: Low streamflows are an increasing problem in Kansas and other areas of the U.S. Stream-aquifer interactions clearly play an important role in the generation and maintenance of these low flows, with ground-water development often being a major factor. Ground-water consumption by phreatophytes is thought to be an important component of the hydrologic cycle in riparian corridors in central and western Kansas, and could also be a significant contributor to the low streamflows. Recently, partly in response to concerns about water consumption, expensive measures for phreatophyte control have been advocated for stretches of rivers in western Kansas. However, reliable estimates of the magnitude of ground-water consumption by phreatophytes, its impact on stream-aquifer systems, and the water savings that could be gained from control activities have yet to be obtained. There is a critical need to develop methods that will enable the impact of phreatophyte activity on stream-aquifer systems to be quantified. That is the purpose of the research described here. In this proposal, we outline activities directed at further refining a method for identifying and quantifying phreatophyte consumption of ground water, and for assessing the ground-water savings gained by phreatophyte control. This method exploits information on plant water use that is embedded in diurnal water-table fluctuations. An approach based on water-table fluctuations has many advantages: 1) it provides direct information on ground-water consumption, which is virtually impossible to quantify using other methods; 2) the water-table variations on which it is based are the integrated response to a highly heterogeneous and difficult-to-characterize group of phreatophyte stresses; 3) it is generic in nature and not dependent on any particular mix of phreatophytes; 4) it can be readily implemented at a relatively low cost; and 5) it is also a convenient means of assessing the impact of phreatophyte control efforts. The primary new aspects of the research proposed here include an assessment of the ground-water consumption by the major invasive phreatophytes in Kansas (salt cedar and Russian olive) relative to that by shallow-rooted vegetation (grasses, forbs, etc.) and direct evaporation from the water table; an evaluation of the utility of a new generation of capacitance sensors for enhancing understanding of the temporal evolution of soil moisture in the presence of phreatophytes; numerical modeling of ground-water flow and evapotranspiration at a well-studied field site; and an assessment of the impact of the screen length and casing radius of an observation well on the measured water-table fluctuations. Methods for estimation of specific yield will also be further refined. The end product of this research will be a technique of demonstrated effectiveness for both identifying and quantifying phreatophyte activity, and for assessing the water savings achieved by removal of invasive phreatophytes from riparian-zone communities. Projects expected to follow from this work include quantifying phreatophyte activity in the major river basins in central and western Kansas by combining this approach with remote-sensing methodologies-This proposal also presents the opportunity to continue the leveraging of Kansas Water Resources Institute and Kansas Water Office funds to better address an important state issue.

Progress/Completion Report, PDF

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