Monday, November 13, 2006

Assessing Constructed Wetlands for Beneficial Use of Coal Bed Methane (CBM) Product Water.

Amber Kirkpatrick, Montana State Univ, LRES, Leon Johnson Hall, Rm 334, Bozeman, MT 59717-3120 and James Bauder, Montana State Univ, PO Box 173120, Bozeman, MT 59717-3120.




Changes in agricultural practices, and irrigation strategies combined with natural processes, have led to increased salinization of soil and water resources worldwide.  In the Powder River Basin of Montana and Wyoming, coal bed methane (CBM) development results in the co-production of large volumes of sodic and moderately saline discharge water, and represents a potential source of salinization of soil and water resources. 

The objective of this study was to evaluate the potential of constructed wetlands as a beneficial use of CBM product water.  This was accomplished by assessing seasonal water use and biomass production of three native plant communities. Native species establish hydrologically distinct communities in former ephemeral channels now running with CBM product water, and nine species of those cataloged were selected and segregated into the three communities.  Closed-system wetland cells were constructed and each community was assigned to four of these cells, i.e., lysimeters.  Chemistry of the supply water was sodic and moderately saline (EC ~ 3.4 dS/m, SAR > 25), typical of northern portions of the Powder River Basin where low to moderate electrical conductivities (EC 2-3 dS/m) and high sodium adsorption ratios (SAR > 20) are common.

Results of this study indicate that constructed wetlands planted with native, salt tolerant species have potential to utilize substantial volumes of CBM product water while remaining robust and viable.  Although results suggest evaporation from an open water surface to be greater than evapotranspiration from a constructed wetland, constructed wetlands have added benefits of providing wildlife habitat, recreation and viewshed enhancement.