State Water Resources Research Institute Program

Project ID: 2008WY43B
Title: A New Method for Tracing Seepage from CBNG Water Holding Ponds in the Powder River Basin, Wyoming
Project Type: Research
Start Date: 3/01/2008
End Date: 2/28/2010
Congressional District: 1
Focus Categories: Groundwater, Surface Water, Water Quality
Keywords: Carbon Isotopes, CBNG co-produced water, Recharge Flowpath
Principal Investigators: Sharma, Shikha ; Frost, Carol ; Reddy, Katta J
Federal Funds: $ 0
Non-Federal Matching Funds: $ 85,830
Abstract: The proposed work will establish and verify the utility of a low-cost and innovative approach for understanding "Groundwater contamination caused by seepage out of CBM water holding ponds," which has been identified as one of the critical areas of research under the CBNG Related Issues category in the Wyoming Water Research Program Request for Proposals (WRP RFP, 2008). Groundwater degradation caused by infiltration from CBNG water retention ponds is an issue of immense importance because groundwater is a major source for stock water, irrigation and drinking water for many small communities and ranchers in the Powder River Basin, Wyoming. It is necessary to develop a tracer that can fingerprint this water in order to trace seepage of water from these ponds into shallow aquifers. Strontium isotopes and other geochemical tracers have limited application in some instances because of significant contributions of these elements from local lithologies and high analysis costs. This study evaluates a low cost tracer that is less readily overwhelmed by near-surface sources.

Based upon preliminary analyses of CBNG co-produced water, we suggest that the carbon concentrations and isotopic composition of Dissolved Inorganic Carbon (δ13CDIC ) can be used as a natural tracer for fingerprinting CBNG co-produced water. Our results show that CBNG co-produced water has strongly positive δ13CDIC (+12 to +22‰) that is readily distinguished from the negative δ13C of most surface and groundwaters (-8 to -11‰). Furthermore, the DIC concentrations in co-produced water samples are also high (>100 mg C/l) compared to the 20-50 mg C/l in ambient surface and groundwaters of the region. The distinctively high δ13C and DIC concentrations allow us to identify surface and groundwaters that have incorporated CBNG co-produced water and can also be used to track the CBNG produced water infiltrating from the ponds. Accordingly, we suggest that the δ13CDIC and DIC concentrations of water can be used for long term monitoring of infiltration of CBNG co-produced water from the CBNG water holding ponds.

Samples will be collected from the CBNG discharge wells, water holding ponds and monitoring wells and analyzed for δ13CDIC and DIC concentrations, pH, dissolved oxygen (DO), electrical conductivity (EC), major cations (e.g., Ca, Mg, Na, and K), and major anions (e.g., alkalinity, sulfate, chloride, fluoride, nitrate, and phosphate) to assess changes in water quality as the CBNG water migrates along the recharge flow path.

The results from this study will demonstrate how we can trace the seepage out of CBNG water holding ponds using a low cost stable isotope approach.

Progress/Completion Report, 2008, PDF
Progress/Completion Report, 2009, PDF

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