CBM Stream Depletion Assessment Studies
These studies were a joint effort by the Colorado Oil and Gas Conservation Commission, the Colorado Geological Survey and the Colorado Division of Water Resources. These agencies are part of the Colorado Department of Natural Resources. The consultant who performed these studies in conjunction with the Department of Natural Resources agencies was S.S. Papadopulos & Associates.
The purpose of these studies was to develop a quantitative assessment of the levels of stream depletion or reduction in formation outflows (spring flows or flowing stream systems gaining from contact with formations) that may be occurring as a result of the removal of water by coalbed methane (“CBM”) production wells. This water historically has been disposed by one or more methods, including re-injection into deep formations, discharge to the surface stream system, and ponding/evaporation. The concern had been raised that the removal of significant volumes of water from aquifers that may be tributary to the surface stream system could be resulting in stream depletions or a reduction in spring flows and/or formation outflows (accretions) that are of a magnitude sufficient to cause injury to senior water rights holders on over-appropriated stream systems throughout Colorado. These studies sought to develop a reliable assessment as to the levels of depletion, definition of the areas where CBM is ongoing that might be classified as nontributary, definition of any potential correlations of water quality, geology, aquifer geometry, or formation/well depth that could lead to general guidelines about the potential for stream depletion that would be useful in either prompting or avoiding more detailed studies, and development of recommendations for further data collection or investigations.