Hydrogeologic, Isotopic, And Geochemical Analysis Of Groundwater-Surface Water Interactions Along The Fruitland Outcrop: The Backdrop For Coalbed Methane Development In The Northern San Juan Basin
Kroepsch, Adrianne 1 ; Williams, Mark 2 ; Nydick, Koren 3 ; Gianniny, Gary 4
1 University of Colorado-Boulder
2 University of Colorado
3 Mountain Studies Institute
4 Fort Lewis College
There remains considerable uncertainty about how coal bed methane (CBM) production from Colorado’s Fruitland Formation may affect the quantity and quality of nearby surface water, springs, wetlands, and groundwater systems along the northwestern margin of the San Juan Basin (SJB) near Durango, CO. Despite being one of the highest-producing and most extensively studied CBM basins in the world (Fasset 2000; Snyder and Fabryka-Martin 2007), controversy remains over the age of Fruitland Formation waters, as well as the extent to which the SJB undergoes active hydrologic throughflow and whether CBM production near the Fruitland Outcrop will impact existing surface-groundwater interactions. In order to more closely characterize basin hydrology near the Fruitland Outcrop, geochemical and isotopic properties of 67 surface water and groundwater sites were monitored from 2008-2009 in neighboring La Plata and Archuleta counties. Water samples were collected from existing CBM wells, domestic wells, piezometers, springs, and the Florida and Piedra Rivers and tributaries using a sampling strategy designed to provide baseline hydrologic information in an area soon to see increased CBM drilling. Isotopic and geochemical results suggest tighter surface-groundwater connections at the edge of the basin than expected, with marked variation between drainages, and may indicate a system that is already over-drafted by existing CBM production and heavy domestic well use. Data also suggest that increased CBM production near the Fruitland Outcrop could indeed affect local hydrology, and that resource management strategies may need to account for spatial variation in these potential impacts.
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