WATER DEVELOPMENT WITHIN SMALL HIGH/EXCEPTIONAL QUALITY WATERSHEDS: NOT ROUTINE

Appalachian Plateau high/exceptional-quality watersheds occur in topographic and anticlinal highs flanked by extensively mined coal-bearing synclinal basins now attracting unconventional gas plays. Historically, communities tapped upland watersheds avoiding treatment of mine-impacted waters often distributed by gravity. Today, interstate compacts, state and federal drinking water standards, ecological and other concerns challenge water procurement projects adding to characterization and development costs, delays and investment uncertainties.

The Susquehanna River Basin Commission for example, places exceptional demands on hydrogeologic assessments for basin areas equal to or less than 10 mi² where stream gauging data are rare or nonexistent. USGS Streamstats methodology may underestimate recharge important in allocation decisions. Unaccounted water may escape within the hyperic zone or as deeper leakage along anticlinal flanks.

Underflow losses within 3-to-10 m thick valley fill and dipping semi-confined aquifers may exceed dry season base flow. Some of this water may appear as base flow lower with the same or adjacent watersheds. Groundwater pumpage can change crossover lines where upwelling confined groundwater reverts downward thereby reducing base flow. This can occur beyond the 10 mi² watershed limit.

Hydrogeological characterization of high quality watersheds require more than one stream gauging station, hydrograph separation, data obtained from channel, nested piezometer and bedrock wells, gauging of springs, wetland observations, detailed overburden, confining bed and aquifer maps, including hydraulic properties, seasonal changes in water table and potentiometric surfaces. Aquifer stress tests one, three or more-months duration maybe required to quantity pumping induced v seasonal surface-groundwater interactions. Seepage losses to surface and subsurface mines and hydraulic significance of faults complicate analyses. Potential contributing groundwater basins can exceed 10 mi² surface basin limits expanding greatly under pumping stress thieving water from adjacent watersheds. Despite proposals to capture and bank excess stormwater to mitigate adverse influences, no such projects have been realized.