Demonstrating Pennsylvania's regulation that insures water withdrawals do not damage stream health, the Susquehanna River Basin Commission has suspended 36 individual water withdrawals, because stream flows fell to a critical point. See http://www.srbc.net/. Or see the Scott Detrow NPR report at http://stateimpact.npr.org/pennsylvania/2011/07/19/srbc-suspends-water-withdrawals-in-36-locations/#more-711.
Most of the suspended water withdrawals are for gas drilling. As Scott Detrow reports, the SRBC receives stream flow data from gauges operated by the US Geologic Survey and also requires all withdrawals--not just gas withdrawals--to be metered each day and then reported quarterly to the SRBC.
While Pennsylvania can have low-flow conditions and drought, our problems pale in comparison to those in Texas and the Southwest where aridification may be unfolding.
Gas drilling accounts for less than 1% of the nearly 10 billion gallons of water withdrawn each day in Pennsylvania.