Consumptive Use Modeling to Optimize Surface Water Withdrawal Sustainability

Elaine Langone Center, Terrace Room

Development of a natural gas well by hydraulic fracturing requires several million gallons of water over a period of days or weeks. Options available to supply this water include surface water take points (with or without storage impoundments), off-site haulage (trucking), or, more rarely, wells. The Susquehanna River Basin Commission (SRBC) establishes restrictions on the amount of water that may be withdrawn from the Susquehanna River or its tributaries by setting a minimum allowable flow that must remain in the channel (passby), and newer permits have been based on a monthly flow frequency distribution for the stream. Conventional statistical methods can provide an estimate of the probability that a surface water take point will provide sufficient water to meet a fracturing project’s needs; however, this does not address the behavior of a stream over time with regards to water availability. A new method of visualizing water use planning is presented based on comparing the projected daily project use requirements to the modeled daily regulatory availability over the historic record for the stream source in association with an existing or constructed storage impoundment. This approach allows better visualization of the behavior of a water supply (i.e. identification of flashy streams and situations where a water supply has a non-normal statistical behavior) to give greater confidence in the sizing of storage impoundments to meet a supply goal of surface withdrawal only. Hydraulic fracturing schedules can then be manipulated within the model to make use of excess flows above passby and avoid periods where direct surface withdrawal is not sustainable. The goal of this modeling is to reduce or eliminate truck hauling requirements for water and its impacts to the local community, carbon emissions, and unbalanced withdrawals from other watersheds.