This executive summary is based on a draft Conowingo Pond Commission report that is undergoing public review until mid-May 2006. Management Plan The report is expected to be complete and available for final approval by April 2006 the commissioners in June 2006. Executive Summary Publication No. 242A

In 2002, the Susquehanna management needs identified by the facilities and Peach Bottom Atomic Basin Commission (the Commission) Workgroup. Additionally, the Workgroup Power Station, local water utilities, and convened the Conowingo Pond was tasked with identifying management the Commission. The Workgroup met Workgroup (the Workgroup) to develop actions that the Commission should several times a year and provided a management plan for the Conowingo incorporate into its regulatory and water direction, oversight, input, and review pond. The primary purpose of this resource management programs. The for the planning effort and its results. four-year planning effort was for the Workgroup completed its report in There is a wide range of interests, Workgroup to evaluate operational March 2006 and it has served as the problems, and potential conflicts related alternatives for the pond and to basis for the Commission’s report on the to the resources, uses, and operation recommend to the Commission a selected Conowingo Pond Management Plan. of the Conowingo pond. Effective management plan that best meets the The Workgroup, which was chaired by management of the Conowingo pond the Department during low flow conditions is critical of the Environment, was for economic, environmental, and intended to represent human welfare needs in the area. the interests of key During low flow conditions on the stakeholders in the , there is the

Photo courtesy of operation and use of the potential for conflicts in management pond. The membership objectives to arise to the point where was comprised of difficult economic and environmental representatives from decisions need to be made. federal and state agencies, The Conowingo pond, created by local jurisdictions, the construction of the Conowingo , operators of the lower is an interstate body of water with Susquehanna hydroelectric approximately 8 miles of the pond in Looking north at the Conowingo dam with the pond in the upper portion. and 6 miles in Maryland. The dam was completed in 1928 to provide hydroelectric power generation for the Conowingo Hydroelectric Station. Operation of the dam by Exelon Generation, Inc. (Exelon) is subject to the requirements of the Federal Energy Regulatory Commission (FERC). Those requirements include provisions related to minimum flow releases and maintenance of recreational pond levels. Current minimum flows, which vary by season, were established to provide protection for fishery resources, with highest minimum flows required during the anadromous fish migratory period in spring, and intermittent flows permitted only during the winter, when fish populations are limited. By virtue of the pond, a stable source of water storage for other purposes was also provided. The Muddy Run Pumped Storage Hydroelectric Facility, built in 1968, Facilities in the vicinity of the Conowingo pond. cycles water back and forth from the benefits, anadromous fish migration, • Consumptive water use in the pond for additional power generation. upstream reservoir storage, environmental Susquehanna River Basin, from and The water in the Conowingo pond is resources, and cooperative management. upstream of the Conowingo pond, is also used for public water supply by the The Workgroup collectively assessed the increasing and could eventually City of and Chester Water interests and identified problems and impact negatively on the pond and Authority, and for industrial cooling by conflicts that needed to be addressed. those who rely on its water. the Peach Bottom Atomic Power Station. They were: Finally, the pond provides a valuable • Commission-owned water supply recreational, fish, and wildlife resource. • Maintaining FERC mandated storage at two federal reservoirs in Under normal and slightly below minimum flow releases from the the upper basin is managed under average flow conditions, there is Conowingo pond can lead to operating rules that were developed generally ample water in the lower disruption in power production, for water supply users elsewhere Susquehanna River to maintain hydro- water supply withdrawal limitations in the Susquehanna River Basin. electric operations; support water and diminished recreational Releases from these reservoirs are supply demands; sustain recreational, opportunities during significant not mandated by FERC license fish, and wildlife activities; and meet low flow events, and depletes requirements and may not provide required flows to downstream river storage that might otherwise be optimum and timely benefits to reaches and the upper . available for release during low the Conowingo pond during low However, during more severe low flow flow events of extended duration. flow conditions. conditions, the available water becomes insufficient to meet all prescribed uses • Temporary waivers to allow inclusion • Increasing public water supply and required needs. During such periods, of gate leakage towards meeting needs for Baltimore City, Harford as Exelon operates the Conowingo dam minimum flow releases have been County, Chester Water Authority, in accordance with its FERC license authorized by FERC four times and the areas of Pennsylvania requirements, storage levels in the (1999, 2001, 2002, and 2005) during and Maryland surrounding the Conowingo and Muddy Run facilities recent droughts, but only under Conowingo pond are expected begin to decline. Declining pond levels emergency or near-emergency to lead to requests for greater pose a threat to Peach Bottom’s cooling conditions when time is critical and withdrawals from the pond or water intake, Muddy Run’s intake, the serious impacts are developing with the Susquehanna River just use of recreation facilities, shore habitat, no projected improvement. upstream. and maintenance of downstream flows. In response to declining pond levels • Increased salinity levels in the • Increased consumptive water use and worsening conditions, FERC has Susquehanna River downstream of needs (i.e., cooling water for a new authorized Exelon on four occasions the Conowingo dam during low thermoelectric power plant) could to temporarily include water leaking flow conditions can negatively impact require additional withdrawals from through closed wicket gates toward the water supply for Havre de Grace. the pond. meeting the dam’s daily minimum flow release requirement. A 1988 settlement agreement specifically excludes that water from the minimum release calculation, but FERC has overridden the exclusion during the four events. In order to investigate and recommend a management plan for the Conowingo pond, it was important that the members of the Workgroup provide insights to the diversified interests related to the pond’s resources. These interests include hydroelectric power generation, public water supply, water use upstream of the Conowingo pond, minimum flow release requirements, minimum dissolved oxygen requirements, summertime minimum recreational pond levels, multipurpose Operation levels of the Conowingo pond.

2 A valuable tool used during the planning study was the Commission’s OASIS computer model. This daily flow model incorporated more than 70 years of hydrologic record throughout the basin and was used to measure the impacts of various operation parameters on the pond and flow conditions downstream. In addition to hydrologic flow records, the model included representations of the operation of large public water supply withdrawals, power plants, and reservoirs in the Susquehanna River Basin, and incorporated basinwide estimates of existing and future consumptive water uses. Comparative output displays of Conowingo pond levels and dam releases allowed the Workgroup to evaluate numerous operation alternatives and make recommendations for the management of the pond. Using the hydrologic model, baseline conditions (i.e., existing operations) were established and a series of 32 initial alternatives was evaluated. Key parameters identified for the evaluation included minimum downstream flow OASIS schematic of the Susquehanna basin. requirements, credit for leakage of water at the dam, water supply withdrawals withdrawal operations, and upstream Details on these alternatives are included under normal and low flow conditions, consumptive use were kept constant to in Section V of the main report. A thorough consumptive water use in the basin allow for direct comparison between evaluation of the six preferred alternatives above the Conowingo pond, and the use alternatives. The alternatives were: led to the selected plan, which contains of Commission-owned storage at two (1) Baseline; (2) Automatic Credit; favorable elements of several of the final upstream reservoirs to augment low (3) Critical Level; (4) System Deficit; alternatives. flows. Details on these alternatives are (5) Stepped Waiver; and (6) Minimum Flow. Based on results of the modeled included in Appendix 3 of the main scenarios, the Workgroup identified the report. Computer-aided negotiations Based on results of leakage and the minimum release (CAN) were used to perform efficient requirement as the most critical parameters evaluations of the long-term implications the modeled scenarios, in managing low flows and enabling of changes in operating policies and the Conowingo pond to remain viable facility configurations. The iterative the Workgroup identified during droughts. While water conservation process embodied in the CAN sessions measures and the release of augmenting served to inform the Workgroup members the leakage and the minimum flow from upstream reservoir storage about the pros and cons of many alternatives release requirement as the were deemed reasonable measures worthy on a consistent and balanced basis. of consideration, the supplemental volume After review of the initial most critical parameters in of water they provide was found to be 32 alternatives, the Workgroup developed small relative to the daily fluctuations 6 final alternatives for closer analysis managing low flows and of the pond, and simply did not offer leading up to the selection of a preferred substantial drought mitigation. Therefore, operating plan. The alternatives differed enabling the Conowingo the selected Conowingo Pond Management mainly in operating rules for release Plan was based on establishing a formal requirements from the Conowingo dam pond to remain viable protocol to implement a credit for leakage, during times of low flow. Parameters and to specifying the hydrologic conditions such as demand for water supply, water during droughts. under which the credit is warranted.

3 The selected plan, “Automatic The Workgroup will convene annually and determination of what measures, Q-FERC + 1000,” includes initiation of to review project operations, assess if any, are necessary to mitigate the an automatic credit for leakage of up to the potential for hydrologic conditions impacts. 800 cubic feet per second (cfs), when the to develop into drought, and conduct flow conditions at the Marietta gage a drought operations exercise. The 2. Investigation of the water supply decline to a flow of 1,000 cfs greater hydrologic model used to develop the storage owned by the Commission than the seasonal flow thresholds management plan is to be kept up at the federal Cowanesque and (“QFERC”) established by FERC. The to date by the Commission for the Curwensville Lakes projects for Marietta flow threshold is 5,000 cfs Workgroup’s use, and will accurately alternative operational strategies to between June 1 and September 14, and reflect current water withdrawals in provide more effective low flow decreases to 3,500 cfs on September 15 both the pond and the Susquehanna augmentation, including benefits to through the end of November. River Basin, as well as current policies the Conowingo pond and instream Modeled simulation runs of operating and operation protocols. The Workgroup resources below the dam. the resource under the recommended will also be responsible for reviewing guideline produced favorable results. and updating, as necessary, the selected 3. Incorporation of key management They demonstrated the most favorable management plan on a periodic basis principles and tools described in balance for preserving adequate levels in not to exceed five years. the Commission’s report, including the pond, ensuring reliable multipurpose the use of the annually updated use of the pond, and meeting the The Workgroup will hydrologic model, into the requirements for the quantity of water Commission’s regulatory and water released to the downstream reaches convene annually to resource management programs. of the Susquehanna River and the Chesapeake Bay. To further avoid review project operations, The report on the Conowingo Pond potential negative impacts, the Workgroup Management Plan, with its documented conditioned the recommendation of assess the potential for thorough analysis, provides valuable “Automatic Q-FERC + 1000” with information for the Commission, public restrictions that prohibit Exelon from hydrologic conditions water suppliers, power companies, automatically taking a credit for leakage and environmental resource agencies in during the spring spawning season to develop into drought, making regulatory and management (April 1 - June 30) and limit the credit to decisions involving the resources of only the portion of the 800 cfs that is and conduct a drought the lower Susquehanna River. Given absolutely necessary to maintain viable the potential for increased water use pond levels. operations exercise. and future withdrawals in the upstream Implementation of the selected plan basin and from the Conowingo pond, will require that Exelon successfully The planning study also identified the adoption of the Conowingo Pond petition FERC for an amendment to the three related actions beneficial to Management Plan and related existing license to include the altered managing the Conowingo pond that actions is intended to ensure disposition of the gate leakage during the Commission supports including sustainable operations and a reliable drought conditions. The thorough in its regulatory and water resource water source for all needs, from public planning effort of the Workgroup over management programs. They are: water supply and power generation to the past four years and formal support recreation and aquatic habitat, for of the proposed license amendment by 1. Consideration of the impacts of many years to come. The full report the agencies involved are expected to be increasing consumptive water use in is accessible by the public via the positive input to the approval process. the basin on the Conowingo pond Commission’s website at www.srbc.net.

SUSQUEHANNA RIVER BASIN COMMISSION 1721 N. Front Street • Harrisburg, Pennsylvania 17102-2391 Phone: (717) 238-0423 • Fax: (717) 238-2436 • www.srbc.net SRBC Contact: Andrew Dehoff, Director, Planning and Operations, [email protected]