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average at least once every 10 years, and it has been used to define low flows for the purpose of setting permit limits. The Minnesota Pollution Control Agency has established The 7Q10 value for the Minnesota River near Jordan is 175 MGD (272 cfs). Low flow in the Mississippi River is of particular concern and is included in the State Drought Plan, which includes a matrix of drought phase triggers. When flow is less than 2,000 cubic feet per second (1,293 MGD) for five consecutive days, public water suppliers and other water users using the Mississippi River implement appropriate conservation measures. Should flow fall below 1,000 cubic feet per second (646 MGD) for five consecutive days, all public water suppliers in the Twin Cities metro area implement mandatory water use reductions with the goal of reducing water use to January levels (Minnesota Department of Natural Resources, 2009). Much discussion about these limits followed the 1988 drought. Critical flow of the Mississippi River was determined to be a flow that supports basic needs for water supply, power and navigation; a minimum flow of 554 cubic feet per second (358 MGD) is needed for these purposes (Metropolitan Council, 1990). Work done by the U.S. Geological Survey indicate that there is less than a 1% probability of flow on the Mississippi River falling below 600 cubic feet per second in any give year; the recurrence interval for flow less than 600 cubic feet per second is 100 years (Kessler and Lorenz, 2010). Stormwater Currently, the State of Minnesota does not have a state -specific code applicable to stormwater harvesting and reuse. The MPCA has developed some guidelines for the use of reclaimed water, and the Metropolitan Council has summarized these and other information in its Stormwater Reuse Guide (Metropolitan Council, 2011). Because of its direct tie to precipitation, stormwater is not consistently available for reuse, so storage is required to ensure water is available when needed. The amount of stormwater available at any given location is also a factor of the size and amount of impervious surface in the area contributing to the site. More work is needed to evaluate the potential for stormwater reuse across the region, but a rough estimate can be made of the amount of stormwater available for reuse, based on some simplifying assumptions: • A one acre parking lot generates 27,000 gallons of runoff during a 1" rainfall, • An average of six 1" rainfall events occur on average in recent years, and • 245,909 acres of impervious area exist in the metropolitan area. Given those assumptions, approximately 100 million gallons per day of stormwater water could be available in the region. Stormwater reuse projects are not tracked consistently through the region, so it is uncertain how much stormwater reuse currently exists. Reclaimed wastewater Opportunities to use reclaimed wastewater as a non -potable water source exist throughout the region. Reusing treated wastewater to supplement groundwater and surface water as sources of water to support regional growth, where economically feasible, will promote sustainability goals. Feasibility depends on site-specific factors. For instance, proximity to treatment plants, regulatory requirements, water quality needs, distribution system requirements, and the benefits of reuse from a total water perspective all contribute to feasibility. Reclaimed wastewater is one of the region's underutilized water supply sources. The amount of reclaimed wastewater available for reuse is ultimately limited by the amount of wastewater produced and the number and size of wastewater treatment facilities. The Council WATER SUPPLY MASTER PLAN- Draft June 2015 37