Recent drought in the Southeast has intensified a tri-state water conflict involving Alabama, Florida, and Georgia over water allocation and management in the Apalachicola-Chattahoochee-Flint (ACF) river basin (see Figure 1 ). The water at stake is vital for the basin's municipalities and industries. These include the Atlanta metropolitan area's populace, industry, and recreational economy; hydropower dams and cooling of thermoelectric power plants throughout the basin; lower basin navigation interests; agriculture, including irrigators; and the regionally significant Apalachicola Bay oyster industry. The water also is vital to threatened and endangered species and basin ecosystems. Management of the current drought may shape long-term ACF management, set precedents for future federal drought responses, and affect the role of the Endangered Species Act (ESA) in water resources management. For more information on ACF species issues, see CRS Report RL34440, Apalachicola-Chattahoochee-Flint Drought: Species and Ecosystem Management , by [author name scrubbed], [author name scrubbed], and [author name scrubbed]. Drought has escalated competition for the water in federal ACF reservoirs. A central issue for the U.S. Army Corps of Engineers (Corps) is how to manage its reservoirs to meet municipal and industrial (M&I) water needs equitably in the upper and lower basin, while complying with federal law (e.g., ESA) and minimizing harm to river and bay ecosystems. The operation of federal reservoirs shapes both the quantity of stored water and the river flows. Predictions for a continued drought have Georgia's upper basin municipal and industrial users concerned about depletion of their principal (and, in some cases, their only) water supply—Lake Lanier—which is slow to refill because of the limited drainage area feeding into it. Lower basin interests (including those in southwest Georgia) are concerned about current and future river flows to meet their municipal, electricity, and ecosystem needs. This report provides an introductory analysis of federal water management issues in the ACF, particularly during drought. The report underscores that decision-makers are faced with the tradeoff of the current harm that reduced flows may cause aquatic species against the benefits of maintaining water in storage for future multi-purpose use later. The first section briefly introduces the basin's water resources and related federal issues. The second section summarizes current federal reservoir operations. The third section discusses how the municipal, industrial, and agricultural uses of ACF waters affect federal reservoir management. The fourth section covers how species protections affect Corps operations and how Corps operations may affect protected species. The fifth section briefly discusses legislation in the 110 th Congress related to the ACF and water supply and management issues in the Southeast. The report concludes with comments about the ACF in the broader context of federal water policies and projects. Many aspects of the complex ACF management issues are not discussed in detail (e.g., ACF navigation and recreation issues, the influence of the Alabama-Coosa-Tallapoosa (ACT) basin). The ACF basin drains areas of northern and western Georgia, southeastern Alabama, and northwest Florida. (See Figure 1 ) The basin extends from the Blue Ridge Mountains to the Gulf of Mexico at Apalachicola Bay. Congress authorized construction of federal facilities for water resources development of the ACF in 1945 and 1946. The Corps now operates five dams—four on the Chattahoochee and one on the Apalachicola River at the confluence of Chattahoochee and Flint Rivers. Four of these dams store water: Buford Dam forming Lake Lanier (62% of the Corps' ACF storage capacity), West Point (18%), W. F. George (14%), and Woodruff forming Lake Seminole (6%). Woodruff's limited storage is primarily for flow regulation and does not function as a water storage reservoir for ACF operational purposes. These four facilities and other nonfederal dams in the ACF also house hydroelectric facilities. The fifth federal dam—Andrews Dam—is operated for navigation and has no storage capacity. No water storage facilities have been built on the Flint River. Water resource use in the ACF has changed since the planning and construction of the reservoirs, which originally were justified based on their navigation, hydropower, and flood control benefits. For example, the Atlanta metro area has developed into a significant economic and population center; basin agriculture has become more dependent on irrigation; and environmental quality and species concerns receive greater public attention and federal protections. These and other factors have increased competition for ACF waters and produced conflicting interests in maintaining water in storage and maintaining river flows for in-stream purposes. It is often difficult to recognize when a drought is starting, and it is challenging to make decisions that entail tradeoffs between current and future costs and benefits based on expectations about when a drought may end. The current drought is already eclipsing conditions experienced by Georgia during the mid-1950s, which is considered the state's most severe drought on record. The year 2007 was the second-driest on record for Atlanta, following 2006, which also was dry. As runoff in the basin fell below the flows necessary to meet both consumptive demand (i.e., M&I and agricultural uses) and in-stream flow requirements (e.g., for species and thermoelectric power plant cooling purposes), water stored in the reservoirs was released to meet these needs. The lower basin reservoirs were drawn down first. In late summer 2007, Lake Lanier was the only reservoir with significant remaining storage. When the Corps released water from Lake Lanier in the upper basin to provide minimum flows in the Apalachicola River in the lower basin, the lake experienced significant drawdown, surpassing the reservoir's previous record low and triggering urgent concern from lake Lanier water users and recreational interests. Lake Lanier water storage is of critical concern because it provides 72% of the water supply for the Atlanta metro area and more than 62% of the storage space in federal ACF reservoirs, but refills slowly. The drainage area feeding the lake is only 5% of the ACF basin. Lake Lanier's drawdown escalated the conflict among the three states. Without a water allocation agreement or decision to guide distribution of available supply among the states, lower basin stakeholders began questioning the sufficiency of Georgia's municipal, industrial, and agricultural long-term and emergency water conservation and demand management efforts. Upper basin stakeholders questioned the justification for the minimum flow requirements in the Apalachicola River and cited the Corps' operating procedures, which had been adopted in 2006 to protect threatened and endangered species, as significantly increasing the risk of depleting ACF reservoirs by allowing their drawdown and insufficient opportunity for refill. In the 1970s and 1980s, Georgia officials became increasingly concerned with water supply for the Atlanta metro area's growing needs. The Corps in 1989 agreed to provide storage space for roughly twice as much M&I water in Lake Lanier by reallocating space from hydropower to water supply; this decision resulted in Alabama and Florida suing the Corps based on the impact that the reallocation would have on the lower basin and for a failure to comply with National Environmental Policy Act (NEPA) (42 U.S.C. §§ 4321 et seq.). (See Appendix A for an introduction to selected ACF suits in federal courts and the history of efforts to establish an ACF Compact. For a discussion of how NEPA relates to current ACF operations, see Appendix B ). The reallocation question has yet to be resolved. Since this first suit, ACF waters have been the foundation of multiple ongoing legal disputes and the subject of a tri-state water compact that failed when the states could not agree on how to allocate basin waters. When states are the parties disputing water allocation, the conflict may be resolved by agreement in an interstate compact, through apportionment by the courts, or through allocation by Congress. The water rights doctrines operating in the ACF states makes allocation particularly challenging. Alabama, Florida, and Georgia, like most eastern states, generally follow a riparian water rights doctrine, which permits those whose lands border waters to use them in a way that is reasonable relative to other users. When the water quantities are insufficient to meet all reasonable needs, all users are to reduce their usage proportionally. In contrast, most western states follow a prior appropriation doctrine, which provides a superior right to those who first put the water to use. When quantities are insufficient to meet all needs, those with the superior right receive their allocation first, and others receiving their share in order of priority. Because the ACF states follow the riparian rights doctrine, their relative rights to use the water are not determined by priority during drought. How to resolve water allocation during drought in a riparian context has few precedents, thus contributing to the challenge of the three states in successfully negotiating a water allocation compact. The three states most recently failed at such an effort in 2003 (see Appendix A ). The federal government has authority under the Commerce Clause of the U.S. Constitution to manage the nation's water resources, but it recognizes the states' authority to allocate and use water within their jurisdictions. Federal laws often require federal agencies engaged in water resources management to defer to state laws or cooperate with state officials in implementing federal laws. Although a state generally has broad authority over waters within its border, exercise of its intrastate authority cannot entirely dismiss the interests of other states. In the case of the ACF, although the three states have authority over their waters, federal investments were built and are operated for multiple purposes, thus affecting the states' water use. That is, the basin's federal dams regulate the flows of the Chattahoochee and Apalachicola Rivers, thereby shaping the states' water use.