This section provides information on the Corps’ organizational structure, its project operations and water control manuals, and the process for formulating its operations and maintenance budget. Located within the Department of Defense, the Corps has both military and civilian responsibilities. The Corps’ civil works program is organized into three tiers: a national headquarters in Washington, D.C.; eight regional divisions that were established generally according to watershed boundaries; and 38 districts nationwide (see fig. 1). Corps headquarters primarily develops policies and provides oversight. The Assistant Secretary of the Army for Civil Works, appointed by the President, establishes the policy direction for the civil works program. The Chief of Engineers, a military officer, oversees the Corps’ civil works operations and reports on civil works matters to the Assistant Secretary of the Army for Civil Works. The eight divisions, commanded by military officers, coordinate civil works projects in the districts within their respective divisions. Corps districts, also commanded by military officers, are responsible for planning, engineering, constructing, and managing water-resources infrastructure projects in their districts. Districts are also responsible for coordinating with projects’ nonfederal sponsors, which may be state, tribal, county, or local governments or agencies. In 1969, the Corps formed the Institute for Water Resources—which is a field-operating activity outside of the headquarters, division, and district structure—to provide forward-looking analysis and research in developing planning methodologies to aid the civil works program. Specifically, the institute fulfills its mission, in part, by providing an analysis of emerging water resources trends and issues and state-of-the-art planning and hydrologic-engineering methods, models, and training. In 2009, the Corps established the Responses to Climate Change program under the lead of Institute for Water Resources to develop and implement practical, nationally consistent, and cost-effective approaches and policies to reduce potential vulnerabilities to the nation’s water infrastructure resulting from climate change and variability. The Corps is responsible for operations at 707 dams that it owns at 557 projects across the country, as well as flood control operations at 134 dams constructed or operated by other federal, nonfederal, or private agencies. Each of these projects may have a single authorized purpose or serve multiple purposes such as those identified in the original project authorization, revisions within the discretionary authority of the Chief of Engineers, or project modifications permitted under laws enacted subsequent to the original authorization. For example, the Blackwater Dam in New Hampshire has the single purpose of flood control, whereas the Libby Dam in Montana has multiple purposes, including hydropower, flood control, and recreation. These 841 dams and their reservoirs are operated according to water control manuals and their associated water control plans, which Corps regulations require to be developed. A water control manual may outline operations for a single project or a system of projects. For example, the Missouri River Mainstem Reservoir System Master Water Control Manual outlines the operations at six dams and their associated reservoirs, and the Folsom Dam Water Control Manual applies to one dam and its reservoir. Water control manuals include a variety of information the Corps uses in operating the dams, including protocols for coordinating with and collecting data from federal agencies, such as NOAA’s National Weather Service and USGS, as well as water control plans. The water control plans, sometimes referred to as chapter 7 of the water control manuals, outline how each reservoir is to be operated and include relevant criteria, guidelines, and rule curves defining the seasonal and monthly limits of storage and guide water storage and releases at a project. According to the Corps’ engineer regulations, the Corps develops water control plans to ensure that project operations conform to objectives and specific provisions of authorizing legislation. Water control plans also generally describe how a reservoir will be managed, including how water is to be allocated between a flood control storage pool and a conservation storage pool, which is used to meet project purposes during normal and drought conditions. The bottom of a conservation storage pool is considered inactive and is designed for collecting sediment (see fig.2). Water levels in the pools are defined based on a statistical analysis of historical rain events. For those projects that have multiple authorized purposes, water control plans attempt to balance water storage for all purposes. Corps engineer regulations require that all water control manuals—except manuals for dry reservoirs that do not fill with water unless floodwaters must be contained—have an associated drought contingency plan to provide guidance for water management decisions and responses to a water shortage due to climatological drought. These plans, which can cover more than one project: (1) outline the process for identifying and monitoring drought at a project, (2) inform decisions taken to mitigate drought effects, and (3) define the coordination needed with stakeholders and local interests to help manage water resources so they are used in a manner consistent with the needs that develop, among other things. According to a 2014 Corps engineer regulation, water control manuals may be revised for reasons such as land use development in the project area and downstream from it, improvements in technology used to operate projects, reallocation of the water supply, new regional priorities, or changes in environmental conditions. The Corps’ engineer regulation also directs districts to include in water control manuals a provision allowing temporary deviations from a project’s approved water control plan to alleviate critical situations, such as a flood or drought, or to realize additional efficiencies without significantly affecting the project’s authorized purposes. Districts are to perform a risk and uncertainty analysis to determine the potential consequences of such a deviation. Division commanders are responsible for reviewing and approving any proposed deviations. According to the engineer regulation, deviations are meant to be temporary and, if a deviation lasts longer than 3 years, the water control manual must be revised. Our prior work has found that the Corps’ headquarters, divisions, and districts are all involved in developing the President’s budget request for the Corps. The development process spans 2 years; for example, development of the fiscal year 2018 budget began in fiscal year 2016. After receiving budget guidance from the Office of Management and Budget as well as the Assistant Secretary of the Army for Civil Works, district staff compile a list of operations and maintenance (O&M) projects necessary in their districts and submit their needs to the relevant division. O&M projects may include, among other things, water control manual revisions, dredging, replacement of dam parts, dam safety measures, or adding capacity at hydropower projects. Division staff then rank the O&M projects from all districts in the division and submit those rankings to Corps headquarters staff for review. Headquarters staff review the rankings to help ensure they are consistent with Corps-wide guidance and result in decisions that emphasize agency-wide priorities. Headquarters staff consolidate the O&M requests across business lines and divisions into a highest-priority grouping. Once the Corps completes its internal review of the budget request, the Assistant Secretary of the Army for Civil Works approves and submits its budget to the Office of Management and Budget for review. The Office of Management and Budget recommends to the President whether to support or change the Corps’ budget request, and the President’s budget request is transmitted to Congress. According to agency officials, the Corps conducts ongoing, informal reviews of selected water control manuals and has revised some of them, but the extent of the reviews and revisions is unclear because they were not documented or tracked. More specifically, district officials said that the Corps reviews the manuals as part of daily operations but does not document the reviews, and there is no guidance on what constitutes a review or how to document it. Further, the Corps does not track consistent information across divisions on the status of manuals to indicate revisions that were made or are needed. It is unclear to what extent the Corps has reviewed its water control manuals because district officials did not document these reviews, which, according to district officials, are informal and conducted on an ongoing basis through daily operations. A 2014 Corps engineer regulation states that water control manuals should be reviewed no less than every 10 years, so that they can be revised as necessary. Most district officials we interviewed said that they informally review the water control plan because this portion of the manual describes how projects are to be operated under different conditions to meet their authorized purposes. However, officials we interviewed from all 15 districts said they do not document these informal reviews because they consider such reviews to be part of the daily routine of operating projects. Because these informal reviews are not documented, knowledge of these reviews and their results may be limited to personnel directly involved with them. Officials we interviewed from four districts said that the loss of institutional knowledge posed a challenge to conducting efficient reviews of manuals. For example, officials from one district said that no Corps officials currently employed at the district had worked on developing the manual for a project and had no supporting documentation of the process, so the officials did not know why prior Corps officials wrote the manual in a particular way. As a result, the officials said it took them longer to review the manual. One Corps district we reviewed had previously documented informal reviews of water control manuals. Specifically, officials we interviewed in this district said that they documented reviews of some water control manuals in 2005 as part of a district-wide effort to ensure these manuals were adequate to meet the projects’ authorized purposes since they had not been revised in a long time. According to these officials, as part of this effort, if they determined that all of the operating conditions in a manual were still current, they submitted a memorandum to their division that revalidated the manual’s water control plan. Officials from that district said they have not documented reviews of water control manuals since 2005 because they chose to focus only on those manuals they knew needed revision. However, the Corps does not have guidance on what activities constitute a review or how officials should document the results of their reviews.