T he U.S. Army Corps of Engineers (USACE) is an agency within the Department of Defense with both military and civil works responsibilities. Congress directs USACE's civil works activities through authorizations legislation, annual and supplemental appropriations, and oversight activities. This report summarizes USACE's annual discretionary appropriations for civil works activities and its supplemental appropriations, principally following major flood and hurricane disasters. The appropriations described are for those accounts and activities that typically are funded through Title I of annual Energy and Water Development appropriations acts. As part of USACE's civil works activities, Congress has authorized and appropriated funds for the agency to perform the following: water resource projects for maintaining navigable channels, reducing flood and storm damage, and restoring aquatic ecosystems, among other purposes; regulation of activities affecting certain waters and wetlands activities; and remediation of sites involved in the development of U.S. nuclear weapons from the 1940s through the 1960s, administered under the Formerly Utilized Sites Remedial Action Program (FUSRAP). For FY2019, Congress has provided the agency with almost $7.00 billion for civil works activities; these funds are primarily used for the agency's water resource activities, and $200 million is available for USACE regulatory activities and $150 million is available for FUSRAP. In February 2018, Congress also provided more than $17.40 billion in emergency supplemental appropriations in the Bipartisan Budget Act of 2018 (BBA 2018; P.L. 115-123) to certain USACE accounts related to water resource projects. Most of these supplemental funds are directed to repairing damage to existing USACE facilities, paying for flood fighting and repair of certain levees and dams maintained by nonfederal entities and constructing new riverine and coastal flood control improvements. Although this report references USACE's FUSRAP and regulatory accounts, its discussion focuses on funding for the agency's water resources projects. Congress generally authorizes USACE water resource studies and construction projects prior to funding them. For information on the authorization process, see CRS Report R45185, Army Corps of Engineers: Water Resource Authorization and Project Delivery Processes, by [author name scrubbed]. The report first addresses USACE annual appropriations; second, it discusses USACE supplemental appropriations. These discussions address various policy issues for congressional and other decisionmakers associated with USACE funding. The Appendix to this report focuses on how the Trump Administration is using the monies provided to USACE through BBA 2018. USACE civil works activities are led by a civilian Assistant Secretary of the Army for Civil Works (ASACW), who reports to the Secretary of the Army. A military Chief of Engineers oversees the agency's civil and military operations and reports on civil works matters to the ASACW. A civilian Director of Civil Works reports to the Chief of Engineers. The agency's civil works responsibilities are organized under eight geographically based divisions, which are further divided into 38 districts. The Trump Administration released a proposal in June 2018 to remove USACE civil works from the Department of Defense. Although some Members of Congress have indicated support for looking at what USACE functions may not need to be in the Department of Defense, the conference report that accompanied the USACE appropriations for FY2019, H.Rept. 115-929 , opposed the Administration's proposal and indicated that "no funds provided in the Act or any previous Act to any agency shall be used to implement this proposal." USACE water resource projects attract congressional attention because these projects can have significant local and regional economic benefits and environmental effects. Unlike federal funding for highways and municipal water infrastructure, the majority of federal funds provided to USACE are not distributed by formula to states or through competitive grant programs. Instead, USACE generally has been directly engaged in the planning and construction of projects; the majority of its appropriations are used to perform work on geographically specific studies and projects authorized by Congress. USACE operates more than 700 dams; has built 14,500 miles of levees; and improves and maintains more than 900 coastal, Great Lakes, and inland harbors, as well as 13,000 miles of deep-draft channels and 12,000 miles of inland waterways. For most activities, Congress requires a nonfederal sponsor to share some portion of project costs. For some project types (e.g., levees), nonfederal sponsors own the completed works after construction and are responsible for operation and maintenance. As nonfederal entities have become more involved in USACE projects and their funding, these entities have expressed frustration with the time it takes USACE to complete studies and construction. Only a subset of authorized USACE construction activities are included in the President's budget request and funded annually by federal appropriations. Consequently, numerous authorized USACE projects or project elements have yet to receive federal construction funding. An estimated $96 billion in authorized USACE construction projects and dam safety work is eligible for USACE construction appropriations; discretionary appropriations for the USACE Construction account in annual Energy and Water Development appropriations bills have averaged $2 billion in recent years. Congress enacted an omnibus USACE authorization bill in 2014, the Water Resources Reform and Development Act of 2014 (WRRDA 2014; P.L. 113-121 ). Congress followed WRRDA 2014 with enactment in December 2016 of the Water Resources Development Act of 2016, which was Title I of the Water Infrastructure Improvements for the Nation Act ( P.L. 114-322 ). Among other things, these laws expanded authorities providing alternative ways to advance and deliver USACE studies and projects. To expand delivery options, Congress increased the flexibility in nonfederal funding of USACE-led activities and nonfederal leadership of USACE studies and projects. Competition for USACE discretionary appropriations also has increased interest in alternative project delivery and innovative financing , including private financing and public-private partnerships. In addition, Congress in WRRDA 2014 authorized new financing mechanisms for water resource projects. These statutes also provided that the costs of these nonfederally led activities generally are shared by the federal government largely as if USACE had performed them. That is, subject to the availability of federal appropriations, nonfederal entities advancing water resource projects may be eligible to receive credit or reimbursement (without interest) for their investments that exceed the required nonfederal share of project costs. These authorities typically require that the nonfederal entity leading the project comply with the same laws and regulations that would apply if the work were being performed by USACE. Congress typically funds USACE water resource activities through an annual Energy and Water Development appropriations bill. Because Congress in recent decades has authorized construction of water resource projects at a rate that exceeds the agency's annual construction appropriations, only a subset of authorized activities typically are included in the President's budget request and eventually funded by enacted appropriations. This situation results in competition for funds among authorized activities during the budget development and appropriations processes. Since the 112 th Congress, site-specific project line items added by Congress (i.e., congressionally directed spending , also referred to as earmarks ) have been subject to House and Senate earmark moratoriums. Consequently, appropriators generally have refrained from inserting in appropriations bills and accompanying reports funds for specific projects that were not requested in the President's budget. This practice has resulted in post-enactment agency work plans that identify how funds provided by Congress that were not requested by the President are being distributed across authorized USACE studies and projects. In the congressional reports and explanatory statements that accompany the annual appropriations bills for USACE, Congress has provided guidance to the Administration on activities to prioritize during the development of the work plan. Congress also has authorized the Chief of Engineers to undertake certain flood fighting activities and to repair damage to certain nonfederal flood control works. To fund these activities and repairs to USACE-operated projects (e.g., dredging to clear a navigation channel following a storm), Congress often has provided supplemental funds to certain USACE accounts. At times, including in BBA 2018, Congress also has funded construction of new flood control projects in areas affected by recent flood disasters. As discussed in detail later in this report (see below section, " USACE Annual Appropriations "), Congress has provided USACE accounts with almost $45 billion in supplemental appropriations in response to flood disasters since FY2005, of which almost $24 billion was for construction of flood control projects. Congress provided $15 billion of the $24 billion in construction funds in BBA 2018. As shown in Figure 1 , Congress often appropriates more for USACE civil works than is requested by the President. In the text of enacted appropriations laws, Congress generally provides money to USACE at the account level. Accompanying appropriations reports (i.e., conference reports, committee reports, or explanatory statements), which sometimes are incorporated into law by reference, often identify specific USACE projects to receive appropriated funds. With the heightened attention to and restrictions on congressionally directed spending since FY2010, the projects identified in these reports have been limited largely to the projects included in the President's budget request; that is, Congress has not been adding new project-specific funding amounts. Instead, congressional action on USACE appropriations generally has been the provision of additional funding for various types of USACE activities (see below section, " Principal Documents and Process, Including Additional Funding ") and guidance on the use of the additional funding. In annual appropriations bills, Congress generally provides the majority of the agency's funding to two accounts—the Construction account and the Operations and Maintenance (O&M) account. The O&M account has made up a growing portion of the agency's use of annual appropriations, as shown in Figure 2 . The O&M account has increased from 39% of the USACE annual appropriations in FY2005 and 37% in FY2006 and FY2007 to 53% in FY2017, FY2018, and FY2019.