This manual provides information on hydrologic engineering studies for reservoir projects. These studies can utilize many of the hydrologic engineering methods described in the manuals listed in paragraph 1-4. Hydraulic design of project features are not included here; they are presented in a series of hydraulic design manuals.

This manual is divided into four parts. Part 1 provides basic hydrologic concepts for reservoirs . Reservoir purposes and basic hydrologic concerns and methods are presented. Part 2 describes hydrologic data and analytical methods. Part 3 covers storage requirements for various project purposes, and the last, Part 4, covers hydrologic engineering studies.

This manual provides guidance and procedures for frequency analysis of: flood flows, low flows, precipitation. water surface elevation, and flood damage.

Frequency estimates of hydrologic, climatic and economic data are required for the planning, design and evaluation of flood control and navigation projects. The text illustrates many of the statistical techniques appropriate for hydrologic problems by example. The basic theory is usually
not provided, but references are provided for those who wish to research the techniques in more detail.

The techniques described herein are taken principally from “Guidelines for Determining Flood Flow Frequency” (46 – Water Resources Council, “Guidelines for Determining Flood Flow Frequency,” Bulletin 17B, Hydrology Committee, Washington, D.C., March 1982), “Statistical Methods in Hydrology” (1 – Beard, L. R., “Statistical Methods in Hydrology,” U.S. Army Corps of Engineers, Sacramento, CA, January 1962), and “Hydrologic Frequency Analysis” (41 – U.S Army Corps of Engineers, “Hydrologic Frequency Analysis,” Volume 3 of Hydrologic Methods for Water Resources Development, the Hydrologic Engineering Center, Davis, CA, April 1975).

This manual describes methods for evaluating flood-runoff characteristics of watersheds. Guidance is provided in selecting and applying such methods to support the various investigations required for U.S. Army Corps of Engineers (USACE) civil works activities. The manual references publications that contain the theoretical basis of the methods and detailed information on their use. The manual is organized into four parts.

The first, Problem Definition and Selection of Methodology, describes the products of flood-runoff analysis and the types of investigation for which these products are required. Aspects of flood hydrology are discussed, including physical processes, data availability, and broad approaches to analysis. Guidance in formulating study procedures is provided, which includes criteria for method selection and recommended content for a hydrologic engineering management plan (HEMP). The reporting of study results is the focus of the last chapter in Part I.

Part II, Hydrologic Analysis, provides information on techniques for simulating various components of the hydrologic cycle, including rainfall, snow, infiltration (loss), surface and subsurface runoff, and flow in channels and reservoirs. Multisubbasin modeling and design storm definition are discussed.

Part III, Methods for Flood-Runoff Analysis, addresses the application of simplified techniques, frequency analysis of streamflow data, precipitation-runoff simulation of storm events, and period-of-record precipitation-runoff simulation. Data requirements and calibration / verification of simulation models are considered.

Part IV, Engineering Applications, deals with several issues associated with the application of methods from Part III. The processing of data can be time-consuming and costly; techniques for efficient data handling are addressed. The lack of historical streamflow data is the source of much difficulty and uncertainty in flood runoff analysis. Aspects of dealing with “ungauged” basins are discussed. Issues associated with the development of frequency-based estimates are covered, including the concept of calibration to “known” frequency information. Various aspects of modeling land use change, as well as the effects of reservoir and other projects, are discussed. Finally, three examples illustrate some of the principles presented in this manual.

Following Part IV, Appendices A and B provide references, a generic HEMP, and a set of example applications.

This engineer manual (EM) relies on references and/or technical information in several other guidance documents. Some of those documents are part of this current guidance effort and others are older documents. The most relevant documents are EM 1110-2-1416, River Hydraulics, EM 1110-2-1415, Hydrologic Frequency Analysis, and EM 1110-2-1413, Hydrologic Analysis of Interior Areas.

This Engineer Manual provides guidance to Corps of Engineers (CE) personnel who are responsible for groundwater-related projects. This manual was written with special attention to groundwater-related applications prevalent within the CE. Thus, sections addressing site investigation procedures and the performance of modeling studies are included. Additionally, a chapter focusing on the interaction between surface water and groundwater is included.

This manual applies to all USACE Commands having civil works responsibilities. This manual provides information for application to common Corps groundwater-related studies, including:

1. Site characterization for contaminant remediation.
2. Computer modeling of groundwater flow.
3. Groundwater and surface water interaction studies.
4. Reservoir operations.
5. Groundwater flow to adjacent locks and dams.
6. Remediation of reservoir leakage.
7. Infiltration of runoff to the subsurface.
8. Baseflow between aquifers and fixed bodies including streams and reservoirs.
9. Effects of aquifer pumping on adjacent lakes and streams.
10. Well installation involved with seawater infiltration barriers.
11. Dewatering of an excavation for construction purposes.
12. General regional and local applications.