**A Hydrology Primer for Engineers & Hydrologists**

*
Patrick C. Garner, PLS, Wetland
Scientist
*

**Course Outline**

*A Hydrology Primer for Engineers & Hydrologists *serves as a refresher for practicing engineers and/or an introduction to hydrology concepts for those working predominately in other engineering concentrations.

Concepts discussed in the course include the hydrologic cycle; precipitation; types of natural storage and infiltration; recharge and base flow; surface runoff; peak rates of flow; rainfall characteristics; return periods; I-D-F curves; hyetographs and hydrographs; watersheds; runoff volume; soils and NRCS hydrologic soil groups; coefficients; curve numbers; cover types; times of travel and concentration; and a lengthy discussion of the differences between the Rational Method and the federal peak flow methods (using TR-20 and 55).

Required data, assumptions and limitations for each method are listed. A references section is included.

The major sections of the course are: (1) The Hydrologic Cycle: (2) Hydrology Specifics: (3) The Rational Method: (4) NCRS (SCS) Peak Flow Methods: (5) Review of Assumptions and Limitations: and (6) References.

Heavily illustrated, the course lists and discusses all data commonly required to model runoff. *A Hydrology Primer for Engineers & Hydrologists *is an essential guide for both new and experienced professionals.

This course includes a multiple-choice quiz at the end, which is designed to enhance the understanding of the course materials.

**
Learning Objective**

At the conclusion of this course, the student will:

- Learn the basic hydrology principles required for an engineer or hydrologist to model surface runoff;
- Learn hydrology concepts for those working predominately in other engineering concentrations;
- Have a refresher for practicing engineers;
- Understand modern concepts of hydrology;
- Understand the data required for modern computer modeling;
- Learn the Hydrologic Cycle;
- Learn Hydrology Specifics;
- Learn the Rational Method; learn NCRS (SCS) Peak Flow Methods; and
- Review Assumptions and Limitations.

** Intended Audience**

This course is intended for Engineers, Hydrologists and other design professionals.

**Benefit to Attendees**

An attendee of this course will learn the basic hydrology principles required for an engineer or hydrologist to model surface runoff. This course serves as a refresher for practicing engineers and/or an introduction to hydrology concepts for those working predominately in other engineering concentrations. This course acts as a both an overview to understanding modern concepts of hydrology, and as a specific discussion of the data required for modern computer modeling. The course neither deals with hydraulics, nor does it take a student through the process of running actual hydrology calculations. The emphasis is on *hydrology*.

Numerous illustrations, definitions and examples are shown in the six sections of the course. Commonly encountered problems are discussed. Upon completion of this course, the attendee will have a thorough knowledge of the basic working principles of surface hydrology required to be able to use today’s available modeling software.

**Course
Introduction**

This course is designed as a refresher to basic **hydrolog**y concepts required for an engineer or hydrologist to model surface runoff. Many design professionals were introduced to these concepts when they started their careers. Yet the science and terminology of hydrology continues to evolve, and this course acts as a both an overview to understanding the basic concepts of hydrology, and as a specific discussion of the data required for modern computer modeling.

Hydraulics is the study of water flow in channels, drainage swales, pipes, culverts and canals. Basic hydraulic principles include flow conveyance; the area, wetted perimeter and hydraulic radius of conveyance devices; velocity; steady, laminar and turbulent flow; hydraulic grade; and energy losses, among others. This course focuses instead on *hydrology*.

**Hydrology** is the study of water on and below the earth’s surface. It is also the study of the circulation of water between the earth and the atmosphere. This infinite circulation of water is known as the **hydrologic cycle**. A basic understanding of the hydrologic cycle is an essential foundation for understanding the material presented in this course. This first section presents an overview of the hydrologic cycle, and describes some of its key components. These will later be examined at the level of stormwater modeling.

In discussing these initial concepts, we will look at key relationships between precipitation, stormwater runoff, groundwater recharge and other components of the hydrologic cycle.

**ACRONYMS**

This course uses a number of common acronyms. Those are:

NEH National Engineering Handbook

I-D-F Intensity-Duration-Frequency

NOAA National Oceanic and Atmospheric Administration

NRCS Natural Resources Conservation Service

NWS National Weather Service

SCS Soil Conservation Service (now NRCS)

**Course Content
**

The course content is contained in the following PDF file:

**A Hydrology Primer for Engineers & Hydrologists**

Please click on the above underlined hypertext to view, download or print the document for your study. Because of the large file size, we recommend that you first save the file to your computer by right clicking the mouse and choosing "Save Target As ...", and then open the file in Adobe Acrobat Reader. If you still experience any difficulty in downloading or opening this file, you may need to close some applications or reboot your computer to free up some memory.

**Course Summary
**

Concepts discussed in the course included the variables of the hydrologic cycle, including rainfall and evaporation; precipitation; types of natural storage and infiltration; recharge and base flow; surface runoff and its iterations; peak rates of flow; rainfall definitions and characteristics; return periods and occurrence intervals; I-D-F curves; hyetographs and their uses; and hydrographs and their components.

In addition, the course covered watersheds; runoff rates and volume; NRCS hydrologic soil groups; coefficients; curve numbers; cover types; times of travel (Tt) and concentration (Tc); as well as a lengthy discussion on the differences between the Rational Method and the SCS peak flow methods (that is, TR-20 and 55). Assumptions and limitations for each method were listed in a table of comparisons.

Students completing this course are now familiar with the broad concepts and data parameters required to model storm events and design stormwater infrastructure. Many courses exist on-line that discuss the step-by-step input for this software. In addition, NRCS occasionally offers hands-on courses in the use of TR-20 and TR-55. Practice with the NRCS programs, or with commercially available packages is recommended before trying to design proposed stormwater infrastructure, as each program has limitations and peculiarities that can influence the design outcome.

**Related
Links**

NRCS Hydraulics and Hydrology

http://www.wsi.nrcs.usda.gov/products/w2q/H&H/H&H_home.html

An Interactive Web Tool for Extreme Precipitation

**Quiz**

**Once
you finish studying ****the
above course content,****
you need to
take a quiz to obtain the PDH credits**.

DISCLAIMER: The materials contained in the online course are not intended as a representation or warranty on the part of PDH Center or any other person/organization named herein. The materials are for general information only. They are not a substitute for competent professional advice. Application of this information to a specific project should be reviewed by a registered architect and/or professional engineer/surveyor. Anyone making use of the information set forth herein does so at their own risk and assumes any and all resulting liability arising therefrom.