Watershed

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NOTICE: This PDF file was adapted from an on-line training module of the EPA’s Watershed Academy Web, found at http://www.epa.gov/watertrain. To the extent possible, it contains the same material as the on-line version. Some interactive parts of the module had to be reformatted for this noninteractive text presentation. A self-test is included at the end of the file. This document does not constitute EPA policy. Mention of trade names or commercial products does not constitute endorsement or recommendation for use. Links to non-EPA web sites do not imply any official EPA endorsement of or responsibility for the opinions, ideas, data, or products presented at those locations or guarantee the validity of the information provided. Links to non-EPA servers are provided solely as a pointer to information that might be useful to EPA staff and the public.

WATERSHED ACADEMY WEB http://www.epa.gov/watertrain

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Introduction to Watershed Ecology

Introduction
This training module introduces watershed ecology. Understanding watershed structure and natural processes is crucial to grasping how human activities can degrade or improve the condition of a watershed, including its water quality, its fish and wildlife, its forests and other vegetation, and the quality of community life for people who live there. Knowing these watershed structural and functional characteristics and how people can affect them sets the stage for effective watershed management. After completing this training, the participant should know the basic biotic and abiotic components of watersheds, the basic natural processes and interrelationships occurring in watersheds, and how watershed structure and functions may vary in time and space. Some background in the life sciences is helpful for comprehending this material, but not required.

Goals
The aims of this unit are to: 1. Introduce terms and concepts associated with watershed ecology. 2. Describe typical watershed structure and how watersheds work, at different geographic scales and through time. 3. Provide related examples of contemporary issues in watershed ecology.

Definitions
Watershed. An area of land that drains water, sediment and dissolved materials to a common receiving body or outlet. The term is not restricted to surface water runoff and includes interactions with subsurface water. Watersheds vary from the largest river basins to just acres or less in size. Watershed Ecology. The study of watersheds as ecosystems, primarily the analysis of interacting biotic and abiotic components within a watershed’s boundaries. Ecosystem. A functioning natural unit with interacting biotic and abiotic components in a system whose boundaries are determined by the cycles and flux of energy, materials and organisms. It is valid to describe different ecosystems with different, overlapping sets of boundaries in the same geographic area (e.g. forest ecosystems, watershed ecosystems and wetland ecosystems). A watershed is just one of many types of ecosystems. Watershed ecology is essential knowledge for watershed managers because it teaches us that watersheds have structural and functional characteristics that can influence how human and natural communities coexist within them. The gross structure of a watershed -- its headwaters area, side slopes, valley floor, and water body, as well as its soils, minerals, native plants and animals -- are, in one sense, raw material for all the human activities that may potentially occur there (Figure 1). The watershed’s natural processes -- rainfall runoff, groundwater recharge, sediment transport, plant succession, and many others -- provide beneficial services when functioning properly, but may cause disasters when misunderstood and disrupted. It is crucial for WATERSHED ACADEMY WEB http://www.epa.gov/watertrain

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Introduction to Watershed Ecology

people to understand watersheds and how they work before they make decisions or take actions that may affect...
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