Water: Watershed Central
Characterize the Watershed - Analyze Data
More info on Characterize the Watershed
- Gather Existing Data and Create a Watershed Inventory
- Identify Data Gaps and Collect Additional Data
- Analyze Data
- Identify Causes and Sources That Need to Be Controlled
- Estimate Pollutant Loads
- Results and Next Steps
Analyzing existing data and updated information to support the identification of watershed pollutant sources and causes of impairment is essential to defining watershed management needs. Data analysis will also identify which sources you will need to focus on during the loading analysis. Through careful analysis of your data you will obtain a better understanding of the major pollutant sources, the behavior of the sources, and their impacts on the waterbodies. An understanding of the watershed conditions and sources is also the basis for determining the appropriate method for quantifying pollutant loads. This phase of the watershed planning process will help you satisfy the first of the nine elements that EPA requires in a section 319-funded watershed plan for impaired waters. Element a requires the "Identification of causes and sources or groups of similar sources that need to be controlled to achieve load reductions, and any other goals identified in the watershed plan".
The types of analyses and the level of detail used in your analytical process will vary within the watershed depending on the pollutants of concern. Less-detailed analyses might be conducted for certain pollutants, whereas more detailed analyses might be conducted for others, depending on the goals of the plan and the pollutants of concern. Analysis of instream data is needed to identify the location, timing, or behavior of potential watershed sources and their effect on watershed functions such as hydrology, water quality, and aquatic habitat. Refer to Chapter 7 (PDF) (22 pp, 781K, About PDF) of EPA's Watershed Handbook for details on instream and watershed data.
Stakeholder concerns and goals will also help to determine what kinds of analyses are needed. For example, if the stakeholders and the earlier characterization identified metals associated with impacts from developed areas as a primary concern, the data analysis will focus on characterizing those parameters and the locations, types, or timing of pollutant loading from urban and residential sources in the watershed. If a specific source is expected to be contributing to water quality problems, more detailed analyses might be conducted on data collected upstream and downstream of that source, or smaller time scales might be evaluated.
Remember that data gathering and analysis is an ongoing, iterative process. Data examined in this phase will continue to be used in subsequent activities such as the identification and evaluation of management measures and tracking implementation efforts. The process of conducting data begins with broad assessments and is then systematically narrowed, with each step building on the results of the previous analysis. Refer to Table 7-1 (PDF) (22 pp, 781K, About PDF) on page 7-3 of EPA's Watershed Handbook for examples of data analysis activities and the tools used in various steps of the watershed management process.
WATERSHEDSS - This is a tool for calculating loads using export coefficients. The system also includes a database of agricultural management practices, references on nonpoint source pollutants and sources, and an annotated bibliography of nonpoint source literature.
USGS - What is LIDAR - Basic description of LIDAR
The Earth Observatory - Remote Sensing Reference Article - An article discussing basic information about remote sensing