Interpreting and analyzing data is a crucial step in the development of any watershed plan. The data analysis supports the identification of watershed pollutant sources and causes of impairment, which is essential to defining watershed management needs. Through careful analysis you’ll obtain a better understanding of major pollutant sources, the behavior of these sources, and their impacts on waterbodies. An understanding of the watershed conditions and sources is also the basis for determining the appropriate method for quantifying pollutant loads.
The process of conducting data analyses to characterize your watershed and its pollutant sources begins with broad assessments such as evaluating the averages, minimums, and maximums of measured parameters at all watershed stations. Data analysis helps to evaluate spatial, temporal, and other identifiable trends and relationships in water quality. Instream data analysis 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. Habitat data analysis is needed to identify areas that need to be restored or protected.
One way to organize and focus the data analysis is to consider the specific watershed characteristics and the questions that need to be answered before an appropriate management strategy can be developed. U.S. EPA’s Handbook for Developing Watershed Plans to Restore and Protect Our Waters is an excellent resource to educate yourself and your stakeholders on this topic. In particular, U.S. EPA’s worksheet 7-1 can help to determine the types of analyses you might need to conduct for water quality. U.S. EPA’s worksheet 7-2 can help to determine the types of analyses you might need to conduct for habitat assessment and protection.
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 identifying and evaluating management measures and tracking implementation efforts.