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Colorado Water Science Center

MEASURING SUCCESS THROUGH WATER-QUALITY MONITORING: "How do we know where we're going, if we don't know where we've been?"

National Water-Quality Assessment (NAWQA) Program
South Platte River Basin Study

by Kevin F. Dennehy 1


Determining changes and trends in surface- and groundwater quality over time is a goal to which scientists aspire when conducting long-term water-quality monitoring. However, because of financial and operational difficulties, it is a goal that is almost never achieved. The question usually asked is, "Why should we care?" It is important to have a trends network because a variety of Federal, State, and local agencies implement, enforce, or pass laws that call for some sort of long-term water-quality monitoring to ensure compliance with some regulation or validation of a new activity. Commonly these monitoring requirements are constituent specific and are inadequate to examine the overall water quality of a specific site. After some period of sampling the effort ends. Can we then answer simple questions like, "Has this activity improved ambient water quality? Can we discern between anthropogenic and naturally caused changes and trends in water quality? Are things better or worse?" Answers to these questions appear simple, but with today's mostly compliance-driven monitoring, they can't be answered.

Defining baseline water-quality conditions for a variety of important environmental settings is necessary before initiating trends monitoring. Detecting changes and trends in water quality in a variety of settings and explaining the causes of these changes and trends to the extent possible are the challenges before us. It is not unusual for several agencies to collect water-quality samples independent of one another at the same sites. The opportunity exists to coordinate monitoring activities that can be designed to meet the needs of each interested agency. Selected areas and sites to be sampled need to be chosen for highest priority water-quality concerns, and the frequency of sampling needs to vary depending on the monitoring objectives and media sampled. To understand if measures taken to improve water-quality conditions are working, we need to have some basis for comparison. Without such comparisons it will be difficult to draw conclusions of statistical significance from the observations. With today's financial and operational constraints, that baseline does not exist. However, if partnerships were formed among interested agencies, the goal of long-term trends monitoring, whereby baseline conditions are defined and project success is measured, could be accomplished.

1 U.S. Geological Survey, Box 25046, MS 415, Denver Federal Center, Lakewood, CO 80225

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