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A sampling plan is a report that describes how you are going to measure water quality. A good sampling plan will help ensure that your measurements answer the right questions, and communicates to other people what you are trying to accomplish. Most sampling plans include the following report sections:
A clear understanding of project goals is crucial to developing a succesful monitoring program. The project goals define what kinds of questions you are trying to answer, and help you decide what methods to use. The following are some typical goals for different types of water quality studies:
Educational Monitoring : The primary goal of these studies is to educate students and volunteers about water quality issues and water quality monitoring. The data may not be used for detailed scientific studies, but can help identify gross water quality problems.
Water Quality Assessments : The goal of these studies is to assess how well a river is meeting water quality standards. The first water quality study of a river is often a screening-level assessment , in which approximate methods are used to get a quick assessment of water quality problems. This is then followed by a comprehensive study , in which more samples are taken and analyzed to a higher level of accuracy.
Permitting Studies : These types of studies focus on a specific source of pollution, such as a wastewater treatment plant, city stormdrain system, or dairy farm. They are usually initiated so that the discharger can get a permit from the Department of Ecology or U.S. EPA. The goals of permitting studies are to assess how much impact the pollutant source is having on the river, and to determine how clean the discharged water needs to be if the river is to meet water quality standards.
Wasteload Allocation Studies : These are similar to permitting studies, except that they include all potential sources of pollution within a watershed. The goal of these studies is to determine how much pollution the river can handle, and to allocate how much pollution each type of source is allowed to discharge. The amount of pollution discharged is defined as a wasteload , expressed in pounds of pollutant per day.
Habitat Studies : The goal of a habitat study is to determine how well a river is functioning as habitat for wildlife, fish, and other aquatic organisms. Water chemistry testing may be a part of a habitat study, but these studies also include biologic indices and measurements of the river's physical structure (sediments, channel shape, woody-debris).
The goals of your study will help you decide what kinds of physical, chemical, and biologic parameters you will measure. The sampling plan should describe these parameters, and give your reasons for selecting them.
All studies have budget limitations, and you can't measure everything. The trick is to develop a practical list of parameters that is affordable and meets your project goals. This isn't always easy, especially when you don't have a clear idea of what types of water quality problems are present. The first step is therefore to inventory what is already known about local water quality problems and sources of pollution. If you are analyzing the impacts of a sewage treatment plant, you would look at pollutants found in sewage (coliform bacteria, ammonia, BOD, metals). If people have observed algae blooms and dead fish, your study would focus on dissolved oxygen, temperature, nitrates, and phosphates. A sampling program located near an oil refinery might look at petroleum byproducts and metals.
The sampling plan should describe the locations where you will measure water quality. Sampling locations should be described in enough detail so they can be found in future studies.
Sampling locations are often identified in terms of river miles , defined as the number of miles you are upstream from the mouth of the river. You should also describe how far the location is from the nearest bridge, tributary stream, or landmark. The description should include how far you will sample from the shore, and the depth where you will sample.
Sampling locations are selected to meet the goals of your study. If you are doing a water quality assessment, locations may be evenly distributed along the length of the river (for instance, you might collect one sample every mile). If the assessment is a screening study, you would collect from fewer locations than if it were a comprehensive study.
In permitting studies you are trying to determine how much the pollutant source changes water quality. To do this you need background samples that are designed to tell you what the water quality would be if the pollutant source weren't there. Background samples are often collected upstream of the source at a location that has conditions similar to those found at the discharge point. To assess the impact of the pollutant source, you then collect samples downstream of the discharge point and compare them to the background samples.
The sampling plan should describe how often you will sample, and at what times of year. Many water quality problems change with the seasons. For instance, low dissolved oxygen levels usually occur in the summer when flows are low and temperatures are higher. Coliform bacteria from manure is more of a problem in the winter when rainstorms wash polluted runoff into rivers. Sewage treatment plants discharge year-round, and therefore can cause water quality problems in all seasons.
Water quality assessments will typically include summer dry-weather sampling, winter wet-weather sampling, and winter dry-weather sampling. Screening studies will sample less frequently than comprehensive studies. Permitting studies will focus on the months when the discharge has the most impact, but usually include monthly or weekly sampling throughout the first year.
The sampling plan should provide a detailed description of your methods, including:
- Field Sampling Techniques
- Storage and Transportation of Samples
- Instrument Calibration
- Laboratory Methods
- Quality Control/Quality Assurance
The method should reflect your budget and the degree of accuracy needed. Educational monitoring projects usually have the lowest budgets and accuracy requirements, and may use either field test kits or calibrated instruments. Screening-level water quality assessments use calibrated instruments that can be taken in the field, supplemented by a few laboratory samples. Comprehensive water quality assesments and permitting studies require greater accuracy, and use a combination of calibrated field instruments and detailed laboratory analysis.
Quality Control and Quality Assurance are methods used to check the accuracy and precision of your data; these will be described in a later unit.
Develop a brief sampling plan to solve the following hypothetical water quality problem:
The Department of Ecology wants to measure the water quality impacts of a sewage treatment plant that discharges into Trout River at River Mile 11. Cow Pasture Creek enters Trout River about 1-mile upstream of the treatment plant, and drains several large dairy farms. Trout River enters the Pacific Ocean about 11 miles downstream of the treatment plant. The plant operates all year.
Be sure to include a few sentences on each of the following elements of your sampling plan:
This water quality course material created by Rob Schanz. Send comments to Rob Schanz
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