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Water: Monitoring & Assessment

Chapter 5 Water Quality Conditions

5.1 - Stream Flow
5.2 - Dissolved Oxygen and Biochemical Oxygen Demand
5.3 - Temperature
5.4 - pH
5.5 - Turbidity
5.6 - Phosphorus
5.7 - Nitrates
5.8 - Total Solids
5.9 - Conductivity
5.10 - Total Alkalinity
5.11 - Fecal Bacteria


Quality Assurance, Quality Control, and Quality Assessment Measures

Water quality monitoring is defined here as the sampling and analysis of water constituents and conditions. These may include:

  • Introduced pollutants, such as pesticides, metals, and oil
  • Constituents found naturally in water that can nevertheless be affected by human sources, such as dissolved oxygen, bacteria, and nutrients

The magnitude of their effects can be influenced by properties such as pH and temperature. For example, temperature influences the quantity of dissolved oxygen that water is able to contain, and pH affects the toxicity of ammonia.

Volunteers, as well as state and local water quality professionals, have been monitoring water quality conditions for many years. In fact, until the past decade or so (when biological monitoring protocols were developed and began to take hold), water quality monitoring was generally considered the primary way of identifying water pollution problems. Today, professional water quality specialists and volunteer program coordinators alike are moving toward approaches that combine chemical, physical, and biological monitoring methods to achieve the best picture of water quality conditions.

Water quality monitoring can be used for many purposes:

  • To identify whether waters are meeting designated uses. All states have established specific criteria (limits on pollutants) identifying what concentrations of chemical pollutants are allowable in their waters. When chemical pollutants exceed maximum or minimum allowable concentrations, waters might no longer be able to support the beneficial uses such as fishing, swimming, and drinking for which they have been designated. Designated uses and the specific criteria that protect them (along with antidegradation statements say waters should not be allowed to deteriorate below existing or anticipated uses) together form water quality standards. State water quality professionals assess water quality by comparing the concentrations of chemical pollutants found in streams to the criteria in the state's standards, and so judge whether streams are meeting their designated uses. Water quality monitoring, however, might be inadequate for determining whether aquatic life uses are being met in a stream. While some constituents (such as dissolved oxygen and temperature) are important to maintaining healthy fish and aquatic insect populations, other factors, such as the physical structure of the stream and the condition of the habitat, play an equal or greater role. Biological monitoring methods (see Chapter 4) are generally better suited to determining whether aquatic life is supported.
  • To identify specific pollutants and sources of pollution. Water quality monitoring helps link sources of pollution to a stream quality problem because it identifies specific problem pollutants. Since certain activities tend to generate certain pollutants (e.g., bacteria and nutrients are more likely to come from an animal feedlot than an automotive repair shop), a tentative link might be made that would warrant further investigation or monitoring.
  • To determine trends. Chemical constituents that are properly monitored (i.e., consistent time of day and on a regular basis, using consistent methods) can be analyzed for trends over time.
  • To screen for impairment. Finding excessive levels of one or more chemical constituents can serve as an early warning "screen" of potential pollution problems.

Designing a water quality monitoring program

The first step in designing a water quality monitoring program is to determine the purpose of the monitoring. This will help you select which parameters to monitor. The program steering committee should make this decision based on factors such as:

  • Types of water quality problems and pollution sources that will likely be encountered (Table 5.1)
  • Cost of available monitoring equipment
  • Precision and accuracy of available monitoring equipment
  • Capabilities of the volunteers
Source Common Associated Chemical Pollutants Table 5.1

Sources and associated pollutants
A volunteer water quality monitoring program should be geared to the types of watershed land uses most often encountered.
Cropland Turbidity, phosphorus, nitrates, temparature, total solids
Forestry harvest Turbidity, temperature, total solids
Grazing land Fecal bacteria, turbidity, phosphorus, nitrates, temperature
Industrial discharge Temperature, conductivity, total solids, toxics, pH
Mining pH, alkalinity, total dissolved solids
Septic systems Fecal bacteria (i.e., Escherichia coli, enterococcis), nitrates, phosphorus, dissolved oxygen/biochemical oxygen demand, conductivity, temperature
Sewage treatment plants Dissolved oxygen and biochemical oxygen demand, turbidity, conductivity, phosphorus, nitrates, fecal bacteria, temperature, total solids, pH
Construction Turbidity, temperature, dissolved oxygen and biochemical oxygen demand, total solids, and toxics
Urban runoff Turbidity, phosphorus, nitrates, temperature, conductivity, dissolved oxygen and biochemical oxygen demand

Because of the expense and difficulty involved, volunteers generally do not monitor for toxic substances such as heavy metals and organic chemicals (e.g., pesticides, herbicides, solvents, and PCBs). They might, however, collect water samples for analysis at accredited labs.

The parameters most commonly monitored by volunteers in streams are discussed in detail in this chapter. They include stream flow, dissolved oxygen and biochemical oxygen demand, temperature, pH, turbidity, phosphorus, nitrates, total solids, conductivity, total alkalinity, and fecal bacteria. Of these, the first five are the most basic and should form the foundation of almost any volunteer water quality monitoring program.

Relatively inexpensive and simple-to-use kits are available from scientific supply houses to monitor these pollutants. Many volunteer programs use these kits effectively. Meters and sophisticated lab equipment may be more accurate, but they are also more expensive, less flexible (e.g., meters generally have to be read in the field), and require periodic calibration. This chapter discusses specific equipment and sampling considerations for each parameter, and usually describes several approaches to monitor them. Table 5.2 lists methods available for monitoring key parameters, including the preferred testing site (lab or field).

General preparation and sampling considerations

The sections that follow will detail specific sampling and equipment considerations and analytical procedures for each of the most common water quality parameters. There are, however, two general tasks that are accomplished anytime water samples are taken. These are discussed below.

Task 1 Preparation of Sampling Containers

Reused sample containers and glassware must be cleaned and rinsed before the first sampling run and after each run by following either Method A or Method B described below. The most suitable method depends on the parameter being measured.

Method A: General Preparation of Sampling Containers

The following method should be used when preparing all sample containers and glassware for monitoring conductivity, total solids, turbidity, pH, and total alkalinity. Wear latex gloves!

  1. Wash each sample bottle or piece of glassware with a brush and phosphate-free detergent.
  2. Rinse three times with cold tap water.
  3. Rinse three times with distilled or deionized water.

Method B: Acid Wash Procedure for Preparing Sampling Containers

This method should be used when preparing all sample containers and glassware for monitoring nitrates and phosphorus. Wear latex gloves!

  1. Wash each sample bottle or piece of glassware with a brush and phosphate-free detergent.
  2. Rinse three times with cold tap water.
  3. Rinse with 10 percent hydrochloric acid.
  4. Rinse three times with deionized water.

Task 2 Collecting Samples

In general, sample away from the streambank in the main current. Never sample stagnant water. The outside curve of the stream is often a good place to sample, since the main current tends to hug this bank. In shallow stretches, carefully wade into the center current to collect the sample.

A boat will be required for deep sites. Try to maneuver the boat into the center of the main current to collect the water sample.

When collecting a water sample for analysis in the field or at the lab, follow the steps below.

For Whirl-pak® Bags

  1. Label the bag with the site number, date, and time.
Figure 5.1

Sketch of a Whirl-pak® bag
Volunteers can be easily trained to use these factory-sealed, disposable water sample collection bags.
  1. Tear off the top of the bag along the perforation above the wire tab just prior to sampling (Fig. 5.1). Avoid touching the inside of the bag. If you accidentally touch the inside of the bag, use another one.
  2. Wading. Try to disturb as little bottom sediment as possible. In any case, be careful not to collect water that contains bottom sediment. Stand facing upstream. Collect the water sample in front of you.
    Boat. Carefully reach over the side and collect the water sample on the upstream side of the boat.
  3. Hold the two white pull tabs in each hand and lower the bag into the water on your upstream side with the opening facing upstream. Open the bag midway between the surface and the bottom by pulling the white pull tabs. The bag should begin to fill with water. You may need to "scoop" water into the bag by drawing it through the water upstream and away from you. Fill the bag no more than 3/4 full!
  4. Lift the bag out of the water. Pour out excess water. Pull on the wire tabs to close the bag. Continue holding the wire tabs and flip the bag over at least 4-5 times quickly to seal the bag. Don't try to squeeze the air out of the top of the bag. Fold the ends of the wire tabs together at the top of the bag, being careful not to puncture the bag. Twist them together, forming a loop.
  5. Fill in the bag number and/or site number on the appropriate field data sheet. This is important! It is the only way the lab coordinator know which bag goes with which site.
  6. If samples are to be analyzed in a lab, place the sample in the cooler with ice or cold packs. Take all samples to the lab.

For Screw-cap Bottles

To collect water samples using screw-cap sample bottles, use the following procedures (Fig. 5.2 and 5.3):


Figure 5.2

Getting into position to take a water sample
Volunteers should sample in the mail current, facing upstream.

Figure 5.3

Taking a water sample
Turn the bottle into the current and scoop in an upstream direction.
  1. Label the bottle with the site number, date, and time.
  2. Remove the cap from the bottle just before sampling. Avoid touching the inside of the bottle or the cap. If you accidentally touch the inside of the bottle, use another one.
  3. Wading. Try to disturb as little bottom sediment as possible. In any case, be careful not to collect water that has sediment from bottom disturbance. Stand facing upstream. Collect the water sample on your upstream side, in front of you. You may also tape your bottle to an extension pole to sample from deeper water.
    Boat. Carefully reach over the side and collect the water sample on the upstream side of the boat.
  4. Hold the bottle near its base and plunge it (opening downward) below the water surface. If you are using an extension pole, remove the cap, turn the bottle upside down, and plunge it into the water, facing upstream. Collect a water sample 8 to 12 inches beneath the surface or mid-way between the surface and the bottom if the stream reach is shallow.
  5. Turn the bottle underwater into the current and away from you. In slow-moving stream reaches, push the bottle underneath the surface and away from you in an upstream direction.
  6. Leave a 1-inch air space (Except for DO and BOD samples). Do not fill the bottle completely (so that the sample can be shaken just before analysis). Recap the bottle carefully, remembering not to touch the inside.
  7. Fill in the bottle number and/or site number on the appropriate field data sheet. This is important because it tells the lab coordinator which bottle goes with which site.
  8. If the samples are to be analyzed in the lab, place them in the cooler for transport to the lab.

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