A Citizen's Guide to Understanding and Monitoring Lakes and Streams

Chapter 4 - From the Field to the Lab

Ground Rules

The following ground rules refer to general sampling guidelines that are applicable to all water quality samples collected. (For each of the parameters described, special precautions may be needed to ensure collection of a good quality sample. These are described later for each parameter.

  • The single most important ground rule for the monitoring program is this: Document everything you do. A permanent record lets others who may want to use your results know how the data were obtained so they can use the same procedures or at least know how to compare them. Documentation becomes even more important in a volunteer monitoring program since it provides a ready-made training aid for new volunteers.Recording Data - Copyright by Sandra Noel
  • Safety first! Never enter a stream or lake if the current is too strong or conditions too rough – use a safety line in swift waters. Always have a buddy along who can help if you get in trouble. Wear a life vest whenever you are in a boat.
  • All sample containers need to be washed with a dilute acid (sulfuric or hydrochloric) and thoroughly rinsed with deionized-distilled water. It is very important to keep these bottles clean between collecting the samples. Keep their caps on tight, and don’t remove them until the sample water is collected. The Puget Sound Estuary Program protocols and standard methods referenced at the back of this guide give detailed washing guidelines.
  • Rinse each container with sample water three times before placing the sample in the container permanently. (Some samples require addition of a preservative that may be added ahead of time. If this is the case, then the bottles should not be rinsed first.)
  • When sampling in a stream, extra precautions are needed to ensure a sample is not collected from a disturbed area. Always begin sampling at the station nearest the mouth of the stream and work your way upstream.
  • When it is necessary to enter a stream to collect a sample, always take a few steps upstream from where you entered the water, face into the current, lean forward, and reach upstream to collect the sample.
  • Always collect samples from a few inches below the surface of a stream, or from the depth of about an arm’s length in a lake.
  • When sampling in a lake or over a bridge where equipment can be sunk and lost, tie off the equipment to a solid, stable object first.
  • Label all sample bottles with station name, date, time, and parameters to be analyzed. Use indelible ink!
  • Take lots of field notes. Include weather observations, visual appearance of the sampling station or water quality, equipment problems, and description of techniques used.
  • Be consistent. Don’t change sampling method, equipment use, or station locations between sampling stations or sampling days without noting why the change was made and permanently identifying which data belongs to which set of sampling techniques or equipment used.

Collecting the SampleSampling Techniques - Copyright by Sandra Noel

There are quite a number of techniques for getting water from the lake or stream into a sample bottle. The one selected depends upon the sampling site.

The most common method is to hand dip the sample. It also is the easiest. Hand dipping is ideal if you’re sampling from a boat and only need a surface sample, or if you can wade far enough from shore to collect your samples. To avoid capturing the tiny organisms and debris that float on the surface film of the water, the sample should be collected from below the water surface. Hand dipping lets you collect water from the right location and depth.

To collect samples as far from the shoreline as possible (lakes) or well out into the main moving channel (stream), use a long or extendable pole. Rig the pole so that it can hold a sample bottle, either temporarily or permanently. Such a device is easy to make and works well. It also allows you to control the depth at which the sample is collected.

Samples also have been collected by using a weighted bucket attached to a rope. This method is handy when sampling from a tall bridge where a long pole won’t work. If the water is shallow, make sure the bucket doesn’t disturb the stream bottom.

More sophisticated equipment is usually needed to collect samples from more than one depth in a lake. Several samplers have been designed for this purpose. The most common are tube shaped samplers with openings on both ends. The ends are propped open – like a mouse trap – while the sampler is lowered to the desired depth. The line used to lower the sampler is marked in 1-foot or 1-meter sections and is equipped with a weight, called a messenger. When the sampler reaches the desired depth, the messenger is released. When the messenger hits the sampler, the trap is sprung, the ends close, and the sample then can be lifted to the surface.

Next Section - Sampling and Measuring Methods

Return to Table of Contents | Lakes | Streams | From the Field to the Lab | Hydrology

 

Last updated on April 01, 2008