Water collection

Introduction
The collection of water samples may seem a relatively simple task. However, it requires more than the simple dipping of a container into water to obtain representative water samples and to preserve their integrity until analyzed. Samples can be easily obtained from well mixed rivers and lakes representing water quality at that point in time. That is, water quality varies over space as well as over time. For instance, water quality changes from month to month and with depth within lakes. This is due to the formation of a warm surface layer of water that does not mix well with the colder bottom layer. The quality of water in rivers and streams can vary even more quickly than in lakes due to their flowing nature. These examples of the dynamic nature of water emphasize the importance of using standard methods for collecting samples.

Procedure

1. Prior to sampling the bottle and cap must be rinsed 3 times. Collect the rinse water from about 0.25 meters below the surface to avoid surface films. Be especially careful not to contaminate bottles with foreign substances (cigarette ashes, oils, fuel, food, insect repellant, sun block, soap, etc.).
2. Tie end of the sampler rope to boat for security against equipment loss.
3. Using the water sample, collect a water sample about 0.25 meters below the water surface.

4. Pour half of the sample collected into another clean, rinsed bottle.
5. Place one of the half-filled bottles back into the sampler and recork it.
6. Collect another water sample from a depth equal to two times the Secchi disk depth or one meter from the bottom, whichever is farther off the bottom.

7. Remove the filled bottle from the sampler, recap, and label.

8. Repeat steps 5 through 7, with the second half filled bottle.
9. Store sample bottles in a cool, dark place until they are delivered to the lab. A cooler and freeze packs will do, but do not use ice.)