This is a continuation of our earlier post – Monitoring and Managing.
We introduced what we should be sampling for and why in the first blog. This entry will discuss where, how, and how often sampling should be done.
This has to be one of the more difficult topics to cover in a short blog, but here goes… Each reservoir, lake or water impoundment is different. The size, shape, depth, water chemistry, retention time, watershed, and even placement on the planet (altitude, latitude) of individual water bodies is different, making the sampling procedures unique and sometimes challenging. To further complicate the picture, mandates required by law or directives, individual expectations or the need to know are different for each water body. No one plan fits all and there is no silver bullet to resolve all the problems- damn!
There are several constants: 1) Think Vertically (sample at various depths) 2) Know the Topography (geological, terrain, geomorphometry) 3) Understand the Watershed (what’s infiltrating the reservoir) and 4) be aware of Weather Events (storms with heavy runoff, extreme temperatures). Notice that the operative words are Think, Know, Understand, and Awareness.
To make this a little easier I am breaking this down into three general categories.
Drinking water reservoirs: Several sampling sites, depending on the size of the reservoir and the topography, should be used. Sampling near the plant intake is a given. Additional sites will depend on topography, the watershed and suspected cyanobacteria “incubator hot spots” such as coves and stream entry points. Sampling weekly or twice monthly should be adequate. Need and expectations will determine the frequency.
Wastewater impoundments: This is a different story. Most wastewater impoundments are oval, square, or rectangular basins where nutrient load and algal densities are essentially equal throughout the enclosure. Sampling just below the surface anywhere will tell the story. We are not typically interested in exact algal densities and speciation (wastewater nutrient loads can be changing drastically by the minute and hour). NPDES requirements will dictate the frequency of sampling.
Recreational lakes/ponds/farm/aquaculture/industry: Monitoring programs in this category is the most diverse with a myriad of choices driven by necessity and expectations. Sampling strategies, schedules, and criteria must be individually designed to meet the needs.
Remember- “If you are not monitoring, you are not managing.”
Whew! I am glad to be finished with this topic. I am much better and prefer looking at each individual situation.