Why Do We Sample Water?
Being a water testing laboratory, one question that we receive all the time is why should we monitor our water, it seems fine? Our response is that monitoring of water should be conducted for a few major reasons. We must consider the end use of the water when we think about why we monitor the water and what we monitor for. In general, people are concerned with health and/or the ecological condition of the water. In most cases contaminated water does not have an unusual smell, taste, or appearance. Also, they are concerned with the use of the water as that will help inform us both of the type of sampling and analytes that we may be looking for.
Let’s begin with surface water. Overall, the surface waters around Door County are monitored for E. coli as the indicator organism for water quality at swimming beaches. It is the test used for regulatory compliance and what dictates if beaches are open, under advisory, or closed. To be under an “advisory” for E. coli contamination the beach would need to have 235-999 MPN/100mL of E. coli present. To be considered “closed” the beach would need to have a concentration of 1,000+ E. coli/100mL. E. coli is an indicator of fecal pollution and the presence of possible pathogens that may be present in the swimming water at beaches. While the E. coli we see in beach water does not typically make you sick (not the same E. coli we see in undercooked beef), the other bacteria, viruses, and protozoans in fecal material can be a health hazard.
Door County has overall very good surface water quality, so the monitoring helps us keep updated in case there are either gradual changes in water quality or sudden changes due to an unforeseen event (i.e., sewer pipe break). Conversely, drinking water well owners typically look for three measures of water quality. These are coliforms and E. coli (same test), nitrate, and arsenic. These parameters look for the presence of both chemical and biological contaminants. The limit for each of these in public drinking water is 1 MPN coliform/100mL, 10 mg/L nitrate, and 10 µg/L of arsenic. These are particularly important to look at annually in Door County because the unique geology (Karst bedrock) makes drinking water very prone to contamination and previous work has shown that the quality of the groundwater can change quickly.
While coliforms are not used for surface water quality determinations, they are used for drinking water as they are more abundant and thus more protective of the health of the water users. In either case the sampling will help identify acute hazards from pipe breaks, spills, channeling through fractured bedrock, etc. Additionally, even if an acute hazard is not present, this sampling and subsequent results allow for the evaluation of longer-term trends in water quality. In both aforementioned cases, it is well worth the relatively small investment of time and cost for the analysis to protect the health of our water users. After all, what does poor well water do to the value of a home or business, and will those that get sick swimming at beaches come back?
By Greg Kleinheinz, RS, Ph.D. Chair and Distinguished Professor UW Oshkosh
