WATER QUALITY SAMPLING – 2004
With a grant from East Central Electric, supplemented by Cross Lake Association funds, water samples were collected from a total of 13 sites during the summer, including the Snake River, Cross Lake, and three streams that affect Cross Lake. Only eight sites were selected each month in July, August, and September. Eight different tests for bacteria, forms of nitrogen, forms of phosphorous, and sediment were performed for each site at a laboratory in Duluth (64 pieces of data each month!). We have received the sample analysis for July and August and are eagerly waiting for the final results for September. The first two reports showed some clear problems that will need further testing and discussion next year.
In addition, Secchi disk readings were taken for each site plus a number of additional sites each month. Clearly, the data shows significant variations in the river and lake from site to site and from month to month. The impact of a lot of rain in June and early July is evident. And just as clearly, the drought for almost two months had a different impact. For example, the Snake River was most clear during the drought (with water coming primarily from wetlands rather than runoff from land surfaces carrying fertilizer and organic and inorganic sediments). Conversely, parts of Cross Lake degraded in transparency during the drought due to an algae bloom (probably from a process called internal loading which involved phosphorous being released from the sediment in an anoxia (now oxygen) condition.
Proper conclusions regarding water quality trends for any lake or river requires collection and analysis of quite a few years of data. However, many people, including myself, felt that overall water clarity was quite good this year. Greg Sheehy and I saw some Secchi disk readings of 5 feet in some places, even during the drought.
Not surprisingly, the Snake River degrades as it passes through Pine City. This also has been obvious in previous official studies. Undoubtedly, most cities have this impact on rivers, primarily from storm water and development.
At least one stream entering the lake on the northwest end has a significant amount of bacteria and nutrients which can cause degradation of Cross Lake. A previous study with less data showed similar results. The sources of cleaner water entering the lake have also been identified and provide a kind of benchmark for wild water entering the lake.
A more complete report of this valuable water sampling project will appear in the first issue of the Crossings in May 2004.