By Tom Hammer
During the year of 1996 and early 1997, at the request of Ann Lake Association, the Minnesota Pollution Control Agency (MPCA) sponsored a lake assessment program on Ann Lake which is just one mile south of Howard Lake.
The assessment included much information and data gathering in and around the lake. The study is to help identify sources of pollution to the lake, characterize the quality of the lake, and develop a program to assist in lake management for the future.
Many water samples and secchi disk measurements were taken throughout this period to determine the clarity and health of the lake. The DNR performed a complete fisheries survey and vegetation study in the lake.
Sampling of runoff into the lake was monitored to determine the contribution from the watershed. The watershed is the land mass around a body of water that drains into any particular body of water. In Ann Lake's case, the watershed is quite large with an area of 33 square miles, that is over 55 times larger than the lake itself.
Since the quality or health of a lake is a reflection of its watershed, it is important to understand what exists in the watershed. To this end, septic system surveys were performed on the lakeshore homes, land use in the watershed was evaluated, the main ditches, tributaries and tiling were identified in the watershed, etc.
There was total involvement from the MPCA, Wright County offices of the DNR, Soil and Water Conservation District (SWCD), planning and zoning, and lake association members. What was found was alarming.
Ann Lake is in the upper 10 percentile of lakes in the state in terms of size. The lake is a very shallow lake with a mean depth of about 9.8 feet and a maximum depth of 19 feet. Land use in the watershed is characterized by 78 percent agricultural crops, 11 percent livestock and pasture, 4 percent marshland, 3 percent forest/woodland, 4 other which includes other lakes within the watershed - Grass, Tuey, Spring, Long and Mary and 0.2 percent urban. Animal feedlots, about 50, are common in the watershed.
The lake's shoreline consisted of 65 percent forest-woodland, 22 percent residential, which consisted of 41 homes and cabins, 7 percent grassland, 3 percent livestock/pasture, and 3 percent marshland.
The septic survey of the 41 homes/cabins surrounding the lake revealed that 26 systems were less than 15 years old, while 15 were either greater than 21 years old and most likely are non-conforming systems, or don't exist at all. In addition, the concern of improper maintenance (pumping) was evident in the fact that most people did not pump their system every 1-3 years and a large percentage reported they never have pumped their system.
Water quality data collected during the study reveal summer-mean total phosphorus (TP) concentration of 302 ug/L, chlorophyll a of 28 ug/L and Secchi transparency of 4.4 feet. All three measurements are outside the range of values exhibited by reference lakes in the ecoregion. TP indicates hypereutrophic conditions for Ann Lake and would rank the lake at the fifth percentile. That is to say that 95 percent of the lakes in this ecoregion would be healthier/cleaner than Ann Lake.
A hypereutrophic lake is described as nutrient-rich, exhibiting algal blooms frequently throughout the summer months and with limited oxygen in the bottom layer of water. The external (watershed) loading accounted for about 25 percent of the phosphorus in the lake, suggesting that 75 percent of the phosphorus was already in the lake and being recycled and resuspended. Contributions to the external phosphorus were estimated from modeling programs to come from: 97 percent agricultural watershed, 2 percent from precipitation, and one percent from septic systems.
Eutrophication is a process where the lakes change because of an overabundant supply of nutrients. Excess phosphorus and nitrogen in the lake cause rapid growth of aquatic vegetation and algae. These excessive nutrients degrade water quality which directly affects the health, safety, and welfare of humans and the fish and wildlife habitat.
TP measurements over 150 are not natural, they are man-made.A TP over 100 indicates that the body of water will exhibit severe algae blooms for the majority of the summer months. In addition, that body of water will pose a health risk to animals and humans.
It is our responsibility to restore the conditions of these lakes. Unfortunately, Ann Lake is one of the largest unhealthy lakes in the state. The community can make a big difference to begin restoration of the water quality of Ann Lake as well as other area lakes and waterways which we all rely on for recreation, employment, or other reasons.
What can we do? Each one of us contributes to water quality degradation in some manner, big or small. Don't use phosphorus containing fertilizers at all. Be sure you even need to fertilize by performing a soil sample test. Properly operate and maintain your septic system or holding tanks by pumping them frequently.
Find out more about your waste treatment system. Maintain buffer strips between your property (urban or rural) and nearby waterways or bodies of water which will allow nutrients to be filtered out from entering our lakes.
The Ann Lake Association is soliciting volunteers from the nearby community to allow representatives from the SWCD to perform land assessment in order to identify problems and provide solutions for land and waste management practices. Should you want to learn more about these issues and how your local lake can benefit, contact your SWCD. Community education, awareness and involvement are the first requirements towards long-term restoration.
The Ann Lake Association is now in the process of developing a lake management plan. The association has also opened up its membership to non-lakeshore landowners. Contact us if you are interested in learning more about the association's efforts and challenges.