Most of you are probably aware that HLPS has been a participant in the Cooperative Lakes Management Programs (CLMP) for almost 20 years. Through this program, volunteers take weekly water samples, dissolved oxygen readings and water transparency and temperature measurements. These key parameters allow us to make comparisons over the years and determine long term trends in our Lake’s water quality. Data comparisons can also be made with other lakes participating in this program. As the newly appointed Water Quality Director for HLPS, I’m still just getting my feet wet, so to speak. However, as I look over 2017 reports and compare them to those of previous years, I do see some issues that cause concern.
A review of the transparency data indicates water transparency (clarity) continues to decline in both the lower and upper lakes. The average transparency reading for the upper lake in 1999 was 10 feet but declined by 2017 to 7 feet. Similarly, the average transparency reading for the lower lake in 2001 was 13 feet but has declined by 2017 to 11 feet. Declining water transparency values are generally related to greater sediment loading and an increase in algae growth. These findings correlate with total phosphorus values, which also increased slightly for the same time period. Total phosphorus is the major plant nutrient contributing to increased weed growth in most Michigan lakes.
Weekly dissolved oxygen levels for 2017 also showed reason for concern in the upper lake. July’s average dissolved oxygen level was 9.0 mg/L at the surface but declined rapidly, below 15 feet, to 0.4 mg/L at 30 feet. This is not good news for those who enjoy fishing in the upper lake. Fish populations generally do not inhabit waters with dissolved oxygen levels below 4 mg/L. It is interesting to note that July dissolved oxygen levels were much more favorable in the lower lake, ranging from 8.6 mg/L at the surface to 6.5 mg/L at a depth of 70 feet.
The water quality team will be watching these values closely with the hope that future trends will be more favorably. Continuing education of riparian owners and watershed protection efforts hold the key to making these values improve. Agricultural runoff, soil erosion, riparian lawn fertilization and poorly maintained septic systems remain the greatest threats to our lake’s well-being.
Future water quality efforts will focus on the collection and analysis of samples from streams and tributaries feeding Hamlin Lake. This needs to be done in the spring-time when maximum snow melt runoff is occurring. Such sampling was last done in 2014 and was scheduled to be done again this past spring in support of our watershed management plan. Unfortunately, mother nature caught us off guard, as snow melt and heavy spring rainfall happened in late February. This was far earlier than normal when our sampling team was still enjoying the warm weather in more tropical climates. Hopefully, weather patterns for 2019 will be more normal and allow us to conduct this valuable study in late March or early April.