How to gain a better understanding of your lake

Monitoring the water quality of your lake is one of the first steps to better understanding your lake; however, most lakes are not just a self-contained basin. Today I will talk about how to gain a better understanding of your lake by looking around the shoreline and upstream. Just like with human health, when trying to keep your lake healthy preventative care is better and more cost effective than having to fix water quality problems after they occur.

First of all, it is helpful to have data on the water quality conditions of your lake as a starting point. Lake associations monitor water quality because it provides a knowledge base that they can use to protect and restore their lake. The reason for starting a lake monitoring program is to acquire knowledge of the lake’s general condition. Recreational enjoyment and fishing and wildlife habitat quality are all tied to water quality. After the lake’s current condition is determined, associations can monitor water quality each year to learn about seasonal variability and year to year variability. If abrupt changes in water quality occur, they’re able to investigate potential causes and respond accordingly.

Once you have an understanding of your lake’s water quality, there are some other easy studies you can do to understand the factors that contribute to the water quality of your lake. Many of these studies can be done by volunteers from the lake association, or by hiring a water quality consultant.

First, you can do a simple ground-truthing exercise. Look at your lake on a map and locate all the inlets and outlets. Inlets are one of the main sources of nutrients and sediment to lakes. Locating these inlets and then looking upstream at land practices can help you gain an understanding of your immediate watershed. If you suspect nutrient runoff upstream from your lake, you can collect water samples in the inlet to measure what is coming into your lake. If you collect water samples from both the inlets and the outlets of your lake and compare them, you can calculate the net amount of nutrients that stay in your lake and feed plants and algae.

Next, you can complete a shoreline inventory. This type of study will show you how much of your shoreline has natural vegetation and trees and how much of your shoreline is clear cut and mowed down to the lake. A natural vegetation buffer along the lakeshore can filter and absorb runoff so that it doesn’t run into the lake. Lakes that have very little natural vegetation around them are more vulnerable to nutrient runoff, which can directly feed plants and algae and cause a decline in water clarity.

To do a shoreline inventory, you can obtain a map of the parcels on your lake from the county. This map is available on each county’s website. Then you establish criteria for evaluating each parcel such as number of watercraft, presence/absence of natural vegetation buffers, presence/absence of riprap, etc. Once criteria are established, you simply drive around the lake in a boat and look at each parcel and evaluate it with your set criteria, take a photo, and compile the results. Once the results are compiled you can report the overall percentage of parcels that have riprap, the percentage of parcels whose frontage is more than 50% natural vegetation, etc.

Another factor that can affect lake water quality is failing septic systems. Even if your lake is not on the county’s current short-list for lake-wide septic inspections, you can still compile information about the age and type of septic systems around the lake. This study involves researching county records on septic systems around the lake. From this information you can summarize the percent of systems that are over 10 years old, over 20 years old, the percentage of holding tanks and septic systems, etc. Individual lake associations don’t have enforcement authority for septic system inspections, but if you have a summary report that shows the overall ages of septic systems it can be a good tool for educating lake property owners. For example, if a summary shows that over 50% of septic systems are over 20 years old it may hit home on the need for people to have their systems inspected.

Finally, a large-scale study of all aspects of your lake is called a mass balance study. This type of study involves monitoring lake inlets and outlets and determining the net phosphorus staying in the lake. This data can then be fed into a model to see what will happen to your lake in the future if you change land-use practices for the better or worse. This type of study must be completed by a professional limnologist.

Once you learn more about all the factors that potentially affect your lake, you can practice preventative care of your lake, and hopefully avoid costly problems.


  1. Peter Tuomisto says:

    Hi Moriya,
    Hubbard County COLA is trying to determine best practices for individuals monitoring for ZM by using a cinder block hung by a rope on the end of the dock. When in the season should it start and end? How far off the bottom should the block be hung – one foot off the bottom? How often should it be checked and what should we be looking for? Is there something better eg a piece of PVC? We will be recording this data for those lakes participating.
    Thank you for your help
    Pete Tuomisto