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.
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.
To obtain a map of your lake and watershed with aerial views, you can use the RMB Labs interactive online mapping tool at http://www.rmbel.info/Reports/Reports.aspx.
Enjoy the lakes!
Moriya
Rufer is the Lakes Monitoring Program Coordinator for RMB Environmental
Laboratories in