Properly managed lakes and reservoirs provide citizens with many fun and exciting opportunities for recreation including swimming, fishing, and skiing. Unlike natural lakes, most reservoirs were not “created” for this purpose. They are usually created for flood control and/or water supply needs. Additionally, lakes and reservoirs can have many other authorized purposes including fish and wildlife support as well as water quality enhancements. While lakes and reservoirs do have unique characteristics, they function similarly and we refer to them collectively as “lakes” in the following text.
In order to meet all of the many purposes and stakeholder interests, lake managers and scientists must monitor the physical, chemical, and biological aspects of the waterbody and their respective watersheds. Physical aspects include a lake’s hydrologic characteristics such as water levels that influence shoreline habitat and residence times, which tell us the average time that water spends in a lake. Chemical characteristics include but aren’t limited to phosphorus, nitrogen, dissolved oxygen, and mercury. Biological aspects include phytoplankton, zooplankton, fish populations, and the macrophyte plant beds.
Metals and nutrients exist in varying concentrations and impact Indiana surface waters. Excessive nutrients are probably the most widespread water quality issue in Indiana lakes. These nutrients such as nitrogen and phosphorus can come from many sources including our individual yards or large factory farms. During heavy rain, these nutrients wash into our streams and, eventually, these receiving water bodies. Once in the lake, they can fuel the growth of cyanobacteria resulting in Harmful Algal Blooms (HABs).
To understand nutrient levels and interactions in these water bodies, scientists must monitor nutrients in the water as well as the sediments. Lakes can also have high concentrations of metals. Examples of metals are mercury, lead and copper. These metals can come from many sources including the atmosphere, sewage, or mining activities. To monitor metal concentrations, scientists will often collect water, sediment and fish tissue samples from lakes. The fish tissue samples can be used to understand the levels of metals that are made available to humans and can inform fish biologists on the necessary fish consumption advisories.
Sedimentation and harmful bacteria are additional concerns facing lake water quality. During heavy rains, sediments (soils and fine particles) from the ground are suspended in fast moving water. When the water reaches the lake or reservoir, it slows down and sediments are allowed to settle to the bottom of the water body. These sediments are frequently carrying nutrients, metals, or other water quality contaminants. Once these contaminants are in the lake sediments, they can become resuspended in the water and further contribute to water quality issues in the lake for many years or even decades. To understand sedimentation, scientists can collect sediment samples or conduct bathymetric surveys (the measurement of depth of water in oceans, seas, or lakes) to see how much sediment is accumulating over time.
E. coli is another water resource issue that reservoir managers must be concerned about. E. coli is an indication of fecal contamination and can become harmful to humans at high concentrations. Lake managers must routinely monitor beaches in Indiana to ensure that E. coli concentrations are not too high for human contact. It is important to monitor such biological trends collectively with lake chemical and physical hydrology to understand when to make certain management decisions.
Water monitoring and proper management of Indiana lakes are vital to local economies that depend on recreation-related revenue during summer months. Furthermore, ensuring good water quality is essential for human health where reservoirs are used as a public water supply source. Lastly, preserving the aesthetic qualities of lakes and reservoirs by limiting algal blooms and sedimentation benefits all Hoosiers that enjoy visiting lakes in their area.
Water-Resource Professionals in Indiana Focusing on Reservoirs
- Jade L. Young (U.S. Army Corps of Engineers)
- Dave Nance (IN Dept. of Natural Resources)
- Cyndi Wagner (IN Dept. of Environmental Management)
- Melissa Laney (IN University & Indiana Clean Lakes Program)
Indiana Clean Lakes Program, 2017, Indiana Lake Information – Lake Data, accessed July 21, 2017 at: http://www.indiana.edu/~clp/indianalakeinfo.php.
Nance, D., 2008, Lake level data for natural lakes in Northern Indiana, Water Column, Vol. 20, No. 1, accessed July 21, 2017 at: http://www.indiana.edu/~clp/documents/WATER%20COL%20V20%20N1.pdf.
U.S. Army Corps of Engineers, 2017, Louisville District Lakes Information, accessed July 21, 2017 at: http://www.lrl.usace.army.mil/Missions/Civil-Works/Recreation/Lakes/.