Like a glass of drinking water, lake water quality typically gets judged by... The clarity (or color) of the water, as well as... How it may smell These two factors (as well as temprature, of course) typically determine whether or not we feel like "jumping in"!! But Delavan Lake is a lake, after all! As such it is a living ecosystem that has its natural processes which determine its water quality and health! How Water Gets IN/OUT of Delavan Lake Matters! - Delavan Lake is a Drainage Lake. Drainage lakes have both an inlet and outlet in which water flows into and out of the lake. Therefore, the main water source is from precipitation and direct drainage from the surrounding land which feed any inlet water sources! The Quality of the Water That Comes INTO Delavan Lake Matters! - Drainage lakes usually have higher nutrient levels than many natural seepage or spring lakes, and Delavan Lake is no exception. This is due to the large amount of farmland which surround the water sources that feed the lake (it's inlet). Delavan Lake Water Quality is Defined and/or Determined by the Quality of the Water which Actually Reaches the Lake!!

When lakes smell bad, we notice. Some basic knowledge of sources of odor may help lake enthusiasts identify odors. Odors can be classied according to some complicated systems, but for our purposes we will stick to some basic descriptions. Rotten Egg - Most people recognize “rotten egg” smell, which is hydrogen sulfide. It is formed when sulfate is metabolized in the absence of oxygen, usually in the bottom of a stratied lake. In lakes, the presence of hydrogen sulfide means that oxygen has been depleted and the demand has become so great that sulfate is being broken down. Blue-Green Algae - Certain cyanobacteria (blue-green algae) produce odorous compounds, specically geosmin and methylisoborneol (MIB), which impart a musty to grassy odor. Often the offending cyanobacteria accumulate as a surface scum, making the odor obvious to those using the lake. If cyanobacteria are abundant enough to produce odor, there is legitimate concern about toxicity, but it is important to know that production of odor and production of toxins are not linked. Still, if enough cyanobacteria are present to create detectable odor, there are enough to create toxins above a safe threshold IF the cyanobacteria are toxin producing forms. Note: Other algae besides cyanobacteria create odor. Actually, any algae will produce some odor if abundant enough, but certain algae can produce specic smells when abundant. Most notable are certain chrysophyta (golden algae), which produce odors such as cucumber, violet, spicy or shy. No one is likely to confuse these options with a wine tasting event. Dead Algae - It would seem obvious, but dead algae tend to give off foul odors usually described as septic or decay. Dying lamentous green algae are particularly malodorous. If mats wash up on shore and start to decay, they are likely to be very noticeable to anyone with a nose.

Eutrophication, the gradual increase in the concentration of phosphorus, nitrogen, and other plant nutrients in an aging aquatic ecosystem such as a lake. The productivity or fertility of such an ecosystem naturally increases as the amount of organic material that can be broken down into nutrients increases. This material enters the ecosystem primarily by runoff from land that carries debris and products of the reproduction and death of terrestrial organisms. Water blooms, or great concentrations of algae and microscopic organisms, often develop on the surface, preventing the light penetration and oxygen absorption necessary for underwater life. Eutrophic waters are often murky and may support fewer large animals, such as fish and birds, than non-eutrophic waters. VIDEO

To answer this question, it is important to understand the following basic realities the effect Delavan Lake Quality: 1. Quality of Water Coming Into The Lake: Delavan Lake is a "drainage lake". That means the lake's water comes from "outside" the lake, as opposed to a "spring" of fresh ground water under the lakes surface/bottom. These other sources include; 1) rain water, 2) water draining into the lake via the shoreline, 3) the water that flows into the lake via Brown's channel, and 4) the water that flows into the lake via inlet (originating from the Jackson Creek Wetlands). Therefore, many issues that effect the quality of Delavan Lake water stem from the quality of the water that comes into the lake from these sources. Phosphorus from the surrounding farmland and lake property constitutes the biggest detractor from good lake quality that can flow into Delavan Lake via these external sources. 2. The Balance of Living Things: The extent to which the natural lake vegetation (weeds/plants) are in balance with the other life forms of the lake (such as fish and the microbiology that the fish eat to survive) is of vital importance! When things get out of balance, the quality of the water will likely decline. If not monitored and managed properly, the imbalance can get out of control quickly and can lead to the need for drastic measures to correct! If the vegetation thrives to excess, it can deplete the oxygen levels within the lake water to sustain the fish and microbiology. A simple equation to pull this together may look like the following... Clean Water In = Reduced Lake Water Nutrient Levels = Balance Of Ecology = Good Lake Quality!

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Most decisions on how best to handle a water quality issue in a lake is based on science and investigation. Once the facts are known as to the source (cause) of the concern, options are identified and evaluated. If "accumulated lake sediment (or MUCK)" is identified as the major source of the issue, dredging is a common and often very effective choice!

As mentioned in previous topics, Delavan Lake primarily gets all of its water from rainfall and the drainage of its surrounding shoreline, including the "inlet" at the northeast corner of the lake. Any water that has "drained" into the lake has the potential to carry with it the "dissolved" solids and chemicals, as well as suspended solids from the land of which it originated. Much of this material contains nutrients (like Phosphorus and Ammonia) that can have an adverse effect on lake quality. Some of the lake benefits of removing sediments include: Reducing dangerous "Algae Blooms" Deepening water to allow for thermal stratification to develop, which helps prevent nutrient movement into the deeper areas of the lake. Removing "rooted" aquatic plants to control their growth through direct removal. Removing oxygen-demanding plants and sediments that can negatively impact fish survival, especially when the water freezes in the winter. Not removing the sediments from the lake, or the ponds/creeks (Inlet Sources) that feed the lake will accelerate the "Natural Eutrophication" process which will ultimately kill the lake!!

Dredging activity should be limited to areas of the lake that are heavily silted and have been identified as having a high sediment load. We recommend consulting with a certified professional to determine the most suitable areas for dredging.