What is silt?

Silt, in its description, is a contradiction in terms – a solid granular material or solid dust-like sediment. Geologically, it’s classified by its grain size and texture through a sieve, and is assigned a letter according to whether it’s gravel, sand, clay, or organic.

How does silt get into your lake?

Silt is created by the erosion of rock; loose materials are transported through flowing water such as rivers, grinding them down until they become silt-sized. At this size, it’s easy for the sediment to be washed into lakes and ponds through an inlet or watercourse.

Alternatively, silt can come from organic matter washed in from surrounding fields or plants. Lakes and ponds that are tree-lined are particularly vulnerable to heavy siltation, as dead plant leaves and other organic material fall from surrounding fauna into the water and build up on the lake bed.

Either way, when left to settle on the lake bed, this material soon becomes the layer of black silt you might be familiar with.

What problems does silt cause?

Bad smells

As silt builds up on the bottom of lakes, it inevitably decays. Natural processes break down organic matter, using up oxygen levels from the water and increasing the demand on dissolved oxygen levels.

Without a sufficient level of oxygen in the water, anaerobic bacteria will break down organic buildup in the water and bottom of the lake. During this process, the bacteria will produce waste gas, which is what smells.

Flooding

Another issue with silt if left is that it reduces the depth of the water body and causes a risk of flooding. 

Similarly, if there is an outlet blocked with silt, heavy rains can cause flooding on adjacent land. That can be particularly disastrous if there’s property, agricultural land, or commercial premises, like a golf course or park, nearby.

Algae blooms

Suppose silt blocks inlets and outlets, preventing water flow. In that case, the possibility of stagnant water, which smells and looks extremely unpleasant, can become a nasty reality. Not to mention the high nutrient levels of the silt encourages dense algae blooms, spoiling the water quality and aesthetics and posing a danger to fish.

Danger to fish

Silt can also often create acidic conditions, which further reduce the quality of the water. Water that has become very shallow due to silt build-up also poses a threat to fish stocks, as they tend to need deeper, cooler water, especially in warm weather.

How to remove silt from your lake or pond

Silt dredging and pumping

Silt pumping and dredging are two ways of removing build up; however, this can be a large operation, costing a great deal of time and money. By adding a quality aeration system, you can avoid emptying your lakes to fix a silt problem by preventing silt build-up in the first place.

Add dissolved oxygen through aeration

Providing water with plenty of oxygen shifts anaerobic bacteria to an aerobic form. Aerobic types can decompose organic matter without producing carbon dioxide waste gas, making the process both harmless and odourless.

Aerobic bacteria, encouraged by proper aeration, work much faster than their anaerobic counterparts, pulling nutrients like phosphorus from the lake and making it unavailable for algae to draw from and use to grow.

Adding dissolved oxygen to water is important when keeping ponds and lakes healthy as it supports the aerobic and oxidative processes of water: oxygen attaches to the phosphorus and converts it into an insoluble form, so algae can’t absorb it. This prevents an algal bloom.

Use multiple types of aeration

Water aerators work by transferring oxygen back into the water, and there are two ways of doing this.

Surface aeration

Surface aeration typically comes in the form of an aerating fountain. These floating surface aerators disrupt the lake’s surface and displace water by throwing droplets into the air where they can make contact with oxygen molecules. 

When they fall back to the surface, that ‘dissolved oxygen’ is released back into the water, becoming available to use in the process of breaking down organic sediment.

These systems operate in a depth of as little as 75 cm of water, making them suitable for ponds and lakes of any size.

Subsurface aeration

As the name suggests, subsurface aeration works beneath the water level and is often unseen altogether. 

Diffused aerators drive air down a tube, releasing it via a diffuser at the lake bed. Air bubbles can then be slowly ‘absorbed’ by the water as they rise to the surface. Because of this process, these aerators are also referred to as bubbler systems.

The deeper the diffuser, the more oxygen it can transfer back into the lake. Because of this, subsurface aeration is recommended for bodies of water that are at least eight feet deep.

Why choose Otterbine?

As independent testing from the University of Minnesota and GSEE shows, Otterbine offers the highest oxygen transfer and pumping rates in the industry. They can add as much as 3.3 lbs or 1.5 kg of oxygen per horsepower hour into the water and can pump over 920 GPM or 199m3/hr per horsepower.

By treating water above and below the surface, Otterbine equipment eliminates the need for chemicals and is, therefore, ideal to undertake silt removal, combat poor water quality, and ultimately extend the lifespan of your lake.