Lake Management Lake Weed Control Water Depth Secchi Depth

Lake Management Lake Weed Control Water Depth Secchi Depth

Lake Management Lake Weed Control Water Depth Secchi Depth
For the best lake management, and lake weed control there are 2 often ignored keys, and they both have to do with the depth to which sunlight penetrates in a lake or pond.

If sunlight can not reach the bottom of your lake or pond, you will not have lake weeds. Aquatic weeds, like all other plants, cannot grow without sunlight. So, the key to stopping a lake weed problem is to prevent sunlight from getting to the bottom.

There are 2 issues to deal with: Water depth, and water color. Both are important.

Water depth

The deeper the water, the less sunlight reaches the bottom. To change the waters depth, you must either raise the water level, or lower the bottom.

Raising the water level

Raising the water level may be difficult, but it can sometimes be done, depending on several factors. If you have a strong dam, and the capacity to raise the level of the outlet, you can add some depth to your impound by doing so.

Lowering the lake bottom

If you can dredge the highest points in the lake or pond, this will lower the bottom, and, of course, make the water deeper. If the pond can be drained, earth moving equipment can accomplish this. If it cannot be drained, there are floating dredges and other equipment for the job. A combination of edge dredging, and raising the water level will often produce the desired effect.

Water color

The darker the water, the less sunlight reaches the bottom. Water color has a direct effect on the amount of sunlight which reaches the bottom of a body of water, and the less sunlight reaches the bottom, the fewer problems you will have with lake weed control.

Artificial colorants

There are colorants available to dye the water, but this is not the best way to manage a lake or pond, unless it is only being used for decoration, or for fed catfish. Artificial colorants interfere with the natural food chain. There is a better way.

Algae bloom

Single cell algae from the plankton family are naturally occurring plants which are suspended in ponds and lakes. If the fertility conditions are right, they will grow and remain suspended in the water profile, and their natural green color provides protection from sunlight. This plankton also provides food for the small aquatic animals which feed the bugs, which feed the small fish, which, in turn, feed the larger fish in the biological chain. Without this “circle of life”, the lake or pond will be little more than a holding tank.

Producing algae bloom

The trick to producing this algae, is to do something which might, on the surface, seem counter productive. Fertilize the lake! The rise in fertility will cause “algae bloom”, the algae will protect the lake bottom from sunlight, the weeds which always start at the bottom will not have sunlight, and the pond or lake will be relatively free of unwanted weeds.

Water pH

Before taking this step, check the pH of the water. A simple water testing kit will tell you the acidity level of your pond or lake. For the best results, pH should not be below 6.8. If it is below this mark, the pH should be raised by adding an alkaline source such as agricultural lime.

Aquatic fertilizer type

Fertilization should be done with a product high in phosphorous, and low in the other 2 chief elements. When you look at a fertilizer container, it will have 3 numbers, divided by dashes. phosphorous is the one in the middle. Most farm and ranch, or chemical supply places will have a fertilizer made for this purpose, complete with instructions on the amount to use, and the best method for application.


You will need to continue to apply fertilizer throughout the summer months, checking the Secchi Depth as you go. If light is penetrating past 18 to 24 inches, more fertilizer is needed, when light penetrates less than 10 or 12 inches, you should back off.

See also: Secchi Disk