Silt and Your Pond
Silt. Soft, gooey, mucky black pond bottom stuff oozing between toes, staining shoes past ankles. Decaying organic contents of silt smell like rotten eggs. Wade the edge of your pond, and take a look.
Nature gives us silt, naturally. It is as normal as fallen leaves, grass clippings and fish poop. As a matter of fact, fallen leaves, grass clipping and fish stuff become ingredients of silt on pond bottoms all over the world.
To know silt is to understand silt.
Merriam Webster’s collegiate dictionary defines silt as “loose sedimentary material with rock particles usually 1/20 millimeter or less in diameter.” I know that’s true because Otto looked it up two issues ago.
The loosest of all soils, silt collects on top of more solid, clay based pond bottom soils. From there, water currents and wave action send silt into convenient areas for deposit. Take a look where water enters your pond. That’s the most likely spot to find new deposits of silt, washed there by recent rains.
If truth be known, most silt into a new pond comes from freshly disturbed soils of construction. As the pond fills, neighboring loose dirt washes downward, eroding shorelines, and pitching fine particles into silt bars and banks, deposited near inflow areas. Don’t step in it. There is a difference between silt and Shinola.
As a pond ages, less dirt comes in, but more organic matter collects. Water composts leaves, twigs, clippings and fish waste, and plops these new deposits on top of older ones. As time goes, silt layers become deeper. Finally, we perceive silt to be a problem. How do we know? Ponds lose depth.
If you think about it, a pond or lake is built, and then begins to age. Part of this process is accumulation of soils. Loose soils, silt, become home to cattails, reeds and rushes, usually in the upper parts of a pond…where water flows in. As silt mounts, cattails and reed families spread. Over time, a pond is covered with tall plants. With more years of age under your pond’s belt, soils collect and peek above the waterline, and terrestrial plants become dominant, The pond becomes land, again, as the shore moves inward.
New Orleans was built on soils deposited from Iowa, Indiana, Missouri and states robbed of dirt by the Mississippi River drainage basin.
Want to minimize siltation of your pond? Keep it out, from the beginning. Vegetate bare dirt, quickly. Compact shorelines. Minimize grades…shoot for 3 to 1 slopes. Where ground falls fast, consider silt fences. It’s easier to shovel silt from behind a silt fence or screen than to dig it out of a pond, underwater.
Have an old pond, with lots of silt? Careful, here. Removing muck is costly. It has to be dug out, pushed up, then spread out. Or, dug up, loaded onto a truck, and hauled away. Bottom line? Silt must be moved two or three times before disposal.
More often than not, it’s cheaper to move to another site and build a new pond than to clean out an old one,
Silt for the garden? After all, it’s been years fermenting and composting at the bottom of a pond. Forget it. Silt has no nutritional benefit to terrestrial plants. Besides, when silt dries, it shrinks and cracks. Then, when wet, it expands…like pudding. Don’t add to gardens.
Small ponds seem to magnify siltation. Smaller areas can be redefined by siltation from one rainfall event. So, if you have a mini-pond, give much thought during the planning stages, before the contractor ever turns a spade of dirt.
Ten years from now, your pond will thank you.
By Bob Lusk, reprinted from Pond Boss Magazine
POND BOSS Magazine is the world’s leading resource for fish, pond and fisheries management information including discussions on muddy water, raising trophy fish, fish feeding, building a pond, algae control and more. Check us out at www.pondboss.com or contact Bob Lusk, the Pond Boss himself, at 903-564-5372. His books, Basic Pond Management, Raising Trophy Bass and Perfect Pond, Want One, may be purchased by calling 800-687-6075 or ordering online at www.pondboss.com