Water, water everywhere!
Up to 71 % of the visible surfaces of the earth are covered by water. Fresh water makes up only about 2.5% of that number! And of the earth’s fresh water resources, the U.S Geological Survey estimates that 30.1 percent of that water is underneath your feet!
Water that remains under the surface of the earth is called groundwater, and it is part of the earth’s water cycle. It flows underground through permeable rock and soil into the rivers, lakes and oceans, where it is absorbed into the air and recycled into rain, which we are all quite familiar with!
The point at which the water saturated rock and soil joins the upper layers of soil that are less saturated is called the water table. This layer of saturated groundwater may occur anywhere from a few feet to a much deeper depth down in a particular area.
Contrary to natural assumptions, this water flows under the surface in a similar plane to that of the surface of the earth. So if you live on a hill, the groundwater, like the surface water, flows downhill, but does it under the surface of the ground.
Subsurface Water Levels
While groundwater does follow the general topography of the earth’s surface, it does not rise or fall at the same levels, rather it will rise and fall at a gentler incline. Thus, as water accumulates the subsurface water depth will rise closer to the surface and may actually seep out onto the surface as streams and springs.
In some cases groundwater may even rise to the level that it will cause water to form into small lakes and puddles over the surface of the ground. If your home is located in a valley, your chances of having subsurface groundwater drainage issues are higher.
Still, ground water can be held in pockets very high in the earth’s crust in what is called a perched water table, so even if you live on higher ground your soil may be saturated with ground water.
A perched water table is a layer of water that lies above the normal subsurface groundwater in a given area. This occurs when a layer of soil or rock that is impermeable traps water at a higher level. This layer may be made of bedrock material or it may be compacted heavy clay soil which does not allow water to pass through its surface.
The rate at which groundwater drains from your property depends upon how permeable the soil and rock beneath it are.
You may be blessed with bedrock or layers of compacted heavy clay soil that can cause soil to become impenetrable. If these situations are present near the surface of the ground, the water depth may rise until it penetrates the surface. This will result in water that will stand in low spots or along depressions in the soil around your home and property.
With the advent of the winter season, groundwater rises. This causes high water levels to be more seasonal in nature. As this seasonal water rises, it is possible that you may experience periodic episodes of standing water. Seasonal standing water that will not drain away after several days during the winter and spring months is likely caused by a seasonal high water.
Here is a fun little video that helps explain a bit how groundwater works. I warn you its "cute", but I really think it does a pretty fair job of explaining how it all works!
“All this is well and good”, you may be thinking, “but what do I do about it!” Well, there are some solutions, depending upon the location of your perch upon the earth.
French Drains may be a solution if you live where you have opportunity to channel water away from a higher, but saturated area, to a hillside or other exit point where you can drain the water above the level of the subsurface saturation point. In most cases however, for high subsurface water accumulations, French Drains are an inadequate solution, since the drain itself can fill with water, therefore become non-functioning.
In most situations where groundwater rises to the surface, an underground system of drainage pipe is the best solution. These pipes can route water away from the property into a storm collection system, or to an area of the property that is free of accumulating water. This system may require pumps and can be expensive to install, depending upon the nature of the drainage solution.
Similarly, a Swale or diversion ditch can provide relief, especially for situations where standing water due to groundwater accumulation is a seasonal concern. Swales and diversion ditches can collect water runoff and create a “holding tank” where water can be allowed to stand while it works its very slow way through the soil or evaporates into the air. With care in design, these can become decorative features in your landscape design as well, and offer the illusion of a small natural pond on your property.
Small drainage systems of just a few pipes may be within the reach of an average homeowner, but in most cases, it is time for the homeowner to cry “Uncle!” and engage a qualified Drainage Contractor.
Some photos used under CC licenses from the following sources:
basykes Wikipedia Duk
Video used by permission from the following contributors:
Animators: Michelle Mansfield, Geoff Harrison, Karen Lewis, Michael Bell; Music Composed and Arranged By: Mike Sebring