the assumption of responsibility for the welfare of the world
Groundwater is simply water beneath the surface of the Earth. It exists soaked into dirt or in underground deposits in sand or rock called aquifers. This groundwater is not necessarily right at the surface; rather, it exists below a certain level, the water table. The water table is the feature that makes an artificial well work as it does. To make a well in the European tradition, a hole is dug in the earth. After digging far enough, the well-makers strike water. The level of the water at the bottom of the well is the water table. To get water from the well, the users lower a bucket down into the well, fill it with water, and pull it back up. Note that the water isnít under enough pressure to force it up out of the well. (Other, more modern wells involve drilling the surface and installing a pump to bring the water up.)
Groundwater is often tapped for human purposes, not only drinking water but agricultural and industrial needs as well. Obviously it is possible to use groundwater at a faster rate than it is replenished, and this is usually the case in modern society. At some point, groundwater is exhausted, which has human and economic consequences, of course. But the net consumption of groundwater is not environmentally cost-free, either. Groundwater is what plant roots are tapping, so reducing groundwater deprives plants. And groundwater provides subsurface tension; it takes up space. As groundwater is depleted, the ground above it will actually subside (sink in).
Modern construction, and even some traditional practices like the creation of trails, have covered the Earth with impermeable surfaces, surfaces that donít allow rainwater to soak in. Buildings, roads, sidewalks, and parking lots are all impermeable. There are two effects of this, both negative. When rainwater doesnít soak in, the groundwater isnít replenished. And when rainwater doesnít soak in, it must run off, changing the hydrological pattern, creating more surface water, often moving faster, causing flooding and erosion. This also increases the presence of other pollutants in surface water, such as motor oil. Motor oil that soaks into the ground is not ideal, but at least it may be filtered before it reaches the water supply for human drinking or an ecosystem. If it runs off in surface water, it is less likely to be filtered. Gradually humans are recognizing the threat of impermeable surfaces, and scaling back the creation of these surfaces, or replacing them with newer materials that are permeable. It will likely be decades before the problem is taken seriously enough to be tackled routinely.
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