adminNote: The content of this post is from answers to questions posed on Quora, written by Dylan Duverge. For the originally published content, Click Here.
Groundwater is a renewable resource. Renewable is defined as “capable of being replaced by natural ecological cycles or sound management practices.”[1] Because groundwater aquifers can be replenished, either through natural processes (e.g., deep infiltration of rainfall) or artificially (e.g., engineered recharge basins or injection wells), groundwater meets the definition of a renewable resource. The fact that groundwater is a resource that can be naturally replenished differentiates it from other underground resources that are clearly not renewable, such as oil reserves and ore deposits, for example.
However, groundwater is not commonly referred to as a renewable resource because we as humans do not use it in a sustainable manner. While some natural resources like sunlight, wind and geothermal heat are immediately and predictably replenished, the time it takes to replenish groundwater is very long and can be difficult to predict. Replenishment is contingent upon rainfall infiltrating deeply into the ground, and depending on location and depth, can take anywhere from a few days to millennia. Replenishment of groundwater aquifers, just like stream flow and reservoir levels, can be diminished by droughts. Over time, humans tend to deplete groundwater volumes through over-pumping and degrade groundwater quality through pollution. Many places are now realizing that they have been pumping excessively for so long that their reserves are running out, and that the only way to fix it is to manage the groundwater basin/aquifer like a balanced bank account. That is, to decrease pumping (impose water rations and pumping limits, promote conservation, etc.), to artificially increase the replenishment rate (create recharge basins or injection wells), and/or to find an alternative sources of water (e.g., seawater desalination, rainwater harvest, wastewater recycling, etc.). In severely overdrafted basins, an “all of the above” approach is required.
Although groundwater can be defined as a renewable resource, it is neither free nor unlimited. For this reason, it is not very helpful to think of groundwater as renewable, because the general public will confuse it with more common renewables such as wind and solar, which are free and unlimited. It is better the think of groundwater in terms of sustainability, so that we limit our use of it to the rate at which it is replenished.