What is Groundwater Depletion?As defined by the United States Geological Survey (USGS), groundwater depletion is the process of long-term water-level decline that is caused by sustained groundwater pumping (USGS, 2013). In other words, it is a very severe loss of water from an aquifer resulting in the loss of a water table.
Our planet's groundwater is the largest source of usable freshwater in the entire world (Water, 2016). This freshwater is found in aquifers, which help counteract the surface water that is lost from drought-depleted lakes, rivers, and reservoirs (National, 2014). Some aquifers are able to replenish, but others that are deeper usually cannot (National, 2014). The USGS uses the analogy of comparing groundwater in aquifers to money in a bank account, or more popularly known by hydrologists as a “water budget”. The water budget is as follows: “Ground water can be recharged (deposited) by infiltration from precipitation, surface water, or applied irrigation water; it can be kept in storage (saved); and it can be discharged naturally to streams, springs, or seeps, or transpired by plants (withdrawn). In a ground- water system prior to development, the system is in longterm equilibrium—discharge is equal to recharge, and the volume of water in storage remains relatively constant. Ground- water levels fluctuate in time over a relatively small, natural range. Once pumping begins, however, this equilibrium is changed and ground-water levels decline. Just as a bank account must be balanced, withdrawals from an aquifer by pumping must be balanced by some combination of increased recharge, decreased discharge, and removal from storage (or depletion). An inventory of ground-water levels in wells reflects the volume of water stored (or occurring) in the aquifer, and is analogous to a financial statement.” (USGS, 2013). Essentially, we are withdrawing water faster than we are depositing it and in the long run problems will arise (Water, 2016). What are aquifers?Aquifers are underground reservoirs for water that are typically lined and filled with sponge-like gravel and sand (National, 2014). Aquifers only surface in the form of springs or wells which are drilled by man.
Aquifers that are relatively shallow naturally recharge and replenish from rain, runoff, or snowmelt into the ground (National, 2011). There are two types of aquifers, the unconfined and the confined aquifer. A unconfined aquifer consists of permeable rock and takes in water from the Earth’s surface, which rises and falls respectively with water addition and removal (National, 2011). A confined aquifer consists of less permeable rocks and is typically completely filled with water from lakes, rivers or nearby unconfined aquifers (National, 2011). |
What does groundwater depletion cause/negative impacts?
(highlight of what other group members will be talking about)
A major problem with groundwater depletion is the lack of response to reverse this damage. National Geographic has been known to refer to this as an “out of sight, out of mind crisis” (National, 2014). Obviously the general public cannot see the levels at which our groundwaters are measuring at unless surveys are done. Because people are relatively unaware of the dangerously low levels of our groundwater and the implications it may have, it is hard to trigger awareness and responses. Also, because officials have a majority of the power over these cases, they can simply set matters aside and carry on as they please.
In 2013, a study done by the USGS on 40 aquifers across the United States revealed that groundwater depletion has drastically increased since the year 2000 (National, 2014). As a country, we are removing about six cubic miles of water each year from the ground, compared to an average of 1.48 cubic miles of water yearly between 1900 and 2008 (National, 2014).
Now that you have an idea of what groundwater depletion is you will learn about the impacts that it has. Some of the negative effects of groundwater depletion that will be discussed later in this website/lecture are (Water, 2016):
In 2013, a study done by the USGS on 40 aquifers across the United States revealed that groundwater depletion has drastically increased since the year 2000 (National, 2014). As a country, we are removing about six cubic miles of water each year from the ground, compared to an average of 1.48 cubic miles of water yearly between 1900 and 2008 (National, 2014).
Now that you have an idea of what groundwater depletion is you will learn about the impacts that it has. Some of the negative effects of groundwater depletion that will be discussed later in this website/lecture are (Water, 2016):
- lowering of water table
- increased costs (to pump deeper wells and bring water to surface)
- reduced surface water supplies
- land subsience (loss of support below ground - soil collapses, compacts, drops)
- water quality concerns