Question

Declining groundwater levels - a widespread problem.

Answer 1

Groundwater depletion

Groundwater is a valuable resource both in the United States and throughout the world. Where surface water, such as lakes and rivers, are scarce or inaccessible, groundwater supplies many of the hydrologic needs of people everywhere. In the United States, it is the source of drinking water for about half the total population and nearly all of the rural population, and it provides over 50 billion gallons per day for agricultural needs. Groundwater depletion, a term often defined as long-term water-level declines caused by sustained groundwater pumping, is a key issue associated with groundwater use. Many areas of the United States are experiencing groundwater depletion.

Excessive pumping can overdraw the groundwater "bank account"

The water stored in the ground can be compared to money kept in a bank account. If you withdraw money at a faster rate than you deposit new money you will eventually start having account-supply problems. Pumping water out of the ground faster than it is replenished over the long-term causes similar problems. The volume of groundwater in storage is decreasing in many areas of the United States in response to pumping. Groundwater depletion is primarily caused by sustained groundwater pumping. Some of the negative effects of groundwater depletion:

drying up of wells

reduction of water in streams and lakes

deterioration of water quality

increased pumping costs

land subsidence

What are some effects of groundwater depletion?

Pumping groundwater at a faster rate than it can be recharged can have some negative effects of the environment and the people who make use of the water:

Lowering of the water table

The most severe consequence of excessive groundwater pumping is that the water table, below which the ground is saturated with water, can be lowered. For water to be withdrawn from the ground, water must be pumped from a well that reaches below the water table. If groundwater levels decline too far, then the well owner might have to deepen the well, drill a new well, or, at least, attempt to lower the pump. Also, as water levels decline, the rate of water the well can yield may decline.

Increased costs for the user

As the depth to water increases, the water must be lifted higher to reach the land surface. If pumps are used to lift the water (as opposed to artesian wells), more energy is required to drive the pump. Using the well can become prohibitively expensive.

Reduction of water in streams and lakes

There is more of an interaction between the water in lakes and rivers and groundwater than most people think. Some, and often a great deal, of the water flowing in rivers comes from seepage of groundwater into the streambed. Groundwater contributes to streams in most physiographic and climatic settings. The proportion of stream water that comes from groundwater inflow varies according to a region's geography, geology, and climate.

Groundwater pumping can alter how water moves between an aquifer and a stream, lake, or wetland by either intercepting groundwater flow that discharges into the surface-water body under natural conditions, or by increasing the rate of water movement from the surface-water body into an aquifer. A related effect of groundwater pumping is the lowering of groundwater levels below the depth that streamside or wetland vegetation needs to survive. The overall effect is a loss of riparian vegetation and wildlife habitat.

Land subsidence

The basic cause of land subsidence is a loss of support below ground. In other words, sometimes when water is taken out of the soil, the soil collapses, compacts, and drops. This depends on a number of factors, such as the type of soil and rock below the surface. Land subsidence is most often caused by human activities, mainly from the removal of subsurface water.

Deterioration of water quality

One water-quality threat to fresh groundwater supplies is contamination from saltwater intrusion. All of the water in the ground is not fresh water; much of the very deep groundwater and water below oceans is saline. In fact, an estimated 3.1 million cubic miles (12.9 cubic kilometers) of saline groundwater exists compared to about 2.6 million cubic miles (10.5 million cubic kilometers) of fresh groundwater (Gleick, P. H., 1996: Water resources. In Encyclopedia of Climate and Weather, ed. by S. H. Schneider, Oxford University Press, New York, vol. 2, pp. 817-823). Under natural conditions the boundary between the freshwater and saltwater tends to be relatively stable, but pumping can cause saltwater to migrate inland and upward, resulting in saltwater contamination of the water supply.

Answer 2

Answer: Declining groundwater levels can increase the cost of water in future. It will adversely impact wildlife and human beings.

Explanation:

There are many causes behind groundwater depletion

1. Growing consumption: The regular pumping of water from the ground is the main cause of groundwater depletion.  A lot of groundwater is needed for agricultural purposes.
2. creating roads and structures out of concrete: Rainwater seepage into the earth is reduced in areas covered with concrete. As a result, there is less ground water available.
3. overuse of irrigation groundwater: While groundwater-fed irrigation improves water table depth and either increases or decreases runoff depending on pumping intensity, surface water-fed irrigation reduces runoff and water table depth.

Effects of groundwater depletion:

1. The depletion of groundwater will require us to pump water from a deeper part of the Earth. The more groundwater we take out from beneath the Earth's surface, the deeper we have to travel to get more. As a result, we will need to invest even more money in creating new strategies for digging deeper.

2. Due to groundwater depletion, large bodies of water will become shallower. This implies that as the existing surface water continues to evaporate, less water will enter over time. Everything in that area, including fish and wildlife, will be impacted as the water depth decreases.

3. Contamination of saltwater is possible. Even though we pump groundwater rather than obtaining it from lakes and rivers, it is still related to larger bodies of water. Deep down groundwater frequently mixes with saltwater that humans shouldn't drink. Because it will be more expensive to pump and filter the water after it has been contaminated, everyone will have to pay more for drinking water.


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