Continued drought represents a significant threat to the water table, especially in California’s Central Valley, a 20,000 square-mile farming area sandwiched between the Sierra Nevada mountains on the east and California’s coastal ranges on the west. Water tables exist beneath the ground below the area of aeration – the space between the land surface and the water table. Filled by rainwater runoff and snowmelt, the water table must be regularly replenished, or it begins to deplete.
TL;DR (Too Long; Didn't Read)
Water tables are affected by several factors:
- Seasonal rainfall and droughts
- Salt contamination
- Nitrates and phosphates from fertilizers
- Bacteria from barnyard runoff or septic systems
- Pesticides and fertilizers
Water Table Drawdown and Pumping
When farmers, manufacturers and even residents continually pump water at a combined rate of thousands of gallons per minute, the water table experiences a drawdown – an unnatural and rapid depletion in the underground reservoir. As the water table rapidly drops, it experiences distress. Like a bank account without regular deposits, eventually the account runs dry. During years of drought, groundwater takes up the load for irrigation, as surface water reservoirs – from snowmelt and runoff – are also depleted, resulting in greater reliance upon these underground aquifers.
Fracking Underground
In Pavillion, Wyoming, a town of 231 people, Stanford researchers discovered in 2016 that the effects of hydraulic fracking contaminated the water table. In addition to injecting toxic chemicals into the ground, such as benzene and xylene, the many companies that fracked the site in the last 40 plus years dumped production and drilling fluids containing diesel fuel directly into unlined pits and failed to adequately create cement barriers to protect the groundwater. Oftentimes these many corporations simply drilled at the same level of local wells – the water table level – and thus polluted the water in the area. Stanford researchers say there are not enough rules in place to keep this from happening elsewhere.
Contaminants Affect the Water Table
A host of contaminants affect the water table from fertilizers, barnyard runoff, salt systems and badly constructed wells to septic system placement and construction. Misuse and overuse of lawn fertilizers can have an environmental impact on groundwater, as well as on surface lakes and reservoirs. Lawn and garden fertilizers enter the groundwater when it rains and leach into rivers that feed the water table. This becomes especially problematic in areas where the soil is compacted and hard, which doesn’t allow the soil to filter out these contaminants. The chemicals in fertilizers, nitrogen and phosphates, contaminate the water and make it unsuitable for drinking or irrigation across the country.
Barnyard runoff poses a health problem by adding bacteria to lakes and streams that feed the water table. Many homeowners use salt to soften water. In several rural homes, the waste water from the salt treatment dumps atop the soil, leaching salt into the ground and surface waterways. Once too much salt enters an aquifer, it can no longer be used for drinking or irrigation. Wells not constructed to meet safety standards to prevent surface water and bacteria from getting into the well pose a problem for the entire aquifer when the well’s depth enters the water table. Improperly built septic systems can percolate effluent into a well with access directly into the water table.
FAQs
In addition to topography, water tables are influenced by many factors, including geology, weather, ground cover, and land use. Geology is often responsible for how much water filters below the zone of saturation, making the water table easy to measure.
What are the effects of a water table? ›
A water table close to the surface affects excavation, drainage, foundations, wells and leach fields (in areas without municipal water and sanitation), and more. When excavation occurs near enough to the water table to reach its capillary action, groundwater must be removed during construction.
What causes changes in the water table? ›
Water-level changes due to aquifer deformation are commonly due to either Earth tides or earthquakes. Other external stresses caused by heavy trucks and trains can also cause groundwater fluctuations in some aquifers.
What are three factors that can affect the amount of groundwater an area will have? ›
Groundwater quality is related to several factors including geology, climate, and land use.
What are the four factors affecting water use? ›
Factors that Affect Water Use
- Population Numbers and Distribution. At the most fundamental level, water is needed to supply people's basic domestic needs, in quantities directly proportional to the number of people. ...
- Technology. ...
- Economics. ...
- Environmental Conditions. ...
- Instream and Withdrawal Uses of Water.
The level of the water table can naturally change over time due to changes in weather cycles and preciptiation patterns, streamflow and geologic changes, and even human- induced changes, such as the increase in impervious surfaces on the landscape.
What is water table answer? ›
The level of groundwater is called the water table. The upper level of an underground surface in which the soil or rocks are permanently saturated with water is called the water table.
How does pollution affect the water table? ›
As ground water works its way through the soil, it can pick up nitrogen and phosphorus and transport them to the water table. This polluted water then can reach public drinking water systems and private wells, where it can pose serious public health threats.
What are the effects of low water table? ›
Some of the negative effects of groundwater depletion:
- Lowering of the Water Table. Excessive pumping can lower the groundwater table, and cause wells to no longer be able to reach groundwater.
- Increased Costs. ...
- Reduced Surface Water Supplies. ...
- Land Subsidence. ...
- Water Quality Concerns.
3.2 Climate Drivers of the WTD Changes
Generally, the water table rises if the precipitation increases and vice versa, whereas an increase (respectively decrease) of evapotranspiration rarely leads to a depletion (rise) of the aquifer (Figure 3).
In addition to topography, water table is influenced by many factors, including climate, land use, geology, etc. Climate: In humid regions, recharge areas through which water percolates underground are found everywhere except streams, and adjacent floodplains.
What are the 3 zones of groundwater? ›
They are vadose water present in the zone of aeration and groundwater present in the zone of saturation. The vadose water is further subdivided into three zones, i.e., soil water zone, intermediate zone and capillary zone. Fig. 1.2 shows the classification of groundwater.
Do water tables change? ›
"The depth to the water table can change (rise or fall) depending on the time of year. During the late winter and spring when accumulated snow starts to melt and spring rainfall is plentiful, water on the surface of the earth infiltrates into the ground and the water table rises.
What are the three factors that affect water quality? ›
What Factors Affect Water Quality?
| Water Quality Parameter | Beneficial Use Affected |
|---|
| pH | Resident Fish and Aquatic Life, Water Contact Recreation |
| Sedimentation | Resident Fish and Aquatic Life, Salmonid Fish Spawning and Rearing |
| Temperature | Resident Fish and Aquatic Life, Salmon Fish Spawning and Rearing |
8 more rowsThe 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.
What two factors determine the depth of the water table? ›
Answer and Explanation: The level of the water table is influenced by the quantity of water that is removed from the aquifer either through natural or human-caused processes, and the recharge rate of the aquifer.
