For our luck, earth is a watery planet. But only 3% of water can be useful to human beings. Rest 97% of the water is salt water. We people depend on water for many things like drinking and irrigation and water is essential in various industrial processes. The unsustained use or overpumping of groundwater and the modernisation will end up in scarcity of freshwater. Beneath our feet, we have a water table and its level is falling down day by day. In this article, we will discuss the water table, its depletion, and what are the reasons of depletion of water table.
What is a Water Table?
The water table can be defined as an underground boundary where atmospheric pressure and water pressure are equal. It is the boundary between the soil surface and areas of sediments and rocks, where groundwater gets saturated. So above the water table soil surface came and below it, sedimentary rocks came. The soil surface is not saturated with water. It contains both water and oxygen. Hence, the soil surface is called an unsaturated zone or zone of aeration.
In the area below the water table, sedimentary rocks are present and the spaces between them are completely filled with water; this is called the saturated zone. Local geology can affect the shape and size of the water table. For example, the water table under hills is curved and drops under valleys. The water below the water table is a result of the water seeping from the soil surface. That process is called precipitation.
The level of the water table may vary according to the seasons. For example, the water table level will be high during winter and spring. Because during this season, snow will melt and precipitation will be high. During the irrigation of crops also, the water table level increases because more water seeps out from the soil surface to the area underneath the water table. The water table level will also be influenced by the use of wells for the use of underground water for drinking and irrigation.
In order to determine the effect of seasons, climate, or human impact, the depth of the water table can be measured in the existing wells. If water is extracted in an unsustainable manner from the wells, it causes the permanent destruction of the water table. The greater extraction of groundwater compared to the rate of replenishment from precipitation causes the depletion of the water table.
Water Table Diagram
Water Table Diagram
Above the water table, soil surface and beneath the water table sedimentary rocks filled with groundwater are present. The areas where underground water meets the land surface springs are forming through which groundwater flows out and eventually reaches a river or stream. Springs are the natural flow of underground water from the underground water sources to the land surface.
Depletion of Water Table
Depletion means a reduction in the quantity or number of something. Depletion of the water table means a significant reduction in the amount of groundwater. The water table gets depleted if the rate of intake underwater is much higher than the water seeps into the soil and recharges the aquifers. There are many reasons for the depletion of the water table. Deforestation and overpumping of groundwater can be considered the main causes of the depletion of the water table. If we plant more trees, we will get a sufficient amount of rainfall since trees help in the evapotranspiration of water. Hence, groundwater will not be depleted due to afforestation.
What are the Causes of Water Table Depletion?
The reasons for the depletion of the water table are deforestation and over pumping of water. Along with that, irregular climate, increased agricultural uses, increased population, and water pollution are also reasons for the depletion of the water table. Let's check all the causes of the depletion of the water table one by one.
Over Pumping of Water from the Ground: Due to the increased population density, the need for people in various fields like agriculture and industrialisation also increases. For the daily consumption of drinking needs and various needs in agricultural and industrial fields, we people start using groundwater in a huge amount and this results in the overpumping of groundwater. The frequent pumping of groundwater leads to difficulties to recharge the groundwater by itself. This is one of the main causes of the depletion of the water table.
Deforestation: The high demand for industrialisation and urbanisation leads to deforestation, that is cutting down the trees of forests to make bare lands. Trees have a key role in bringing rainfall. If there is a reduction in the number of trees, the rate of evapotranspiration will be less and this leads to less rainfall. If the rainfall is less, only less amount of water will seep into the ground and recharge the aquifers. Hence, deforestation is also one of the main causes of the depletion of the water table.
Irregular Climate: The water table recharges primarily by rainfall. If we get poor monsoons, then only less water seeps into the ground. Also, poor monsoon leads to drought. Poor monsoon also forces farmers to dig so deeply to get groundwater which results in the further pushing down of water tables deeper down.
Increased Agricultural Needs: It is a result of the population explosion. As the population increases, the food requirement also increases. To cultivate more food products, a high amount of groundwater is required. This leads to the overpumping of groundwater from aquifers and aquifers don't get enough time to recharge by themselves.
Decreased Recharging Time of Aquifers: Aquifers are the largest reservoir of groundwater. Higher population, increased agricultural needs, urbanisation, and industrialisation lead to the overuse of groundwater, hence aquifers do not get time to recharge by themselves. This leads to the depletion of the water table.
On the earth, only 3% of water is freshwater and 97% of water is saline.
Qatar is the prime country which faces a higher water crisis.
The water table is the underground boundary between the soil surface and sedimentary rocks which are saturated with groundwater.
The decline in the level of the water table is called depletion of the water table.
Deforestation and overpumping of groundwater are the main causes of the depletion of the water table.