Key Factors Affecting the Water Table’s Shape and Height
Water is an essential component of the earth. Whether it is living beings or non-living beings, everybody needs water. Water on earth is present in various forms such as jet streams, oceans, lakes, glaciers and is then stored in the form of groundwater. The water table is basically an underground boundary that is present in between the soil surface and the spaces where groundwater saturates. At this boundary the water pressure and the ground pressure are equal. Underneath this water, the table is a zone known as the saturated zone where water fills all spaces between the sediments.
What is a Water Table?
As we read above, it is an underground boundary that is present between the soil surfaces and the area where the groundwater saturates. The unsaturated zone is the area of the soil surface that is present above the water table. It is a space where oxygen and water fill the area between the sediments. Another name for an unsaturated zone is the zone of aeration. Underneath this water table, there is a saturated zone where water fills spaces between the sediments.
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Water Tables around Us
Water tables are present almost everywhere in the world but the amount of water in these tables vary. The levels of water tables can also drop significantly if the water is not extracted in a well-sustained manner. This non-sustainable practice has shown that the large reservoirs of water are being depleted around the world. The largest affected areas are India, the USA, China where they are almost depleted to a point where they can’t be restored.
Shape and Height of Water Table
It is basically influenced by the land surface that lies above a water table. When it curves under hills it is called a tall water table and when it drops under valleys it is called the small water table. The source of the water table is precipitation. When a water table naturally meets the land surface then it makes springs.
Variations in the Water Table
The levels of the water table can vary in different areas and even within the same areas. These are basically caused by the changes in precipitation between the seasons and years. In winter and spring season it is cold conditions outside so the level of water is high and hence the level of water table rises which makes them best water table. However, there is a gap when the saturated zone is infiltrated by precipitation. The reason being that water takes time to trickle through the spaces that are present in the sediments to reach out to the saturated zone. The process of irrigation is also helpful in raising the water table as excess water reaches the ground. But during the summer months when the temperature is hot and humid outside the levels of the water table depletes. Also at this time, the plants take up more water from the ground and a lot of water is wasted in the process of transpiration. We, humans, are also responsible for lowering levels of the water table by our practice of extracting the groundwater and not using it efficiently. The levels of depth of water table can be measured which are further used in determining the effects of season, climates, or human impact on groundwater.
Uses of the Water Table
As we studied in the above paragraphs that water is an essential part of every living being on this earth therefore a water table also holds good importance and is very useful. Some of the uses are listed below.
Water tables are useful for measuring aquifers that are saturated areas beneath the water table. These aquifers are used to extract the water for plants and human beings.
The water from the water table can be used for bathing and cleaning purposes.
It is used to water plants as in this way some water goes back to the ground and can be used again and again.
But more and more extraction of this water on daily purposes is causing the water tables to deplete.
This depletion of water is also known as aquifer depletion.
Basically, the water from water tables finds its most uses in irrigation, drinking, industries, and hygiene.
People of the particular areas where they have a good amount of water in their water table often put them on sale which is known as water table sale.
FAQs on Understanding the Water Table in Biology
1. What is the definition of a water table as per the CBSE syllabus?
The water table is the upper level of an underground surface where the soil or rocks are permanently saturated with water. Below this level, all the empty spaces (pores and fractures) in the ground are filled with water, which is known as groundwater. The area above the water table is called the unsaturated zone, where the spaces contain both air and water.
2. What is the main difference between groundwater and the water table?
The key difference lies in what they refer to. Groundwater is the actual water stored underground in saturated soil and rock layers. The water table, on the other hand, is not water itself but the 'surface' or boundary line that marks the top of this saturated zone. In simple terms, groundwater is the resource, and the water table is its upper level.
3. What are the primary factors that cause the water table level to change?
The level of the water table is not fixed and can fluctuate due to several factors, including:
- Rainfall and Infiltration: Heavy rainfall increases the water table level as more water seeps into the ground. This seepage process is called infiltration.
- Extraction: Pumping water from the ground for agriculture, industry, and domestic use lowers the water table.
- Seasons: The water table is typically higher during the monsoon or rainy season and lower during dry, summer months due to a lack of recharge and increased evaporation.
- Vegetation: Areas with dense vegetation have a higher rate of infiltration, which helps maintain the water table.
4. How does the process of infiltration help in recharging the water table?
Infiltration is the natural process where rainwater and water from rivers and lakes seep down through the soil and porous rocks to reach the saturated zone. This process is crucial because it acts as a natural refilling mechanism for groundwater. By adding more water to the underground reservoirs (aquifers), infiltration directly helps in raising the level of the water table, ensuring the long-term availability of groundwater.
5. Why isn't the water table always a flat, horizontal surface underground?
This is a common misconception. The water table is rarely flat because it tends to follow the general shape of the land surface above it. It is higher under hills and lower in valleys. Furthermore, its level can vary due to differences in rock permeability (how easily water passes through) and uneven rates of water recharge and extraction across an area.
6. How does urbanisation, such as building roads and concrete pavements, cause depletion of the water table?
Urbanisation significantly impacts the water table by preventing natural recharge. Concrete roads, parking lots, and building foundations create an impermeable layer on the ground. This layer blocks rainwater from seeping into the soil, drastically reducing infiltration. As a result, most rainwater becomes surface runoff that flows into drains, preventing the groundwater from being replenished and causing the water table to drop over time.
7. What is an aquifer, and what is its relationship to the water table?
An aquifer is a large underground layer of water-bearing, permeable rock, or materials like gravel, sand, or silt from which groundwater can be extracted using a well. The relationship is simple: the water table forms the upper boundary of an unconfined aquifer. When you drill a well, you must go below the water table to access the water stored within the aquifer.
8. Why is it important to prevent the depletion of the water table?
Preventing the depletion of the water table is critical for several reasons. A falling water table can lead to the drying up of wells, springs, and even rivers. It increases the cost of pumping water for agriculture and drinking. In coastal areas, severe depletion can cause saltwater intrusion into freshwater aquifers, making the water unusable. Therefore, sustainable management through practices like rainwater harvesting is essential for ecological balance and human survival.
