Question

With removal of groundwater, which of the following may result? A. subsidence B. sinkholes C. cone of depression D. decreased water table E. All of the above.

Short answer

E. All of the above

Step-by-step solution

- Understand removal of groundwater

Groundwater is the water that fills the porous spaces in soil, sediment, and rocks beneath the Earth's surface. If it is removed, this can have several impacts on the surrounding environment.

- Define subsidence

Subsidence refers to the gradual sinking or caving in of an area of land. This can occur when groundwater is removed, causing the soil structure to collapse.

- Define sinkholes

A sinkhole is a depression or hole in the ground caused by the collapse of a surface layer. The removal of groundwater can lead to the formation of sinkholes as the support provided by the water is lost.

- Explain cone of depression

A cone of depression occurs in an aquifer when groundwater is pumped from a well. The pumping creates a drop in the water table that forms a cone shape around the well.

- Decreased water table impact

The water table is the upper surface of the zone of saturation. Removing groundwater will lower the water table, which can lead to drought conditions and affect water availability.

- Conclusion

All the mentioned effects (subsidence, sinkholes, cone of depression, decreased water table) are results of groundwater removal. Therefore, the correct answer is 'E. All of the above'.

Key concepts

subsidence

Subsidence refers to the gradual sinking or caving in of an area of land, a process often triggered by the removal of groundwater. When groundwater is extracted, it can lead to the consolidation of soil and rock structures beneath the surface. These porous materials rely on the presence of water to support their structure. When the water is removed, the ground above may start to collapse and settle. Subsidence can have significant consequences, including damage to buildings, roads, and other infrastructures. Additionally, it can disrupt natural water flow, increasing the risk of flooding in certain areas. It’s a serious environmental issue that can cause irreversible damage.

sinkholes

Closely related to subsidence, sinkholes are another potential outcome of groundwater removal. A sinkhole is a depression or hole in the ground caused by the collapse of a surface layer. The removal of groundwater reduces the pressure that supports the underground structures.
When the support provided by the groundwater is no longer there, the ground above can suddenly collapse, forming a sinkhole. These formations can be small and harmless or large enough to swallow entire buildings.
Sinkholes are particularly common in areas with limestone bedrock because the acidic groundwater can dissolve the limestone over time, making the ground even more unstable.
Prevention requires maintaining a balance in groundwater extraction and ensuring that natural water support is not excessively depleted.

cone of depression

The 'cone of depression' is a specific phenomenon that occurs when groundwater is pumped from a well. When water is extracted, it creates a drop in the water table around the well, forming a cone-shaped depression.
Imagine pulling water from the middle of a sponge; the water level near the point you are pulling from will be lower than the water level further away, creating a cone shape. This can create several issues:

• It can affect nearby wells by lowering their water output.
• It can reduce the hydraulic gradient, slowing the natural flow of groundwater.
• It can increase the risk of subsidence and sinkholes near the well due to the loss of water pressure.

The cone of depression is a clear sign of the interconnected nature of groundwater systems.

decreased water table

The water table is the upper surface of the zone of saturation in the ground, where the pores and fractures are filled with water. When groundwater is removed at a faster rate than it is replenished, the water table decreases.
This lowering can have several effects:

• Reduction in the availability of water for plants, affecting agriculture.
• Decreased water levels in lakes and rivers connected to the groundwater.
• Potential for wells to run dry, impacting drinking water supplies.

A lower water table can also lead to drought conditions and affect ecosystem balance. Sustainable groundwater management is crucial to prevent significant drops in the water table.

water table

The water table is crucial to understanding groundwater systems. It represents the boundary between water-saturated ground and the unsaturated ground above.
Key factors about the water table include:

• Its level fluctuates naturally due to seasonal changes, rainfall, and human activities.
• It's vital for maintaining the flow of springs and rivers.
• It supports plant roots, influencing vegetation types and agricultural practices.

Groundwater removal directly affects the water table, lowering its level and causing the previously mentioned issues: subsidence, sinkholes, cones of depression, and decreased availability of fresh water. Proper management and sustainable use of groundwater resources are essential to maintain a stable water table.