Change in groundwater level/quality

The availability of groundwater as a water source depends largely upon surface and subsurface geology as well as climate. The porosity and permeability of a geologic formation control its ability to hold and transmit water. 

The projected increase of groundwater levels will influence the soil-water balance and could potentially change the vegetation. In case of increased rooting depth and/or a vegetation with higher transpiration rates, this could potentially result in lower groundwater levels.

Groundwater occurs almost everywhere beneath the land surface. The availability of groundwater as a water source depends largely upon surface and subsurface geology as well as climate. The porosity and permeability of a geologic formation control its ability to hold and transmit water. Porosity is measured as a ratio of voids to the total volume of rock material and is usually described as a percentage. Unconsolidated sands and gravels make some of the most productive aquifers because they have many internal voids (porosity) that are well-connected.

Change in groundwater level is considered a land degradation process because it can have significant adverse effects on the overall health and productivity of the land. Here are a few reasons why:

• Depletion of water resources: Excessive extraction of groundwater can lead to a decline in the water table, which is the level below which the ground is saturated with water. When the groundwater level drops, it becomes harder to access water for various purposes such as drinking, irrigation, and industrial use. This depletion of water resources can result in water scarcity, affecting both human activities and ecosystems

• Ecological impacts: Groundwater plays a crucial role in sustaining ecosystems by providing water to streams, rivers, wetlands, and other natural habitats. When the groundwater level declines, it can negatively impact these ecosystems. Reduced groundwater levels may lead to the drying up of streams and wetlands, which disrupts the habitat of various plant and animal species. It can also result in the loss of biodiversity and disrupt the balance of ecosystems.

• Land subsidence: Groundwater extraction, particularly when done excessively and without proper management, can cause land subsidence. When water is withdrawn from underground aquifers faster than it is replenished, the soil compacts and settles, resulting in the sinking or subsiding of the land surface. Land subsidence can damage infrastructure such as buildings, roads, and pipelines, and it can also affect the stability of the land, leading to increased erosion and reduced soil quality.

• Saltwater intrusion: In coastal areas, excessive groundwater extraction can lead to saltwater intrusion. When the groundwater level drops, it creates a pressure imbalance that allows saline water from the ocean to infiltrate into the freshwater aquifers. Saltwater intrusion can contaminate drinking water sources, rendering them unsuitable for human consumption and agricultural use. It can also harm the vegetation and agricultural productivity in affected areas.

• Groundwater-dependent agriculture: In many regions, groundwater is a critical source of irrigation for agriculture. When the groundwater level declines, farmers may face difficulties in accessing water for irrigation, which can lead to reduced crop yields or even crop failure. This can have significant economic implications for agricultural communities and can contribute to land degradation by reducing soil fertility and productivity.

It is important to manage groundwater resources sustainably by implementing measures such as water conservation, improved irrigation techniques, and monitoring of groundwater levels to mitigate the negative impacts of changing groundwater levels and prevent further land degradation.

References:

van Engelenburg, J., Hueting, R., Rijpkema, S., Teuling, A. J., Uijlenhoet, R., & Ludwig, F. (2018). Impact of changes in groundwater extractions and climate change on groundwater-dependent ecosystems in a complex hydrogeological setting. Water resources management 32(1), 259-272. 

Vandas, S.J., Winter, T.C., and Battaglin, W.A. 2002. Water and the Environment, p. 23,25. Published by the American Geosciences Institute Environmental Awareness Series.