Groundwater detection methods

ArabiaWeather - When we talk about groundwater resources and their importance, human society must work to preserve them and use them sustainably, and one of the most important steps in benefiting from these resources is the ability to detect groundwater and determine places to drill wells. In this article, we will take a look at Methods of detecting groundwater and locating wells.

Indications of the presence of groundwater

The presence of groundwater is often discovered through natural and visual signs that indicate its presence beneath the surface. Geologists and excavators rely on these signs and phenomena to determine the locations of underground water basins. Below are some of the most common signs that are used for this purpose:

• Sandy and gravel terrain

Sandy and gravel areas at the bases of valleys are often home to groundwater, and clay or silt usually covers these layers, so these areas are carefully examined as potential groundwater detection points.

• Natural springs

The presence of natural springs often indicates the presence of groundwater nearby, and when grass and trees remain active year-round in dry areas, this reflects the presence of an aquifer flowing toward the surface.

• Running water tables

The direction of running water flowing on the Earth's surface is conclusive evidence of the existence of an underground water basin. Simply put, researchers can determine the sources of this water by tracing its flow paths.

• Plants and trees

Plants and trees often derive the water needed for their growth from groundwater in shallow layers, and trees and shrubs that retain their green colors throughout the year in dry areas can indicate the presence of groundwater close to the surface.

• Inferential animals

Some animals, such as bees and pigs, are able to effectively track groundwater sources, and their ability to reason can be exploited when searching for the locations of aquifers.

• Salt crust and mineral deposits

In some places, a white salt crust can be seen mixed with other mineral deposits on the surface of the Earth. This phenomenon results from the flow of water from underground, and indicates the presence of an underground water basin.

The importance of detecting groundwater

Groundwater is those water resources that are concentrated within the Earth's crust below the soil surface at different depths. In many cases, this water is found very close to the soil surface in humid areas, especially after heavy rains. On the other hand, some groundwater is present at depths of up to tens of metres, and it takes decades to accumulate. For example, there is groundwater at a great depth that can reach hundreds of metres, and even more than a thousand metres. Research and studies show that the amount of groundwater Available below the surface of the soil is not limited, exceeding the amount of surface water in all rivers and lakes around the world. However, access to these sources requires careful treatment, filtering and rationing, and they are often not ready for immediate human use.

The simplest ways to purify, sterilize and filter water

The importance of groundwater

• For human uses
• Economic importance
• Environmental importance

Ancient methods of detecting groundwater

The art of water prospecting, also known as "water prospecting" , is one of the oldest methods of searching for water and has been used for thousands of years. This method is called water prospecting, where a stick, pendulum, or similar instrument is used to determine the location of groundwater. .

This method remains in use in remote areas or poor environments where modern water detection techniques are not available. The braking stick can be made using a variety of trees such as peach trees or willows, and wire can also be used in this context.

In traditional methods, the prospector would make a stick in a “Y” formation, hold it with both hands, raise it up, and then walk around the area back and forth with it. It was assumed that when he passed over the water site, the stick would be drawn down.

This method has been successful in many cases, however, it is not based on any scientific foundations and in fact, some call it “water astrology”. This is because in areas that receive regular rainfall, there is a high probability of groundwater being present wherever drilling is done.

Groundwater search strategies

When they have the intention of building a well in populated areas that suffer from drought, geologists often resort to using aerial photographs. These aerial photographs often reveal rock formations and fault lines in the Earth’s crust, which can be a rich source of water, and are used to drill wells. In addition to that, Hydrogeologists rely on collecting information and statistical data to develop a three-dimensional model of the areas that exist above a groundwater basin. They rely on factors such as the characteristics of the land and the composition of rocks at the site, in addition to analyzing the history of drilling and previous exploration in the area. Based on this information, hydraulic scientists issue Their recommendations.

Layers containing groundwater

Groundwater aquifers usually consist of materials such as gravel, sandstone, and broken rocks, such as limestone. These materials are characterized by the presence of large, connected voids in their composition, which makes them rocks permeable to water molecules. The speed of groundwater flow to the Earth’s surface depends on the size of these voids and cracks. In the rock crust, the groundwater level varies from deep places to shallow places depending on the type of rocks that contain water. Large groundwater pumping can lead to a decrease in the basin’s water level, while the groundwater level may increase depending on multiple factors, including:

• The amount of rain and different forms of precipitation, including heavy rain.
• The process of melting snow on mountain peaks.

Groundwater in Gaza

Groundwater in the Gaza Strip is the only source that residents rely on to meet their various water needs, whether for residential, agricultural or industrial purposes. This water comes from a coastal reservoir that extends across the entire area of the Strip, where the thickness of its water-bearing layer ranges between several meters in the east and south. The eastern part of the strip, and about 120-150 meters in the western areas, and along the coastal strip. These coastal layers consist mainly of sand deposits, gravel, and sandstone (karkar), with interspersions of clay and silt.

The non-water-saturated part of this rock formation, which rises above the productive aquifers, also consists of sand, gravel, clay, and sandstone, and its thickness ranges from several meters in the west to about 80 meters in the east and southeast , and its permeability varies from one region to another based on its geological formations.

In the large northern and southern parts of the Gaza Strip, there are sand dunes with a thickness of about 20-30 meters and characterized by high permeability that facilitates the infiltration of surface water into the lower aquifers easily, which over time led to the formation of layers of fresh groundwater.

Therefore, the coastal reservoir is considered the only source that produces water in the Gaza Strip, and on which the residents of the Strip depend completely to meet their various water needs. The quantities of water that are fed into the groundwater reservoir within the Gaza Strip for this season have been estimated at approximately 76 million cubic meters, which is a percentage that constitutes 138% of the annual feeding rate

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Sources:

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