🌱 Soil Particles and Water Movement

Soil is made up of particles of different sizes. The size of these particles affects how the soil behaves. For example, the amount of empty space and the way water moves through soil depend on particle size. If the soil has a high sand content, it does not retain water well and the water moves quickly down into lower layers. But if the soil contains more clay, the water does not move easily and stays near the surface.

In your opinion, what mix of sand and clay makes soil best for farming?

💧 Permeability of Soil Materials

Some materials, like sand, allow water to pass through easily. This property is called permeability. In contrast, materials like clay do not let water pass through easily; these materials have very low permeability.

💦 Groundwater and Cave Formation

After surface water seeps into the ground, it fills the empty spaces between particles in soils and rocks, forming underground water reserves. These waters move slowly underground — at speeds ranging from 0.5 to 500 meters per year — depending on the slope of the land.

Water moves more easily through coarse sediments like gravel, and more slowly through fine sediments like clay. When groundwater passes through limestone, it gradually dissolves the rock and enlarges the spaces inside. Over time, this leads to the formation of large voids and eventually limestone caves.

🌿 Porosity and Aquifer Suitability

The amount of empty space (porosity) and permeability in rocks and sediments varies. For example, in aquifers, porosity and permeability are high, making them suitable for storing groundwater. Although clays also have small spaces between particles, their fine texture prevents water from moving through easily. As a result, clay layers are not good for extracting underground water.

🌍 Infiltration and the Water Table

Some surface water seeps into the ground and continues moving until it reaches a layer where it can no longer infiltrate. Along the way, it fills the empty spaces between sediment and rock particles. In sloped areas, this creates two distinct zones: a top zone where pore spaces contain both air and water, and a lower saturated zone where all pore spaces are filled with water. The boundary between them is called the water table.

The deeper the water table lies below the surface, the greater the depth of groundwater storage. This is referred to as the depth to the water table.

⛏️ Groundwater Well Depth

The depth of water wells varies across different regions. In areas close to the sea, the water table is shallow, and it is possible to reach groundwater by digging just a few meters. However, in dry inland areas of the country, the water table lies much deeper, and the depth can exceed 150 meters.

💧 Unconfined Aquifers

There are two main types of groundwater aquifers. One type is the unconfined aquifer. In this type, a permeable layer lies directly above an impermeable layer. These aquifers are commonly found in plains and mountain slopes. Water from these aquifers can be accessed using wells and qanats.

In sloped areas, groundwater may naturally flow to the surface and form springs. Many hot springs are also formed near volcanic areas.

🚿 Confined Aquifers

Confined aquifers form when a permeable layer is trapped between two impermeable layers underground. These aquifers are more common in mountainous or sloped areas. The groundwater stored in confined aquifers is often tapped using deep wells.

Confined groundwater is usually colorless, odorless, and free of visible impurities. Its chemical composition and temperature remain relatively stable, and it contains more dissolved minerals than surface water. Microbial contamination in these aquifers is also lower compared to surface water.

⚠️ Groundwater Pollution

Groundwater can become polluted if contaminants from the surface seep down into aquifers. This often occurs near residential or industrial areas where wastewater is not properly managed. Polluted water can spread underground and affect drinking water sources far from the original contamination site.

🧪 Minerals in Groundwater

Calcium and magnesium are among the most important dissolved minerals in groundwater. If the concentration of these minerals is high, the water is referred to as "hard water." Excessive mineral content in drinking water can also pose health risks over time.

🕳️ Qanats (Kariz)

Qanat is a system for accessing underground water using a series of wells and tunnels. Qanats were especially common in mountainous or sloped terrain where groundwater was available at depth. Water was channeled toward the surface using gently sloped tunnels.

🔄 The Water Cycle

As water moves over and through the Earth, it is constantly circulating. This continuous exchange between oceans, seas, the atmosphere, and land is known as the water cycle. Water changes state and location as it evaporates, condenses, precipitates, and flows.

🚱 Freshwater is Scarce

Although about 75% of Earth’s surface is covered by water, only a very small portion of it is freshwater suitable for drinking and agriculture. Most of this freshwater is difficult to access and the availability of usable freshwater is limited.