Infiltration Is – Do Reader often wonder why the rainwater that reaches the surface of the ground does not all flow to other places, but some is also absorbed into the ground? Yes, it turns out that simple things are very influential in maintaining the stability of the environment around us . That is why, every region needs the existence of a suitable rainwater catchment area. The process of rainwater seeping into the soil surface is called infiltration, which turns out to be an important part of the hydrological process or water recycling on the face of the earth.
This process of infiltration is often associated with the management of river basins (DAS) for several regions, especially in determining which areas should be used as seepage areas or built-up areas. So what exactly is infiltration? Is it just the process of seeping rainwater into the ground? How does this infiltration process happen? What about the relationship between infiltration and land use? Well, for Reader to understand that, let’s read the following comments!
Definition of Infiltration
If you look at KBBI (Kamus Besar Bahasa Indonesia), the term “infiltration” is related to matters in the field of Soil Science which has a definition of ‘ inflow of water downwards into the soil ‘. In other words, infiltration is a process of rainwater entering the soil as a result of the capillary force as well as the gravitational force so that the water can enter the deeper soil. This infiltration can also be referred to as the way water moves into the soil through the cracks and pores of the soil and rocks to the surface of the ground water.
This rainwater can move into the ground because of capillary action that has vertical or horizontal movement under the surface of the ground until finally the water successfully re-enters the surface water system. Meanwhile, with the influence of gravity, the rainwater will naturally enter the soil through the pores of the soil. The continuation of this process of infiltration is percolation.
The infiltration rate will usually be expressed in the same units as the rainfall intensity units, namely millimeters per hour (mm/hour). The rate of water percolation is also influenced by several factors, namely:
- Soil texture
- Soil organic matter
- Soil density
- Type and amount of land
As this infiltration is still an important part of the hydrological process, the infiltration water that cannot return to the atmosphere through the evapotranspiration process, will become groundwater to flow into the surrounding rivers. This infiltration process is also highly determined by time. In this case, there is also a term about “infiltration capacity”, which is the maximum infiltration rate for a certain type of soil. In the quantity of infiltration, this usually occurs when the intensity of rainwater exceeds the soil’s ability to absorb soil moisture. On the other hand, if the rainwater intensity is smaller than the infiltration capacity, then the infiltration rate will be the same as the rainfall rate.
The rate of infiltration can of course be used in human daily life, starting from liquid waste disposal studies, evaluating the potential of septic tank land, washing and drainage efficiency, irrigation needs, water distribution and groundwater recharge, to anticipating channel or dam leaks.
Well, so that Reader better understand the terms of this infiltration process, here is a brief description.
- Infiltration Capacity : That is the maximum infiltration speed, which depends on the nature of the soil surface.
- Infiltration Rate : That is, the actual infiltration rate, influenced by several factors ranging from the nature of the soil surface as well as the nature of the soil layer at the bottom.
- Percolation ( Percolation ): The speed of percolation determined by the nature of the existing soil.
- Field Capacity : The amount of maximum water content that can be held by the soil against the force of gravity.
- Soil Moisture Deficiency : The amount of water content that is still needed to bring the soil to Field Capacity .
- Initial Abstraction: The amount of interception and basin storage that must be filled first, before there is an overflow of rainwater.
Process of Infiltration
The process of infiltration begins when the rainwater has touched the soil surface, where some or all of the rainwater will definitely enter the soil through the pores of the soil surface. The process of rainwater entering the soil is caused by the pull of gravity and soil capillaries. The speed of the infiltration process will usually be influenced by the force of gravity and limited by the size of the diameter of the soil pores.
On the other hand, the existence of a capillary style that drains the water will later make the water go vertically upwards, downwards, and horizontally. This soil capillary style works on soil that has small pores. Meanwhile, if on soil with large pores, the capillary force tends to have negligible influence so that water “prefers” to go inside with the influence of gravity. In the course of the water, it will later spread towards the edge as a result of being affected by the capillary force of the soil, especially towards the soil that has smaller pores.
Well, this infiltration process will at least involve three processes that are not interdependent but still interrelated, namely in the form of:
- The process of rainwater entering through the pores of the soil surface.
- The storage of the rainwater in the ground.
- The process of water flowing to another place, either downwards, sideways, or upwards.
Factors Affecting Infiltration
Basically, the percolation of rainwater to the soil surface both vertically and horizontally is called infiltration. Meanwhile, the amount of water that goes through the infiltration process in a unit of time is called the infiltration rate.
It should be known , Reader , that this infiltration process can change according to the intensity of rainfall. However, if the intensity of rainwater has reached its limit, then the amount of infiltration will continue according to the speed of absorption in each soil. Remembering that each soil has a different infiltration capacity, depending on the condition of the soil surface, soil structure, vegetation, and others. In addition to the intensity of rainfall, the infiltration process can also change due to the influence of air humidity and the air in the soil.
Well, here are some internal and external factors that affect infiltration:
- The height of the water puddle above the soil surface and the thickness of the saturated soil layer.
- Water level or soil moisture.
- Soil compaction by rainfall.
- Clogging of soil pores by fine soil particles, for example sediments from clay particles.
- Soil compaction done by humans, animals, or a machine.
- Soil structure.
- The condition of plant roots, both active and dead roots.
- The proportion of air in the soil.
- Topography or land slope.
- Rainwater intensity.
- Roughness on the ground surface.
- The quality of the water that will go through the infiltration process.
- The temperature of the ground air and the surrounding air.
- Soil properties.
Well, from those factors it can be categorized into two main factors namely:
- Factors that influence water to stay in a place, so that the water gets the opportunity to go through the infiltration process ( opportunity time )
- Factors that affect the process of water entering the soil.
Specific Property Factors from the Soil
Not only that , Reader , in addition to the factors that have been described, there are also special properties of the soil that are very influential in determining and limiting the infiltration capacity, namely:
a) Pore size
Previously, it was explained that the rate of rainwater entering the soil is determined by the size of the pores and the arrangement of the pores in the soil. Yes, large soil pores or macros are called aeration, which have a diameter large enough to allow water to escape quickly.
b) Pore stability
The capacity of the infiltration process can only be maintained when the porosity is all fixed and undisturbed during the time when there is no rain.
c) Water Content
The greatest infiltration rate can occur especially at low and moderate water content.
d) Soil Profile
The nature of the layers of a soil also determines the speed of rainwater entering the soil.
Important Meaning of the Infiltration Process
This infiltration process of course has several important meanings in other environmental ecosystem processes, namely:
1. Runoff Process ( Run Off )
It should be noted that the term “runoff” has a definition in the form of ‘the part of rainfall that appears to flow in rivers or artificial channels on the surface of the land’. Well, the power of infiltration really determines the amount of rainwater that can be absorbed into the soil. The greater the infiltration power, then the difference between the intensity of rainwater and the infiltration power also becomes smaller. As a result, the runoff on the surface will also be smaller, so the peak discharge will be smaller.
2. Replenishment of Soil Moisture and Ground Water
The term “langas” means ‘ containing water or moist ‘, so this soil langas can be interpreted as a condition of soil that is moist and contains water. Well, the effort to make the soil in wet conditions and filling the soil with water is of course important for agricultural purposes.
Benefits of the Infiltration Process for Human Life
The existence of this infiltration process turns out to be useful for human survival and is often used as the main discussion in learning environmental geography and water management. Well, here are some of the benefits of the infiltration process for human life.
1. Maintaining Ecosystem Stability
The benefits can certainly be felt because remembering the infiltration process is an important part of the hydrological and biogeochemical cycle. Just imagine, if this infiltration process “disappears” from the hydrological cycle, then the water recycling chain on the face of the earth will be disrupted, right? So that it will have an impact on the capacity of water as a basic need for all living things.
2. Water Conservation Study and River Basin District (DAS)
The existence of the infiltration process is greatly used by humans to determine which areas can be used as seepage and built-up areas, especially when building new residential areas.
3. Groundwater and Aquifer Water Research
Since this infiltration process is an important part of the hydrological cycle as well as a method of replenishing groundwater on the surface of the earth, its existence must be studied by research.
4. Preventing Runoff Flooding
The infiltration process can be applied by humans, especially when planning water seepage areas and built-up areas. It must be planned in detail so that the potential for flooding, especially due to rain runoff, is lower.
Infiltration Rate Measurement
The infiltration rate process can be measured using various tools and of course by applying a special formula. Well, here are some ways to measure infiltration rate.
1. Using the Infiltrometer
The infiltrometer in its simplest form consists of a fertilizer tube pressed into the soil. Later, the surface of the soil in the tube will be filled with water. The water level in the tube will decrease due to the infiltration process. Then, the amount of water added to maintain the water level in the tube should also be measured.
The smaller the diameter of the tube, the greater the disturbance due to the side flow under the tube. Through this method, the infiltration process can be calculated based on the amount of water added to the inner tube per unit of time.
2. Using Test Plots
Measuring the infiltration rate using an infiltrometer is known to only be possible in a small area, so it will be difficult to draw conclusions about the magnitude of the infiltration force in a wider area. Therefore, another option is to use a test plot.
The use of test plots can be applied to flat land surrounded by embankments and flooded with water. The rate of infiltration will later be obtained from the amount of water that has been added so that the surface becomes constant. So, it can be concluded that the plot test tool is a form of infiltrometer that has a larger scale.
3. Using a Lysimeter
This lysimeter device is in the form of a concrete tank planted in the ground, then filled with the same soil and plants as the surrounding area. In addition, this lysimeter should also be equipped with drainage and water supply facilities.
The use of the lysimeter will use the water balance equation as follows:
P + I = D + ES …………………….. (2.18)
Description:
I = water supply
D = water removed
E = evaporation (evapotranspiration)
S = water reservoir in the ground
Influence of Texture or Soil Form on Infiltration Rate
Does Reader realize that the texture or shape of the soil also affects the rate of infiltration? Yes, especially on the number and size of the pores on the skin. The larger the pores of the soil, the greater the rate of infiltration. Based on the size of the pores, there are clays that have a lot of fine pores and there are clays that have a few large pores. But on the other hand, sandy soil actually contains many large pores and few fine pores. Well, thus it can be concluded that the rate of infiltration in sandy soil is much greater than in clay soil.
Soils that have a rough texture can create a light soil structure. But on the other hand, soils that have a fine soil texture can cause the formation of the soil that has a heavy structure.
Well, that’s a review of what infiltration is and how the process of infiltration is the main part of the hydrological cycle. Did Reader ever play on the dirt when it rained as a child?