Essay # 3 Measurement Of Infiltration:
The rate of infiltration is initially high. It goes on reducing with time and after some time it becomes steady. A usual graph of the rate of infiltration is shown in Fig. 1.14. The rate of infiltration for a soil is measured in the field as well as in the laboratory. These are known as infiltrometers.
The most common types are the following:
i. Flooding type infiltrometers
ii. Sprinkling type infilitrometers or rain, simulators.
A. Flooding Type Infiltrometers:
There are two types of flooding-type infiltrometers:
a. Single-tube flooding infiltrometer.
b. Double-tube flooding infiltrometer.
a. Single-Tube Flooding Infiltrometer:
The single-tube flooding infiltrometer consists of a metal tube 250-300 mm in diameter with both ends open. This tube is driven in a vertical position into an open level ground surface up to depth of 500 mm, leaving about 100 mm above the ground. The tube is so driven into the ground that the soil is disturbed to a minimum.
Water is then added to this tube to maintain a constant level, sufficiently deep to submerge the plant or the grass crowns. If the soil is bare, i.e., there is no vegetation grass, the soil is protected by a perforated metal disc to avoid turbidity.
A pointer gauge is used to measure the water level accurately. As the infiltration starts, the water level may drop down but it is maintained at a constant level by adding a measured quantity of water at successive time intervals, till a constant rate of infiltration is achieved.
What Is Infiltration In The Water Cycle
Infiltration is the movement of water into the ground from the surface. Percolation is movement of water past the soil going deep into the groundwater. Groundwater is the flow of water under- ground in aquifers. The water may return to the surface in springs or eventually seep into the oceans.Jun 8 2010
Which Factors Are More Important In Controlling The Amount Of Discharge In A Drainage Basin
The answer to this lies in the location and composition of the drainage basin.
In central London, there is no doubt that human factors have the most significant influence over discharge, whereas in rural Wales it could be argued that physical factors play a more central role.
However, it is estimated that while over 80% of the population in the UK lives in an urban settlement, only 5-10% of the country is actually classed as “urban”. Urban areas comprise a lot of green spaces , making the drainage pattern of basins extremely complex.
It is inevitably going to be a combination of physical and human factors which control how much discharge is in a drainage basin.
This is a must-read article from the BBC, suggesting our image of the UK as a concrete jungle may not quite be reality!
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Dwater Infiltration And Retention
In the southeastern United States, soil organic matter content, water infiltration rate, and aggregate stability all increased as the proportion of sod in the rotation increased . Wischmeier and Mannering also reported a positive correlation between water infiltration rate and soil organic matter content for several midwestern soils with organic matter concentrations from 1 to 14%. Allison attributed increased water infiltration to improved soil structure and higher soil organic matter content. Recent farming systems studies in Iowa support this conclusion, i.e., steady-state infiltration measurements were somewhat higher for longer rotations where soil organic matter concentrations were slightly higher than those for shorter rotations .
Hudson used a critical review of literature on soil organic matter effects on plant available water capacity to argue against this position. He found that for sand, silt loam, and silty clay loam soils, the volume of water held at field capacity increased at a much faster rate than that held at the permanent wilting point. Hudson concluded that on a volumetric basis, soil organic matter is an important determinant of available water-holding capacity, thus indicating a reevaluation of crop rotational effects on plant available water might be warranted.
Process Of Infiltration In Water Cycle And Why It Is Important
Infiltration refers to the process where precipitation or water infuses into subsurface soils, is absorbed by the soil and travels deeper through pore spaces and cracks into rocks. The bulk of water collected from melted snow and rain end up infiltrated.
Where exactly does it reach in the ground?
Water is often soaked up by the soil and can stay there for some time until it gets evaporated. In an area with a lot of vegetation, the infiltrated water can get absorbed by a plant root and later transpired. Usually, the infiltration happens in the higher layers of the ground, but sometimes it can continue further in the deep.
Infiltration usually occurs in the upper surface of the ground, but may also proceed downwards to the water table. The rate at which water is absorbed depends on the soil type, pre-saturation levels, land topography and the amount of vegetation in an area.
A good soil has continuous pores and well-developed structure that readily allow snowmelt water and rainfall to enter. This enhances the water cycle process. Lets dive into the water cycle process and learn how infiltration makes it complete.
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How Significant Is The Infiltration Process In Agriculture
Why it is important: Infiltration is an indicator of the soils ability to allow water movement into and through the soil profile. Soil temporarily stores water making it available for root uptake plant growth and habitat for soil organisms. When runoff occurs on bare or poorly vegetated soil erosion takes place.
Soil Hydraulic Conductivity And Infiltration Rate
Balks et al. found at an effluent plantation project in Australia that the soil’s dispersion tendency increased after 5 years, but this did not impact on the hydraulic conductivity. No significant change in permeability was detected after 5 years of irrigation with tertiary-treated wastewater in a major Californian study . In contrast, Magesan et al. reported that applying secondary-treated sewage effluents increased the macroporosity of a sandy loam soil from 11% to 19% and consequently, the hydraulic conductivity increased from 39 to 57 mm h 1. The infiltration rate influences the transport velocity of heavy metals in soils. If the infiltration rate is small, transport of heavy metals will also be limited or the transport time of heavy metals to the groundwater will increase .
Ibrahim Halil Yanarda, … Ahmet Ruhi Mermut, in, 2015
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Determining The Rate Of Infiltration
Infiltration is sometimes estimated by measuring how long it takes for a given quantity of water ponded or sprinkled on an enclosed soil surface to disappear. This method gives relative values for different soil types, but for various reasons, including boundary effects, it overestimates the actual rates of infiltration that occur at surfaces over a large area. For the same reason, laboratory measurements of this process in different soil columns are difficult to transfer to the field.
Infiltration is more rapid into a sandy soil than a clay, but beyond this statement, soil texture data do not serve as good predictors of infiltration capacity . Both capillary potential and capillary conductivity at all levels in the soil profile are important, but for many soils these parameters are not known, even in relation to other soil properties.
J.W. Hopmans, in, 2011
Infiltration And Water Cycle
Infiltration is a part of the water cycle. Once infiltrated, it becomes groundwater.
Depending on how saturated the ground is, the water can continue downwards to replenish water tables and aquifers. This is called percolation.
If there are water bodies nearby, the infiltrated water can seep into it where its lost back to the atmosphere through evaporation.
They are various factors that affect the infiltration rate of soils.
Not to worry, we have curated an article that talks about the: 7 major factors affecting infiltration
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Essay # 4 Estimation Of Infiltration:
The rate at which water infiltrates into a ground is called the infiltration capacity. When a soil is dry, the infiltration rate is usually high compared to when the soil is moist. For an initially dry soil subjected to rain, the infiltration capacity curve shows an exponentially decaying trend as shown in Fig. 1.25. The observed trend is due to the fact that when the soil is initially dry, the rate of infiltration is high but soon decreases, as most of the soil gets moist. The rate of infiltration reaches a uniform rate after some time.
Interestingly, if the supply of continuous water from the surface is cutoff, then the infiltration capacity starts rising from the point of discontinuity as shown in Fig. 1.26 below.
For consistency in hydrological calculations, a constant value of infiltration rate for the entire storm duration is adopted.
The average infiltration rate is called the Infiltration index and the two types of indices commonly used are explained below:
Infiltration Indices:
The two commonly used infiltration indices are the following:
1. Ï-Index.
2. W-Index.
1. The Ï â Index:
This is defined as the rate of infiltration above which the rainfall volume equals runoff volume, as shown in Fig. 1.27.
2. The W-Index:
This is the average infiltration rate during the time when the rainfall intensity exceeds the infiltration rate.
Total infiltration may be fund out as under:
Total Infiltration = Total Precipitation-Surface Runoff â Effective Storm Retention
Summary Infiltration Vs Percolation
In brief, percolation is a process that involves in processing of liquids. On the other hand, infiltration is a process that refers to the motion of fluids through the soil surface. Therefore, they are somewhat similar processes. However, percolation occurs via tiny holes, especially through porous materials. In soil, infiltration takes place in the root zone and soil surface while percolation takes place in between transition zone and saturated zone. Furthermore, infiltration replenishes the soil moisture deficiency while percolation replenishes the underground aquifers. Hence, this is the difference between infiltration and percolation.
Reference:
1.How to Measure the Infiltration of Water by Soil? | Ground Water. Geography Notes, 31 Mar. 2018. Available here 2.Percolation. Wikipedia, Wikimedia Foundation, 22 Sept. 2018. Available here
Image Courtesy:
1.Natural & impervious cover diagrams EPABy U.S. Environmental Protection Agency, Washington, D.C. U.S. Environmental Protection Agency, Washington, D.C. Protecting Water Quality from Urban Runoff. Document No. EPA 841-F-03-003, via Commons Wikimedia 2.SoilLeachingBy R.J.Oosterbaan via Commons Wikimedia
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Flows And Processes Water Moving From One Place To Another
Baseflow water that reaches the channel largely through slow throughflow and from permeable rock below the water table.
Channel flow the movement of water within the river channel. This is also called a rivers discharge.
Groundwater flow the deeper movement of water through underlying permeable rock strata below the water table. Limestone is highly permeable with lots of joints and can lead to faster groundwater flow.
Infiltration the downward movement of water into the soil surface.
Interflow water flowing downhill through permeable rock above the water table.
Percolation the gravity flow of water within the soil.
Stemflow water running down a plant stem or tree trunk.
Surface Runoff the movement of water over the surface of the land, usually when the ground is saturated or frozen or when precipitation is too intense from infiltration to occur.
Throughflow- the movement of water downslope within the soil layer. Throughflow is fast through pipes .
Printable Versions Of Our Water
You can’t see it, but a large portion of the world’s freshwater lies underground. It may all start as precipitation, but through infiltration and seepage, water soaks into the ground in vast amounts. Water in the ground keeps all plant life alive and serves peoples’ needs, too.
Note: This section of the Water Science School discusses the Earth’s “natural” water cycle without human interference.
Anywhere in the world, a portion of the water that falls as rain and snow infiltrates into the subsurface soil and rock. How much infiltrates depends greatly on a number of factors. Infiltration of precipitation falling on the ice cap of Greenland might be very small, whereas, as this picture of a stream disappearing into a cave in southern Georgia shows, a stream can act as a direct funnel right into groundwater!
Some water that infiltrates will remain in the shallow soil layer, where it will gradually move vertically and horizontally through the soil and subsurface material. Some of the water may infiltrate deeper, recharging groundwater aquifers. If the aquifers are porous enough to allow water to move freely through it, people can drill wells into the aquifer and use the water for their purposes. Water may travel long distances or remain in groundwater storage for long periods before returning to the surface or seeping into other water bodies, such as streams and the oceans.
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Essay # 1 Definition Of Infiltration:
Infiltration may be defined as entry and movement of water through the land surface into the sub strata. When rainwater falls on the ground, there is some resistance offered by the soil surface for the entry of rainwater and also to the flow of water through the soil.
There are cracks, vertical as well as lateral in the soil, so also there are some voids between the soil particles, which are ordinarily occupied by air or water. Water flows through these cracks and gaps until it reaches the saturated zone below. Naturally the passage of water experiences some resistance.
The rate at which water enters the ground surface and then flows downwards is known as infiltration rate. This rate is high in the beginning because it has to meet the requirements of the dry soil. However, it attains a steady constant constant lower value after passage of time.
Introduction: Importance Of Soil Organic Matter
Some soil properties such as water-holding capacity, water infiltration rate, erodibility, nutrient cycling and pesticide adsorption are strongly related to soil organic matter . Information on the relationship between the stability and chemical structure of organic matter is essential. Although it is generally thought that humic substances are non-labile, have various chemical structures and consequently their degradation rates also vary with initial organic substances. They may become refractory by losing their aliphatic moieties, during polymerizationcondensation and oxidation processes . Humic acids are a major fraction of humic substances that account for up to 40% of total SOM .
The animal manure application increases SOM quantity, nutrient availability, soil aggregation and other soil functions . Therefore, management of manure is very important to SOM content and consequently to the fate of agriculture. Many studies have also recognized SOM as a central indicator of soil quality and health .
Composition of SOM is very complex, and also includes a complex mixture of living organisms, dead organic debris and anthropogenic inputs. During the decay of plants, a major part of plant carbon is biodegraded and recycled to the atmosphere as CO2. The organic matter remaining in soils is thus a carbon pool exhibiting high resistance to biodegradation. Also some SOM may be in the minor classes: carbohydrates, amino acids, lipids and phenols have so far been identified .
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Annex 2 Infiltration Rate And Infiltration Test
INFILTRATION RATE
The infiltration rate is the velocity or speed at which water enters into the soil. It is usually measured by the depth of the water layer that can enter the soil in one hour. An infiltration rate of 15 mm/hour means that a water layer of 15 mm on the soil surface, will take one hour to infiltrate.
In dry soil, water infiltrates rapidly. This is called the initial infiltration rate. As more water replaces the air in the pores, the water from the soil surface infiltrates more slowly and eventually reaches a steady rate. This is called the basic infiltration rate .
The infiltration rate depends on soil texture and soil structure and is a useful way of categorizing soils from an irrigation point of view .
The most common method to measure the infiltration rate is by a field test using a cylinder or ring infiltrometer.
Table 7 BASIC INFILTRATION RATES FOR VARIOUS SOIL TYPES
Soil type
Timber Hessian or jute clothAt least 100 litres of water
Ring infiltrometer of 30 cm diameter and 60 cm diameter. Instead of the outer cylinder a bund could be made to prevent lateral water flow.
Measuring rod graduated in mm
Figure 74 Set-up of field test
Method
Step 1:
Hammer the 30 cm diameter ring at least 15 cm into the soil. Use the timber to protect the ring from damage during hammering. Keep the side of the ring vertical and drive the measuring rod into the soil so that approximately 12 cm is left above the ground.
Step 2:
Step 3:
Step 4:
Step 5:
Step 6:
Table 8:
Terrain Data And Potential Infiltration Map
The infiltration process is controlled by the morphology of the terrain and permeability of the lithology in the respective area. Using the 3D surface configuration of the study area and the potential infiltration coefficient of the aquifers, the infiltration map was drawn according to Nistor et al. procedure. They consider that where the PIC is higher and the slope angle is lower, the infiltration values will be higher. Based on the digital elevation model the slope angle was generated. The operations were done at the spatial scale in ArcGIS using the normalized values of slope angle and PIC.
Rao S. Govindaraju, Abhishek Goyal, in, 2022
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What Is The Difference Between Infiltration And Percolation
Infiltration and percolation explain the movement of water through soil surface and through a porous material respectively. In the aspect of rainwater absorption onto soil, infiltration occurs at the soil surface while percolation occurs below the infiltration area that is in between unsaturated zone and saturated zone. Hence, this is the difference between infiltration and percolation.
The below infographic on difference between infiltration and percolation shows the differences in more detail.
What Is Infiltration The Water Cycle
Infiltration is the process by which precipitation or water soaks into subsurface soils and moves into rocks through cracks and pore spaces. As we mentioned before, the bulk of rainwater and melted snow end up infiltrated.
But where does it go in the ground?
Water may get absorbed by the soil and may stay in the soil for a long time until it gradually gets evaporated. If there is a lot of vegetative covers , the infiltrated water can also get absorbed by plant roots and later transpired. Infiltration occurs in the upper layers of the ground but may also continue further downwards into the water table.
Depending on how saturated the ground is, the water can continue downwards to replenish water tables and aquifers. This is called percolation. If there are water bodies nearby, the infiltrated water can also end up in the water bodies after.
The rate of infiltration depends on factors such as, the amount of precipitation, the type of soils, the amount of vegetative cover over the area, pre-saturation levels, the topography of the land, as well as the levels of evapotranspiration in that region.
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