Naturally, the soil ought to absorb the water on the surface and regain its natural state.
However, sometimes, the soil is either unable to do that, or human activity makes it difficult for groundwater to go anywhere, causing a condition referred to as waterlogging, where the land is soaked up, and water just rises up.
For instance, during periods of heavy rainfall or extreme weather conditions, the soil might become waterlogged and fail to dry up.
As such, people residing within the area might be forced to evacuate the place while their crops sink under the water or dry out.
In this article, we’ll dive into all the information you might want to know about waterlogging, so let’s dive right in!
Understanding Waterlogging
Waterlogging is simply the saturation of soil with water, either temporarily or permanently. When there is too much water in an area, the soil is unable to absorb the water as it should ordinarily.
It can also happen when the water table rises to saturate the soil pores in the crop root zone. When that happens, the result is a restriction in the normal supply of air in the soil, a decline in the levels of oxygen, and an increase in the levels of carbon dioxide and ethylene.
When the air phase is restricted, anaerobic conditions prevail, adversely affecting crops.
Waterlogging constrains plant growth and fosters anaerobic conditions, causing the death of certain crops and plants. Also, plant roots fail to respire as a result of the excess water in the soil profile, making them weak and either die or fall.
Waterlogging is serious as it does not have to be characterized by excess water on the surface, meaning it could be a continuing problem even without seeing the water on the surface.
Regrettably, due to the uniqueness of each plant species, there is no universal threshold of soil oxygen that can be used to identify waterlogged conditions applicable to all plants. Moreover, a plant’s requirement for oxygen in its root zone fluctuates based on the specific stage of growth it is in.
In 2001, about 2.04 million hectares of land in India suffered from the problems of waterlogging under irrigation commands. The area represented about 4% of all irrigated area in the country, which makes it a very big area, considering India is the world’s seventh-largest country by land area.
About 1.4 million hectares of the 2.04 million affected by waterlogging, suffered from surface water stagnation, while 0.64 million hectares had a general rise in the water table, meaning sometimes, the problem is natural, and at times, it is man-made. About 10% of the world’s irrigated lands suffer from waterlogging.
Now, waterlogging can be categorized into various types, based on certain factors.
First, we have causes, meaning the cause is either natural, like natural swamps, or human-induced, like through agriculture.
Secondly, we have permanence, where waterlogging can either be temporary, lasting between a few days to several months, or permanent, meaning it occurs throughout the year.
Thirdly, we look at the source of water, meaning the water could either be rainfed, coming from excess rainfall, or from irrigation sources, being the excess water from agricultural plantations.
Finally, we look at the location of the waterlogging, which could either be on agricultural land, including cultivated lands, or other utility lands, like urban areas.
Different Types of Waterlogging
Some of the different types of waterlogging include:
1. Riverine Flood Waterlogging
It is a type of waterlogging that occurs during the rainy seasons, where floods come to nearby lands from the river because it carries excess water. The water is waterlogged in the land and leads to the death of a number of plants or crops.
2. Oceanic Flood Waterlogging
As the name suggests, oceanic flood waterlogging is characterized by oceanic waters spreading onto nearby lands and causing waterlogging.
This particularly can happen when there’s extreme weather affecting the oceans, such as hurricanes and tsunamis.
3. Seasonal Waterlogging
Sometimes during the rainy seasons, runoff water might accumulate in the lowlands and depressions, leading to waterlogging.
4. Perennial Waterlogging
This happens when deep water or swamps get rainwater, and the resulting runoff and seepage water spreads onto neighboring lands, causing perennial waterlogging.
5. Sub-soil Waterlogging
It is another type of waterlogging that occurs when water tables rise up high, especially during the rainy seasons, causing waterlogging.
Causes of Waterlogging
Waterlogging results from several reasons, some of which:
1. Physiography
The topography, slope, shape, and drainage patterns of a place could cause waterlogging. In other words, physiography determines the speed of surface runoff and the time it takes for the soil to drain surface water.
For instance, low-lying areas such as valleys, depressions, and flat lowlands experience more waterlogging naturally since surface flows concentrate on the lowlands, resulting in natural swamps and other waterlogged lands.
In such areas, water cannot easily move under the influence of gravity, making it accumulate over time.
2. Weather, Especially Atmospheric Conditions That Result in Heavy Rainfall and Flooding
Weather is another natural cause of waterlogging, meaning that areas facing constant or prolonged rainfall will tend to become waterlogged, either temporarily or permanently. Heavy and consistent rains make the water table rise, resulting in waterlogging.
3. Soil Type
Heavy clay soils, like black cotton soils and soils prone to surface sealing, hold moisture for long periods, meaning they become waterlogged easily. That’s unlike other soils with better drainage, like sand and loam.
4. Geology
An impervious stratum below the topsoil obstructs the infiltration of rainfall, causing a false water table or perched water table. Areas with shallow soils, a hardpan close to the surface, and those with high water tables are also likely to become waterlogged, especially if they are subjected to heavy rainfall.
5. Seepage Inflows
Interflows and seepage from nearby water bodies like lakes, shallow aquifers, canals, and rivers could cause waterlogging. Furthermore, subsoil flows from upper regions to lower areas could also result in waterlogging.
6. Excessive Irrigation and Poor Drainage System by Farmers
This is a man-made cause of waterlogging, and if irrigation is not well planned, drainage problems could further worsen the problem. Irrigation adds extra water to the soil profile, over and above the naturally occurring rainfall.
Irrigation could result in waterlogging if there is overirrigation, inadequate drainage, poor irrigation management, obstruction of natural drainages, seepages from canals as in Pakistan, and the parches are landlocked without outlets.
Effects of Waterlogging
As waterlogging takes its toll on the land, several detrimental consequences emerge, profoundly impacting both the environment and agricultural productivity.
1. Poor Soil Aeration
Waterlogging causes the air within the soil to move out into the atmosphere, replacing it with more water.
The inadequate supply of oxygen retards or ceases the growth of a plant as the accumulating carbon dioxide hampers the growth of the plant’s roots.
Poor aeration also facilitates the growth of toxins and other harmful substances. Such saturated soil also reduces microbiological activity, which is vital for the formation of plant food.
2. It Alters the pH of the Soil
In the flooded soils, the pH changes and becomes more acidic. The soil, therefore, decreases in its alkalinity and makes the growth of plants more difficult. The increasingly acidic soil cannot support plant life.
3. Change in Soil Temperatures
Waterlogging lowers the temperature of the soil. Low temperatures of the moist soil affect the microorganisms and their activities, subsequently lowering the rate of nitrogen-fixation
4. Affecting Soil Nutrients
Nitrogen is vital to the soil, and waterlogged soils suffer from nitrogen deficiency. The nitrogen is lost through denitrification, a process by which nitrogen in the soil is converted into gaseous oxides of nitrogen.
But nitrogen isn’t the only affected element: the water-saturated soil also affects other essential minerals, such as sulfur, zinc, iron, manganese, phosphorous, and potassium.
Some of the minerals are available in excess, causing the toxicity levels in plants to go up, while in others, the minerals cannot survive and, subsequently, the plants.
5. Retard Cultivation
There is difficulty in cultivating waterlogged soils. All crops fail to survive because of the underlying conditions, so crops are adversely affected. Only rice can survive in such an environment.
6. Accumulation of Harmful Salts
Waterlogging creates an atmosphere that brings toxic salts to the crop root zone. The accumulating salts also turn the soil more alkaline and hamper the growth of crops.
7. The Growth of Water-loving Wild Plants
Waterlogging causes wild plants which thrive in waterlogged environments to grow. These weeds effectively kill useful crops, and getting rid of them is an extra investment, especially in extreme waterlogged conditions.
8. The Loss of Cash Crops
Most cash crops cannot survive or be cultivated in waterlogged soils. It, therefore, makes farmers starve and lose out on the cash they would otherwise get from selling their crops. Some are even forced to switch to rice, assuming it can grow in such areas.
9. Effects on Human Health
Waterlogging has an effect on the environment by the fact that it harbors disease vectors like mosquitoes, slugs, and snails. They, in turn, bring illnesses like malaria, bilharzia, typhoid, and others, which affect the human population, animals, and plants, effectively affecting the environment.
Various Ways of Preventing Waterlogging
To address the challenges posed by waterlogging, a range of effective preventive measures can be implemented, safeguarding against its detrimental impacts on land and water systems.
1. Control the Loss of Water
Several measures can reduce the seepage loss from the canals. First is by lowering the full supply level (FSL) of the canals to a sufficient extent. Secondly, is by lining the canal section by providing the lining with the seepage loss, which makes the canal section reasonably watertight. Thirdly, introducing intercepting drains constructed parallel to the canal.
2. Augmenting Outflow and Preventing Inflows
Artificial open and underground drainage grids can be introduced. The same can also be achieved by improving the flow conditions of existing natural drainages.
3. Disposing of the Rainwater
Rainwater should be quickly removed from the soil’s surface, thereby preventing a rise in the level of the water table and subsequent waterlogging.
4. Preventing the Loss of Water
The loss of percolation can be eliminated by using water more economically. It can also be achieved by keeping the intensity of irrigation low.
Only a small portion of the irrigable land becomes flooded, and the only loss in percolation happens in the limited area. This also keeps the water table sufficiently low.
5. Not Using Alkaline Water
Alkaline water used in irrigation affects the soil and makes it more susceptible to waterlogging in the future. For this reason, alkaline water should not be used for irrigation purposes.
The mineral Alkali salts can accumulate on top of the soil – creating a crust on the surface that prevents the surface water from draining as required.
6. Raise the Beds
If you are working on a small garden that is becoming waterlogged, you might consider raising it and growing your plants on raised beds.
You can also slightly slant the bed so that the excess water goes down the bed. It is tiresome, but it keeps your plant roots from sitting in the water.
7. Install Proper Drainage Systems
Draining the water means both the surface and sub-surface waters. It removes the water in a controlled and quick manner.
Before and when draining the water, be sure not to adversely affect the environment or neighboring lands which might also be affected by the waterlogging.
8. Mulching
It is not a preventative but a treatment measure that can help a plant grow even in waterlogged soil. Mulching involves adding organic or inorganic materials spread on top of the soil.
The mulch covers the affected land by covering the soil and helping reduce evaporation losses. Crops can continue to grow even in the waterlogged area, while at the time, working with the aforementioned preventative measures to fix the problem.
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