Water Logging | Civil Engineering Optional Notes for UPSC PDF Download

Water Logging 

• Waterlogging refers to a condition where soil becomes saturated with water, either temporarily or permanently, due to an excess of water in an area. This saturation can have detrimental effects on soil quality and plant growth.

Causes of Waterlogging:

• Waterlogging can occur when there is an excess of water in the soil, leading to a situation where the soil is unable to absorb water properly.
• Insufficient oxygen in the soil pores can hinder plant roots from respiration, contributing to waterlogging.
• Rising water tables can cause soil pores in the crop root zone to become clogged, further exacerbating the issue.
• Factors such as flooding or poor irrigation practices with inadequate drainage can also lead to waterlogging.

Impact of Waterlogging:

• Waterlogging negatively affects plant growth by impeding root respiration and nutrient uptake.
• It can lead to a decline in soil quality and beneficial soil characteristics.

Examples:

• Imagine a field that receives heavy rainfall for several days, leading to waterlogging. The excess water prevents plant roots from accessing oxygen, stunting their growth.
• In another scenario, a poorly drained agricultural area experiences waterlogging after irrigation, causing crops to wilt due to water-saturated soil.

Water Logged Soil

What is Water Logging? 

Causes of Water Logging 

• Over and intensive irrigation: Excessive watering can overwhelm the soil's capacity to absorb water.
• Excessive rainfall: Heavy rains saturate the soil, increasing water absorption levels.
• Seepage and runoff: Water from higher grounds and canals can flow into lower areas, causing waterlogging.
• Floods: Soil submersion during floods can trigger waterlogging issues.
• Inadequate natural drainage: Insufficient natural drainage systems can exacerbate waterlogging problems.
• Terrain conditions: Irregular topography can also contribute to waterlogging issues.

Effects of Water Logging

• Reduction in oxygen availability to plant roots, leading to root suffocation.
• Impaired nutrient uptake by plants, affecting their growth and development.
• Increased susceptibility to root diseases due to prolonged exposure to water.
• Decreased microbial activity in the soil, hampering nutrient cycling processes.

Effects of Waterlogging on Soil and Plant Health

• Poor Soil Aeration - When soil becomes waterlogged, air in the soil voids is replaced by water, depriving plants of essential oxygen, leading to their eventual demise.
• pH Level Alteration - Waterlogging causes soil pH to decrease, turning it acidic, thereby reducing soil productivity significantly.
• Depletion of Soil Nutrients - Excessive water leads to a reduction in soil nutrients, diminishing the soil's ability to support plant growth and productivity.
• Increased Salinity - Waterlogging results in the accumulation of salts in the soil post-drying, posing a significant threat to soil health and fertility.
• Impact on Health and Environment - Waterlogged conditions create breeding grounds for disease-carrying insects, causing foul odors and facilitating the spread of waterborne diseases like cholera and typhoid.
• Cultivation Challenges - Growing crops in waterlogged soil becomes arduous, with rice being an exception due to its high water requirement.
• Soil Temperature Reduction - Waterlogging lowers soil temperature, adversely affecting the growth and nitrogen-fixing activities of soil microorganisms.

Types of Water Logging

• Perennial Water Logging: This type occurs when groundwater intersects with nearby streams, causing runoff to spread in the vicinity.
• Seasonal Water Logging: Poor drainage characteristics in the catchment area result in improper drainage of rainwater, leading to water logging.
• Oceanic Flood Water Logging: Flooding of seawater in nearby areas triggers this type of water logging.
• Riverine Flood Water Logging: Common during the rainy season, this occurs when rivers swell from excessive rain, causing water logging in adjacent regions.
• Subsoil Water Logging: Elevated groundwater levels contribute to this form of water logging.

Prevention of Water Logging

Constructing Drainage Systems:

• Building artificial open and underground drainage grids is crucial. These systems help in preventing water accumulation.
• Improving natural drainage conditions can also be beneficial in reducing water logging incidents.

Optimizing Water Usage:

• Managing water wisely to prevent percolation losses is essential. This can be achieved by reducing irrigation intensity.
• Avoiding the use of alkaline water for irrigation is important as it can lead to water logging issues.

Promoting Sustainable Practices:

• Encouraging rainwater harvesting helps in reducing stormwater runoff into drainage systems.
• Implementing mulching techniques aids in minimizing moisture evaporation, thereby reducing the need for intense irrigation.

Leaching Process for Water Logging

• Leaching Process for Water Logging

  Leaching is the method utilized in reclaiming saline soil. It involves flooding the land with a sufficient amount of water. The salts within the soil dissolve in this water, which then either percolates down to the water table or is carried away by surface or subsurface drainage systems. This cycle is repeated until the salts in the top layer of the soil diminish to a level where certain inferior crops can be cultivated. This entire procedure is known as leaching.

• Inferior Crops

  Inferior crops refer to those that can thrive under unfavorable conditions, such as poor soil quality or inadequate irrigation. For instance, tobacco is considered an inferior crop.

  
  

• Effect of Salt in Soil

  When salts accumulate in soil, it adversely affects plant growth and overall soil quality. The presence of excessive salts can hinder nutrient uptake by plants, leading to stunted growth and reduced crop yields.

Understanding Alkali Salts in Agricultural Soil

• Every agricultural soil contains various minerals, some beneficial and others detrimental to plant growth. The harmful salts, known as alkali salts, include Na2CO3, Na2SO4, and NaCl.
• The formation of a thin crust on the soil surface post water evaporation is termed efflorescence.
• NaCl and Na2SO4 are termed white alkalis due to their white efflorescence, while Na2CO3 is referred to as a black alkali, producing black efflorescence.
• White alkalis are more water-soluble compared to black alkalis.
• Black alkali, being less soluble, is more harmful and challenging to eliminate through leaching. Gypsum addition to soil or leaching water aids in black alkali removal.
• Plant roots, acting as semi-permeable membranes, allow water and dissolved solids to pass through. Excessive salt absorption by roots reduces water availability for plants.
• The Indian Agricultural Research Institute (IARI) categorizes salt-affected soil into three classifications:

Salt Classification by IARI

• Electrical Conductivity in μS/cm
• Exchangeable sodium (%)
• pH levels

Classification

• Electrical Conductivity in μ-Mho/cm
• Exchangeable sodium (%)
• pH

Waterlogging has a detrimental impact on plant growth, posing a significant challenge to their development. The excessive presence of water in the soil diminishes the availability of oxygen to plant roots, resulting in decreased respiration and hindered nutrient absorption. This unfavorable environment fosters the growth of anaerobic microorganisms that generate toxic byproducts, which are harmful to plants.

Water Logging Problems

Waterlogging denotes the excess accumulation of water in the soil, leading to adverse effects on plant growth and soil fertility. It occurs when the soil fails to absorb or drain water adequately, resulting in oxygen deficiency in the root zone. This deprivation causes root decay, impeding nutrient uptake and escalating the risks of soil erosion, nutrient leaching, and the spread of waterborne diseases.