7. (b) Enunciate the reasons for waterlogging and describe various management strategies to mitigate waterlogging.

Reasons for Waterlogging

Waterlogging can result from a combination of natural factors and human-induced activities that disrupt the natural drainage of agricultural lands.

• Heavy and Prolonged Rainfall:
  • Intense precipitation exceeding the soil's infiltration capacity leads to surface runoff and accumulation of water.
  • Continuous rainfall can raise the groundwater table, saturating the root zone even without visible surface water.
• Poor Soil Permeability and Structure:
  • Soils with a high clay content and low permeability, such as heavy clay soils, hinder water infiltration and drainage.
  • Compacted soil layers (hardpans) due to heavy machinery or poor tillage practices restrict water movement downwards, leading to a perched water table.
• Inadequate or Obstructed Drainage Systems:
  • Lack of proper natural slopes or artificial drainage channels (e.g., field drains, subsurface drains) prevents the removal of excess water.
  • Blockages in existing drainage infrastructure due to siltation, debris, or encroachment further exacerbate water accumulation.
• High Groundwater Table:
  • In areas with naturally high water tables or where recharge exceeds discharge, the groundwater can rise to the crop root zone, causing waterlogging.
  • Seepage from unlined irrigation canals, reservoirs, or adjacent highlands can contribute to the rise in the water table in lower-lying areas.
• Over-irrigation:
  • Excessive application of irrigation water, especially in canal-irrigated areas with poor drainage, can lead to saturation of the soil profile.
  • Inefficient irrigation methods (e.g., flood irrigation) often supply more water than crops require or the soil can absorb, contributing to waterlogging and often soil salinity.
• Topography and Landform:
  • Flat or depressed low-lying areas, floodplains, and basins are naturally prone to water accumulation due to limited gravitational runoff.
  • Poorly leveled lands can create depressions where water collects.
• Deforestation and Land Use Changes:
  • Removal of trees reduces soil infiltration and increases surface runoff, contributing to higher water accumulation in agricultural fields downstream.

Management Strategies to Mitigate Waterlogging

Mitigating waterlogging requires a multi-pronged approach involving engineering, agronomic, and policy interventions.

1. Engineering and Structural Measures:

• Improved Drainage Systems:
  • Surface Drainage: Construction and maintenance of open ditches, field drains, and collector drains to remove excess surface water quickly. Land leveling and grading to create appropriate slopes for water runoff (e.g., uniform slopes, contour farming).
  • Subsurface Drainage: Installation of perforated pipes (tile drains) beneath the soil surface to lower the water table and facilitate the removal of excess groundwater. This is particularly effective in areas with high water tables or impermeable subsoil layers.
  • Deep Tillage: Breaking up compacted soil layers (hardpans) through deep ripping or subsoiling to improve subsoil permeability and drainage.
• Rainwater Harvesting and Storage:
  • Constructing farm ponds, check dams, and reservoirs to capture and store excess rainwater, reducing runoff and providing water for irrigation during dry periods. This also helps in groundwater recharge.
• Canal Lining:
  • Lining irrigation canals with impermeable materials (e.g., concrete, geomembranes) to prevent seepage and reduce the rise in the groundwater table in adjacent agricultural lands.

2. Agronomic and Crop Management Practices:

• Crop Selection:
  • Cultivating waterlogging-tolerant crop varieties (e.g., certain rice varieties, some wheat and maize hybrids) in areas prone to waterlogging.
  • Practicing crop rotation to improve soil structure and enhance water infiltration. For instance, alternating deep-rooted crops with shallow-rooted ones.
• Raised Bed Farming:
  • Growing crops on raised beds or furrows elevates the root zone above the saturated soil, improving aeration and drainage around the roots.
• Organic Matter Addition:
  • Incorporating organic matter (e.g., farmyard manure, compost, crop residues) into the soil improves soil structure, aggregation, and water infiltration capacity, reducing surface runoff and compaction.
  • Using cover crops during fallow periods to enhance soil structure and water absorption.
• Efficient Irrigation Management:
  • Adopting precision irrigation methods like drip irrigation and sprinkler systems to deliver water directly to the root zone, minimizing over-irrigation and water wastage.
  • Implementing soil moisture monitoring to apply water only when necessary, preventing saturation.
• Appropriate Sowing Time:
  • Adjusting planting schedules to avoid critical growth stages coinciding with periods of anticipated heavy rainfall or peak waterlogging risk.
• Nutrient Management:
  • Applying essential nutrients, especially nitrogen, can help mitigate some negative effects of waterlogging, as nutrient uptake is reduced in anoxic conditions.

3. Policy and Institutional Interventions:

• Integrated Water Management:
  • Developing and implementing integrated watershed management plans that consider both surface and groundwater resources, focusing on sustainable use and management.
  • Promoting community participation in water management through farmer associations and local bodies.
• Government Schemes:
  • Pradhan Mantri Krishi Sinchayee Yojana (PMKSY) (Launched 2015): Aims to enhance water use efficiency in agriculture, promoting micro-irrigation, watershed management, and rainwater harvesting. Its motto "Har Khet Ko Pani" and "More Crop Per Drop" directly address water availability and efficiency.
  • Atal Bhujal Yojana (ABHY) (Launched 2018): Focuses on sustainable groundwater management with community participation in water-stressed areas, including demand-side management and recharge.
  • National Water Mission (NWM): Under the National Action Plan on Climate Change, it aims to conserve water, minimize wastage, and ensure equitable distribution, promoting water use efficiency through technological interventions and policy initiatives.
  • MGNREGA: Supports the construction of water harvesting structures, check dams, and farm ponds, contributing to enhanced water availability and sustainable agricultural practices.
• Land Use Planning:
  • Implementing land-use zoning regulations to prevent agricultural development in highly waterlogging-prone areas.

A holistic strategy, combining advanced engineering solutions with improved agronomic practices and supportive government policies, is essential to effectively combat waterlogging and ensure the long-term sustainability of agricultural productivity.