Model Answer
0 min readIntroduction
Water is a critical input for agriculture, and its judicious management is paramount for ensuring food security and environmental sustainability. India, home to 18% of the world's population but only 4% of its freshwater resources, faces significant challenges in water management, including over-reliance on a single water source and the widespread issue of poor quality irrigation water, particularly due to salinity. The concept of 'conjunctive use of water' offers a holistic approach to optimize available water resources, while effective management practices are crucial to mitigate the adverse impacts of saline irrigation water on agricultural productivity and soil health.
Conjunctive Use of Water
Conjunctive use of water refers to the planned and coordinated management of both surface water (such as rivers, canals, reservoirs) and groundwater resources (from aquifers) in an integrated manner to achieve optimal water utilization and sustainability. This approach aims to maximize the benefits of each water source while mitigating their individual limitations.
Objectives of Conjunctive Use:
- Optimizing Water Availability: It ensures a balanced and reliable water supply by utilizing surface water during periods of abundance (e.g., monsoon) and supplementing with groundwater during lean periods or droughts.
- Reducing Groundwater Over-exploitation: By integrating surface water, the pressure on groundwater resources can be significantly reduced, addressing issues like declining water tables, especially in states like Punjab where over 70% of groundwater is exploited.
- Mitigating Waterlogging and Salinity: Strategic groundwater pumping can help lower high water tables caused by excessive surface irrigation, thereby preventing waterlogging and secondary salinization of soils.
- Improving Water Quality: Mixing poor quality groundwater (e.g., saline) with good quality surface water can make it suitable for irrigation.
- Enhancing Drought Resilience: Aquifers can act as natural storage, recharged during wet periods and drawn upon during dry spells, offering a buffer against climatic variability.
- Cost-effectiveness: It can be more economical than developing entirely new large-scale surface or groundwater projects by making efficient use of existing infrastructure.
Management Practices to Improve Poor Quality Irrigation Water with Reference to Salinity Hazards
Poor quality irrigation water, characterized by high salt concentration, is a major impediment to agricultural productivity. Salinity can lead to reduced crop yields, degradation of soil structure, and long-term land infertility. Effective management practices are essential to mitigate these hazards:
1. Water Management Strategies:
- Blending: Mixing saline groundwater with fresh surface water (e.g., canal water) to reduce the overall salt concentration to permissible limits for irrigation. This is a common practice in areas with access to both sources.
- Cyclic or Rotational Use: Alternating the application of saline and fresh water. For instance, irrigating with fresh water to leach accumulated salts after a few irrigations with saline water. This prevents excessive salt buildup in the root zone.
- Leaching Requirement (LR): Applying water in excess of crop evapotranspiration needs to flush soluble salts below the root zone. Effective drainage is crucial for this practice to prevent waterlogging.
- Improved Irrigation Methods:
- Drip Irrigation: Applies water directly to the plant root zone, minimizing evaporation and salt accumulation on the soil surface. It also allows for precise application of water, reducing overall water usage.
- Sprinkler Irrigation: Can be used, but careful management is needed to avoid leaf burn due to direct contact of saline water with foliage.
- Subsurface Drip Irrigation (SDI): Even more efficient in water delivery and minimizing surface evaporation and salinization.
- Drainage Management: Installing surface and subsurface drainage systems (e.g., tile drains) to remove excess water and dissolved salts from the soil profile, preventing waterlogging and salt buildup.
2. Soil Management Strategies:
- Application of Soil Amendments:
- Gypsum (Calcium Sulfate): Particularly effective for sodic (alkali) soils where sodium is the predominant issue. Gypsum replaces sodium ions on the soil exchange complex with calcium, improving soil structure and permeability.
- Organic Matter: Addition of farmyard manure (FYM), compost, or green manures improves soil aggregation, water infiltration, and nutrient holding capacity, making soils more resilient to salinity stress.
- Sulphuric Acid or Sulphur: Can be used in calcareous sodic soils to lower pH and release native calcium for sodium replacement.
- Deep Ploughing: Helps break up impervious layers, improving drainage and allowing salts to be leached.
- Raised Bed Cultivation: Growing crops on raised beds can help move salts away from the root zone, particularly in furrow-irrigated systems.
3. Crop Management Strategies:
- Cultivation of Salt-Tolerant Crops: Selecting crops and varieties known for their ability to withstand saline conditions.
- Highly Tolerant: Barley, Cotton, Date palm, Sugarbeet
- Moderately Tolerant: Wheat, Rice (some varieties), Sorghum, Maize, Sunflower, Mustard
- Least Tolerant: Pulses, most vegetables, fruits
- Stage-Specific Irrigation: Using good quality water during critical growth stages (e.g., germination, flowering) and saline water during more tolerant stages.
- Seed Priming and Treatment: Treating seeds with certain chemicals or osmo-protectants to improve germination and seedling establishment under saline conditions.
4. Policy and Institutional Support:
- Water Quality Monitoring: Regular monitoring and testing of irrigation water quality to understand salinity levels, pH, and nutrient content, enabling informed management decisions.
- Research and Development: Continued investment in developing salt-tolerant crop varieties and cost-effective reclamation technologies. The ICAR-Central Soil Salinity Research Institute (CSSRI) plays a crucial role in this.
- Farmer Training and Awareness: Educating farmers on best practices for managing saline irrigation water and utilizing conjunctive water use principles.
By implementing a combination of these management practices, the negative impacts of poor quality irrigation water, especially due to salinity, can be significantly minimized, leading to sustainable agricultural production and safeguarding arable land.
Conclusion
The 'conjunctive use of water' is an indispensable strategy for efficient and sustainable water resource management, offering a robust solution to the challenges posed by water scarcity and uneven distribution. Simultaneously, addressing salinity hazards in irrigation water through a combination of scientific management practices—including blending, appropriate irrigation techniques, soil amendments, and strategic crop selection—is critical for preserving agricultural productivity and preventing land degradation. Integrated approaches, backed by government schemes like PMKSY and Atal Bhujal Yojana, are vital for ensuring long-term food security and environmental health in India's agrarian landscape.
Answer Length
This is a comprehensive model answer for learning purposes and may exceed the word limit. In the exam, always adhere to the prescribed word count.