मराठी
CISCEISC (Arts) Class 12
प्रश्नपत्रिका३७२
पाठ्यपुस्तक उत्तरे१६६८१
महत्वाचे प्रश्न आणि उत्तरे५८७१
संकल्पना स्पष्टीकरण आणि व्हिडिओ९५३
टाइम टेबल१५
अभ्यासक्रम

Overview of Water Resources and Types of Irrigation

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Estimated time: 30 minutes
CISCE: Class 12

Key Points: Water Resources of India

  • Limited water availability: India has only 4% of the world’s water resources despite having about 17% of the world’s population. Usable water is limited due to evaporation and other constraints.
  • Surface water: Rivers are the main source of surface water. However, only about one-third of total surface water can be effectively utilised. Major rivers like Ganga, Brahmaputra and Indus carry most of the water.
  • Groundwater resources: Groundwater is an important source, mainly used for irrigation. It is abundant in the Northern Plains but limited in the Peninsular Plateau due to hard rocks.
  • Uneven distribution and development: Groundwater and surface water are unevenly distributed across India. Some states like Punjab and Haryana have highly developed groundwater resources.
  • Other water sources: Lagoons and backwaters along the coastal regions (especially Kerala, Odisha and West Bengal) also provide water for fishing and irrigation.
CISCE: Class 12

Key Points: Emerging Water Problems

  • Water scarcity risk: Increasing demand and wastage of water may lead to a serious water shortage in the near future.
  • Water quality deterioration: A large portion of India’s surface water is polluted, making it unsafe for drinking and domestic use.
  • Sewage pollution: Untreated municipal sewage is directly dumped into rivers, polluting about 14 major river basins.
  • Industrial pollution: Many industries discharge toxic waste and chemicals into rivers, severely contaminating water bodies.
  • Agricultural pollution: Excessive use of fertilizers, pesticides and insecticides pollutes both surface water and groundwater.
CISCE: Class 12

Key Points: Conservation of Water Resources

  • Need for conservation: Water conservation is essential due to limited supply, rising demand, pollution, and uneven distribution of water resources.
  • Main conservation steps: Important measures include water-saving technologies, prevention of pollution, rainwater harvesting, recycling, watershed development, and conjunctive use of water.
  • Prevention of pollution: Rivers and groundwater are polluted by sewage, industrial waste, and chemicals. Laws like the Water Act (1974) and Environment Protection Act (1986) were made, but need better implementation.
  • Recycle and reuse: Used water can be recycled for industries, gardening, and other non-drinking purposes, helping to conserve fresh water.
  • Watershed management: Watershed development helps in soil and water conservation, increasing agricultural production, and preventing ecological degradation.
  • Rainwater harvesting: It involves collecting and storing rainwater to recharge groundwater, reduce flooding, control soil erosion, and meet domestic needs.
  • National Water Policy (2002): Priority is given to drinking water, followed by irrigation and other uses. It stresses groundwater regulation, water quality monitoring, efficient use, and public awareness.
CISCE: Class 12

Key Points: Irrigation in India

  • Meaning of Irrigation: Irrigation is the artificial supply of water to crops through canals, wells, tubewells, tanks, etc., to support agriculture.
  • Uneven Rainfall: Rainfall in India is uneven in space and time—some areas face water scarcity and rainfall is limited to 3–4 months, making irrigation necessary.
  • Uncertainty & Variability: The monsoon is uncertain and irregular, causing droughts and crop failure. Irrigation provides stability to agriculture.
  • Crop Requirements: Water-intensive crops like rice, sugarcane, and jute, and high-yielding varieties require regular water supply, which is ensured through irrigation.
  • Increase in Productivity: Irrigation increases crop production, supports multiple cropping, and improves agricultural productivity, especially in states like Punjab and Haryana.
CISCE: Class 12

Key Points: Primitive Methods > Wells

  • Meaning of Well Irrigation
    A well is a hole dug in the ground to obtain underground water. It is one of the oldest and simplest methods of irrigation in India.
  • Areas of Well Irrigation
    It is mainly used in regions where sufficient groundwater is available, such as parts of the Northern Plains and some states like Uttar Pradesh, Rajasthan, and Madhya Pradesh.
  • Advantages of Well Irrigation
    It is cheap, simple, independent, and can be used whenever required. It also does not cause the problem of waterlogging like canal irrigation.
  • Limitations of Well Irrigation
    A well can irrigate only a small area (about 1–2 hectares), and it depends completely on groundwater availability.
  • Problems of Well Irrigation
    Wells may dry up during droughts or if too much water is used. It is not suitable in areas with rocky land or brackish (salty) groundwater.
CISCE: Class 12

Key Points: Primitive Methods > Tank Irrigation

  • Meaning of Tank Irrigation
    A tank is a water storage system made by building bunds (walls) across small streams to collect rainwater for irrigation.
  • Main Areas of Tank Irrigation
    It is mainly practiced in the peninsular plateau region, especially in Andhra Pradesh, Telangana, Tamil Nadu, and Karnataka.
  • Reasons for Its Practice
    It is suitable in rocky and uneven areas where canals and wells are difficult to build. Seasonal rivers and heavy rainfall make tank construction useful for storing water.
  • Merits of Tank Irrigation
    Tanks are low-cost, long-lasting, and can be owned by individual farmers. Fishing is also carried out in tanks, which increases farmers’ income.
  • Demerits of Tank Irrigation
    Many tanks dry up in summer. They require regular desilting, water gets evaporated easily, and sometimes water cannot reach fields due to rocky land.
CISCE: Class 12

Key Points: Modern Methods > Tube-Wells

  • Meaning of Tube-well Irrigation
    A tube-well is a deep well (usually more than 15 metres) from which water is lifted using an electric motor or diesel engine. It is an improved method of irrigation.
  • Conditions Required
    It requires sufficient groundwater, regular electricity or diesel supply, water table within about 50 metres, and fertile nearby land to make it economical.
  • Main Areas
    Tube-well irrigation is widely used in Uttar Pradesh (largest area) and also in Rajasthan, Punjab, Madhya Pradesh, Bihar, Gujarat, Haryana, and other states.
  • Advantages
    It irrigates about ten times more area than an ordinary well, works independently of canals, and can be used whenever needed.
  • Disadvantages
    It is costly due to electricity/diesel expenses, cannot be used in brackish water areas, and excessive use may lower the groundwater level, especially during droughts.
CISCE: Class 12

Key Points: Modern Methods > Canals

  • Importance of Canals
    Canals are one of the most important modern sources of irrigation in India. They are mainly useful in northern plains like Punjab, Haryana, and Uttar Pradesh.
  • Major Canal Irrigated States
    Important states with large canal irrigation are Uttar Pradesh, Punjab, Haryana, Andhra Pradesh, Rajasthan, Bihar, Odisha, Karnataka, Tamil Nadu, and Maharashtra.
  • Merits of Canal Irrigation
    Canals provide perennial (regular) water supply, increase farm production, deposit fertile silt in fields, and are economical in the long run.
  • Demerits of Canal Irrigation
    They may cause waterlogging and soil salinity, spread diseases like malaria, flood nearby areas, and are suitable mainly in plain regions.
CISCE: Class 12

Key Points: Modern Methods > Sprinkler Irrigation

  • Meaning
    Sprinkler irrigation is a modern method in which water is sprayed over the fields like rainfall through pipes and sprinklers.
  • Method of Supply
    Water is supplied through hoses from the main source and sprayed directly on crops using a sprinkler.
  • Water Conservation
    This method reduces water loss due to seepage and evaporation, as water is properly controlled and evenly distributed.
  • Suitable Areas
    It is mainly used in dry and semi-arid regions where rainfall is low.
  • Present Status
    It is comparatively new in India and is not yet widely used, but it is becoming popular because it saves water.
CISCE: Class 12

Key Points: Dangers of Over Watering

  • Meaning of Over-Watering
    Over-watering happens when farmers supply excessive water to fields, especially in canal irrigation areas, to increase crop production.
  • Main Problems Caused
    It leads to waterlogging (rise in groundwater level) and increases soil salinity and alkalinity, which harm the soil.
  • Effect on Soil and Crops
    Excess salts (like sodium, calcium, chlorides and sulphates) collect in the soil. This reduces soil fertility, affects germination, blocks root growth, and lowers crop yield.
  • Most Affected Areas
    The problem is common in canal irrigated states like Punjab, Haryana, and Uttar Pradesh, where large areas have become saline or alkaline.
  • Measures for Reclamation
    Affected soils can be improved by using gypsum, green manuring, proper drainage, and leaching methods. Government schemes have also been started to reclaim alkali soils.
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