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Watershed Conservation: Method, Management & Challenges

December 12, 2023 1223 0

Sustainable Water Practices, Rainwater Harvesting, 

Watershed Conservation: The practice of using water more efficiently and responsibly to ensure its sustainable availability for current and future generations. It is a critical aspect of environmental stewardship, given that water is a finite resource and essential for various human activities, agriculture, industry, and ecosystems

  • Watershed Management: Exploring Conservation and Community in Addressing Water Challenges 
    • Definition: It refers to efficient management and conservation of surface and groundwater resources. 
    • Enhancing Water Sustainability: It involves prevention of runoff and storage and recharge of groundwater through various methods like percolation tanks, recharge wells, etc. 
      • However, it includes conservation, regeneration and judicious use of all resources – natural (like land, water, plants and animals) and humans within a watershed.
    • Achieving Harmony: It aims at bringing about balance between natural resources on the one hand and society on the other. 
    • The success of watershed development largely depends upon community participation. 
    • Haryali is a watershed development project sponsored by the Central Government which aims at enabling the rural population to conserve water for drinking, irrigation, fisheries and afforestation. 
      • The Project is being executed by Gram Panchayats with people’s participation. 
    • Neeru-Meeru (Water and You) programme (in Andhra Pradesh) and Arvary Pani Sansad (in Alwar, Rajasthan) have taken up constructions of various water-harvesting structures such as percolation tanks, dug out ponds (Johad), check dams, etc. through people’s participation. 
    • There is a need to generate awareness regarding benefits of watershed development and management among people in the country, and through this integrated water resource management approach water availability can be ensured on a sustainable basis. 

Roof top rainwater harvesting is the most common practice in Shillong, Meghalaya. Cherapunjee and Mawsynram situated at a distance of 55 km. from Shillong receive the highest rainfall in the world, yet the state capital Shillong faces acute shortage of water. Nearly 15-25% of the total water requirement of the household comes from roof top water harvesting.

  • Rain Water harvesting: 
    • Rain water harvesting is a  low cost and eco-friendly method to capture and store rainwater for various uses. 
      • Benefits of rainwater harvesting: It is also used to recharge groundwater aquifers. 
        • It increases water availability, checks the declining groundwater table.
        • It improves the quality of groundwater through dilution of contaminants like fluoride and nitrates.
        • It prevents soil erosion, and flooding and arrests salt water intrusion in coastal areas if used to recharge aquifers within the watershed. 
        • It also decreases the community dependence on groundwater for domestic use. 
        • Besides bridging the demand supply gap, it can also save energy to pump groundwater as recharge leads to rise in groundwater table.  

Bamboo Drip Irrigation System: In Meghalaya, a 200-year-old system of tapping stream and spring wate by using bamboo pipes, is prevalent. About 18-20 litres of water enters the bamboo pipe system, gets transported over hundreds of metres, and finally reduces to 20-80 drops per minute ate the site of the plant.

 

Bamboo Drip Irrigation System: In Meghalaya, a 200-year-old system of tapping stream and spring wate by using bamboo pipes, is prevalent. About 18-20 litres of water enters the bamboo pipe system, gets transported over hundreds of metres, and finally reduces to 20-80 drops per minute ate the site of the plant.

    • Traditional Rainwater Harvesting Methods in the Watershed: In rural areas it is done by using surface storage bodies like lakes, ponds, irrigation tanks, etc. 
      • In hill and mountainous regions, people built diversion channels like the ‘guls’ or ‘kuls’ of the Western Himalayas for agriculture. 
      • A Kul: It is a circular village tank, from which water is released as and when required.
      • Lhadin and Johad: In arid and semi-arid regions, agricultural fields were converted into rain fed storage structures that allowed the water to stand and moisten the soil like the ‘khadins’ in Jaisalmer and ‘Johads’ in other parts of Rajasthan. 
      • Kund or Tanka: In the semi-arid and arid regions of Rajasthan, particularly in Bikaner, Phalodi and Barmer, rainwater harvesting structures locally known as Kund or Tanka (a covered underground tank) are constructed near or in the house or village. 
      • Many houses constructed underground rooms adjoining the ‘tanka’  within the watershed to beat the summer heat as it would keep the room cool. 
      • Palar pani or Rainwater, as commonly referred to in these parts, is considered the purest form of natural water. 

 Hydraulic Structures in Ancient India

  • In the 1st century B.C., Sringaverapura near Allahabad had sophisticated water harvesting system channelling the flood water of the river Ganga.
  • During the time of Chandragupta Maurya, dams, lakes and irrigation systems were extensively built.
  • Evidences of sophisticated irrigation works have also been found in Kalinga, (Orissa), Nagarjunakonda (Andhra Pradesh), Bennur (Karnataka), Kolhapur (Maharashtra), etc.
  • In the 11th Century, Bhopal Lake, one of the largest artificial lakes of its time was built.
  • In the 14th Century, the tank in Hauz Khas, Delhi was constructed by Iltutmish for supplying water to Siri Fort area.

Source: Dying Wisdom, CSE, 1997.

  • Watershed in Multi-Purpose River Projects And Integrated Water Resources Management: 
    • Dams:  Dams were traditionally built to impound rivers and rainwater that could be used later to irrigate agricultural fields. 
      • Dams are now referred to as multi-purpose projects. 
    • Example: 
      • In the Sutlej-Beas river basin,  the Bhakra – Nangal project water is being used both for hydel power production and irrigation; 
      • The Hirakud project in the Mahanadi basin integrates conservation of water with flood control (Refer Figure 7.18).
    • Watershed in Multi-purpose Projects: These are launched after Independence with their integrated water resources management approach, and were thought of as the vehicle that would lead the nation to development and progress, overcoming the handicap of its colonial past. 
      • Jawaharlal Nehru proudly proclaimed the dams as the ‘temples of modern India’.

Dam

  • A dam is a barrier across flowing water that obstructs, directs or retards the flow, often creating a reservoir, lake or impoundment. 
  • “Dam” refers to the reservoir rather than the structure. 
  • Most dams have a section called a spillway or weir over which or through which it is intended that water will flow either intermittently or continuously. 
  • Dams are classified according to structure, intended purpose or height
  • Based on structure and the materials used, dams are classified as timber dams, embankment dams or masonry dams, with several subtypes. 
  • According to the height, dams can be categorised as large dams and major dams or alternatively as low dams, medium height dams and high dams.

Watershed: Major Rivers and Dams

Controversies and Impacts: Watershed Issues in Multi-Purpose Projects

  • In recent years, multi-purpose projects and large dams have come under great scrutiny and opposition for a variety of reasons. 
    • Disruptions to Natural Flow and Aquatic Habitats within the Watershed: Regulating and damming of rivers affect their natural flow causing poor sediment flow and excessive sedimentation at the bottom of the reservoir, resulting in rockier stream beds and poorer habitats for the rivers’ aquatic life. 
      • Dams also fragment rivers making it difficult for aquatic fauna to migrate, especially for spawning. 
    • Vegetation Submersion: The reservoirs created on the floodplains also submerge the existing vegetation and soil leading to its decomposition over a period of time. 
    • Social Movements Against Large Dams  within the Watershed:  They have also been the cause of many new social movements like the ‘Narmada Bachao Andolan’ and the ‘Tehri Dam Andolan’ etc. 
      • Resistance  within the watershed to these projects has primarily been due to the large-scale displacement of local communities. 

Narmada Bachao Andolan or Save Narmada Movement is a Non Governmental Organisation (NGO) that mobilised tribal people, farmers, environmentalists and human rights activists against the Sardar Sarovar Dam being built across the Narmada river in Gujarat. It originally focused on the environmental issues related to trees that would be submerged under the dam water. Recently it has re-focused the aim to enable poor citizens, especially the oustees (displaced people) to get full rehabilitation facilities from the government.

    • Ecological and Social Impacts: Irrigation has also changed the cropping pattern of many regions with farmers shifting to water intensive and commercial crops
      • This has great ecological consequences like salinisation of the soil. 
      • At the same time, it has transformed the social landscape i.e. increasing the social gap between the richer landowners and the landless poor. 
    • Inter-state Water Disputes: These are also becoming common with regard to sharing the costs and benefits of the multi-purpose project.
    • Paradox of Flood Control Dams: Ironically, the dams that were constructed to control floods have triggered floods due to sedimentation in the reservoir. 
      • The floods have not only devastated life and property but also caused extensive soil erosion. 
      • Sedimentation also meant that the flood plains were deprived of silt, a natural fertilizer, further adding on to the problem of land degradation.
    • Unintended Consequences within the Watershed: The multi-purpose projects have induced earthquakes, caused water borne diseases and pests and pollution resulting from excessive use of water.

Do You Know?

The Krishna-Godavari dispute is due to the objections raised by Karnataka and Andhra Pradesh governments. It is regarding the diversion of more water at Koyna by the Maharashtra government for a multipurpose project. This would reduce downstream flow in their states with adverse consequences for agriculture and industry.

Conclusion

Addressing the complexities of multi-purpose projects requires a nuanced approach centered on the watershed. Recognizing the impact on aquatic habitats, social movements, and unintended consequences, watershed management emerges as a vital strategy for sustainable water practices and environmental stewardship.

Also Read: Non-Conventional Energy: Exploring Energy Sources & Power of Nature

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