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Although three-fourths of the Earth's surface is covered by water, only a small portion of this vast amount is freshwater suitable for human use. This usable freshwater primarily comes from surface run-off and groundwater. Freshwater is continuously replenished and recharged through the hydrological cycle (water cycle), making water a renewable resource.
Water Scarcity And The Need For Water Conservation And Management
The Paradox of Water Scarcity
Given that most of the globe is covered by water and it's a renewable resource, it might seem counterintuitive that many countries and regions experience water scarcity. However, despite its abundance and renewability, water scarcity is a real and growing problem worldwide. Projections even suggest that a significant portion of the global population could face absolute water scarcity in the coming years.
Association With Low Rainfall
When thinking about water shortages, it's common to associate them primarily with regions that receive low rainfall or are prone to droughts, visualising dry landscapes and people struggling to access water.
True Causes Of Scarcity
While variations in rainfall do affect water availability across space and time, water scarcity is primarily caused by human actions. The main reasons include over-exploitation (using water excessively), excessive use beyond what is needed or replenished, and unequal access to water resources among different social groups.
Where Scarcity Occurs
Water scarcity can occur not only in low rainfall areas but also in regions with ample water resources. Many cities, for instance, face water scarcity despite having access to significant water bodies. This paradox is often the result of large populations and unsustainable usage patterns.
Outcome Of Population Growth
A large and growing population contributes to water scarcity by increasing demand for water. More people need water not just for domestic use but also for producing the additional food required to feed everyone.
Irrigated Agriculture's Role
To boost food production, especially for dry-season agriculture, water resources are often over-exploited to expand irrigated areas. Irrigated agriculture is the largest consumer of water. Farmers increasingly rely on private wells and tube-wells, leading to falling groundwater levels and negatively impacting overall water availability and food security. This highlights the need for more sustainable agricultural practices, such as developing drought-resistant crops and employing dry farming techniques.
Industrialisation And Urbanisation Impact
Intensive industrialisation and urbanisation in post-independent India have aggravated water stress. Industries are heavy users of water and also require significant power, much of which comes from water-intensive hydroelectric sources. Growing urban centres with large, dense populations and modern lifestyles increase water and energy demands. Urban housing societies often use private groundwater pumping devices, further depleting fragile water resources in cities.
Pollution And Bad Quality Water
Beyond quantitative scarcity, the quality of water is a major concern. Even where water is available in sufficient quantity, it may be heavily polluted by domestic and industrial waste, chemicals, pesticides, and fertilisers used in agriculture, making it hazardous for human consumption. This pollution poses significant health risks.
Need To Conserve And Manage Water
Given the threats of over-exploitation, mismanagement, and pollution, conserving and managing our water resources is urgently needed. This is essential to safeguard against health hazards, ensure food security, sustain livelihoods and productive activities, and prevent the degradation of natural ecosystems. Mismanagement risks impoverishing this vital resource and creating ecological crises with profound impacts on our lives.
Multi-purpose River Projects And Integrated Water Resources Management
Conserving and managing water has a long history in India. Archaeological and historical records show the construction of sophisticated hydraulic structures since ancient times.
Ancient Hydraulic Structures
Evidence of impressive water management systems exists from ancient India:
- In the first century B.C., Sringaverapura near Allahabad had a complex system to channel floodwater from the Ganga.
- During the time of Chandragupta Maurya, extensive dams, lakes, and irrigation systems were built.
- Sophisticated irrigation works have been found in Kalinga (Odisha), Nagarjunakonda (Andhra Pradesh), Bennur (Karnataka), and Kolhapur (Maharashtra).
- The 11th century saw the creation of the large artificial Bhopal Lake.
- In the 14th century, Iltutmish constructed the tank in Hauz Khas, Delhi, to supply water to the Siri Fort area.
This tradition of building hydraulic structures has continued in modern India, with the construction of dams across river basins.
Purpose Of Modern Dams
While traditionally built to store rainwater for irrigation, modern dams serve multiple purposes. They are constructed not only for irrigation but also for generating electricity, supplying water for domestic and industrial use, controlling floods, providing recreational opportunities, facilitating inland navigation, and fish breeding.
Dams As Multi-purpose Projects
Because they integrate many uses of the impounded water, modern dams are often referred to as multi-purpose projects. For example, the Bhakra-Nangal project in the Sutluj-Beas basin provides both hydroelectric power and irrigation. The Hirakud project in the Mahanadi basin combines water conservation with flood control measures.
*(A dam is a barrier constructed across flowing water to obstruct, direct, or retard its flow, creating a reservoir. Dams are classified by structure (timber, embankment, masonry), materials, and height (low, medium, high, large, major).)*
Dams As 'Temples Of Modern India'
Launched after India's Independence, multi-purpose projects were envisioned with an integrated water resources management approach. Leaders like Jawaharlal Nehru hailed dams as the 'temples of modern India', believing they would propel the nation towards development and progress, overcoming the challenges of its colonial past. The hope was that these projects would integrate the development of agriculture and the rural economy with rapid industrialisation and urban growth.
*(Traditional songs from regions like the Damodar valley highlight the historical struggles with river floods, known as the 'river of sorrow', underscoring the initial perceived benefit of dams for flood control.)*
Disadvantages And Opposition
In recent years, multi-purpose projects and large dams have faced increasing scrutiny and opposition due to a variety of negative consequences:
- Effects on River's Natural Flow: Regulating and damming rivers disrupts their natural flow. This leads to poor sediment flow downstream and excessive accumulation of sediment (sedimentation) at the bottom of the reservoir.
Fragmentation Of Rivers
Disruption of natural flow and sediment changes result in rockier riverbeds and poorer habitats for aquatic life. Dams also physically fragment rivers, creating barriers that hinder the migration of aquatic fauna, especially for breeding (spawning).
Submergence Of Vegetation And Soil
The reservoirs created by dams on floodplains submerge existing vegetation and soil, leading to their decomposition over time, which can release greenhouse gases and impact water quality.
Changing Cropping Patterns
Irrigation from dams has often encouraged farmers to shift towards water-intensive and commercial crops. While potentially increasing income, this has severe ecological consequences, such as the salinisation of soil in irrigated areas.
Failure To Control Floods
Ironically, dams built for flood control have sometimes triggered floods due to heavy sedimentation reducing reservoir capacity. Large dams have often proven unsuccessful in controlling severe floods during periods of excessive rainfall.
Soil Erosion And Land Degradation
Floods linked to dams can devastate life and property and cause extensive soil erosion. Sedimentation behind dams also means that flood plains downstream are deprived of nutrient-rich silt, which acts as a natural fertiliser, contributing to land degradation problems.
Other Problems (Earthquakes, Diseases, Pollution)
Multi-purpose projects have also been associated with other negative impacts, including inducing earthquakes, causing water-borne diseases and pests, and contributing to pollution due to excessive water use or industrial activities facilitated by water availability.
Inter-state Water Disputes
The allocation and diversion of water for multi-purpose projects can lead to disputes between states, particularly those located downstream who fear reduced water flow. The Krishna-Godavari dispute between Karnataka, Andhra Pradesh, and Maharashtra over water diversion is a well-known example.
*(The Pradhan Mantri Krishi Sinchaee Yojana is a program aiming to enhance access to irrigation and promote efficient water use in agriculture across India.)*
Rainwater Harvesting
Given the disadvantages and growing opposition to large multi-purpose projects, water harvesting systems have emerged as a viable alternative, offering socio-economic and environmental benefits.
Water Harvesting As Alternative
Many advocate for traditional and innovative water harvesting methods as a more sustainable and less disruptive way to conserve and manage water compared to large dams.
Traditional Systems In Ancient India
Ancient India had a rich tradition of diverse water-harvesting systems alongside sophisticated hydraulic structures. People possessed deep knowledge of local rainfall patterns and soil types, developing techniques tailored to regional ecological conditions and water needs to harvest rainwater, groundwater, river water, and flood water.
Specific Harvesting Techniques
Examples of traditional methods include:
- Diversion channels: 'Guls' or 'kuls' in the Western Himalayas, built to divert water for agriculture.
- Rooftop rainwater harvesting: Commonly practiced, especially in Rajasthan, to collect and store drinking water.
- Inundation channels: Developed in the flood plains of Bengal to irrigate fields using floodwaters.
- Rain-fed storage structures: Agricultural fields in arid and semi-arid regions converted into structures like 'khadins' in Jaisalmer and 'Johads' in other parts of Rajasthan to allow water to stand and moisten the soil.
Underground Tanks (Tankas) In Rajasthan
In the semi-arid and arid parts of Rajasthan (Bikaner, Phalodi, Barmer), houses traditionally featured underground tanks or tankas built within the main house or courtyard for storing drinking water. These could be quite large. Tankas were integrated with rooftop rainwater harvesting systems: sloping roofs were connected to the tankas via pipes. The first rainfall was usually not collected to clean the roofs and pipes; subsequent rainfall was channelled into the tankas.
Construction And Use Of Tankas
Tankas were constructed underground and connected to house roofs via pipes. They stored rainwater (referred to as 'palar pani'), which was considered the purest form of natural water and served as a reliable source of drinking water, particularly during dry summers when other sources failed. Some houses included adjacent underground rooms that stayed cool due to the tankas, providing relief from the summer heat.
*(Tamil Nadu has mandated rooftop rainwater harvesting for all houses, with legal provisions for defaulters. Shillong, Meghalaya, despite proximity to high rainfall areas, faces water shortages and widely uses rooftop harvesting, meeting a significant portion of household needs.)*
Decline In Western Rajasthan
Sadly, in western Rajasthan, the practice of rooftop rainwater harvesting is declining due to increased water availability from the perennial Indira Gandhi Canal. However, some houses still maintain tankas due to a preference for the taste of stored rainwater over tap water.
Adaptations In Other Areas (Gendathur)
Fortunately, rooftop rainwater harvesting is being successfully adapted in many rural and urban areas across India. In Gendathur, a remote village in Karnataka, nearly 200 households installed systems, earning the village a reputation for being rich in rainwater. With an average annual rainfall of 1,000 mm and efficient collection systems, each house can collect and use a substantial amount of water annually.
Bamboo Drip Irrigation System
Meghalaya has a remarkable 200-year-old traditional system for tapping stream and spring water using bamboo pipes.
System Description
This system uses bamboo pipes to divert perennial stream and spring water from hilltops and transport it to lower reaches by gravity. About 18-20 litres of water initially enter the bamboo pipe network and are carried over hundreds of meters. The system is designed to reduce the water flow to a slow drip (20-80 drops per minute) directly at the base of plants.
Channel sections made of bamboo are used to divert water, and branching pipes, also made of bamboo, distribute the water to specific plant sites. The flow is controlled by manipulating the position of the pipes. If the pipes need to cross a road or obstruction, they are elevated above the ground. At the final stage, reduced channel sections and diversion units ensure water is delivered precisely near the plant roots.