Water ResourcesClass 10 Geography Notes

WATER RESOURCES

Water is a fundamental resource, essential for all life. We need it to drink, cook, and wash, but it's also critical for industries, agriculture, and even generating power. For centuries, human civilizations have flourished near water sources like rivers, lakes, and springs.

Although about three-fourths of the Earth's surface is covered with water, only a very small portion of it is freshwater that we can actually use. This freshwater is a renewable resource, meaning it is constantly being replenished through the hydrological cycle (the continuous movement of water on, above, and below the surface of the Earth).

If water is renewable and covers so much of the planet, why do we hear about water shortages? It is predicted that by 2025, nearly two billion people will face absolute water scarcity. This happens because the availability of usable water doesn't always match where and when people need it.

Water Scarcity and the Need for Water Conservation and Management

When we think of water scarcity, we often picture deserts like those in Rajasthan, where women walk long distances carrying pots (matkas) to fetch water. While low rainfall and drought-prone areas certainly face challenges, water scarcity is a much bigger problem. In most cases, it is caused by:

• Over-exploitation: Using water faster than it can be renewed.
• Excessive use: Wasting water or using it inefficiently.
• Unequal access: When some social groups get more water than others.

Water scarcity isn't just about the quantity of water available; it's also about its quality.

Causes of Water Scarcity

1. Growing Population and Increased Demand:

• A large population needs more water for domestic use (drinking, cooking) and for producing more food.
• To grow more food, especially during the dry season, farmers rely on irrigation. Irrigated agriculture is the largest consumer of water. Many farmers have their own wells and tube-wells, which can lead to falling groundwater levels and threaten water availability.

2. Industrialisation and Urbanisation:

• After independence, India saw rapid industrial growth. Industries are heavy users of water and also require large amounts of electricity, much of which comes from hydroelectric power.
• Growing cities (urban centres) with dense populations and modern lifestyles have increased the demand for both water and energy.
• Many housing societies in cities pump their own groundwater, which puts immense pressure on fragile water resources and has led to their depletion in many urban areas.

3. Water Pollution (Qualitative Scarcity):

• Sometimes, there is plenty of water available, but it is too polluted to use.
• Waste from homes and industries, chemicals, pesticides, and fertilizers from agriculture can all contaminate water sources.
• This pollution makes the water hazardous for human use, effectively creating scarcity even in water-rich regions.

The Need for Water Management

The over-exploitation and mismanagement of water can lead to an ecological crisis. It is essential to conserve and manage our water to:

• Safeguard ourselves from health hazards.
• Ensure food security for our growing population.
• Continue our livelihoods and economic activities.
• Prevent the degradation of our natural ecosystems.

Multi-purpose River Projects and Integrated Water Resources Management

So, how do we conserve and manage water? For centuries, people in India have built sophisticated hydraulic structures.

Hydraulic Structures in Ancient India

• First Century B.C.: Near Allahabad, a water harvesting system channeled the floodwaters of the river Ganga.
• Time of Chandragupta Maurya: Dams, lakes, and irrigation systems were built extensively.
• 11th Century: Bhopal Lake, one of the largest artificial lakes of its time, was constructed.
• 14th Century: The tank in Hauz Khas, Delhi, was built by Iltutmish to supply water to the Siri Fort area.

This tradition continued in modern India with the construction of dams in most of our river basins.

Dams and Multi-Purpose Projects

A dam is a barrier built across flowing water to obstruct or slow its flow, creating a reservoir or lake. In the past, dams were mainly built to hold rainwater for irrigating fields. Today, they are built for many reasons at once and are called multi-purpose projects.

The functions of modern dams include:

• Irrigation
• Electricity generation
• Water supply for domestic and industrial use
• Flood control
• Recreation and tourism
• Inland navigation
• Fish breeding

After independence, Prime Minister Jawaharlal Nehru proudly called dams the 'temples of modern India'. He believed these projects would help develop agriculture and the village economy while also supporting rapid industrialisation and the growth of cities.

Problems with Multi-Purpose Projects

In recent years, large dams have faced significant criticism for several reasons:

• Ecological Damage:
  • Damming rivers affects their natural flow, causing poor sediment flow and making the riverbeds rockier. This harms the habitats of aquatic life.
  • Dams fragment rivers, making it difficult for fish and other aquatic creatures to migrate, especially for spawning.
  • The reservoirs created by dams submerge existing forests and soil, which then decompose over time.
• Triggering Floods: Ironically, dams built to control floods can sometimes cause them. Sedimentation at the bottom of the reservoir reduces its capacity to hold water, leading to flooding during excessive rainfall.
• Land Degradation: Because dams trap sediment, the floodplains downstream are deprived of silt, which is a natural fertilizer. This contributes to land degradation.
• Other Issues: Large dams have also been linked to inducing earthquakes, causing water-borne diseases, and pollution from the excessive use of stored water.
• Social Consequences:
  • Building large dams often leads to the displacement of local communities, causing them to lose their homes and livelihoods.
  • Irrigation from dams has changed cropping patterns, with farmers shifting to water-intensive commercial crops. This can lead to soil salinisation.
• Inter-State Water Disputes: Sharing river water is a common source of conflict between states. [!example] The Krishna-Godavari dispute arose from objections by Karnataka and Andhra Pradesh over the Maharashtra government diverting more water at Koyna for a multi-purpose project, which would reduce the flow of water to their states.

Rainwater Harvesting

Given the problems with large dams, many people see rainwater harvesting as a better alternative, both socially and environmentally. India has a long and extraordinary tradition of water harvesting systems tailored to local conditions.

Traditional Rainwater Harvesting Methods

• In hilly regions like the Western Himalayas, people built diversion channels called 'guls' or 'kuls' for agriculture.
• In the floodplains of Bengal, people developed inundation channels to irrigate their fields.
• In the arid regions of Rajasthan, agricultural fields were converted into rain-fed storage structures like 'khadins' in Jaisalmer and 'johads' in other areas.
• Rooftop rainwater harvesting was common for storing drinking water, especially in Rajasthan.

Rooftop Rainwater Harvesting in Rajasthan

In the semi-arid regions of Rajasthan, like Bikaner, Phalodi, and Barmer, nearly all houses traditionally had underground tanks called 'tankas'.

• These tankas were connected to the sloping roofs of houses with a pipe.
• Rainwater would flow down the pipe and be stored in the tanka. The first spell of rain was usually not collected, as it served to clean the roofs and pipes.
• This stored rainwater, known locally as 'palar pani', is considered the purest form of natural water and was a reliable source of drinking water during the dry summer months.

Today, this practice is declining in western Rajasthan because of the availability of tap water from the perennial Indira Gandhi Canal. However, in many other parts of India, rooftop rainwater harvesting is being successfully adapted.

Bamboo Drip Irrigation System

In Meghalaya, a 200-year-old system of irrigation using bamboo pipes is still in practice.

• This system taps into stream and spring water on hilltops.
• Water is transported over hundreds of metres through a network of bamboo pipes.
• The system is designed to reduce the flow of water so that it is delivered drop by drop (20-80 drops per minute) directly to the roots of the plants, making it a highly efficient method of irrigation.