29 August 2015

Chapter 3 Water Resources

CBSE NCERT Class X (10th) | Social Studies | Geography

Chapter 3 Water Resources

Water Sources

Water is a renewable resource. Water is essential for domestic use, cultivation and also for industries. The majority of human uses require fresh water.

97 % of the water on the earth is salt water only 2.5 of the total water on the earth is exists as fresh water. Around 70 % of fresh water is frozen in glaciers and ice sheets.

Only 30 % of water is stored as ground water. The source of almost all fresh water is precipitation. India receives nearly 4% of the global precipitation.

Around 0.3 % of the total fresh water exists in rivers, lakes, streams, ponds and springs are natural sources of water.

India has ample water resources in certain regions still India is in 133rd position in water availability per person per year.

Water scarcity is posing an alarming threat in most parts of the world, including India.

Water Scarcity

Water scarcity is the lack of sufficient available water resources to meet the demands of water usage within a region.

The increase in water demand is a contribution of various factors including growing population, increased agricultural needs, industrial use  and  for electricity production.

Large amounts of industrial pollutants dumped in the rivers are responsible for destroying and leading to water shortage of the whole planet.

Pesticides and fertilizers used in agriculture also get mixed with water bodies and pollute them.
Overuse of tube wells for irrigation and use of bore wells for  domestic use also leads to over exploitation of underground water , decreasing the level  water table  resulting in water scarcity.

The problem of water waste is severe in countries where people are using the traditional inefficient irrigation methods for  agricultural land.

Government should invest to build more dams to fulfil the water demands and reduce the water shortage

Multi-purpose River Projects

People have always felt the need to store river water in the rainy season for use in the dry season. People in ancient India built many hydraulic structures like dams, artificial lakes, tanks and canals to store and divert water for irrigation.

A dam is a structure that forms a barrier across a river to regulate the flow of water. Dams can be classified into several types based on their height and material used for construction. We have built many large dams across major rivers in India.

The primary purpose of dams has always been to provide water for irrigation. Modern dams are also used to generate electricity and to supply water to industries and households. Dams are used to control flooding in flood-prone areas by regulating the flow of water downstream.

The reservoirs created behind several dams are used for breeding fish. Dams can also be used to divert water into existing smaller streams to promote inland navigation. Several dams are popular tourist attractions and recreation spots. Dams are called multi-purpose river projects due to the many ways that they offer to manage our water resources. A dam creates an enormous reservoir of water that submerges vast stretches of the surrounding area.

Major benefits of large multi-purpose projects go to big landowners and industrialists, while the local, poor, landless people have little to gain. Better irrigation facilities attract farmers to grow more water-intensive commercial crops, leading to over-irrigation and increase in soil salinity. Construction of dams cause ecological problems as well like these block the migration of fish, upsetting the ecological balance and putting several aquatic species in danger.

The sudden release of large quantities of water from dams results in large-scale flooding in plain areas. Large dams obstruct the free flow of river water, resulting in disputes between different states over water sharing, and also over the sharing of costs and benefits of the project. Environmentalists associate large dams with causing of earthquakes, spread of water-borne diseases and degradation of soil. Most of the multi-purpose river projects in India so far have not met their desired objectives.

Rainwater Harvesting

Rain water feeds our rivers and seeps into the ground to recharge our underground water resources. Rainwater is one of the purest forms of water available in nature but is available to us only for a few months in a year.

The process of collecting rain water during the wet season, to meet our fresh water requirements in the dry season, is called rainwater harvesting. In Himachal Pradesh and Jammu rain water is harvested using diversion channels called kuls or guls. Water flowing through the kuls is collected in reservoir tanks in the villages and used for irrigation as and when required.

Farmers in Bengal traditionally used inundation channels cut through river embankments at times of floods to irrigate their fields. In some areas of Rajasthan, earthen embankments, called khadin, are built around farms to collect rain water during the rainy season. This saturates the soil for cultivation. In the semi-arid regions of Rajasthan, earthen check dams, called johads, are used to collect rainwater that percolates into the ground, raising the level of groundwater.

One of the most widely used methods of collecting rain water is rooftop rainwater harvesting. In a rooftop rainwater harvesting system, rain water falling on the roof is collected and then filtered before being stored in tanks for immediate use. Excess water is diverted to wells to recharge groundwater.

In many parts of Rajasthan, rain water collected through rooftop harvesting is collected in large underground reservoirs, called tankas. Almost all households in Shillong in Meghalaya use rooftop rainwater harvesting to meet almost 20% of their total requirement of water.

Each of the 200 households in Gendathur, Karnataka, that adopted rooftop rainwater harvesting can collect 50,000 litres of rain water every year for its use. In bamboo drip irrigation, bamboos are split to make shallow channels. A complex network of such bamboo channels is used to divert and carry water from rain-fed springs to the farms. Channel sections in the farm allow the water to drip near the roots of the plants.