HYDROLOGICAL / WATER CYCLE

 Water cycle is circulation of water in environment. Water from land or sea surface evaporates due to solar energy. Water vapor rises into the atmosphere, cools and after a particular level is converted to water, snow, etc. (condensation). A part of the water that falls on the land is evaporated back to the atmosphere. Some water seeps into the soil to form ground water and the remaining flows over the land in the form of streams and rivers from where it evaporates again.

Human Impact and Hydrological Cycle

The total amount of water on the earth’s surface remains constant. Human actions bring about serious alterations in the natural hydrological cycle. The demand for water has grown with the increase in population not only for domestic use, but also for agricultural, industrial and economic growth.

Water use has also resulted in larger discharge of waste water from domestic, industrial, agricultural and other sources. These discharges are mixed with various types of pollutants, hazardous chemicals and bacteria. This results in reduction in availability of drinking water.

Large urban centers lead to increase in surface runoff through drains and sewer systems thus increasing events of urban flooding.

To provide water dams were constructed. The dams change the flow of water and affect the amount of fresh water flow to the sea.

Agricultural activities have seriously hampered natural hydrological cycle. Clearing of forests for agriculture leads to increase in soil erosion. Use of fertilizers, insecticides, pollutes the natural system.

Extraction of ground water for irrigation or drinking may lead to depletion or sinking of land damaging property. Human activities have polluted ground water e.g. industrial chemical sewage and other pollutants.

Activities like mining also lead to alterations in the natural water cycles by pumping out large proportion for dewatering the mines and washing of minerals. Both these activities release water hat has high levels of mineral content thus polluting streams.

Oil slicks develop due to spills of oil from tankers and containers used for transport and storage. Oil impairs the exchange of gases and destroys natural systems. This results in death of marine animals.

Changes in the natural water or hydrological cycle can also result in contributing towards global warming, disruption in climatic systems, erratic and sudden occurrences of floods, cyclones, etc.