Water Conservation and Management

Irrigation is the method by which water is collected, stored and supplied controllably when required by artificial means.

Dams are one of the sources of irrigation. This is achieved by construction of reservoirs where water is stored and utilised when required in the absence of rain.

B.  Reduction of Water table

One of the main threats to tubewell irrigation is that of over-abstraction leading to a lowering of the water table. If the rate of withdrawal is greater than the rate at which an aquifer is re-charged from surface water intrusion, there is a risk of eventual exhaustion.

Groundwater use and over use can raise important equity issues, particularly in rural areas when, following increased consumption, the level of water tables has been lowered. Only the richer farmers or land owners can afford to sink deep wells and boreholes and to purchase the more powerful pumps necessary to abstract groundwater.

Based on the availability, resources are classified as renewable and non-renewable.

• Renewable resources: These are the sources which can be replenished over a period of time. An example is forest wood because wood can be grown by reforestation.
  
• Non-renewable: These are the sources that cannot be renewed and available in limited quantities. Examples include coal, nuclear, oil, and natural gas.
  

As ground water can continuously supply water resources it falls under the category of renewable resource. 

Freshwater sources include:

• Groundwater - Water found in shallow aquifers beneath the earth's surface. This water is generally found at depths up to 2,000 feet deep.
  
• Precipitation: It is nothing but the rain water which is an important source of fresh water. In fact it is the purest natural source of freshwater.
  
• Surface water - Water found in streams, rivers, lakes, and reservoirs.
  

 Dams are built not just for irrigation but for electricity generation, water supply for domestic and industrial uses, flood control, recreation, inland navigation and fish breeding. Hence, dams are now referred to as multi-purpose projects.

In India monsoon usually lasts from July to September. It is very irregular and unpredictable. India usually have no rains when needed and hence India requires highly sophisticated irrigation facilities and construction of reservoirs by which rain water can be stored and used all along the year. This is the major problem with Indian water potential though it has abundant rainfall. 

The geological structure of South India consists largely of hard crystalline rocks (peninsular shield), which makes digging wells difficult and expensive compared to the soft alluvial soil of the North.

• Karez is also called turpan water system. It is usually followed in China. Turpan's karez water system is made up of a horizontal series of vertically dug wells that are then linked by underground water canals to collect water.
  
• These are not followed in India.
  

• Sprinklers are used as irrigation tools that supply water to agricultural crops.
  
• It is very much useful as water is let out and sprinkled through small knobs. This checks wastage of water by seepage and evaporation.
  
• Apart from irrigation sprinklers are also used in industrial purposes.
  

In India monsoon usually lasts from July to September. It is very irregular and un predictable and hence India requires highly sophisticated irrigation facilities by which rain water can be stored and used all along the year. 

• Irrigation is the method by which water is collected, stored and supplied controllably when required by artificial means.
  
• All the given options like increase in salinization, groundwater depletion, etc., are not the outcome of irrigation projects. But sometimes reservoirs may result in floods due to loss of capacity in the reservoirs caused by sedimentation.
  

South India's geology features hard granite rock formations covered by thin soil layers. Traditional well-digging through this rock is extremely difficult and expensive. Tube wells requiring drilling equipment are more common, but still challenging compared to alluvial regions.

India's agriculture is heavily dependent on the monsoon, which is seasonal and often unpredictable. Irrigation is necessary to provide water during dry periods when rainfall is absent.

Irrigation is generally considered necessary in areas where annual rainfall is less than 75 cm, as these regions are prone to drought and water scarcity for crops.

In India, the irrigation of agricultural land is carried out maximum by Canals (29%). The longest canal in India is Indira Gandhi Canal about (650 km) this canal is also called Rajasthan feeder.