Tag: tanks and fisheries

Irrigation in India includes both major and minor canals from Indian rivers, tanks, and other rainwater harvesting projects for agricultural activities. The Economic Survey of $2018$ states that agriculture in India even today relies heavily on weather because the percentage of irrigated land in India is $34.5\%$ as per the survey.

Based on the availability of surface (river) and groundwater, relief, soils, and climatic conditions, different means of irrigation are utilised in India. The conventional means of irrigation include wells, tanks and inundation canals. 

It is the most advanced and efficient method of irrigation. It is usually used to irrigate fruits and vegetables. It helps in water conservation.

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.

Excessive use of water for cultivation of rice and other crops leads to environmental degradation, fall of groundwater level and threatening to the sustainability of agricultural development.

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. 

• A dam is a man-made structure built across a river.
•  Most dams are built to control river flow, improve navigation, and regulate flooding.
  
• Dams are made from earth, rocks or concrete and are usually constructed on rivers to store the water in a reservoir.
  
• All rivers contain sediments: a river, in fact,can be considered a body of flowing sediments .
•  When a river is stilled behind a dam, the sediments it contains sink to the bottom of the reservoir. 
  
• The amount of sediment carried into a reservoir is at its highest during floods .
  
• The construction of a dam blocks the flow of sediment downstream,  and increased sediment build-up in the reservoir.
  
• This triggers floods,

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.