WATER RESOURCES (Notes)

                  WATER RESOURCES 

                         NOTES

Sources of water:  (i) Surface water  (ii) Groundwater

Surface water:The water which is found on the land surface.

                          Example: River, Ponds, Lakes,etc.

Groundwater: the water which is found underground( i.e) well water

Why we need to conserve water?

Ans:We need to conserve water for following purpose:

1.Due to overexploitation the underground water had led to lowering of water table.

2. Due to increase in population had results in water scarcity.

3. Irrigation utilises 90% of total fresh water and thus there is again  a scarcity of water.

4. Surface water like lakes and ponds are polluted and thus it is not  used without adequate treatment .

5.Due to deforestation the water table had been lowered and thus causes scarcity of water.

How can be conserver water?

Ans: We can conserve water through rainwater harvesting ,adopting water saving technologies, encouraging watershed development, water recycling and preventing the pollution of water.

 What is Rainwater harvesting ?

Ans: Rainwater harvesting is the collection and storing of rainwater of future use .

These method also help in

 (1) harvesting surface and underground water

 (2) It helps in preventing loss of water through evaporation and seepage .

What is Watershed Management ?

Ans: Watershed Management refers to the efficient management and conservation of both the surface and groundwater resources.

These method helps in 

(1)Recharging of groundwater 

(2)helps is maintaining  the water level.

Ø  The Central Government has started a watershed development project ,called ‘Haryali’ .This aims at enabling the rural people to conserve water for irrigation, drinking, fisheries and afforestation.

Why we need to harvest water?

Ans: This is because rainfall in India occurs in short spell of high intensity because of high intensity and short duration of heavy rain , most of the rain falling on the surface tends to flow away rapidly, leaving very little for the recharge of groundwater.

Water Harvesting Mechanism

1. Catchments: The catchment of a water harvesting is the surface which receives rainfall directly. Example: paved area, terrace, etc

2. Conduits/Conveyance: Conduits are the pipeline or drain that carry rainwater from the catchment to the harvesting system.

3.Storage facility: Rainwater need to be stored in storage container like RCC(Reinforced cement concrete), masonry or plastic water tanks.

4. Recharge facility: These can be done through any suitable structure like dugwell, borewells,etc.

                               IRRIGATION

Irrigation refer to the process of watering of agricultural plants through artificial means from wells. Tanks, tubewells, canals, etc       

Why is Irrigation needed?

Ans: Irrigation is needed because of the following ways:

(1)Uncertainty of Rainfall

 (2)Uneven distribution of Rainfall 

(3)Crop Requirements 

(4) Nature of the soil

 (5) To Utilise River Water Effectively 

(6)To maximise Production

Means of Irrigation

1.Wells: A well is a small hole dug in the surface of the earth to obtain water from subsoil of irrigation and other purposes.

Areas where well irrigation it mostly used are: Uttar Pradesh, Goa, Punjab, Haryana, Bihar, Rajasthan, Gujarat, Maharashtra, Madhya Pradesh, Andhra Pradesh, Karnataka and Tamil Nadu.

The water from wells can be lifted for irrigation in a number of ways:

1.Persian wheel method: It is mainly used is Western Rajasthan.It is party submerged vertical wheel with buckets attached to the rim. As the wheel is turned by draught animals rotating a geared horizontal wheel, the bucket are filled and emptied into a trough above, which carries the water to  crop-sown fields.      

 2.Lever Method: It is used in Bihar and Andhra Pradesh. It is very economical and efficient method of lifting water from shallow wells to a height of 3.5m to 4.5 m.The lift consists of a strong log laid across a fulcrum , a bucket attached to the long ar5m by means of a bamboo or a rope and a heavy weight attached to the other side of the log.When the bucket is full one person gently releases the rope and the bucket comes up as the stone gose down. The bucket is emptied into the field channel and again lowered into the well.

3.Inclined plane method: This method is also called ‘mhote’  +.In this type a pair of bullocks move down from the slope (inclined plane) specially constructed from the wall of the well, a bucket or a lether bag which is discharged into the connecting channel pulling from behind.The rope goes through pulley in this process.After discharging the water, the bullocks walk up the slope until they reach the top by which time the bucket reaches the surface of water and gets filled. The process is repeated again and again to irrigate the fields.

Advantage of Well Irrigation

1.Wells can be dug in low cost.

2.It is dependable sources.

3.By the use of pumps and wells the water can be lifted even from a greater depth.

4.Rain water can also be harvested.

Disadvantage of Well Irrigation

1. It cover very large area.

2.It is difficult to dig wells on hilly areas.

3. It will be a waste if the well water becomes brackish.

Tubewells:- It is a deeper well at a depth of 20-30m from which water is lifted up with the help of power driven pump to be used by man.

Advantage of Tubewells:

1. It is independent source of irrigation.

2. It can irrigate over large area.

3. Bring up clean water.

4. It cannot be dried up as it is dug up upto permanent water table.

5.It requires very less area.

Disadvantage of Tubewells:

1. It is expensive as it requires continuous electric supply.

2. It will be a waste if the tubewell water becomes brackish.

3. Excessive use of tubewells lead to depletion of underground water.

Canals : These are of Two types(i)Inundation Canal

                                                    (ii) Perennial Canals
Canals are widely used in Rajasthan

(i)Inundation Canal:- These canals are taken out directly from the rivers without constructing any barrage or dam.

Therefore these canal have limited use.

(ii)Perennial Canal:- These canals are taken out from the perennial rivers by constructing barrages or dams to regulate the flow of water.

Advantages of Canal Irrigation:

1.  Rain water can be harvested .

2. It had removed rainfall deficiency from dry areas like Rajasthan.

3. It can Irrigate larger area from state to state.

Disadvantages of canal irrigation:

1. It takes very large area.

2.Water gets logged up.

3. Water becomes unproductive.

4. Requires continuous electric supply. 

Tanks: This are natural depressions which are widely found in Tamil Nadu.

Advantages of Tank Irrigation

1. Helps to Irrigate large amount of cultivated areas.

2. Cheaper to construct.

3. It can be used in aquaculture .

4. It utilize the rain effectively.

Disadvantage of Tank Irrigation

1. It is expensive as it requires continuous electric supply.

2. Tanks get silted up.

3. When monsoon fails tanks get dried up.

4. It requires larger area.

5. Water also get evaporated.

6.Tanks get waterlogged.

Why southern India has Tanks?

Ans: There are three main reasons they are:

1. Since southern India river are seasonal.

2. Southern India lies in Plateau region.

3. Presences of hard rocks or impermeable rocks dose not help to dig wells or tubewells therefore people uses Tanks

Drawbacks of conventional methods of Irrigation:

1. In fields 10-15% is used to make wells ,tubewells, Canal or tanks.

2.Water is not properly utilized.

3. The fields get waterlogged due to low areas.

4. Evaporation of water takes place.

5. It also causes siltation of water.

Modern Irrigation Methods

1.Furrow Irrigation: In this type of irrigation the water poured on the fields is directed to flow through narrow channels dug between the rows of crops, instead of evenly distributing the water throughout the whole field.

* It is mainly used for the cultivation of vegetables.

2.Spray Irrigation: In spray system a long hose is set to a water sources on one side on the other side the water is released through spray guns to the field.

*It is used for cultivation of vetetables.

3. Drip Irrigation:- In this system a perforated pipes are placed between rows of crops or buried  along their roots lines and give water directly on to the crops.

*It is mainly used to cultivate fruits and costly vegetables.

4. Sprinkler Irrigation: In this method of irrigation a pipe fitted with a nozzle on the top is used through which water is sprayed directly to the required plants.

*It is used to cultivate crops.

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