METHODS OF LIFTING WATER
- Water is to be lifted from wells before it is used for irrigation.
- Sometimes water may have to be lifted from canals, streams, and rain water filled in low lying areas to use it for irrigation.
- The methods of lifting water vary depending on the source, depth, quantity to be lifted and availability of power.
- The following are the various methods of lifting water:
- Rope, pulley and bucket method
- Dhenkli or lever or let method
- Mote, charas or leather bag method
- Nar, Rahat or Persian wheel
- Basket method
- Doon method
- Archimedian screw method
- Pump method. Each of the above methods have been briefly discussed as follows.
1. Rope-pulley and Bucket Method.
- This method consists of a pulley over which a rope is passed.
- A bucket is tied tothe end of the rope hanging in the well and other end of the rope is held by a man standing at the surface.
- The bucket is lowered into the well, and pulled out with help of rope and pulley after being filled with water.
- This method is suitable only when well is not deep and quantity of water to be lifted is small.
2. Dhenkli or Lever Method.
- This method consists of a lever-rod rocking over the top of a vertical upright post.
- A suitable counter weight is tied on one side of the lever and a bucket is suspended from the other end into the well.
- Length of the lever rod on the side of the bucket is longer than that on the side of counterweight.
- The bucket when filled is lifted a little to set the lever action.
- The bucket full of water moves up automatically due to moment of the counter weight.
- When bucket reaches the ground it is used for irrigation and empty bucket is again sent into the well.
- But this time lever will have to be pulled against the moment of counter weight so that bucket may reach water and get filled with it.
3. Mote, Charas or Leather Bag Method.
- This method has a pulley fitted on the well on two uprights.
- A large leather bag also called Moteor charas is tied at one end of the rope.
- The other end is used tolift filled leather bag of water. In this
- case lifting force is applied by apair of bullocks.
- This method is used when water level in the well is quite deep and irrigation is to be provided to a little larger area.
- About 1.5 hectare land can be irrigated by this method. In this case bullocks move on straight inclined path
4. Nar, Rahat or Persian Wheel.
- This method was very common in Northern India.
- Still it can be noticed in U.P., Haryana and Punjab.
- Persian wheel consists of an arrangement of wheels and gears run by bullocks.
- An endless chain of several buckets is put on a big wheel. The lower end of chain of buckets remains under well water.
- As the wheel is moved by bullocks through a system of gears, the buckets filled with water come to the top and discharge water into a trough from where water flows to the fields.
- In this case pair of bullocks moves on circular path.
- By this method 3–5 hectare of land can be irrigated.
5. Basket Method.
- This method is used for lifting rain water from low lying areas to the near by fields.
- By this method water can be lifted for 60 to 80 cm only.
- The basket can be worked by one man or two men.
- The basket has ropes.
- It is filled and discharged by swing motion.
- Like Basket method it is also used for lifting water for small heights of say 1 m.
- Doon is a wooden or metallic channel closed at one end and open at
- the other. Itis supported on a wooden bully which acts as its fulcrum. A doon in action is shown in Fig. 8.16.
- This method is very much prevalent in Bengal.
7. Archimedian Screw.
- It consists of a cylinder in which a screw is fitted.
- The cylinder is kept inclined with its lower end immersed in water to be lifted. Upper
- Archimedian screw.
- end is kept abutting the field to be irrigated. When screw in the cylinder is rotated, it lifts water as water enclosed in screw cannot go back. In this case also lift of water seldom exceeds 1 m.
- Inclination of the cylinder is about 30° with the horizontal.
- There are several types of pumps which can be used for lifting water.
- Pumps may be divided into
(1) constant displacement and
(2) variable displacement pumps.
- Constant displacement pumps deliver the same volume of water against any head within which they can operate.
- Variable displacement pumps deliver water in volume varying inversely with the head.
- The use of constant displacement pumps is confined to places where discharge is low.
- Variable displacement pumps which are mostly used for pumping water may be divided into the following classes.
- Centrifugal pump
- Bore hole type pump
- Jet pump 4. Air lift pump.
1. Centrigugal Pump.
- This pump lifts water by creating the required pressure with the help of centrifugal action.
- The maximum suction head under which the pumps can practically work effectively is about 6 m to 8 m.
- Hence this pump can be used only at places, where the fluctuations in water table plus the depression head is limited to about 8 m.
- For larger values the bore hole type pump is to be used.