O-Level Geography Chapter 3 Water Resources Use of Fresh and Ground Water

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Uses of fresh water

Ground water the water beneath the surface of the ground, consisting largely of surface water that has seeped down: the source of water in springs and wells

Irrigation systems

Small Scale Systems Traditional methods

Karez

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 from the water surface runoff from the base of hills or mountable beneath a mountain/hill slope.

The canals channel the water to the surface, taking advantage of the gravity. The canals are mostly underground to reduce water evaporation. Vertical wells are dug at various points to tap into the groundwater flowing down sloping land from the source. These vertical wells are also used for maintenance of Karez.

Persian Wheel

This is a system of continuous supply of water and irrigated a comparatively larger area. in this method blind folded Bullock is used to move a horizontal wooden wheel. This wheel is geared to a field is vertical wheel at the distant end of the shaft. This carries the vertical metal attached to a chain of bucket. The bucket raise water from the well and is spill their contents into the channel landing to the irrigation field.

1. Simple lift irrigation:

It is mostly practiced in the remort and back ward villages of Pakistan in this method people take out water from a Shallow well with the help of a rope and bucket. Through this system farmers can irrigate a small piece land ,it is a time consuming method of irrigation.

2. Shaduf

In the shadows system water is drawn from a Shallow well river organised by a bucket which is attached to a wooden pole on one side on one side and weight heavy rocks on the other side a small area a small can be irrigated by this method in some of the places also use of pulley to take water out from a well.

Charsa

In this method animal powder is used to pull water from the well. in this method a bucket is suspended by a rope and with the help of animals people take out water from slightly deep Wells.

1. Seasonal canals

these canals are only active during the rainy season they are mostly in the old flood plains on Punjab and Sind these canals are also found near the dam reason

2. Inundated canals:

Long canals taken from large rivers are called inundation canals .They received water when the river is highly enough and especially when it is in floods.

Tank irrigation Tank irrigation is practiced by constructing mud banks across small stream to make a small reservoir which collect excess water during the rainy season These reservoir are sometimes covered with plastic and the water is used for irrigation domestic purpose live stock etc.

Modern methods

1. Perennial canals

These canals run throughout the year and are linked to dams and barrages for continuous supply. They irrigate large pieces land.

2. Tubewell

These are electrical or diesel powered machines which are used full water from the depth of 92 metres or more to irrigate large from lands. These also help in lowering the water table where by protecting the land from water logging and salinity.

3. Sprinklers spray irrigation

Sprinklers our devising attached to the public water supply or tubewells. They are centrally located in the field of irrigate/ water the plant mainly in Orchard and Gardens it is an efficient method of irrigation as water is not wasted but it is very expensive. This is rarely used to irrigate agricultural crops.

4. Tanker irrigation

This is the most expensive method of irrigation. Tankers collect water from small water bodies( in land) and supply them to household in case of emergency.