Ans: Water Resources of Pakistan and the Existing Irrigation System:
Sources of irrigation:
Pakistan is located in that region of monsoon climate where there is less
rainfall. In Pakistan agricultural development depends upon resources of
irrigation. The most important resources of irrigation are rivers. Other
resources include tube wells, Karez, wells and springs etc.
Canals:
In Pakistan, 80% of agricultural land is dependent upon stream water. Most
of Pakistan’s streams are found in Punjab. This canal system is composed of
big and small dams, barrages and link canals. Most of these streams are
perennial which flow throughout the year. Other canals are seasonal, which
flow only in the monsoon season. When snow melts on the mountain, water
increases in the rivers. The flood water is then released into the streams,
Important streams have been diverted from River Ravi, Chenab, Jhelum,
Sutlej and Indus, which irrigates different regions.
Rain:
Rain is a natural source of water. In Pakistan the monsoon rains are more
common. Water from rainfall on mountains and melting glaciers gathers in
rivulets and keeps them flowing throughout the year. Barren areas and their
production is more dependent on rain than canal irrigated areas, Tarbela and
Mangla are important irrigational dams in which not only lakhs of acres feet
water is collected but also cheap hydro electricity is produced. Besides these
two reserves Chashma Barrage has 5 lakh acre feet reserves of water as
well.
Tube wells:
To compensate for the scarcity of water from streams, tube wells are used to
obtain water from below, the ground. There are nearly 1.2 million tube wells
in the country. Water is obtained from a depth of hundreds of feet below the
ground with the help of electric motors or diesel erigines. Most of the tube
wells are found in Punjab. Water from tube wells is not suitable for crops as
it produces water logging and salinity in the land. Due to the shortage of
water from canals, farmers are forced to use this water.
Karez:
Below the surface of land, small canals or covered water ways are dug
which are called Karez. Underground canals in Baluchistan are used for
irrigation. Water is collected in underground streams in the mountain valleys,
This water is then transported to the land to be cultivated so as to prevent
water loss through evaporation. Such underground streams are found in the
base of mountains. Karez is mostly made in those areas where water is
scarce and the process of evaporation is more. Groups of people make
Karez so that water can be used and not lost through becoming water
vapors. To keep such underground canals clean, blocks are placed at
intervals (below the ground), which can be removed when necessary for
cleaning purposes…
Wells:
Wells are the most ancient method of obtaining underground water. In
Pakistan, the areas where canals are not found, wells are dug. Persian
wheels are placed on these wells and water is then transported to fields.
Wells are not very deep. During monsoon season the water level rises in the
wells due to underground water. During droughts underground water level
falls and the wells become dry.
Springs:
An underground water source which emerges naturally above the surface of
land is called a spring. In the mountainous areas in Northern Pakistan, there
are countless such springs. They are the most important source of water
there. These springs fulfill a small part of the water requirements for
domestic and farming purposes. Sometimes spring are found naturally in
desert areas.
System of Irrigation:
Pakistan has a vast and strong system of canals. This system comprises of
big and small dams, barrages, irrigational and link canals. There are 3 types
of canals in our country
Perennial canals:
These canals provide water throughout the year for irrigational purposes.
Upper Chenab Lower Chenab, Upper Jhelum, Lower Jhelum and Lower
Ban Doab are important perennial rivers.
Seasonal canals:
Rivers which only flow during the monsoon season or summer season are
called seasonal rivers. When snow melts in mountainous regions, the
increased water level in rivers releases water in these canals in winter
season, these rivers are not functional. The Bahawal and Qaimpur canals
emerging from Islam Barrage located on River Sutlej and all the canals of
Guddoo Barrage are seasonal
Flood canals:
These canals have water released into them only at the time of severe floods
so as to stop the destruction caused by floods. In summer and monsoon the
water level rises in rivers and heavy floods raise water levels to dangerous
extreme as well. To protect the barrage from harm, water is then released
into these canals. Many streams enterging from River Indus and Chenab
belong to this type.