water resources Flashcards
hydrological cycle
Water = natural resource
Water that reaches the ground from the atmosphere may fall as rain, snow or hail which are all included in the term precipitation.
Some of the water runs off the earth surface as rivers & streams draining into lakes and the sea. The rest is either utilized by plants or soaked into the ground
Water is returned to atmosphere as water vapors through evaporation from surface water and by transpiration from plants
As water vapor rises, it cools to form water droplets. This system is called ‘condensation’
This is the hydrological cycle
Most effective source of water in Pakistan are the rivers, esp river Indus and its tributaries.. Rainfall is scanty and its usefulness to farmers is limited, groundwater can only be utilized in areas where water tables are high, however water from rivers is available all year round thus they constitute the most important source of water supply
uses of water
Main uses of water: agricultural, domestic & industrial
Most important use of water in Pak is for agriculture
Present: over 69% of water used for irrigation purposes
Domestic uses of water:
Drinking
Cooking
Washing
Sanitation
Industrial uses of water:
Pharmaceutical industry:
Injections
Syrups
Drips
Chemical industry:
For making:
Acids
Liquid bleach
Solutions
Textile industry:
Washing
Bleaching
Dyeing
Printing
Water supply is one of the most important factors in location industry
Wet point locations (near to sea, lakes, rivers) are preferred for many types of industries
Many heavy industries in pak are located near rivers or close to arabian sea
Amount of water used varies from industry to industry i.e large amount of water is required to produce steel while pharmaceutical industries consume little water
Agricultural uses of water
Irrigation:
Irrigation is the artificial supply of water to the land to encourage plant growth
V important in arid regions but also used in humid regions to improve yields
In Pak 75% of cultivated area is under irrigation
Irrigation system of pak developed from traditional lift irrigation to complex canal system of today
Paks agriculture mainly depends on irrigation
why we need irrigation
most areas of Pak experience arid to semi-arid conditions with aridity incready from north to south
Ineffectiveness of rainfall:
High variability in distribution
Long dry spells
Rainfall in heavy showers increases surface run off
High variability in timings of rainfall
Small number of rainy days
High rate of evapo-transpiration
Low amount of rainfall
Monsoon winds bring most of the rainfall.
These rainfalls are extremely variable in timing and distribution
Rainfall mostly occurs in heavy showers → useless for farmers as the land either absorbs too much or the water drains away too quickly
After rainy season there are long and frequent dry spells
Such conditions demand a well developed irrigation system
Water stored behind dams and accumulates behind barrages on the river Indus and its tributaries to provide it to the crops throughout the year through perennial canals
Tube wells installed in some areas to make use of sub-soil water
Traditional irrigation methods i.e persian wheel, charsa and karez
shaduf system
Water is drawn from a well, river or canal by a bucket which is attached to a pole on one side and a weight on the other
Small area can be irrigated by this method
Shaduf system rarely used today
charsa system
Uses animal power to pull water from a well
Not used by many farmers now
persian wheel
Provides continuous supply of water
Irrigates larger area
Animal powered, turns a horizontal wooden wheel geared to a vertical wheel at the far end of a shaft. This carries a vertical metal wheel which is attached to a chain of pots. These raise water from the well and spill it into a channel that leads to the fields
karez system
Karez = horizontal underground canal in the foothills that brings underground water to the surface
Canal = several kilometers long
Dug by a group of people who then share the water for irrigating their crops
Vertical shafts dug down to the canal so that it can be cleared and repaired to prevent any blockage in the flow of water
This is an old system practiced only is Balochistan where water is scarce and rate of evaporation is high
By building the canal, evaporation losses are minimized
Inundation of canals
Long canals taken off from large rivers
Receive water when the river is high enough esp when it is in flood
diversion channels
Diversion channel is a narrow inundation canal
Common in highland areas, esp in northern mountains, where they divert river water often high up on valley sides, to small terraced fields.
tank irrigation
Practiced by constructing mud banks across small streams to make a small reservoir which collects excess water during rainy season
uses and effectiveness of conventional methods of irrigation
Have been used for centuries
Small-scale subsistence farms still use the charsa or persian wheel
Large farms = shift from conventional to modern methods
Disadvantages of conventional methods:
Irrigated limited areas as only a small amount of water can be obtained
Require manual labor or animals and are more time consuming
Difficult to build, maintain and use (i.e Karez)
Inundation canals only flow during rainy period or when water from melting snow and ice enters the rivers
modern systems
Perennial canals:
Linked to dams and barrages to provide water throughout the year
Irrigate a vast area
Extensively used in Pak
Initial cost is high but water is made available throughout the year
Schemes may provide for flood control and HEP development
Tube wells:
Are diesel or electrically operated pumps that can raise water from depths of 92 metres (300 ft) or more to irrigate farms of more than 1000 hectares
Help to lower the water table, protecting the land from waterlogging and salinity
Some modern tubes = solar powered
Indus Water Treaty
1947: with creation of Pak, province of Punjab was divided into east and west Punjab
Headworks of the canals of Sutlej and Rav remained in India as the share of India while the drained areas became part of Pak.
1948: India threatened to stop the water supply from these headworks, which would have endangered the prosperity of the Indus plain
Water dispute eventually resolved through the mediation of the world bank
Sept 1960: an agreement known as the “indus water treaty” was signed
Under this treaty: Pak received exclusive rights to the water of the three western rivers (Indus, Jhelum, Chenab) and India to that of the eastern rivers (Ravi, Beas, Sutlej).
During transitional period till 1973 India agreed to supply water to Pak
During transitional period Pak was expected to construct two storage dams, five barrages, one gated syphon and eight link canals
Construction cost was to be met by Australia, Canada, USA, UK, West Germany & New zealand
India was also expected to pay some of the cost
Remaining expenditure was to be met by Pak
WAPDA (water and power development authority) of Pak entrusted to supervise the projects
dams, barrages and link canals
Dams
Mangla dam
Tarbela dam
Barrages
Chashma barrage
Rasul barrage
Maraia barrage
Qadirabad barrage
Link canals
Marala - ravi
Rasul - qadirabad
Qadirabad - balloki
Balloki - Sulaimanki 1
Balloki - Sulaimanki 2
Mangla dam
Located on river jhelum
One of the longest earth-filled dams in the world (3100m at crest)
Multipurpose project designed to:
Control and conserve flood waters of Jhelum for irrigation
Generate hydroelectric power
Mangla lake:
Serves as a reservoir of the dam
Developed as a fishing centre and tourist resort
Tarbela dam
Built on the Indus at Bara near village of tarbela
30 km from town of attock
When Indus leaves himalayan foothill and enters potwar plateau, water is stored in reservoir of the dam
143 metres high
Reservoir area: 243 sq km
Storage capacity: 119 billion cubic metres of water
9 huge gates to control outflow of water
Worlds largest earth filled dam
The second project constructed under Indus water treaty
2 big spillways (impressive features)
Siltation = major problem
small and large dams
Large dams: higher than 15 metres
Pak has 2 dams in this category (tarbela and mangla)
small:
irrigate local areas only
construction time less and yields quick results
supply little or no electricity
silting problem easier to solve
low initial investment, low maintenance cost
Large:
irrigate vast area
major suppliers of HEP
silting problem difficult to solve
more imp for flood control
large scale evacuation
diameter Bhasha dam
Multipurpose dam project on river Indus in KPK and gilgit baltistan
When completed, it will be one of the tallest dams in the world (272m high, reservoir covering area of 100 km square)
Will produce 4500 megawatts of hydroelectricity
Likely to extend life of tarbela dam by 35 yrs (by removing sediment from the Indus upstream of tarbela)
Will significantly reduce frequency and extent of river flooding
barrages
Are very long structures used for irrigation and flood control
Construction cost of barrage = significantly less than that of a dam
Unlike dams which require mountainous terrain, barrage can be made in flat areas
Encourage human settlement, commercial and industrial activities
Number of barrages on river Indus and its tributaries (larger ones on lower Indus plain)
Width of river Indus at Sukkur = 1.6km
Size and capacity of barrage depend on width of river
siltation in reservoirs
When rivers leave foothills of the himalayas, they carry a large quantity of silt eroded from the mountain areas
This is deposited in the plains of Punjab and Sindh
Siltation = menace that can destroy the purpose of dams and barrages
Tarbela dam: inflow of 0.5 million tons of silt = 132 ft mound 8 km from the powerhouse
Water-storage capacity at Tarbela and mangla dam is decreasing due to siltation
Storage capacity of chashma barrage has come down to 42%
Before tarbela chashma and jinnah dams/barrages were built, river Indus at kalabagh carried approximately 1115 tonnes of silt and sediment per sq. km
Causes
Abundance of silt eroded from Karakoram, Hindu kush and Himalayan mountains
Deforestation → soft soil
Rivers form deep narrow valleys in mountainous areas. Most eroded material is washed down to plains and piles up in reservoirs of dams
Effects
Blockage of canals
Weakens dam foundations
Reservoir capacity is reduced → lower flow of water → affects generation of hydroelectric power → reduces amount of water for irrigation
Flow of flood water is hampered → can cause heavy damage to dam due to mound of silt which block the flow of water
Control
Large scale afforestation (esp in foothills of himalayas)
Cement canal embankments for easier cleaning
Silt traps before water enters dams
Regulate flow of water e.g by operating reservoir at lower lever during flood and allowing free flow during low flow season to wash out sediment
Raise dam height to increase reservoir capacity
waterlogging and salinity
Canal irrigation system accompanied by many problems eg waterlogging and salinity
Inundation canals = water for crops available only in summer, balance bw precipitation and evapotranspiration kept water table low
Perennial canals = water available throughout the year → rise in water-table → brought salts in the soil to the surface
Water evaporates, salts deposited on surface of soil making land unsuitable for farming
Rise of water table to surface = waterlogging
Appearance of salty patches = salinity
Control:
Lining of canals to control seepage of water
Canal closure on temporary basis
Installing tubewells to lower water table
Planting eucalyptus trees bec their roots absorb water from water table
Surface drain
Detailed plan framed in 1959 to solve this problem
Divided Indus Basin into 28 zones of reclamation
Program = SCARP (salinity control and reclamation project)
water as a resource for economic development
Agriculture
Agriculture, which depends on water from irrigation and rainfall, is the main income-generating sector in Pak
Crops i.e sugarcane, cotton, wheat, rice etc. are grown here, which meet domestic demand and contribute to 20% of GDP
Around 40% of labour force employed in agriculture
Agro based industries i.e cotton textiles, food processing, leather etc use agricultural products as raw material. Their final products are exported → earn foreign exchange → increase in GNP and generating income for the country
Industries
Used in processing and manufacturing industries (steel, HEP generation, pharmaceuticals etc.)
Such industries = vital for economic development as they provide employment for industrial labour force & meet local demands for industrial goods
Provide electricity for domestic and commercial users
Export of industrial goods – foreign exchange → contributes to GNP and GDP
Health
Clean water is vital for survival of population
Healthy people → more productive at workplace → contribute more to economic development
management of water resources
water scarce in Pak
fair distribution of water among provinces is essential
water accord signed in 1991 and IRSA was to carry out its implementation
constant droughts and institutional mismanagement = not followed = disputes bw provinces = fall in agricultural output
water supply issues leading to conflict
70-80% of Indus water comes from glaciers
glaciers melt away = less water in Indus
negative impact on irrigation
international lvl:
impact of IWT:
due to iwt pak lost control over 3 eastern tributaries (Ravi, Sutlej and Beas)
reduced water to upper of indus plain
effort to solve problem by constructing Mangla and Tarbela reservoirs to divert water fro western tributaries of Indus system to Eastern Punjab but due to increasing demand from farming and other users = shortage of water in upper indus plain
violation of IWT by India:
India constructed several dams on Indus and other rivers of Pak
Pak opposed these dam projects eg Kishanganga project, Baglihar dam, Neelum-Jhelum power project on Western tributaries of Indus system
these projects release less water for Pak as well as less HEP generation (bec it requires high vol of water in rivers)
provincial:
Punjab and KPK:
conflict: construction of the proposed Kalabagh dam on river Indus
KPK concerns:
i) most of the water stored in Kalabagh dam may be diverted to Punjab thru link canals (Punjab agreed not to construct canals to irrigate Punjab)
ii) electricity generated from dam will be used in much of Pak thru national grid system according to requirements of areas = KPK gets no extra electricity
iii) project = large scale evacuation of areas included in KPK. fear that affected ppl will not receive rehabilitation/ compensation (30k)
iv) large areas of Noshwera district would be submerged by the dam and even wider areas would suffer from waterlogging and salinity as has occured as a result of the Tarbela dam
Punjab and Sindh:
Sindh in LIP = fear abt distribution of Indus water bw Sindh and Punjab
Sindh always complained bat receiving a smaller share of water from Punjab for its Rabi crops
Kalabagh dam strongly opposed by Sindh cuz:
i) water availability for SIndh would be further reduced as water stored in the dam might be used to irrigate lands in Punjab and KPK
ii) coastal regions of Sindh require constant flow of water down the Indus into the Arabian sea so that the flowing water can keep the sea water from intruding inland as such seawater intrusions = wast areas of Sindhs coast into an arid saline desert, destroy Sindh’s mangroves and reduce fish population
iii) would reduce flow of the Indus downstream at Kotri Barrage near Hyderabad = ore water shortages in Canal irrigated areas of lower Sindh
iv) silt deposition = reduced storage capacity = reduced water supply to machester lake and Haleji lakes in lower sindh
Users:
agriculture 69% Industry 23% domestic 8%
