all about kolkata's water supply scheme from source to distribution network

1. By Isha Raman

2.  Kolkata: One of India's eight Metropolitan Cities and capital of West Bengal.
 Distance: 120 km from Bay of Bengal, on the banks of River Hooghly (Ganga).
 Population:
◦ Infrastructure Development: Extensive private and public sector projects, driving population influx.
◦ Water Demand: Rapid population growth has led to high demand for domestic water supply
Area
(sq. km)
Year Population Population
Density
3, 638.49
1971 7,420,000 2,039
1981 9,030,000 2,482
1991 10,890,000 2,993
2001 13,217,000 3,632
2011 14,112,536 3,879

3.  Water demand:
 2012: >293 MGD
 2026: >402 MGD
 Total daily potable water supply (in million litre): >1350 MLD that is 300 MGD
 Per capita availability of water per day (in litre): > 202 litres/per day
 Unaccounted water: > 35%
 Average supply hour: 8 hours
 Coverage of Household connection: 92.70%
 % of house hold covered by surface water: > 82.70%
 % of house hold connection by ground water: > 10%
 Public Access Standard Posts (in nos.): > 17,019
 Unfiltered water through street hydrants (in nos.): > 2000
 No. of reservoirs Present: > 7
 No. of reservoirs Present (under construction): > 14
 No of Booster Pumping stations: > 17+1 (Tala)
 No of Booster Pumping stations (under construction): > 5
 Length of distribution net works: > 5800KM

4.  Surface Water Sources:
 River:
 The western part of city follows along the right bank of river Hooghly.
 Hooghly River serves as the primary source of potable water, supplied by the Palta Water Works,
now known as the Indira Gandhi Water Treatment Plant.
 All surface water treatment plants are on the right bank of the Hooghly, part of the Ganges
Delta.
 Storage Reservoir:
 Tala water tank of Kolkata Municipal Corporation was built in 1909.
 It has the capacity to hold 9 million gallons of water.
 It is the largest overhead reservoir in the world.
 Except Tala there are many other reservoir.

5.  Subsurface Water Sources:
 Officially, 15% of Kolkata's water comes from groundwater sources, but in reality, it accounts for up to 25-30% of
household water usage.
 Central Groundwater Board (CGWB) allocates about 320 MLD of groundwater for domestic and industrial use in the
KMC area.
 The depth to the groundwater level in the confined aquifer ranges from 12.09 to 19.59m in pre-monsoon and 10.72 to
15.42m in post-monsoon periods.
 Groundwater withdrawal by KMC was 144.30 MLD in 2006 and reduced to 114 MLD in 2011.
 KMC aims to further reduce and discourage groundwater usage.
 Groundwater depletion may lead to land subsidence due to the underlying clay and sand layers.
 Changes in groundwater flow patterns over the years have created pressure troughs in the city, impacting recharge.
 The groundwater level near the sea has dropped by 15-16 meters over the past five decades.

6.  Water Quality Index (WQI) variations:
 Increases during monsoon and post-monsoon periods
 Remains relatively low during summer
 Factors showing strong correlation with pollution levels:
 BOD (Biochemical Oxygen Demand)
 Total coliform count
 pH
 Dissolved oxygen
 Total Dissolved Solids (TDS)
 Electrical conductivity
 Average pH of river water:
 Ranges from 8 to 9 throughout the year
 Principal Component Analysis (PCA) findings:
 BOD, total coliform, and turbidity vary together as a result of unregulated sewage water discharge from urban
local bodies in the river.

8.  Capacity of WTP:
Name Capacity (MGD)
Palta Water Works 242
Garden Reach Water Works 190
Jorabagan Treatment Plant 8
Watgaunge Treatment Plant 5
Jaihind Treatment Plant 30
Deep Tube Well 110

9. Hooghly
River
(Source)
Intake
Structures
Settling
Tanks
Filter Beds Chlorinators
Storage Tank
& Pumping
Station
Booster
Pumping
Station
Overhead
Tank
Distribution
Network
House
Connection

10. • Intake Structure: The system features one
intake jetty with two 600mm diameter
cast-iron intake pipes drawing water from
the River Hooghly.
• Boiler and Engine Room: It includes a
boiler and engine room equipped with a
chimney housing three 50 horsepower
(HP) engines. These engines were
responsible for lifting raw water from the
river to masonry settling tanks.
• Settling Tanks: Six settling tanks, each
with a plan area of 152 x 76 meters and
varying depths, were constructed to arrest
silt in the raw water.
• Slow Sand Filters: The system boasts 12
slow sand filters, each with a capacity of
4.54 million liters.
• Gravity Main: 42" cast iron gravity main.
• A new intake pumping station, additional
settling tanks, slow sand filter beds, a
separate water main to Tallah was
installed due to industrial, population
growth.

11.  Intake works at Palta:
 Treatment facilities in operation:
Year Withdrawal Capacity
(mld)
Discharging to Comments
Original Intake 1868 - - Now abandoned
Intake 1 1927 455 WTP 1 Installed with three 1350mm
dia. suction mains
Intake 2 1971 273 WTP 2 Installed with two 1500mm dia.
steel suction mains
Intake 3 2004 455 WTP 3 located adjacent to intake 1
Capacity (mld) Year System Components Observations
Treatment plant group 1 (WTP 1)
27.3 1868 Settling tank and slow sand filters Now being gradually phased out
455 1888 - 1977 Rapid gravity filters, Conventional clariflocculators, Final
settling tank
A new unit (91 mld) with plate settlers and rapid gravity sand
filters now under construction
Treatment plant group 2 (WTP 2)
273 1968 Conventional clariflocculators and rapid gravity sand filters Under operation with minor repairs done
Treatment plant group 3 (WTP 3)
91 1997 Pulsator clarifier and Aquazur filters Commissioned in April 1997
91 + 91 2004 Pulsator clarifier and Aquazur filters constructed as two
modules of 91 mld (20 million gallons per day) each
Commissioned in July 2004
182 2006 Plate settler clarifier and rapid gravity sand filters Commissioned in March 2006

12.  Storage and Reliability:
 Tala waterworks includes four separate pumping stations and ground storage
reservoirs with a total capacity of nearly 160 million liters (excluding the overhead
tank).
 Such substantial storage capacity ensures system reliability.
 Intermediate chlorination was introduced to maintain water potability after prolonged
storage and distribution through the network.
Development
Year
1868 - 1870 1888 - 1992 1992 - 1936 1957 - 1961 1997 – 2004 2008 - 2014
Diameter (inch) 42 48 60 72 62 64
Material Cast Iron Cast Iron Mild Steel
(riveted)
Mild Steel
(with
catholic
protection)
Mild Steel Mild Steel
(with concrete
jacket)
Type Gravity Pressure Pressure Pressure Pressure Pressure
Capacity (mld) 27 105 174 289 164 422
Comments Yet to be phased out
gradually
Installed by
microtunneling

13.  World's largest overhead water reservoir.
 Stores clean drinking water.
 Specifications:
 Supported by steel columns and girders.
 Dimensions: 33.5m high, 98m length, 98m width, 5.5m depth.
 Divided into four independent compartments for cleaning and repairs.
 Support components and tank weigh 44,000 metric tons; water weight: 36,000 metric tons.
 Total capacity: nine million gallons of water.
 Operational Efficiency:
 No separate pipelines for filling and delivery.
 Tala Tank activated when pumping engine at Palta couldn't meet heavy daytime demand.
 Automatically supplies water to town mains, ensuring that the supply matches the demand.
 Refilled during nighttime hours when demand is lower, using the same network of pipelines.
 delivers over 160 MLD of water at a rate of about 150 lpcd.

14.  Storage reservoirs at Tala waterworks:
Reservoir Year Capacity (million litres) Supply Pipe Diameter (inches)
Reservoir 1 1865–1868 and 1888–
1893
36·37 42 and 72
Reservoir 2 1955 45·46 48 and 72
Reservoir 3 1963–1965 31·82 48 and 72
Reservoir 4 1992–1995 45·46 64 and 72
Overhead tank 1909–1911 40·91 60
 Dual-Supply System:
 providing a separate unfiltered supply system alongside potable water.
 Advantages include resource optimization, loss reduction, energy
savings, alternative supply during emergencies, and sewer flushing.
 Unfiltered Supply System:
 serve a portion of the population during high tides in the River
Hooghly.
 Water Allocation and Charges:
 Implemented a system of water allocation and varying charges based
on the type of water use.
 Direct house connections for residents, while common standposts were
provided for economically disadvantaged sections of the population,
ensuring equitable access to water.

15.  Causes of surface water pollution
 Sewer Leakage & Wastewater Treatment Causes:
 Sewage leaks from the distribution network, contaminating surface water sources.
 Unprocessed sewage disposal into the Hooghly River.
 Human Causes:
 Direct dumping of waste and garbage into the Hooghly River.
 People using surface water for bathing, excreting, and domestic purposes.
 Water Transport & Other Causes:
 Fuel and oil spills.
 Immersion of idols in the river after festivals.
 Disposal of ashes from cremations.

16.  Solutions to surface water pollution problems
 Maintenance and Upgrades:
 Regular inspection of water and sewer pipe joints.
 Replacement of aging pipes with new ones.
 Industrial Effluent Monitoring:
 Frequent COD monitoring for industrial effluents.
 Ensuring BOD levels meet discharge standards at STPs.
 Infrastructure Improvement:
 Construction of new STPs in areas with direct river sewage disposal.
 Avoiding direct disposal of waste into the Hooghly River.
 Public Facilities:
 Building public lavatories for proper sanitation.
 Solutions to groundwater contamination problems
 Groundwater Monitoring:
 Regular assessment of arsenic and heavy metal levels in Deep Tube-well water.
 Waste Disposal Management:
 Establishing sanitary landfills at garbage disposal sites to prevent hazardous chemical leaching.