Text & Visuals | Abdul Rehman
The provision of safe water supply has remained an important concern of all responsible governments. At the time of advent of subcontinent by the British, there was serious outbreak of cholera in the towns and cities of the subcontinent. A large number of military personals died. The civil surgeons were asked to check the quality of water from its sources and in this regards several reports were published describing the quality of water. At the same time water supply schemes were prepared for all major towns. I would like to present the important case study of water supply in Karachi based on the lengthy paper “The Karachi Waterworks” written by its designer James Strachen. The purpose of this paper is draw lessons from the basic design concepts taken in to consideration and our way forward to combat the current situation.
The paper begins with the comprehensive analysis of geography of Karachi including description of Malir and Lyari rivers, their origin, the rainfall, different torrents which joins them and availability of the water. (Fig.1) It was mentioned that although the Malir River is dry for grater part of the year, yet water is readily available and can be obtained any time in the sandy bed by digging down a few feet below the surface. At a depth of 10 to 30 feet below the bed, water is plentiful. The only sources of water supply before the project were few wells in the gardens and shallow wells in the bed of the Lyari River.
The quality of water in Karachi has remained an important concern of the British since their conquest of Sind. Sir Charles Napier was of the opinion that the want of good drinking water in Karachi was the one great drawback to the place as large military stations. Since that time a number of schemes have been proposed and considered. These included the schemes of Col. Baker, in 1845, Capt. De Lisle, in 1854, John Brunton, in 1860, Mr. Newnham, in 1864, Colonel Merriman, in 1868. The major problem in the implementation of these schemes was the non-availability of the funds. Eventually, it was intimated to the Municipality that the work was of the nature with which the government could not be concerned, further than to grant permission to the municipality to raise a loan for the purpose.
In 1873, James Strachan, the author of the said paper, took the charge of Municipal engineer and brought the subject prominently before the Municipal Commissioners. After having carefully considered the various proposals made from time to time he submitted a scheme that was finally implemented. (Fig. 2) The majority of the earlier schemes proposed the Malir River water as source of supply, but not until 1868, when Colonel Merriman carried out important and conclusive tests on the underground capabilities of that river. The test consisted in ascertaining, by means of pumping, at what level below the dry bed of the river 1,200 gallons of water per minute could be obtained, this being the quantity necessary to supply Karachi with about 22 gallons daily per head of population reckoned at about 80,000. The excavations of the trial wells was carried down to the depth of 10 feet below the water level, or twenty four feet below the surface bed of the river, and a trench 180 feet long by 9 feet wide to a depth of twenty feet was excavated below the surface bed. The pumps employed were centrifugal pumps and found that these, when throwing over 1,200 gallons per minute, failed to reduce the water in the wells below 6 feet under the water level. It was further noticed that on the engines being stopped the level of the water by the gauges in the wells and trenches rose from 5 feet in depth to 4 feet in nine and half minute, equivalent to the supply of 1272 gallons per minutes, or rather more than what was wanted. It was recommended that top of the main delivery pipe should be laid at the level of 6 feet below the water line.
In the previous schemes it was proposed to connect the wells with distribution reservoir by pipes, but due to high price of iron, Strachen resolved to take advantage of excellent stone, easily procurable in the neighborhood, to construct a masonry conduit, instead of using cast iron pipes. To accomplish this, another site was chosen two miles higher up the river at which earlier experiments was carried out by Col. Marimann. The Municipality gave a go ahead and asked him to prepare detailed plan and estimates for approval of the government. These were in due time approved, the total estimate of the work amounting to 1200, 000 rupees. The daily quantity of water which it was estimated could be supplied to the inhabitants of Karachi, was about 25 gallons per head of the population estimated at 80,000.
The financial difficulties delayed the commencement of the work till the year 1879, it was recommended by the Strachen that in order to bring the cost estimate within the means of municipality, the large 24 inch main and several sub-mains which formed part of the original scheme, should not be laid at first. By thus reducing the capacity of the main to 8 gallons per diem per head of population, and shortening the length of distribution pipes, the cost of the works was brought down to within the means which Municipality had in hand namely, 850,000 Rupees. The suggestions were adopted, and on the 21st of February, 1880, the foundation stone of the distributing reservoir was laid by Sir, Richard Temple, the Governor of Bombay, who had taken great interest in the proposed work, and who, by his personal influence with the Municipal Commissioners, had done much to bring about its commencement.
The supply of water was obtained from the two wells situated on the right bank of Malir, about 7 miles from the Landhi station of the Sindh, Punjab and Delhi Railway, and about 16 ½ miles in a bee-line from Karachi. As the river in times of flood suffers much from the erosion of its banks, it was deemed desirable that the wells should be so situated as to be sufficiently removed from any such action. They were accordingly sunk 400 feet apart, at a distance of 1,000 feet from the riverbank. They were 40 feet in diameter inside and were excavated to the full depth of 36 feet without the aid of pumps of any kind, on account of the favorable position of the Thudda river, which is a tributary of Malir. The river crosses the line of conduit about three miles from the wells, and as such the level enabled the whole of the water from the excavations of the wells to discharge in it. The wells were stained 3 feet thick with rough ashlar blocks 3 feet by 1 foot 6 inches by 1 foot, laid header and stretcher alternatively, set dry with bed and joints roughly dressed to facilitate the inflow of the water. The walls are carried 23 feet above ground, and are finished with ashlar cornice. Between the wells and the Thudda river, the water is conveyed partly in pipes and partly in conduits.
For a distance of 5,000 feet from wells, the pipes are enclosed in masonry culvert 2 feet 6 inches wide by 6 feet high built dry structure. The pipe is protected from the great weight of the superincumbent mass of earth, and at the same time the water in the trench finds an easy means of access to the wells. (Fig. 3) The masonry conduits commences at the junction tank, and has for nearly 9 ½ miles, a sectional area of 7.31 square feet with a fall of 2 feet to the mile. The remaining portion of the conduit has a sectional area of 5.62 square feet with a fall of 3.91 feet per mile. The total length of the conduit was 16 miles 20 chains, and it ends at the inlet well near the distributing reservoir at Karachi. The conduit was covered in for the entire distance, and is provided with ventilating shafts and manholes, some placed one mile apart where excavation was shallow, and other ½ mile apart where depth of the conduit from the distance of the ground was above 15 feet. These ventilating shafts had teak doors giving access to a wrought iron ladder for the convenience of inspection. (Fig.4) The side walls and invert were built of rubble masonry, no stone being of less breadth of bed than 12 inches. The whole of the inside of the conduit to the underside of the covers was rendered in cement ½ inch thick of proportion of 1:3 Portland cement and clean river sand. The covers were 8 inches in thickness with 6 inches of concrete above.
Where the line of conduit was crossed by watercourses at about the same level, the conduit was carried underneath by siphons. The siphon under the Thudda river was formed by a double row of 24 inches cast iron pipes 500 feet long, laid about 8 feet under the bed of the river, with wells 10 feet in diameter at each end which act as a ventilation shaft. Branches 12 inches in diameter closed with black caps, were cast at the center length of each row of pipes, to afford an easy mean of removing any deposit which may accumulate. (Fig. 5) The conduit was carried in several instances under nallah by siphon built entirely of masonry and concrete. The concrete composed of 1 part of lime, two parts of river sand and 5 parts of broken stone. The masonry of the side walls was common rubble, and that of arch block in course. In another siphon 24 inch diameter cast iron pipes were used (Fig. 6).
As the supply of water was known to be much in excess of the quantity which could be used in the town, for at least some years to come, the author suggested that surplus should be utilized for irrigation purposes. Accordingly at about two miles from Karachi, where arable land was available, and where the level of the ground was suitable, irrigation well was built (Fig. 7). In this well two 24 inches valves were placed at right angle to each other, one valve on the direct line of the conduit, and other on the pipe leading to the irrigation channel. At the time of completion of the project 500,000 gallons of water was surplus and disposed of on the land. This quantity was equal to 1, 666,666 cubic yard per annum, and allowing 8000 cubic yards to be required per acre for two crops per annum, the available quantity was sufficient to irrigate about 146 acres. At that time only 30 acre was placed under irrigation, but it was proposed to increase this area from time to time. The distribution reservoir was built on the side of the hill about one mile east of cantonment, it was 200 feet long 150 feet in width, the water surface 10 feet 9 inches above the floor (Fig. 8).
The main delivery pipe, after leaving the inlet-well and reservoir, is continued of a diameter of 24 inches for a distance of 150 feet when it bifurcates, one branch, 12 inches in diameter, being taken through the cantonments and civil lines, past the railway quarter and old town, to the shipping at Keamari; and the other, 21 inch in diameter, by a straight route through the Saddar bazar to the native town. This latter main is the one of which the laying was deferred at the commencement of the work for financial reason. No sooner, however, had the partial supply of 8 gallons daily per head had been introduced. Accordingly, on the 11th of June, 1883, the Municipality sanctioned the raising of a loan of 289,000 rupees to complete the scheme. The additional works consist mainly in supplying and laying pipes, and in the erection of services at various places in the town.
Hydrants of the ordinary pattern were placed at varying distances, in some streets 200 feet apart, to facilitate road watering, and in other 400 feet apart. The total number of hydrants was six hundred and thirty five. The public hand services are twenty-eight in number and consist of fountains furnished with ¾ inch brass thumb push cocks. For those who live at a greater distance, and who cannot send a member of the family to draw water as those do who live in the immediate vicinity of the street fountains, the bhishtie with his bullock puckhal is required, and for him bullock services were provided. (Fig. 9) This service consists of a horizontal pipe having two branch pipes cast on it, sufficiently far apart to fit the mouth of the bhishtie puckhals, which are two leather bags, one on each side of the bullock. The horizontal pipe is supported on stone pillars, of such a height and distance apart as to enable the bullock to stand comfortably underneath it. The bhishtie opens the cock by lifting the weighted liver, and while it is open the water flows through the two branches of the pipes, filling equally both puckhals. The total number of bullock services was forty. Carts requiring water for any purpose can fill from the ordinary street stand-post, of which these were fifty five.
Special supplies of water have been furnished to the Sind, Punjab and Delhi Railway Company workshop, the arsenal and jail, to all the troops in the garrison, both European and native, and various mills and factories in Karachi. A 6-inch branch was taken along the Napier mole to Keamari, a distance of two miles, for the supply of shipping in the harbour, the Keamari station of Sind, Punjab and Delhi Railway, and the hydraulic machinery connected with the Meriwether pier. A branch-pipe has also been laid along the Meriwether pier, when steamers lying alongside can fill their boilers anytime. In carrying the pipe along the Napier mole, a wrought iron screw pile bridge of thirty spans of 40 feet each had to be crossed. The pipes were suspended below the cross girders special joints were designed for expansion and contraction.
The total cost of the scheme had been 1,150,000 rupees, and as the maximum daily supply of water was 2, 500,000 gallons, the cost of 20 gallons per day was 9 rupees. The cost of reservoir was 67,000 rupees. It was capable of containing 2,000,000 gallons of water.
The work was commenced on the 18th of February, 1880, and was formally opened on the 21st of April, 1883. The work connected with the extension of the distributing pipes was commenced in July, and finished in October 1884. The work was carried out by both local and British contractors. The contractors were: Messers. Burn and Company, Calcutta, for the conduit and wells; Messers. Meherally and Lalu Gugoo of Karachi for reservoir, the iron work was supplied by Messers, R. Laidlaw and sons of Glassgow, and the work of laying the distributing pipes, and fixing of meters valve, &c., was entrusted to Messers. T. Cossor and Co. of Karachi.
In conclusion the design was carefully done taking into consideration the cost factor as well as the provision of water to all segments of society. The surviving remnant of the project may be preserved as a monument. The stone blocks and cast iron pipes were chosen to complete the task. Both the pipes and conduits were used to convey the water to end-users. The details were carefully worked out. Syphon system was used wherever necessary. The provision of inspection boxes to check possible accumulation of silt in the system was an important consideration.
The second important feature of design was the provision of fire hydrants. The British engineers ensured fire hydrants everywhere wherever thy laid out water supply scheme. In the recent excavations in the walled city of Lahore, several fire hydrants have been identified after excavations. In the housing for railway employees, fire hydrants were provided in the very bungalow and in all lanes. The recent fire incidences in the industrial areas highlighted their provision in all major cities. We have forgotten this important aspect after independence in the new housing schemes.
In the recent years Karachi has seen serious cases of urban flooding but no significant efforts has taken into consideration of rainwater harvesting. How much area has been allocated for the land cover and for the construction of water bodies especially in area under depression need to be reviewed. The wastewater recycling is almost non-existent in Pakistan and same is the case with Karachi. It is at this juncture we must save, recycle and reuse as much as possible.
The Malir river exhibits high levels of pollution due to various types of unregulated human activities taking place along its banks and in the vicinity of the Malir estuary. Untreated domestic and industrial wastewater discharges, solid waste dumping, agricultural runoff and soil erosion are all sources of pollution in the river. These sources adversely affect the freshwater ecology and wetlands, both in the upper reaches of Malir River and in the Malir estuary. The estuary, for now, still supports the wetland ecosystems such as mangrove forests but its characteristics are being modified due to land reclamation practices in the vicinity.
Despite all these obvious constraints, however, it is felt that there is sufficient justification for exploring the possibility of a ‘recreation-based waterfront development’ along this water body. This will indirectly help preserve whatever is left of its ecological bio-diversity. Firstly, there is the need to consider the Malir River and estuarine wetland ecology as an integrated ecosystem and ensure the involvement of relevant stakeholders. The status of the existing research and documentation has to be assessed and updated. Identification of critical knowledge gaps can point to areas for generation of appropriate social and ecological data. The viable wetland ecology in separate sections of the Malir River and estuary need to be identified and the local communities can be involved to act as ‘environmental stewards’. Field surveys would be able to identify viable wetland ecosystems, both in the riverine stretch and in the estuary. While the estuary’s ecosystems are known to exist, artificial riverine ecological systems can also be created by using advanced technology for the treatment of wastewater and augmentation of the water flow.
It is understandable that though the above article was penned much earlier than the recent urban flooding and the forever acute shortage of water that the city Karachi faces, what is interesting to note that after such mammoth work in the 1880’s the city that has grown to a phenomenal population the infrastructure development by the government or the municipalities have lagged behind resulting in the fiasco that Karachi witnessed this end August after the monsoon rains.
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