Intermittent water supply interventions for India’s cities

The average water availability in Indian cities is approximately four hours. The urban supply deficit shows up also as a need resort to tanker deliveries. © iStock / ertyo5

Widespread intermittent supply in India requires coherent action at different levels to bring about improvement. S Mohan and GR Abhijith set out a proposed ‘Three Elephants’ approach.


Water supply systems intended to meet demands at any time of the day, of any month of the year, by supplying water of adequate quality and quantity are an integral infrastructural component of every modern city. In many cases, the prospect that these systems may stop operating, even for a day, is almost unthinkable.

Unfortunately, the luxury enjoyed by consumers served by reliable and continuously operated systems is not the experience of those served by intermittent water supply (IWS) systems.

IWS systems are those that operate for less than 24 hours a day. The hours of water supply experienced around the world are shown in Figure 1. Around 41% of the water supply systems operating worldwide are operated intermittently, serving almost 309 million people. This includes 60% of the water supply systems operating in Latin America and the Caribbean, more than one-third of the systems in Africa, and more than half of the systems in Asia.

Figure 1. Minimum, mean, and maximum hours of water supply around the globe

Categorisation of IWS systems

Based on the water volume made available to consumers and the water supply duration, IWS systems can be broadly categorised into three types: predictable, irregular, and uncertain. Predictable IWS systems are operated with relatively constant water pressure. The water is supplied to the consumers in schedules that are on the scale of days or longer. These systems resemble continuous systems when they are operated with sufficient water storage. Similar to these predictable IWS systems, consumers served by irregular IWS systems can expect to receive a certain quantity of water at relatively constant water pressure. However, these systems supply water only at intervals of no more than a few days. Meanwhile, uncertain IWS systems supply insufficient water quantity at unknown supply intervals, generally on the scale of a few hours. This makes clear that, as the IWS categorisation changes from predictable to uncertain, the implications for the water consumers become more serious.

Regrettably, looking at South Asia – and, specifically, India – we may find that almost all the IWS systems fall under the third category. The water supply periods are reported to vary from one to 11 hours a day, and the average water availability in Indian cities is approximately four hours. It is also reported that, in certain Indian cities, water supply occurs only once every 5-10 days. These figures indicate that the problems India faces are of grave significance.

Factors contributing to IWS practice

There are many multi-dimensional factors that can contribute to the poor performance of the supply infrastructure in India. The five factors highlighted here are the absolute scarcity of water resources, scarcity because of poor system management, economic scarcity, unscientific infrastructure development, and unaccounted-for water losses from a macroscopic perspective.

Water resources scarcity is a significant problem faced by many Indian cities, exacerbated by changing weather patterns. The recent 2019 water crisis in Chennai illustrates this. In June 2019, the city’s residents were forced to cut their water usage to 30-40 litres/day during the crisis from the benchmark value of 135 litres/day.

Poor management of the supply system can be a causative factor for intermittency. This encompasses inadequate operation and maintenance and inadequate electricity supply. This is generally viewed as a self-induced factor. Economic scarcity becomes a causative factor for intermittency when the municipal authorities fall short of financial funds to expand/improve the existing system.

Unscientific infrastructure development is another factor that has a significant, or the most significant, role in causing intermittency in India’s supply systems. Most Indian cities are plagued by the problems of population growth and rapid urbanisation. As a result, they are in continuous water demand stress. So, when the municipal authorities attempt to meet the water demands beyond the existing systems’ hydraulic capacity, problems of pressure deficiency, followed by water scarcity, arise at vulnerable locations. Ultimately, water rationing and intermittent operation become the inevitable effects. Another major factor that forces intermittency in systems is the unaccounted-for water losses. Factors such as ageing infrastructure, apparent losses, and corruption contribute to significant water losses in Indian cities. Unaccounted-for water losses in Asian cities, including Indian cities, are so large that cutting such losses by 50% could facilitate meeting the water demands of almost 150 million people.

Problems associated with IWS practice

It is no surprise that IWS has countless far-reaching consequences in Indian cities, given the effects inadequate water volumes and uncertain supply schedules have on consumers. Water consumers cope by adopting many alternative strategies to deal with its impacts. The primary problem of inadequate water quantity is dealt with, generally, by approaches such as supplementing with alternate water sources or storing the water, or pumping from groundwater reserves. However, the significant problem that essentially hinders the reliability and the dependability of the IWS systems is the deterioration of quality, particularly the presence of pathogens.

The effects of IWS on microbiological quality degradation and its impact on human health have been reported extensively. For microbiologists, water supply systems are diverse microbial ecosystems, where all microbial life types flourish, including bacteria, viruses, and protozoa. Two mechanisms contribute to the presence of microorganisms/pathogens within the supply lines: their intrusion from the external environment, and their growth within the systems. The intrusion of pathogens from the environment surrounding the supply lines has been identified as the most important mechanism as far as IWS systems are concerned.

Many studies have hypothesised that alternate filling and emptying of pipes during intermittent practice is the primary factor facilitating pathogen intrusion into IWS systems. The periodic operation encourages the entry of diverse contaminants, specifically those present in sewage, at vulnerable locations with significantly low pressures. The sewer lines running parallel with supply lines, both to the side and above, turn out to be their primary source in developing countries. Unscientific city planning and execution must undoubtedly be blamed for this.

In many Indian cities, the sewer lines generally follow the same layout as that of supply lines. They are laid adjacent to or above distribution lines, with a gap of only about one metre as a result of municipal administrations’ unscientific planning and execution. The sewage from leaking sewer lines may enter the IWS lines through the vulnerable locations, which can be the locations of infrastructure deficiencies – such as pipe cracks – or cross-connection points. An extensive water quality survey conducted on two Indian cities, Hubli and Dharwad, with continuous and IWS practices substantiated this problem. The survey revealed faecal coliform (Escherichia coli) presence to be 31.7% for water samples collected from the part of the system that is operated intermittently, against only 0.7% in the water samples collected from the part that is operated continuously. The typical remedial measure adopted is the addition of chlorine to address the water quality deterioration problems discussed above. However, a major issue associated with chlorination is the formation of carcinogenic disinfection by-products. Even though this is a problem of significant concern during the operation of the developed world’s supply systems, a similar concern is not presently given while designing the operation of IWS systems in Indian cities.

There are many other practical implications associated with IWS systems, such as adverse health impacts, increased water costs, increased maintenance requirements, and lower capital recovery. Consequently, the IWS systems in Indian cities fall into a ‘low-level equilibrium trap’, leading to low cost recovery and continually declining performance.

The Three Elephants approach and possible interventions

The present condition and the extent of the problems associated with the IWS systems in India give the impression that any interventions to improve their performance are practically and economically infeasible. However, from an optimistic viewpoint, these supply systems are not beyond repair. Evidently, it would be a tough job. Nevertheless, a systematic approach foreseeing and considering all the possible alternatives could inevitably bring back the existing systems to their desired performance. These possible interventions could be regarded as critical nation-building steps, considering the significance of water in human civilisation development. A ‘Three Elephants’ approach is anticipated here to develop practical interventions for improving the performance of supply systems in India.

Elephants are the largest existing land animals. Humans have been trying to domesticate them for thousands of years. Yet, they remain a wild animal that is a challenge to tame. The problems that we need to recognise, or the interventions that we need to recommend concerning the IWS systems in Indian cities, could be viewed as elephants. In this approach, the problems/interventions are categorised into three: national/state level; city/regional level; and zonal/local level. These levels are analogous to three elephants. Engineers, scientists and practitioners have to accept the role of the mahout – or elephant keeper – and tame these three elephants.

The first level of problems assumes national/state level importance, so the first elephant could only be tamed or controlled through proper planning. The first stage of planning involves the forecasting of future development of Indian cities. This includes population growth, future water use, industrial development, spatial expansion, and socio-economic development. The second stage involves identifying the city’s potential water sources, which may include surface/sub-surface or seawater sources. The effects of changing weather patterns and the overall change in the temperature must be taken into account during this stage. Planning adequate policies to prevent the pollution of the existing drinking water sources must also be integrated into the second stage. The third stage involves fixing the price of water. This stage also involves arriving at national/state-level interventions to reduce the unaccounted-for water losses/non-revenue water and increase revenue generation from the existing/future systems. The fourth stage involves the holistic integration of the water and sanitation sector. This is crucial for scientific planning and implementation of the water supply and the wastewater collection infrastructure in Indian cities.

The second level of problems is of city/regional scale, so the focus while taming the second elephant must be on operation and management. The second level deals with the infrastructure related to water and sanitation in cities. Specifically, it deals with the raw water collection system, water treatment plants, the wastewater collection system, and wastewater treatment plants. The first stage at this level involves arriving at the conjunctive use of all the available water resources. The second stage concerns the design of the operation and management of the raw water transmission system. This includes providing necessary pre-chlorination before transmission to prevent the biofilm growth inside the pipelines, supplying pressure control devices, and monitoring and controlling the leakage losses.

Overhead reservoirs have an important role to play in maximising water supply duration © iStock / Vikram Kumar

The third stage deals with the operation and management of water treatment plants. The process train for water treatment must be adequately selected to produce the best quality water devoid of organic matter. This would reduce the dosage of chlorine and microbial growth while conveying the treated water through supply lines. The water treatment plant operation must also be designed to balance the peak and off-peak water demands, considering diurnal water demand patterns. The fourth and fifth stages concern the operation and maintenance of the wastewater collection system and the wastewater treatment plants. As mentioned above, their operation and management must be integrated with that of the supply system of the city.

The third level of problems are of zonal/local level, and these concern the operation and management of the water supply system. Problems corresponding to this level would be the most difficult of the three to solve. Therefore, the regularity, certainty and reliability of the system will depend on how effectively ‘elephant number three’ is tamed/controlled. The first stage of level three involves designing a proper schedule of water supply for the city, which must take into account the operation of service reservoirs and the city topography. This must involve setting up strategic plans considering every scale of operation up to the utility operator’s scale. The primary aim of planning must be to meet the consumer’s desired water demands to the maximum possible extent.

The second stage is concerned with the management of water utility operations. This would comprise conducting skills development programmes for utility operators and developing an effective two-way communication system between utility operators and engineers, using information and communication technology.

The third stage is concerned with water consumers, with the design and implementation of proper systems to update them with information on the supply quantity and quality. The fourth stage deals with the operation of overhead reservoirs. The majority of Indian cities employ combined gravity and pumped systems, which has a crucial role to play. The management of overhead reservoirs must maximise the water supply duration, balance the peak and off-peak demands, and minimise the depressurisation and stagnation conditions in supply lines.

The fifth stage involves the design of the secondary/booster disinfection points in the supply network. This includes identifying the booster disinfection locations, optimising the disinfection dosages, and minimising the pathogen growth and disinfection by-products formation in supply lines. Designing and implementing an effective monitoring framework (Figure 2) must be an integral component of the sixth and final stage.

Figure 2. Information and communication technology (ICT) cloud-based monitoring framework for integrating the operating engineers, water utility operators, and consumers of a water supply system

Looking forward

Continuous water supply systems are an essential boon for the water consumers who enjoy their benefits. There is no doubt, therefore, that continuous, or 24×7, operation must be regarded as the international benchmark for evaluating the performance of systems. However, it would be unwise to advocate that the only solution for improving water supply infrastructure in Indian cities is to change the operation practice from intermittent to continuous. Even though that must be our ultimate goal, it is unattainable within a fortnight.

Also, it must not be forgotten that most of the water supply systems in Indian cities have already fallen into the ‘low-level equilibrium trap’. Hence, rather than going for ambitious and unscientific policies, the focus now must be on rejuvenating the existing systems. So, the practical and economically feasible strategy would be to go for a systematic approach, such as the Three Elephants approach.

Inevitably, a tough job awaits us. However, we must not be ‘tired’. We must find inspiration in the words of American philosopher and anthropologist Loren Eiseley: “If there is magic on this planet, it is contained in water.”

Considering this magic that water possesses, and considering its significance in human evolution, we should look forward to the marvels that a well-performing water supply infrastructure can bring to our cities’ socio-economic development. •

Professor S Mohan ( and Dr GR Abhijith ( are IWA Members and are at the Environmental and Water Resources Engineering Division, Department of Civil Engineering, Indian Institute of Technology Madras, Chennai, India.