Intermittent Water Supply Systems Research Articles

Optimal Rehabilitation Procedure for Intermittent Water Supply Systems

Optimal Rehabilitation Procedure for Intermittent Water Supply Systems

Planning the Liveable If Not the Ideal: Frontline Planners’ Discretionary Actions and Inequalities in Everyday Intermittent Water Supply Planning in Tiruppur, India

Millions of urbanites across the Global South receive intermittent water supply (IWS). This paper examines how discretionary action by street-level bureaucrats (SLBs) in everyday water supply planning in IWS systems redistributes water quantities and service quality to alleviate unequal scarcity burdens. Ethnographic findings from the small city of Tiruppur, India, reveal that SLBs’ supply plans aim to distribute water volumes equitably within the network. However, SLBs’ communicative strategies to manage socio-material uncertainties and improve supply predictability, a critical dimension of service quality, reinforce existing socio-spatial inequalities. Rethinking SLBs’ contradictory discretionary actions in everyday water supply plans is crucial for managing water scarcity equitably in the IWS systems of Global South cities.

Air entrapment modelling in water supply networks during pipe filling events

ABSTRACT Intermittent water supply systems are prone to air entrapments during the pipe filling phase. This work aims to analyse and discuss the numerical results obtained by applying the recently developed AirSWMM model, an extension of SWMM incorporating air phase, to a laboratory network. Experimental data consisting of pressure-head at multiple locations and video recordings of air entrapments are collected in a single loop network with a high point, for different pipe-filling conditions, system layouts and node elevations. Experimental tests have shown that the air entrapment occurred not only at the high point but also throughout the pipe network, creating air pockets with elongated shapes and larger volumes than for single pipes. AirSWWM model with air-entrapment formation, growth and transport is tested in the pipe network, and results are compared with measurements. AirSWWM model can correctly locate large air pockets but underestimates their volume.

Calibration of intermittent water supply systems hydraulic models under data scarcity

Abstract Intermittent water supply systems (IWSSs) are unable to meet customer demands due to water scarcity from the sources or due to economic or/and technical scarcity. Conversion to continuous water supply as a means of tackling IWSSs’ inherent problems of inequitable water distribution, limited water supply hours, high non-revenue water, system operation and maintenance costs, and poor water quality is essential for sustainable water supply. Modelling and optimisation techniques have been used to aid the conversion process, optimisation of the operation of these systems, and guiding leakage reduction actions. However, modelling IWSSs have several challenges. These include the lack of accepted existing modelling techniques that include leakage modelling and the lack of comprehensive methodology for calibrating IWSS hydraulic models under limited calibration data. This study proposes a methodology for calibrating IWSS hydraulic models that include leakage modelling. The proposed methodology involves distinct steps to mitigate the problem of data scarcity, it eliminates the trial-and-error procedure of determining the leakage emitters' coefficients by using optimisation and it presents an approach for estimating the lower and upper bounds of the emitters' coefficients. The methodology was applied to a case study in Zambia. The calibration procedure gave accurate results given the limitation of data.

Air entrapment modelling during pipe filling based on SWMM

The paper proposes a novel methodology to locate and quantify entrapped air pockets created during pipe-filling events often found in intermittent water supply systems. Different filling conditions were tested in an experimental pipe with a high point. Measurements were taken and video recordings were carried out to assess air pocket volumes for different air release conditions at the downstream end of the pipe. The stochastic nature of air pocket creation resulted in varying air volumes. A new numerical model capable of simulating the air pocket creation, dragging and entrainment has been proposed. The new model, AirSWMM, was implemented as an extension of the Stormwater Management Model (SWMM) with stochasticity of air pocket formation reproduced by simulations with different air entrainment rates. The obtained numerical results show that the proposed model, even though based on a single-phase one-dimensional flow, can accurately locate and approximately quantify the entrapped air pocket volumes.

Unequal, Unreliable, and Unfixable?—The Need to Investigate Water Infrastructure Improvements in Intermittent Supply Systems

AbstractInfrastructure deterioration threatens urban water security and the pursuit of Sustainable Development Goal 6 (SDG 6, “water for all”). One billion urban residents worldwide already face intermittent piped water access, making their public water supply unreliable and unequal. Thus, effective investments in water infrastructure improvements are critical. In a recent WRR paper, Jeuland et al. (2023, https://doi.org/10.1029/2022WR033897) evaluate the impacts of a large infrastructure improvement project on various water security metrics and assess the challenges of such an investigation. They apply a rigorous difference‐in‐difference approach to data from a US$275 million investment in upgrades to water supply and sewage networks in the Zarqa governorate in arid Jordan, analyzing its effects on households, businesses, farms, and the water utility. The authors find a range of moderate improvements to water access and re‐use metrics, including a significant reduction in reported shortages. Key water security indicators related to access intermittency, however, such as the supply duration per day and the expenditure on water deliveries by tanker trucks, saw little to no improvement. The findings reveal that the efforts required to overcome the insecurity and inequity of intermittent public water supply systems might be considerably larger than expected. This suggests an urgent need to further enhance both the accuracy of impact evaluation methods and the effectiveness of infrastructure investments to support the pursuit of SDG 6.

Simulating equity in intermittent water supply using pressure sustaining valve in EPANET 2.2

ABSTRACT Intermittent water supply (IWS) system refers to a system of water supply that delivers water to consumers for a fixed period (2 hours, 3 hours, 4 hours, etc.), which is less than 24 hours a day. Literature shows that the issue of inequity has been a major concern in IWS. In this study, an attempt has been made to simulate a new way of operation of IWS by including volume of nodal demand, such that, the flow becomes uncontrolled volume-driven pressure dependent. The novel methodology presented makes use of a pressure sustaining valve (PSV), which rearranges the flow within the network, thus improving the equity in IWS. Further, the study aims to quantify the equity in IWS by formulating two different approaches: uncontrolled pressure-dependent analysis (UC-PDA) and uncontrolled volume-driven pressure-dependent analysis (UC-VDPDA). Both approaches have been applied to three different water distribution networks. Results show that UC-VDPDA provides a more equitable supply in terms of getting a fair share of water to the consumers.

Intermittent Water Supply System Rehabilitation through a Multiphase Methodology Based on Network Analysis and Hydraulic Modeling

Intermittent Water Supply System Rehabilitation through a Multiphase Methodology Based on Network Analysis and Hydraulic Modeling

Analyzing the role of consumer behavior in coping with intermittent supply in water distribution systems

Abstract A substantial number of water distribution systems (WDS) worldwide are operated as intermittent water supply (IWS) systems, delivering water to consumers in irregular and unreliable manners. The IWS consumers commonly adapt to flexible consumption behaviors characterized by storing the limited water available during shorter supply periods in intermediate storage facilities for subsequent usage during more extended nonsupply periods. Nevertheless, the impacts of such consumer behavior on the performance of IWS systems have not been adequately addressed. Toward this direction, this article presents a novel open-source Python-based simulation tool (EPyT-IWS) for WDS, virtually acting like an IWS modeling extension of EPANET 2.2. The applicability of EPyT-IWS was demonstrated by conducting hydraulic simulations of a typical WDS with representative IWS attributes. Different IWS operation cases were considered by varying the amount and consistency of the water availability to the consumers. EPyT-IWS outputs showed that domestic storage of water within underground tanks and subsequent pumping into overhead tanks allows consumers to cope with the intermittent water availability and suitably meet their demands. Besides the interval, the clock time of the water supply was predicted to influence IWS consumers’ ability to meet water demands.

Analysis of Intermittent Water Distribution Networks Using a Dummy Emitter Device at Each Demand Node

The pipe component of a water distribution network (WDN) is sized based on the fixed design demand considering a peak factor and design period. Simulation of the designed network by a hydraulic solver provides nodal pressure head, head loss, velocity, and flow in each pipe as the prime outputs for the design demand, and it can also be used for extended-period simulation for a particular demand pattern over the supply hours. But, in reality, the behavior of the network does not match with such a result in an intermittent water supply (IWS) system due to the fact that all house service connections behave as an uncontrolled orifice. This has made it a challenging task in understanding and in predicting the behavior of the networks by the municipal engineer once the water starts flowing through the house service connections (HSCs). Though the municipal engineer provides the same pipe size for HSCs to all residences, the flow received by each house could vary based on the available pressure head at the ferrule point of the main water supply pipeline. In reality, maintaining constant pressure at each HSC is not feasible due to frictional head loss. Hence, variation in flow at the HSC is inevitable even with a small water supply system. This paper illustrates how to simulate the behavior of an IWS system based on the number of HSCs provided to each pipeline using a hydraulic solver. Hydraulic simulation of the water distribution network that provides IWS to consumers can be implemented easily by adding a fictitious node by assigning an appropriate emitter coefficient to each demand node through a fictitious link having a check valve in it. The method for finding the appropriate value of the emitter coefficient that helps in simulating HSCs is illustrated in the present work.

Equity analysis of intermittent water supply systems by means of EPA-SWMM

Abstract Intermittent water supply (IWS) is a frequent operation approach in developing countries. A number of factors contribute to IWS, such as leakage and water shortage, leading to inequitable water distribution. A way to reduce the inequity in IWS systems is by planning or adapting the network for equitable water distribution, which requires software capable of describing IWS conditions, including not only pressurized flow but also free-surface. In this paper, a new index for equity analysis is presented and compared with the existing indices available in scientific literature. The comparison is based on the EPA-SWMM modelling framework and standard IWS operations, including pipe emptying and filling, have been considered. Results reveal that EPA-SWMM has great potential in simulating IWS systems, especially in the application for equity analyses, as it provides a more realistic description of the pipe filling and emptying operations compared to standard water distribution modelling software. Furthermore, a novel equation called volumetric coefficient was developed which has a significant advantage in identifying the nodes with a higher impact on network equity, and ensuring the fair distribution of supply along the distribution network, considering the relevance of nodal demand, which none of the other indexes in the literature were addressed.

Improved SWMM Modeling for Rapid Pipe Filling Incorporating Air Behavior in Intermittent Water Supply Systems

Stormwater management model (SWMM) software has recently become a modeling tool for the simulation of intermittent water supply systems. However, SWMM is not capable of accurately simulating the air behavior in the pipe-filling phase, missing therefore a relevant factor during pipe pressurization. This work proposes the integration of a conventional accumulator model in the existing SWMM hydraulic model to overcome this gap. SWMM source code was modified to calculate the air piezometric head inside the pipe based on the system boundary conditions, and the air piezometric head was incorporated in the SWMM flow rate pressure component. Experimental data were collected during the rapid filling of a pipe system for three possible configurations that are likely to occur in intermittent water supply pipe systems: no air release, small air release, and large air release. Results show that the improved SWMM better describes the effect of the air behavior using the extended transport (EXTRAN) surcharge method when compared to the original SWMM. Results also show that the SLOT method with predefined slot width is not suitable for this purpose; thus, further research is needed to assess if an adjusted slot width could provide better results.

Intermittent water supply and self-rated health in rural China's karst region.

With rapid economic and social development, surging demand for domestic water, and the increasing shortage of water resources, the applications of intermittent water supply systems have become more common in rural China and other developing countries. The accompanying hygiene risks require our more attention. Based on the Grossman model, this paper conducted an IV-Oprobit model to investigate whether and how intermittent water supply affect rural residents' self-rated health status. Our data came from "China Karst Rural Economic Survey (CKRS)", which covers 8 provinces and 641 villages in rural China's karst region. We found that: (1) Intermittent water supply has adverse effects on the self-rated health status of rural residents. Compared with the rural residents under continuous water supply, the probability of "fair" health status under intermittent water supply significantly increases by 18.2%, while the probability of "excellent" significantly reduces by 58.8%. (2) Residents' water storage behavior and sanitary water habit are important mechanisms for intermittent water supply to affect residents' self-rated health status; (3) Intermittent water supply has a greater impact on the self-rated health of females and the groups with lower education levels. The results of our study have the following policy implications: relevant departments should make a rational plan about water supply methods and improve related supporting measures; we should strengthen health education for rural residents on water behavior to standardize their water storage and sanitary water behavior; government should enhance the pertinence of policy implementation and favor specific measures to specific populations.

Risk-Based Inspection and Rehabilitation Planning of Service Connections in Intermittent Water Supply Systems for Leakage Management in Arid Regions

Most of the leakage in water distribution systems operating with plastic pipes occurs at service connections (SCs), while the existing tools plan rehabilitation of pipes. With limited water resources, intermittent supplies in arid regions further enhance the failure vulnerability of metal fittings on water mains due to scale formation and large pressure transients. The present research developed a risk-based methodology for the proactive maintenance of SCs in intermittent water supply systems. A five-generation bottom-up hierarchical approach aggregated the basic hydraulic, physical, and water quality factors to determine the vulnerability of structural failures of SCs. Hydraulic parameters (pressure and velocity) were estimated by simulating a distribution network of 366 water mains of diameters ranging from 110 mm to 225 mm serving 371 SCs in a residential neighborhood located in the Qassim region of Saudi Arabia. Age, depth, and length of SCs’ estimated the condition index, while soil corrosivity and condition of the water mains were also counted when assessing the structural failure index for each SC. Water quality parameters, e.g., pH, turbidity, and iron, that can contribute to the vulnerability of an SC’s failure were also included. Fuzzy-based methods first assessed the relative importance weights of the basic input parameters at the bottom of the hierarchy and the risk factors in the middle of the hierarchy. Subsequently, the performance and condition scores were aggregated to develop respective indices. As the consequence of structural failure is high for the SCs serving households with a large number of residents, the final risk index aggregates the vulnerability and consequence at the hierarchy’s top. The developed model was effectively validated by comparing the SCs of high priority with the leaking and repaired SCs in the past. The method will be a useful tool for planning proactive inspection and rehabilitation of SCs of intermittent supply systems to minimize water losses (less than 8% of the national benchmark) in Saudi Arabia and elsewhere.

Review of hydraulic modelling approaches for intermittent water supply systems

Abstract Intermittent water supply (IWS) is widely used around the world, and with the increase in population and predicted future water scarcity, IWS applications seem to continue. While most of the existing studies on water supply concentrate on continuous water supply (CWS), the research focused on the IWS is now becoming mainstream. Hydraulic modelling is an effective tool for the process of planning, design, rehabilitation, and operation of water distribution systems. It helps significantly in engineers’ decision-making processes. The necessity of modelling IWS systems arises from the complexity and variety of problems caused by intermittency. This paper offers a review of the state-of-the-art IWS modelling and identifies the key strengths and limitations of the available approaches, and points at potential research directions. Currently, neither computer software nor a practically used approach is available for modelling IWS. For a rigorous simulation of IWS, system characteristics first need to be understood, i.e., the user behaviour under pressure-deficient conditions, water losses, and filling and emptying processes. Each of them requires further attention and improvement. Additionally, the necessity of real data from IWSs is stressed. Accurate modelling will lead to the development of improved measures for the problems caused by intermittency.

Volume driven analysis for house level water supply assessment in an intermittent water supply system

ABSTRACT Intermittent water supply (IWS) system delivers the drinking water for a short duration of a day. Customers’ satisfaction with such a system highly depends on the volume of water delivered at each house service connection rather than the pressure-dependent flow rate. In most of the systems, the supply is made until emptying of the source storage reservoir or tank happens. The advantaged consumers (who belong to the high-pressure zone) receive water quicker than the disadvantaged consumers. As the IWS has trusted with the volume of water delivered, volume-driven analysis (VDA) is required to understand the supply rate at demand nodes and the actual duration of supply to the consumers located across the network. Supply to each house service connection (HSC) depends on the availability of static pressure at the ferrule points in the distribution main. The aggregated volume of water that can be delivered by the node corresponding to the available pressure requires an equivalent arrangement that represents house service connections (HSCs) in the modeling. In the present work, a modified method of volume-driven analysis is presented to simulate the aggregated flow from the HSCs at each node and to evaluate the actual volume of water delivered within the supply duration. The application of the method is illustrated through a hypothetical rural water supply network. The volume of water that can be received by the group of houses and its duration of supply to fulfill the demanded volume can be obtained from the proposed analysis and also it is shown how the uncontrolled withdrawal of water affects the disadvantaged consumers in the water supply system.

Short-term impacts of the filling transition across elevations in intermittent water supply systems

ABSTRACT Intermittent Water Supply (IWS) is characterised as drinking water distribution systems that are supplied with water for less than 24 hours/day on average. The filling transition from non-supply to pressurised supply is a period of hydraulic instability that negatively impacts water quality, deteriorates infrastructure integrity and intensifies social inequalities. Understanding the factors contributing to the severity of impact from filling is vital to develop effective management strategies. This paper investigates the hydraulic phenomena induced during the short-term IWS filling period and how this behaviour can be exacerbated by elevation and other hydraulic system factors, such as velocity and pressure. Controlled laboratory experiments conducted in the UK and field studies performed in operational networks across South Africa are presented. Results demonstrate the crucial role elevation plays in the network response during the filling transition, emphasising the need for greater consideration of elevation in IWS and well-maintained air relief valves in strategic locations.

Study of domestic water consumption in intermittent supply of the Riberas de Sacramento sector in Chihuahua, Mexico

Abstract User water demand can be met in intermittent water supply systems, and normally it is met if they have sufficient capacity to store water in their homes to be used in the hours when it is not supplied from the public pipe network. The situation in many intermittent water supply systems is that they have enough water to cover the demand of the users but are supplying it intermittently, and the challenge is to achieve a transfer from intermittent to continuous supply. If the delivery of water is continuous, which supplies drinking water 24/7, it covers not only the basic needs of the user, but all the needs for water they may have. The present study was carried out using smart domestic water meters to obtain consumption information in an intermittently supplied pilot sector. The electromagnetic meters record the water flow through pulses and generate consumption information, which gives us the consumption pattern in volume of water and in the time it is used. During the study, multivariate statistical methods were applied to obtain information from the domestic meters and to identify, as realistically as possible, the consumption of drinking water and the relationship between consumption and specific characteristics of the users and thus anticipate future demand. The results showed a close relationship between consumption and the size of the residence. The most influential factors were the number of bathrooms and the number of occupants. A direct relationship between the pressure and the volume supplied was presumed at the beginning of the study but the opposite was found. Equipment was installed to measure the pressure in the network at the time of establishing the continuous supply of drinking water. The multivariate analysis provides a selection of the most important variables that influence and explain the behavior of the water use and consumption pattern, with the operation determined by the operating agency.

Mapping and Visualizing Global Knowledge on Intermittent Water Supply Systems

Intermittent water supply systems (IWSSs) are prevalent in most developing countries and some developed ones. Their usage is driven by necessity rather than as a principal objective, mostly due to technical and economic deficiencies. Major health risks and socio-economic inequities are associated with such systems. Their impacts are aggravated by climate changes and the COVID-19 crisis. These are likely to have profound implications on progress toward advancing sustainable development goals (SDGs). Motivated by providing a comprehensive overview of global knowledge on IWSSs, the present work proposed to track and analyze research works on IWSSs utilizing bibliometric techniques and visual mapping tools. This includes investigating the trends and growth trajectories of research works on IWSSs and analyzing the various approaches proposed to expand our understanding with respect to the management, modeling, optimization, and impacts of IWSSs. The national and international contributions and collaboration figures are further analyzed at country, institution, author, and source levels. This analysis indicates that research works conducted on IWSSs have certain expectations in terms of productivity (total global productivity; 197 documents). The United States was the best country in terms of productivity (58 documents; 29.4%), while the Water Switzerland journal was the most productive journal (19 documents; 9.6%). The impacts of IWSSs on health and well-being have attracted considerable attention. The outcomes showed deep and justified worries in relation to the transition from intermittent to continuous supply, equity, and mitigating the health risks associated with IWSSs in the foreseen future. The utilization of artificial intelligence techniques and expert systems will drive and shape future IWSS-related research activities. Therefore, investments in this regard are crucial.

Development of scenarios for evaluating conversion from intermittent to continuous water supply strategies’ sustainability implications

ABSTRACT Planning the conversion from intermittent to continuous water supply (CWS) is rife with uncertainties. Although scenarios can be used to incorporate uncertainties in planning processes, their development and application to intermittent water supply systems are uncommon. Using drivers of water demand in water supply systems, this study developed four scenarios (business-as-usual, consumption demand management, non-revenue water (NRW) management, and holistic) for water supply systems. The scenarios were applied to the Lusaka water supply network in Zambia. The results showed that the NRW management scenario, which used the projections in the water supply investment master plan for Lusaka, is unsustainable because of insufficient water as the 15% NRW target is practically unattainable by 2035. The holistic scenario is the most sustainable, but the commitment to ensure its occurrence in Zambia is currently lacking. Possibly, donors’ directives can instil the commitment needed to attain the holistic scenario and the conversion to CWS.