Designing Resilient Water Distribution Systems Under Demand Uncertainty: A Kohat City Case Study

Abstract

This study explores the impact of accurate water demand forecasting and the integration of diurnal consumption patterns on the design and efficiency of water distribution systems, particularly in Pakistan. Due to the lack of a comprehensive metering infrastructure, water demand patterns remain poorly understood, complicating optimal system design. In response, a hypothetical diurnal pattern based on Iranian water usage behaviours was adopted to simulate and assess the performance of water supply systems under varying demand scenarios. The study compares two models: one based on instantaneous peak demand and the other incorporating realistic diurnal fluctuations over a 24-hour period. Simulations revealed that designing systems based on instantaneous peak demand leads to overdesign, resulting in excessive pressure during low-demand periods, thus increasing operational costs, risking pipeline damage, and reducing system lifespan. In contrast, designing with a diurnal pattern proved to be more cost-effective, sustainable, and reliable, as it better matched actual consumption patterns. The findings emphasize the necessity of integrating dynamic pressure management, seasonal and peak demand considerations, and advanced flow regulation techniques in future infrastructure projects. These recommendations aim to enhance the sustainability and efficiency of water distribution systems, ensuring adequate water supply and equitable distribution, while minimizing resource wastage and operational inefficiencies.

Introduction

The study addresses the challenges of water supply planning in rapidly urbanizing regions like Pakistan, where unpredictable water demand hinders efficient infrastructure development. It proposes a comprehensive solution integrating statistical analysis, hydraulic modelling, and optimization techniques to design a flexible and cost-effective water supply system.

Key Elements:

1. Objective:

To design a resilient water distribution system that accommodates uncertain, time-varying demand—a critical issue in cities like Kohat, Pakistan.

2. Methodology:

• Statistical analysis identifies demand trends and fluctuations using historical data.

• Hydraulic modelling simulates network performance in tools like EPANET, accounting for pipe sizing, pressure, elevation, and layout.

• Optimization ensures resource allocation is cost-effective and reliable under varying demand conditions.

3. Demand Forecasting & Simulation:

• Compared two demand models:

  • Instantaneous (uniform): Constant daily demand, peaking factor = 2.7.

  • Diurnal (realistic daily variation): Based on an Iranian pattern, peaking factor = 1.54.

• Population projections and per capita consumption (100 LPCD) were used to calculate base demand per node.

• Simulations showed that designing for peak instantaneous demand led to overdesign, resulting in oversized components and excess cost.

4. Key Findings:

• Systems designed on instantaneous demand performed under diurnal loads but showed high pressures during low-demand hours, indicating inefficiency.

• Diurnal-based design more closely aligns with actual usage, improving cost efficiency and sustainability.

• Using diurnal patterns allows for better planning of pipe sizing, reservoir capacity, and energy consumption.

Conclusion

This study assessed Kohat\'s water supply scheme, highlighting that designing for instantaneous water supply without demand data results in overdesign and higher costs. In contrast, a system designed with a diurnal pattern is more reliable, sustainable, and cost-effective, reflecting real-life usage. It also ensures long-term effectiveness by keeping pressure within acceptable limits at each node. Designing an optimal water distribution network in Pakistan is challenging due to the lack of a metering system and accurate diurnal usage patterns. This study adopted a diurnal consumption pattern from Iran, reflecting local water use behaviors. The findings highlight the importance of incorporating a diurnal pattern in system design to improve efficiency, reduce costs, and extend infrastructure lifespan. While instantaneous demand design may seem cost-effective initially, it is unsustainable in the long term. Future infrastructure projects should focus on dynamic pressure management, reservoir integration, and advanced flow regulation for reliable, efficient, and cost-effective water systems.

References

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Copyright

Copyright © 2025 Rab Nawaz Khan. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.