Socio-Hydrological Modelling to Assess Reliability of an Urban Water System under Formal-Informal Supply Dynamics

Rakhshinda Bano,Steven Burian,Mehdi Khiadani

doi:10.3390/w12102795

Abstract

Increasing water scarcity in developing world cities combined with poor performance of water supply systems has led to an increasing reliance on informal water supply systems. Although the availability of informal supply provides a coping mechanism that enables water consumers to be resilient to failures in water supply, the longer-term effects on formal water supply systems (FWSS) are uncertain, with a potential reduction of tariff recovery (RT), and in turn a service provider’s financial sustainability. This motivates an analysis of the coevolving dynamics and feedbacks involved in water systems where formal and informal components co-exist. Investigating Hyderabad, Pakistan as a case study, a dynamic socio-hydrologic system model is built, comprised of a formal system’s water and fund balance, consumer behaviour and infrastructure conditions. Simulations are executed on a monthly basis at a household level and for a 100-year period (2007–2107) using data available from years 2007–2017. Demand shift to informal is observed to be weakly associated with lower recovery rates, with household income as a major predictor. The FWSS’s financial balance, predominantly driven by infrastructure condition, appears to be less sensitive to recovery of a tariff to generate sufficient revenue.

Highlights

Informal water supply systems (INFWSSs), hereby referred to as non-piped or non-networked water supply managed by private suppliers [1], have emerged as a common adaptation strategy to increasing domestic water scarcity, especially in developing countries [2,3,4]
While multiple studies [9,22] have discussed the possible impact of INFWSS in terms of cost incurred to the consumer, the present study presents a dynamic view of the impact an informal water system in terms of water security at the HH level as well as a formal system’s fund balance
Trajectories of the water balance at both the city and the HH level are displayed in Figure 2, followed by demand shift patterns from formal to informal (Figure 3) and their impact on RT (Figure 3: (a) Water demand shift to informal at HH and (b) city level under current infrastructure capacity and population increase versus income change

Summary

Introduction

Informal water supply systems (INFWSSs), hereby referred to as non-piped or non-networked water supply managed by private suppliers [1], have emerged as a common adaptation strategy to increasing domestic water scarcity, especially in developing countries [2,3,4]. While informal water supply has emerged as a coping mechanism enabling users to deal with uncertain water supply [7], it has contributed concomitant negative feedbacks to the financial sustainability of FWSSs, which further feeds back in to a vicious cycle of poor performance in formal water system [8]. This suggests an analysis of the dynamics and feedbacks involved in a system where formal and INFWSSs co-exist, to support advancing urban water sustainability [9].

Results

Discussion

Conclusion