Determining Minimum Network Input Volume for The Transition from Intermittent Water Supply (IWS) To Continuous Water Supply (CWS): A Seasonal Analysis of Supply Hours in Tillo, Turkey

The transition from intermittent water supply (IWS) to continuous water supply (CWS) is a critical goal for global water security, but it continues to be hampered by the difficulty of precisely determining the resources required for 24-hour service. Traditional water audits are often designed for ideal systems with CWS and rely on static, annual, or system-wide water balances that fail to capture temporal variability. This study addresses Network Input Volume (NIV), which represents the daily amount of water delivered to consumers from the service reservoir supplying the city, and hours of supply (SH). By focusing on dynamic system behavior instead of static averages, this approach provides water companies with a more nuanced operational perspective for planning infrastructure transitions in data-scarce environments.

The methodology was applied to the Tillo district of Siirt, Turkey using service reservoir outlet data and recorded hours of supply from January to August 2023. To account for the network's inherent scholastic structure, we used regression analysis across bi-monthly periods, including both 95% confidence intervals and forecast bands. Our findings reveal a strong positive correlation between NIV and SH, but this varies considerably across seasons. For the March-April period, the adapted regression suggests a CWS threshold of approximately 600 m³/day. Specifically, the wider forecast range indicates that continuity could theoretically be ensured at values as low as 390 m³/day, whereas at 650 m³/day, at least 15 hours of supply is guaranteed.

As climatic demand increases towards the summer months, the model captured a significant increase in requirements. Extrapolations for the May-June and July-August periods showed that the CWS thresholds would rise to approximately 870 m³/day and 970 m³/day, respectively. However, the analysis also identified a critical hydraulic phenomenon: "compensatory flow". On days when water returned following periods of supply shortages, the system experienced temporarily elevated NIV values as it compensated for the previous deficit. This cumulative adjustment dynamic demonstrates that the relationship between input and supply is not merely instantaneous but is shaped by the system's memory of previous IWS cycles.

Consequently, this research shows that the seasonal and daily relationship between SH and NIV is another point to consider during the transition to CWS. This daily monitoring approach, which goes beyond annual balances and captures daily and seasonal variability, allows water companies to establish realistic metrics for the transition. Furthermore, these findings highlight the importance of integrated controls that account for both physical losses and human-induced demand shifts, providing a replicable model for improving urban water resilience in similar contexts worldwide.