Assessing service reservoir performance for preventative asset maintenance

Service reservoirs are critical assets of drinking water distribution systems, providing
storage and balancing demand and supply. A variety of operational and integrity issues,
such as water age and ingress or leakage, are known to impact chemical and microbiological
water quality, with the risk of deteriorated water reaching end users. To ensure that
service reservoirs are functioning effectively water companies conduct inspections every 3-5
years. However, due to the lack of a precise assessment method, maintenance interventions
are currently scheduled according to predetermined time intervals rather than specific
performance indicators. This research presents findings from newly developed metrics
derived from routinely monitored hydraulic and water quality parameters at service
reservoirs, designed to assess their performance and maintenance requirements. Data
from 11 service reservoir sites within operating drinking water distribution networks was
analysed over a span of 5 years. Data-driven multi-parameter metrics based on level and
flow time series were developed to calculate mass balances and daily residence times. To
rank service reservoir water quality performance, data from regulatory sampling and flow
cytometry testing was investigated. Results showed that the mass balances were able to
identify integrity issues up to 3 months prior to scheduled inspections. Furthermore, sites
with residence times greater than 48 hours were found to have higher average values of
3-day colony counts and intact cell counts. This research showcases the inherent value
of hydraulic and water quality parameters already monitored at service reservoirs to
provide insights on asset performance. This contribution carries significant implications
for water infrastructure management, as the use of data-driven metrics can effectively
guide water companies in prioritising site inspections. Consequently, this advancement
marks a departure from a purely reactive approach, fostering a more proactive mindset in
infrastructure maintenance and management practices.