Page 249 - Water Loss Control

222 Cha pte r T h i r tee n

consumption for peak and off-peak periods, as well as the aggregate consumption for
the billing cycle. TOU billing is also being employed to mitigate high peak flows and
allow water utilities to design smaller capacity into their infrastructure. Wide Bay Water
Corporation on the east coast of Australia has installed a data-logging AMR system to
provide consumption data in a TOU billing structure to motivate smaller daytime peaks
by spreading consumption rates more evenly throughout the day, thereby reducing
capacity needs. This is one of many benefits expected from this AMR system. 6
In addition to TOU billing, some water utilities have begun to develop sophisti-
cated water rates tailored to individual customer consumption patterns. Also known as
a water budget rate structure, these rates reward customers that are able to implement
water reductions to notable levels below their characteristic budgeted consumption
levels. Likewise, the structure requires customers using water well above their bud-
geted level to pay for the additional water at a premium rate. For each customer an
individual consumption pattern is measured and their budget is determined. One
approach is to base each customer budget on typical annual indoor use as well as a
monthly determination of actual needs for outdoor irrigation. Such an approach, while
requiring considerable data management, recognizes that many people will conserve
water if a clear financial benefit is available to them. However, there is often a small
portion of the customer population—usually those owning expansive, well-cultivated
landscapes—that is willing to pay a premium rate for high water consumption. Tailored
or budget water rate structures work to promote water conservation in the community
while providing equity among ratepayers and a stable revenue base for the water util-
ity. The City of Boulder, CO is a recognized pioneer of budget rates, which it enacted in
response to drought and the need for an effective, long-term strategy for water conser-
vation and revenue equity and stability. 7,8
Another use of granular customer consumption data is to assist distribution leakage
assessments in pressure zones or district metered areas (DMA). DMAs are small zones
of the distribution system usually encompassing 500 to 3000 customer service connec-
tions. A boundary is established that permits the DMA to be supplied by one or more
water supply mains that are metered. In this way the supply to the DMA can be moni-
tored directly and the variations in supply flow observed. Granular customer consump-
tion data from AMR systems provide minimum hour consumption volumes that can be
compared directly to the water supply input flows to DMAs such that a water balance
can be constructed for individual DMAs and water supply tracked specifically. Precision
is added to leakage assessments in DMAs when the input supply volume is compared to
the customer consumption volume during minimum hours. In regions where nighttime
irrigation systems are not in use, minimum hour residential consumption usually occurs
during the early morning hours between 1 a.m. until 5 a.m. Night flow analysis for leak-
age quantification relies on the fact that, during the minimum consumption hours, leak-
age is at the highest proportion of the supply input to the DMA. Therefore, a reasonably
precise measure of DMA leakage can be obtained by subtracting customer consumption
from the supply input during the minimum consumption period. In regions where night
irrigation flows are common, this analysis may need to be scheduled for an off season
(winter) period when irrigation equipment is not in use.
In Philadelphia, the Philadelphia Water Department (PWD) has periodically
employed its mobile-read AMR system to obtain nighttime customer meter readings in
order to compare them with supply input in a DMA. This technique was initially
employed in a temporary DMA and has been used successfully on a number of occa-
sions in PWD’s first permanent DMA (DMA5) which was designed and implemented