Peak Demand

Securing a sustainable water supply for the residents of Castle Rock now and in the future is part of the long-term plan. Having enough supply is only one piece to the puzzle. Castle Rock Water must also manage the volume of water residents use in a single day. Water use from year to year and month to month is heavily influenced by weather. About half of water used by single-family residents is used outdoors, and a hot, dry period can mean customers use more water than normal.

This increased volume of water used in a relatively short period of time is considered peak demand. Imagine four people in a household each taking long, hot showers at the same time - all while the dishwasher and laundry machine run on the hot cycle. The water heater cannot keep up with the demand all at once. There is enough water supplied to each activity, but not enough hot water. Taking a shorter shower (conservation) and staggering when the activity occurs (watering schedule) helps manage peak demand.

Ensuring the water system can accommodate these fluctuations in demand is part of the Water Use Management Plan. The plan models various weather conditions and populations. One tool for managing the peaks of high usage is a watering schedule. In 1985, watering schedules were put in place for single-family homes, which make up about 73% of the customer base. The peak demand curve flattened when residents were asked to irrigate no more than every third day and only between 8 p.m. and 8 a.m. This schedule also has had the fortunate effect of helping create the 20% in water conservation that has been realized in recent years.

In 2013, Castle Rock Water began using renewable water. This water, pulled from East Plum Creek, is dependent upon snow and rain to renew this supply. A Summer Operations Plan is necessary to balance the increase in demand for water during the summer and the potential decrease in supply in East Plum Creek. The plan was put to the test in July 2017, and additional measures were needed. Unusually dry weather spurred exponentially more irrigation as well as creating extremely low levels of water in East Plum Creek.

The tools outlined in the Water Use Management Plan called for commercial customers, which only make up about 26% of the customer base, to be put on a three-day-a-week irrigation schedule. The schedule worked, allowing the storage tanks to maintain levels for customer use as well as for fire suppression.

The Summer Operations Plan also takes into consideration how the Town's water infrastructure is managed. During the summer, Castle Rock water customers have used more than 16.5 million gallons of water in a single day. To get this volume of water to every resident, business, and landscape, four to five water treatment plants must be online. All 10 pump stations, 13 alluvial and 52 deep water wells could potentially be working at full capacity. This is a lot of infrastructure to run at peak demand for only 8 weeks in the summer. In contrast, during the five months of winter, when water is generally allocated to indoor usage, about 4 million gallons is treated and distributed in a single day. Only one water treatment plant is needed to handle this volume. Peak demand not only impacts the volume of water used, but also how much infrastructure is required.