PRODUCTION REQUIREMENTS

The State of Utah Division of Drinking Water recently conducted an analysis of the City's water usage of the past 3 years. The result of this analysis was a System-Specific Minimum Sizing letter that sets source requirements for average annual demand, peak day source demand and storage sizing as follows:

   •   Average Annual Demand = 237,250 gallons per ERC

   •   Peak Day Source Demand = 1,764 gallons per day per ERC

   •   Minimum Equalization Storage = 650 gallons per ERC

These sizing standards have been used for this analysis. The State will review the City's water usage and adjust these requirements every few years. These updates will take into account actual water usage which may be affected by conservation efforts, drought, or other factors. It should be noted that the production requirements of the State include a "variability factor" above and beyond actual historical use. This helps assure that water supply is available regardless of the variability of actual demand.

Production requirements have been compared to source availability to determine if City supplies are adequate to meet existing and future demands. The results of this analysis are summarized in a series of table below. Included in the tables is the following information:

   •   Projected future demands 1 . It will be noted that this is not a single value for any given year, but a range. As has been seen in the historical data, demand can vary significantly from year to year depending on weather conditions and other factors. The range shown incorporates the maximum and minimum per ERC water use in the historic record.

   •   Source sizing requirement based on the State of Utah minimum requirement.

   •   Source capacity. The City has two main sources of water: City-owned wells and water purchased from the Jordan Valley Water Conservancy District. These sources provide the City with 26,500 acre-ft/year of supply at a peak production rate of about 78 million gallons per day.

Results are summarized in Tables ES-2 through ES-5. Table ES-2 shows the projected annual demand and Table ES-3 shows the projected peak day demand through 2060. Table ES-4 shows the projected annual peak day supply compared with demand through 2060 and Table ES-5 shows the same comparison for peak day.

Table ES-2
Annual Water Demand Projection

Year	Projected Water Demand (Acre-Ft/Yr)		State Sizing Requirement (Acre-Ft/Yr)
	Low Estimate	High Estimate
2021	21,600	25,600	29,000
2026	24,300	28,300	32,200
2031	27,000	31,000	35,500
2041	29,600	33,600	38,600
2051	30,900	34,900	40,300
2060	31,200	35,200	40,700

 

Table ES-3
Peak Day Water Demand Projection

Year	Projected Water Demand (MGD)		State Sizing Requirement (MGD)
	Low Estimate	High Estimate
2021	41	59	75
2026	47	65	82
2031	54	72	90
2041	60	78	98
2051	63	81	102
2060	63	81	102

 

1 It should be noted that both projected demands and the State sizing requirement have been projected assuming that the City can successfully achieve the State of Utah Regional Conservation goal. This includes a reduction in per capita water use from 198 gallons per day (gpd) in 2020 to 183 gpd in 2030 and to 166 gpd in 2065.

Table ES-4
Annual Water Supply Projection

 

Year	JVWCD Contract (Acre-Ft/Yr)	JVWCD Contract - Extra 20% (Acre-Ft/Yr)	Well Production (Acre-Ft/Yr)	State Sizing Requirement (Acre-Ft/Yr)	Surplus / (Deficit) (Acre-Ft/Yr)
2021	20,000	4,000	2,500	30,800	(4,300)
2026				34,000	(7,500)
2031				37,200	(10,700)
2041				40,300	(13,800)
2051				41,900	(15,400)
2060				42,300	(15,800)

 

Table ES-5
Peak Day Water Supply Projection

 

Year	JVWCD Contract (MGD)	Well Production (MGD)	State Sizing Requirement (MGD)	Surplus / (Deficit) (MGD)
2021	70.5	7.1	74.6	3.0
2026			82.3	(4.7)
2031			90.2	(12.6)
2041			97.7	(20.1)
2051			101.6	(24.0)
2060			102.4	(24.8)

 

As can be seen in Tables, the City has enough annual supply to satisfy projected demands for the next few years. However, it does not have enough redundant supply to meet the State sizing standard with its current variability factor. It is recommended that the City explore options for gradually increasing its annual supply. At a minimum, the City will need to have access to additional supply no later than 2024 when its projected demand will exceed available supply, even without the recommended redundancy factor. There are a couple options to consider for future source capacity as demand increases. This includes increasing the City's JVWCD contract, moving large outdoor watering locations to secondary water, increasing conservation efforts, or increasing well capacity. Increasing well capacity may be limited due to groundwater quality and availability concerns.

Source capacity looks a little better as shown in Table ES-5. Even with the current variability factor, the City has adequate production capacity to meet needs through at least 2025. When compared to actual demands, existing sources are expected to be adequate to meet demands through 2045. Since peak demands have been trending downward in recent years, it is recommended that the City wait on developing additional peak day capacity as it monitors demand trends over the next few years. If the City continues its current trend, it may not be necessary to add peak day capacity for several decades.