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Well

Water Use
Demand Forecast

Joe Stump, P.E., Utilities Manager
Joe.Stump@co.yakima.wa.us

Office Hours: M - F, 8:00 AM - 4:00 PM
Accounting Office: 574-2290
Engineering Office: 574-2300

 

6, 20 & 50 Year Demand Projections

Future water demands are estimated based on historical demands plus the demand from an additional 40 new equivalent residential units (ERUs) per year.  Demand estimates for new ERUs are as follows:

Average Day Demand                670 gpd/ERU          
Peak Day Demand                  1,800 gpd/ERU          
Peak Hour Demand                3,600 gpd/ERU          

In estimating future demands, it is assumed that separate irrigation will not be available and that the distribution of new connections between the pressure zones will be similar to what has occurred in the past.  Actual demands will vary depending on the progress of developments that are being proposed. 

Table 3-15 includes a water demand forecast for the system and Pressure Zone 3.  A separate forecast is not included for Zone 4 since a significant increase in connections is not expected in this zone in the near future.  Before new connections are installed in Zone 4, additional pumping, storage, and distribution system improvements are necessary.  The cost of these improvements makes it more likely for the lower zones to develop first.  The lower zones include sufficient undeveloped land to accommodate 20-years of growth.

 Table 3-15
Water Demand Forecast

 

 2008

2014

2028

2058

 Demands without projected water savings from Water Use Efficiency Program

System        
Projected Additional ERUs
240
800
2000
Average Day Demand (gpd)
831,000
992,000
1,367,000
2,171,000
Peak Day Demand (gpd)
1,865,000
2,297,000
3,305,000
5,465,000

Peak Hour Demand (gpm)

2,450

3,050

4,450

7,450

 
Zone 3        
Projected Additional ERUs  - 150 500 1,300
Peak Day Demand (gpd) 1,488,000 1,760,000 2,400,000 3,800,000
Peak Hour Demand (gpm) 1,960 2,340 3,200 5,200
 
Zone 4        
Projected Additional ERUs
-
0
0
See Note
Peak Day Demand (gpd)
72,000
72,000
72,000
3
Peak Hour Demand (gpm)
100
100
100

 

Demands with projected water savings from Water Use Efficiency Program

Systems

       
Projected Additional ERUs
-
240
800
2000
Average Day Demand (gpd)
831,000
962,000
1,326,000
2,100,000
Peak Day Demand (gpd)
1,865,000
2,228,000
3,206,000
5,300,000
Peak Hour Demand (gpm)
2,450
2,960
4,320
7,230
 
Zone 3        
Projected Additional ERUs
-
150
500
1,300
Peak Day Demand(gpd)
1,488,000
1,707,000
2,330,000
3,690,000
Peak Hour Demand (gpm)
1,960
2,270
3,100
5,040
 
Zone 4        
Projected Additional ERUs
-
0
0
See Note
Peak Day Demand (gpd)
72,000
70,000
70,000
3.
Peak Hour Demand (gpm)
100
100
100

 Notes:

  1. Number of customers and demands for Zone 3 include all zones except Zone 1 and 1a.
  2. Water demand forecasts are based on the highest recorded average day, peak day and peak hour demands through 2008, plus demand projections for future single-family residential customers without separate irrigation.
  3. Development of Zone 4 is likely within the next 50-years, and possibly within the next 20-years.  To what extent is difficult to predict.
  4. Demands without projected water savings from water use efficiency program will be used in the system analysis.

 

Demands Per Acre

Single-family demand projections per acre are listed below.  The projections are based on 3.5 units per acre, which is similar to Terraced Estates (423 units per 120 acres) and Mount Adams Estates (79 units per 22 acres).   

 
Without Separate Irrigation
With Separate Irrigation
Average Day Demand 
2,350 gpd per acre, or 2.6 acre-feet per acre per year 1,330 gpd per acre, or 1.5 acre-feet per acre per year
Peak Day Demand  
6,300 gpd per acre, or 4.4 gpm per acre 2,450 gpd per acre, or 1.7 gpm per acre