1. WATER RESOURCES Spokane County Residential Water Use Survey Results Mike Hermanson Water Resources Specialist Spokane County Utilities

2. WATER RESOURCES Overview Background & Purpose Survey Development Survey Distribution Survey Response Results

3. WATER RESOURCES Purpose Refine estimate of self supplied residential water use for Spokane County Water Demand Forecast Model –Other water use estimates utilize public water system data of similar areas. Is this assumption valid?

4. WATER RESOURCES Background USGS & the State of New Hampshire conducted a study to test the “public supply is similar to self supply” assumption. The study concluded that the assumption is valid, but it did not incorporate outdoor water use, and important component in Spokane County.

5. WATER RESOURCES Survey Development 4 page survey based on USGS & AWWA surveys. Local input provided by water purveyors, Ecology, Conservation District, local government. Survey included: –Household information # of people, home size, parcel size location water source –Indoor use # of fixtures, # of low flow toilets, shower heads –Outdoor use size of irrigated landscape type of irrigation system # of days/week, time per station, time of day Other uses – livestock, gardens, pools,

6. WATER RESOURCES Survey Distribution Classroom – Water on Wheels –204 classrooms/4,763 students –799 responses Post card to households outside water district boundaries –15,000 postcards –450 responses

7. WATER RESOURCES Survey Response Locations

8. WATER RESOURCES Survey Response Was the survey representative? –In 2008 there were approximately 150,000 single family housing units –A representative sample with a 99% confidence interval and a 3.75% error rate is 1,174 samples collected randomly. –The surveys were not collected randomly – How does the demographic data correspond to County averages?

9. WATER RESOURCES Survey Response Distribution method favored homes with children. Bias towards larger, newer homes –All county average is impacted by City of Spokane residences

10. WATER RESOURCES Survey Results Focused on differences in amount of irrigated landscape: Comparisons between groups distinguished by a particular variable –Average amount of irrigated landscape of public supply vs. self supply

11. WATER RESOURCES Survey Analysis Independent two sample t-test for samples of unequal size and unequal variance 8,358 ft 2 7,646 ft 2 8,358 ft 2 7,646 ft 2 Insignificant Difference between groups Significant Difference between groups Average area of irrigated landscape Public supply = 8,358 ft 2 Self supply = 7,646 ft 2

12. WATER RESOURCES Public vs. Self Supplied Table 6 –1: Public vs. Self Supplied - Average Irrigated Landscape Group Average Landscaped Area (sq ft) Standard Deviation Sample Size Significant Difference Public Supply83588110550 No Self Supply76469372486

13. WATER RESOURCES Public vs. Self Supplied

14. WATER RESOURCES Public vs. Self Supplied

15. WATER RESOURCES Public vs. Self Supplied

16. WATER RESOURCES Public vs. Self Supplied

17. WATER RESOURCES Public vs. Self Supplied Table 6-2: Watering Time Per Week-Public vs Self Supplied Group Watering time per week (hours) Standard Deviation Sample Size Significant Difference Public Supply1.321.25606 No Self Supply1.401.41502

18. WATER RESOURCES Influences on Self Supplied Water Use – Well Yield Table 6 - 3: Well Yield and Average Area of Irrigated Landscape Well Yield Range Average Landscaped Area (sq ft) Standard Deviatio n Sample Size Less than 5 gpm3,6846,09476 5 – 15 gpm8,77010,321158 15 – 40 gpm8,5388,987145 Greater than 40 gpm10,65212,45523 Table 6 -4: Well Yield Grouping Significance Testing Well Yield RangeLess than 5 gpm5 – 15 gpm15 – 40 gpm Less than 5 gpm - 5 – 15 gpm Significant- 15 – 40 gpm SignificantNot Significant- Greater than 40 gpm SignificantNot Significant

19. WATER RESOURCES Influences on Self Supplied Water Use – Residence Setting Table 6 -5: Residence Setting and Average Area of Irrigated Landscape Residence Setting Average Landscaped Area (sq ft) Standard Deviation Sample Size Rural-Forested6,1358,514206 Rural Pasture-Agricultural8,8279,969246 Suburban Neighborhood8,6289,78425 Table 6 –6: Residence Setting Significance Testing Residence SettingRural-ForestedRural Pasture-Agricultural Rural-Forested - Rural Pasture-Agricultural Significant- Suburban Neighborhood Not Significant

20. WATER RESOURCES Influences on Self Supplied Water Use – Lot Size Table 6 -6: Lot Size and Average Area of Irrigated Landscape Lot Size Average Landscaped Area (sq ft) Standard Deviation Sample Size 1 – 2 acres8,0688,88522 2 – 5 acres6,4749,18049 5 – 9 acres7,3388,525133 10 – 19 acres8,71710,138161 20 – 39 acres7,95010,15460 40 – 99 acres8,52010,93924 100 acres or greater4,9238,97113

21. WATER RESOURCES Influences on Self Supplied Water Use – Home Size Table 6 - 7: Home Size and Average Area of Irrigated Landscape Home Size Average Landscaped Area (sq ft) Standard Deviation Sample Size Less than 1600 sq ft5,0147,101108 1600 – 2400 sq ft7,9749,513153 2400 – 3600 sq ft7,4158,626141 Greater than 3600 sq ft11,25311,96077 Table 6 - 8: Home Size Significance Testing Home SizeLess than 1600 sq ft1600 – 2400 sq ft2400 – 3600 sq ft Less than 1600 sq ft - 1600 – 2400 sq ft Significant- 2400 – 3600 sq ft SignificantNot Significant- Greater than 3600 sq ft Significant

22. WATER RESOURCES Influences on Public Supplied Water Use – Residence Setting Table 6 - 9: Residence Setting and Average Area of Irrigated Landscape Residence Setting Average Landscaped Area (sq ft) Standard Deviation Sample Size City3,5433,70723 City Neighborhood5,8345,794122 Suburban Neighborhood8,7688,238357 Rural-Forested9,96210,63235 Rural Pasture-Agricultural8,9679,56839 Table 6 - 10: Residence Setting Significance Testing Well Yield Range CityCity NeighborhoodSuburban NeighborhoodRural-Forested City - City Neighborhood Significant- Suburban Neighborhood Significant - Rural-Forested Significant Not Significant- Rural Pasture-Agricultural Significant Not Significant

23. WATER RESOURCES Influences on Public Supplied Water Use – Lot Size Table 6 - 11: Lot Size and Average Area of Irrigated Landscape Lot Size Average Landscaped Area (sq ft) Standard Deviation Sample Size Less than ¼ acre4,7084,196126 ¼ acre6,8414,307150 ½ acre8,7256,284117 ¾ acre17,19110,34036 1-2 acres14,94112,39355 2-5 acres9,27511,50820 5-9 acres9,05710,65227 10 – 99 acres4,5269,21119

24. WATER RESOURCES Influences on Public Supplied Water Use – Lot Size Table 6 - 12: Lot Size Significance Testing Lot Size < ¼ acre¼ acre½ acre¾ acre1-2 acres2-5 acres5-9 acres < ¼ acre - ¼ acre Significant- ½ acre Significant - ¾ acre Significant - 1-2 acres Significant Not Significant- 2-5 acres Significant Not SignificantSignificant - 5-9 acres Significant Not SignificantSignificant Not Significant- 10 – 99 acres Not SignificantSignificant Not Significant

25. WATER RESOURCES Influences on Public Supplied Water Use – Home Size Table 6 - 13: Home Size and Average Area of Irrigated Landscape Home Size Average Landscaped Area (sq ft) Standard Deviation Sample Size Less than 1600 sq ft4,2456,034127 1600 – 2400 sq ft8,2427,411160 2400 – 3600 sq ft8,7807,687211 Greater than 3600 sq ft12,02310,64481 Table 6 - 14: Home Size Significance Testing Home SizeLess than 1600 sq ft1600 – 2400 sq ft2400 – 3600 sq ft Less than 1600 sq ft - 1600 – 2400 sq ft Significant- 2400 – 3600 sq ft SignificantNot Significant- Greater than 3600 sq ft Significant

26. WATER RESOURCES Water Use Influences Summary Self Supplied –well yield, residence setting, & home size impact landscape irrigation. –lot size does not impact landscape irrigation Public Supplied –residence setting, home size and lot size impact landscape irrigation

27. WATER RESOURCES Comparison of other outdoor water use Table 6 - 15: Comparison of other outdoor water use Type of water use Public SupplySelf Supply #%#% Total Households662579 Households with Livestock9111720 Horses only618915 Cattle only30153 Cattle and Horses00132 Households with Garden or Greenhouse2333531054 Garden only2263426847 Greenhouse only2071 Both51356 Size of landscape related to fire protection Yes1352039059 No1983010015 Wild fires not a concern28743467 Pool7411.186211.00

28. WATER RESOURCES Comparison of Indoor Water Use Table 6 - 17: Comparison of Indoor Fixtures & Appliances Fixture/Appliance Self Supplied Public Supplied sample size = 563sample size = 653 Average Standard Deviation Average Standard Deviation Toilets2.61.02.60.9 Bathtub with shower1.30.81.40.7 Bathtub only0.30.60.30.5 Shower only1.00.80.90.8 Whirlpool bathtub with jets0.20.40.20.5 Bathroom sink2.91.22.71.1 Kitchen faucet1.10.31.10.3 Indoor utility/garage sink0.6 0.40.5 Garbage disposal0.40.50.70.5 Top-load clothes washing machine0.60.50.60.5 Front-load clothes washing machine0.5 0.40.5 Dishwashing machine0.90.41.00.3 Showers with low flow head1.61.2 1.1 Toilets with 1.6 gallons per flush or less1.91.41.81.3

29. WATER RESOURCES Source Problems/Limitations Table 6 - 18: Number of Water Quality or Quantity Issues Identified Total Self Supplied Households579 Quantity or Quality Problem151 Quantity Problem identified54 Quality Problem identified61 Both Problems identified10 Holding tank or cistern175 Haul water58 Water source limitations181

30. WATER RESOURCES Water Quality/Quantity Problems

31. WATER RESOURCES Hauled Water

32. WATER RESOURCES Source Limits Water Use