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Spokane County Residential Water Use Survey Results

Mike Hermanson Water Resources Specialist Spokane County Utilities. Spokane County Residential Water Use Survey Results. Overview. Background & Purpose Survey Development Survey Distribution Survey Response Results. Purpose.

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Spokane County Residential Water Use Survey Results

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

  2. Overview • Background & Purpose • Survey Development • Survey Distribution • Survey Response • Results

  3. 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. 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. 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. 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. Survey Response Locations

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

  10. 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. Survey Analysis • Independent two sample t-test for samples of unequal size and unequal variance 7,646 ft2 8,358 ft2 Average area of irrigated landscape Public supply = 8,358 ft2 Self supply = 7,646 ft2 Insignificant Difference between groups 7,646 ft2 8,358 ft2 Significant Difference between groups

  12. Public vs. Self Supplied Table 6 –1: Public vs. Self Supplied - Average Irrigated Landscape

  13. Public vs. Self Supplied

  14. Public vs. Self Supplied

  15. Public vs. Self Supplied

  16. Public vs. Self Supplied

  17. Public vs. Self Supplied Table 6-2: Watering Time Per Week-Public vs Self Supplied

  18. Influences on Self Supplied Water Use – Well Yield Table 6 - 3: Well Yield and Average Area of Irrigated Landscape Table 6 -4: Well Yield Grouping Significance Testing

  19. Influences on Self Supplied Water Use – Residence Setting Table 6 -5: Residence Setting and Average Area of Irrigated Landscape Table 6 –6: Residence Setting Significance Testing

  20. Influences on Self Supplied Water Use – Lot Size Table 6 -6: Lot Size and Average Area of Irrigated Landscape

  21. Influences on Self Supplied Water Use – Home Size Table 6 - 7: Home Size and Average Area of Irrigated Landscape Table 6 - 8: Home Size Significance Testing

  22. Influences on Public Supplied Water Use – Residence Setting Table 6 - 9: Residence Setting and Average Area of Irrigated Landscape Table 6 - 10: Residence Setting Significance Testing

  23. Influences on Public Supplied Water Use – Lot Size Table 6 - 11: Lot Size and Average Area of Irrigated Landscape

  24. Influences on Public Supplied Water Use – Lot Size Table 6 - 12: Lot Size Significance Testing

  25. Influences on Public Supplied Water Use – Home Size Table 6 - 13: Home Size and Average Area of Irrigated Landscape Table 6 - 14: Home Size Significance Testing

  26. 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. Comparison of other outdoor water use Table 6 - 15: Comparison of other outdoor water use

  28. Comparison of Indoor Water Use Table 6 - 17: Comparison of Indoor Fixtures & Appliances

  29. Source Problems/Limitations Table 6 - 18: Number of Water Quality or Quantity Issues Identified

  30. Water Quality/Quantity Problems

  31. Hauled Water

  32. Source Limits Water Use

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