Intro Page Shifting Patterns of Water Demand: Socio-Demographic Challenges for Water Managers Gary Woodard, Ass t. Director NSF STC for Sustainability of Semi-Arid Hydrology and Riparian Areas (SAHRA) College of Engineering & Mines, University of Arizona Drought Briefing, Phoenix A SAHRA-CLIMAS INITIATIVE Thursday March 20, 2003
Tendency to focus on a few demand factors Water demand factors always considered: Population levels Price Sometimes considered: Conservation Weather & Climate Rarely considered: Socio-demographic factors Changes in housing stock Impacts of Wealth
Population Growth Rates
National trends in water and sewer rates
Tendency to focus on a few demand factors Water demand factors always considered: Population levels Price Sometimes considered: Conservation Weather & Climate Rarely considered: Socio-demographic factors Changes in housing stock Impacts of Wealth
Factors Affecting Residential Water Demand Housing Type Duplex/triplex Mobile home Single family detached Townhouse/condo Apartment Residency Age of home Years lived in home Years lived in community Monetary Factors Own or rent home? Value of home/monthly rent Annual income Pay the water bill? Demographics Children under 5 Children 5 to 18 People home during day Head of household retired? Appliances Clothes washer Dishwasher Garbage disposal Evaporative cooler/ac Installed low-flow device? Landscape Factors Amount of turf How landscape is irrigated Swimming pool
Effects of selected water demand factors* Factor of Water Demand % Homes with Factor Indoor Demand Peak Outdoor Total Peak Demand Clothes Washer 91.3 21.9 n/a 21.9 Dishwasher 57.1 11.0 n/a 11.0 Garbage Disposal 49.1 11.5 n/a 11.5 Evaporative Cooler 63.5 n/a 26.6 26.6 Installed Low-flow Device 47.5-19.8 n/a -19.8 Turf w/in-ground sprinkler 11.5 n/a 0.043/ft 2 0.043/ft 2 Turf w/hose & sprinkler 22.3 n/a 0.038/ft 2 0.038/ft 2 Turf w/o regular irrigation 3.9 n/a 0.034/ft 2 0.034/ft 2 Swimming Pool 19.6 68.3 86.1 154.4 *Values in gallons/day/household in Tucson, AZ. Source: Woodard & Rasmussen.
Types of trends affecting domestic water demand Socio-Demographic Factors Changes in Housing Stock Impacts of Wealth
Socio-Demographic factors of water demand Population growth rates Persons per Household (PPH) Migration patterns Demographic tree (age cohorts)
Fewer persons per household affects water demand Lower PPH decreases per capita indoor demand, but it increases per capita outdoor demand. 3.4 3.2 PPH in Pima Co 3 2.8 2.6 2.4 2.2 2 1970 1980 1990 2000
Demographic trees & water demand impacts
Housing Stock Factors Housing mix SFRs, Townhomes, Apartments SFR Lot Sizes, Phoenix & Tucson SFR Characteristics Microclimates Second Homes
Trends in Housing Stock Mix
Trends in Lot Sizes for Single Family Residences
Housing Factors Affecting Water Demand Ctl-A; Ctr-H
Pools, Patios and Spas Significant outdoor water demand is generated by: swimming pools misting systems on patios spas
Percent homes with pools by age of home Pool area
Pool cover frequency and patterns of use Roughly 3 out of 5 pools have pool covers, but most describe them as hard to use. Annual usage patterns show covers are used half the time, but mostly to prolong the swim season, and not in mid-summer. 70 60 50 40 30 20 10 0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Pool area
Evaporative cooling vs. refrigerative air conditioning
Bathroom fixtures
Problems found with aging ULF toilets 45 40 35 30 25 20 15 10 5 0 Percent of Households Experiencing Problem 13.5 Double Flush 15.3 Flapper Leak 26.4 High Flush Volume 42.9 Some Problem Bathroom
Frequency of re-use by water source 35 Frequency of Water Reuse Tucson Water Residences % households 30 25 20 15 10 5 0 rooftop runoff swamp cooler bleedoff gray water surface runoff pool/spa filter backwash
Urbanization Increases Existing Water Demands mm per month 400 Pan evaporation, Phoenix, Arizona t Island and Pan Evaporation Monthly Averages, Phoenix, Arizona 350 300 250 1969-200 150 1917-100 50 Jan. Mar. May Jul. Sep. Nov.
Wealth increases domestic water demand Arrowhead Ranch, Arizona features artificial lakes, golf, and swimming pools.
Wealth Factors of Residential Water Demand Wealth-related factors of demand include: household income housing affordability home ownership rates price of water
Household income 45000 40000 35000 30000 25000 20000 15000 10000 5000 0 1969 1979 1989 2000 Maricopa Pima
Housing affordability has increased for 20 years
Impacts of home ownership Rising home ownership rates increase outdoor demand. % households 69 68 67 66 65 64 63 62 61 60 59 58 1995 1996 1997 1998 1999 2000 2001
What is cumulative effect of all trends? Demand Factor Trend Indoor demand Outdoor demand Population up up up Price of water, sewer up down down Socio-Demographic PPH down down up % Children????????? % Retirees up --- up Wealth Household income up up up Housing afford. Up --- up Home Ownership up --- up
Cumulative effect of all trends (cont.) Demand Factor Trend Indoor demand Outdoor demand Housing Stock SFRs (vs. Apts.) up --- up Lot size??? ---??? Turf (vs. xeric) down --- down % homes w/pools up --- up % pools w/covers up? --- down? AC (vs. evap.) up --- down ULF toilets up down --- Low-flow showers up down --- Water re-use??? ---??? Urban heat island up --- up Urban sprawl up --- down NET RESULT down up