2.1. Residential Water Consumption Survey
The 2015 residential water consumption survey was designed and conducted by mailing questionnaires to residents across the city of Fresno in California. The city of Fresno provides a GIS-shapefile containing all the family addresses in Fresno. We first discarded those who are not single families, because only single families would receive their monthly water bill in Fresno. Then, 6000 single-family addresses (about 5% of total households in Fresno) were randomly selected for this survey. The survey data were kept confidential in several ways. We did not ask for the names of respondents. The finding results were also reported at the aggregate level to make sure that any individual respondent cannot be identified. In total, 294 residents completed the survey and sent back their questionnaires. This low response rate (5%) most likely resulted from the lack of incentives provided for the respondents to complete the survey. Respondents were asked to record their water consumption in the unit of 100-cubic feet (1 HCF = 748 gallons = 2.83 m3), based on their water bills of September 2015, together with the physical attributes of their houses, their economic conditions, and the attitudes toward water-saving options, such as house size, lot size, the number of bathrooms, the status of water heater, the presence of pools, the frequency of pool use, the methods and frequency of backyard watering, landscaping plant types, house aspects, household income, and the attitude relating to water use and saving. Note that the total amount of monthly residential water use is shown in HCF on the water bill, and therefore respondents can easily find the accurate number when filling out the questionnaire. One limitation is that we did not provide options for respondents to select if they are not willing to or not able to answer the questions in the survey. We acknowledge that this might limit the interpretations for the survey results, and this will be certainly considered in future research.
The survey data show that average residential water consumption per household is 27 HCF (76.45 m
3) (see
Table 1). About 87% of the 273 respondents reported that they used less water as compared to that at the same time last year, most likely due to the increasing awareness of the five-year drought in California. Indeed, these respondents used less water (with a mean of 26.5 HCF (75.03 m
3)) than those who did not change their water-use behavior (with a mean of 30.7 HCF (86.93 m
3)). This finding confirms the argument in former studies [
5,
11] that drought experience influences water-use behavior. About a quarter (25%) of the respondents have pools in their backyards, and they used their pools about 1.5 times a week. Twenty-three percent (23%) of them reported that they used their pools less often in the study year (2015). The average number of backyard watering across the 279 respondents is two (2), which is exactly the same as the restricted number of watering days required in the emergency regulation issued by the State of California in early 2015. In addition, statistical tests (
F-tests for continuous variables and Chi-square-tests for nominal variables) were conducted to see if these variables show any differences among various income groups (see the last column in
Table 1). The results show that differences exist between different income groups in monthly water consumption, the number of waterings per week, the number of pool uses per week, and the use of hand watering. For instance, high income households (annual income > $100,000) use water the most (40 HCF (113.26 m
3) on average), while the medium income households (annual income between $40,000 and $100,000) use the least amount of water (20 HCF (56.63 m
3)). Additionally, high-income families tend to use their pools and water their backyards more often than the other two income groups (see
Table 1).
A sprinkler irrigation system with/without a timer (80%) is the most populous watering method among our survey respondents, as compared to a drip irrigation system (8%) and hand watering (19%). Note that a respondent could use a multi-irrigation system, depending upon the design of landscaping. High and medium income families prefer using sprinklers with a timer (80% and 68%, respectively) for watering, while low income families are more likely to choose sprinklers without a timer (22%) and hand watering (39%). Landscaping in the backyard of a house usually comprises varied plants (e.g., lawns, shrubs, and trees) and a portion of bare land. As shown in
Table 1, most high income families have more than one landscaping plant in their backyards. This reflects the fact that high income families can afford more for a multi-planted landscaping design than other income groups. Furthermore, it is interesting to see that more than half of the 234 respondents consider themselves heavy water users (51%). Particularly, most low (65%) and medium (51%) income families reported that they are heavy water users, while most high-income families (61.2%) thought themselves as medium water users.
In addition, the survey asked respondents about their water-saving applications in the house (see
Table 2). In general, most respondents reported that they were reducing indoor (77%) and landscaping (89%) water uses, most likely due to the recent severe drought impacts. Only less than half (40%) of respondents considered saving indoor waste-water for outdoor landscaping watering, such as irrigating the backyard using drains from the washing machine. Around 16% of the respondents used other waster saving applications, such as artificial grasses, less toilet flushing, watering trees only, less clothes and car washing, and short showers. It is also interesting to note that the higher the household income, the more likely they responded that they were reducing water use. Nevertheless, as shown in
Table 1, high income families still used more water than the other two income groups. Medium income families seem interested in applying more diverse and creative options to save water, as compared to the other two income groups.
Respondents were asked to select water-saving policies, which they would support for implementation. Public outreach (50%) and free water-wise landscaping consultation (49%) were ranked as the top-two water-saving policies, indicating that respondents generally favor policies that do not incur costs for water saving. Particularly, more low income families cited “I do not support any water-saving policy” than the other two income groups. It is not surprising that the higher the income families, the more willing they become to support costly water-saving policies. Geller et al. [
37] also reported that only the installation of low cost water conservation devices would have significant effects on water saving. Several water-saving policies were also suggested by the respondents, such as tax rebates for water-wise landscaping, technologies on recycling waste water, increasing water awareness, fines for wasting water, improvements of water related infrastructure and facilities, incentives for drought tolerance landscaping, limits on new buildings, and additional dams and reservoirs. A number of respondents also reported that the behavior of wasting water really bothered them, particularly seeing that from their neighbors. Corral-Verdugo et al. [
26] also supported this finding that the perception of externalities would have positive effects on residential water consumption. In addition, it is interesting that the statistically insignificant results show that income level makes no difference to either water-saving applications or water-saving polices (see the last column in
Table 2 and
Table 3).