Insights into Efficient Irrigation of Urban Landscapes: Analysis Using Remote Sensing, Parcel Data, Water Use, and Tiered Rates

Abstract

To understand how landscape irrigation can be better managed, we selected two urban irrigation systems in northern Utah, USA, and performed a statistical analysis of relationships among water use, irrigated area, plant health (based on the Normalized Difference Vegetation Index), and water rate structures across thousands of parcels. Our approach combined remote sensing with 4-band imagery and on-site measurements from water meters. We present five key findings that can lead to more efficient irrigation practices. First, tiered water rates result in less water use when compared to flat water rates for comparable plant health. Second, plant health does not strictly increase with water application but has an optimum point beyond which further watering is not beneficial. Third, many water users irrigate beyond this optimum point, suggesting that there is water conservation potential without loss of aesthetics. Fourth, irrigation is not the only contributor to plant health, and other factors need more attention in research and in water conservation programs. Fifth, smaller irrigated areas correlate with higher water application rates, an observation that may inform future land use decisions. These findings are especially pertinent in responding to the current drought in the western United States.

Why Is Residential Irrigation So Hard to Optimize?

“…Second, the typical components of residential sprinkler systems are too imprecise. The physical layout of residential landscapes-the engineered part-often results in small, irregular, isolated areas such as park strips (between the road and the sidewalk) and flower beds (Figure 2) that are difficult to cover efficiently with standard sprinkler heads [5,9]. Second, the typical components of residential sprinkler systems are too imprecise.…”

“…Finally, customers, as a group, are too untrained. Several studies document that many customers overwater landscapes due to the lack of adequate irrigation training, skills, and knowledge [3,5,11]. While a few are well informed, most know little of plant, soil, and water science, yet millions of them make daily decisions about how to use water resources.…”

“…However, residential irrigation is often inefficient and, as such, is naturally at the forefront of contemporary water management discussions. Shurtz et al [5] found that half of residents in two Utah study areas were overwatering and that the excess water was harming rather than helping their landscapes. For a study area in Texas, Lewis et al [6] determined that overwatering customers were a minority of the customer population yet were responsible for the largest percentage of overwatering by volume.…”

Transforming Great Salt Lake from Afterthought to Asset

“…Because consumptive water use is the culprit [5,6], we need strategies to reduce consumptive water use upstream-ideally without losing the intended benefits-and leave more water available for the lake. One prime candidate is residential landscape irrigation, which recent studies show can be done far more efficiently even without changing the landscapes [9,10]; another is agricultural irrigation, where Utah has a well-funded program for water optimization [11,12]. Utah has had water conservation goals since 2000, and a 2019 update revised them to capture new technologies, policies, and regionally specific opportunities [13].…”

Use of Level-of-Service-Based Water Pricing to Sustain Irrigated Agriculture: A Case of Modernized Irrigation System in Vietnam

“…More studies have shown the efficiency of applying the LoS concept in different areas such as Shurtz, et al [15], in exploring water use for irrigation in urban settings and the role of pricing in encouraging users to match their water use to the LoS, or Atwater, et al [16], in suggesting an individualized approach to determining water rates based on customers' water-use patterns using smart meters, and Han, et al [17], in recommending the use of customer-driven LoS to set appropriate service levels in water infrastructure asset management. In Australia, rural water prices are determined based on the cost of supply as "cost reflective pricing" and crucially reflecting the LoS provided [18].…”