Identifying Seasonal Opportunities to Save Water: Using Weekly Rainfall and Evapotranspiration Patterns to Evaluate Outdoor Water Restriction Policy in South Florida

Abstract

Evaluating trends of historical rainfall and lawn water demand on a weekly and seasonal basis is needed for optimizing lawn and landscape water conservation policy. Outdoor water restrictions are a common conservation strategy and typically feature a Bday of the week^schedule to limit the frequency and duration of urban lawn water use. However, outdoor water restrictions may not necessarily result in more conservative behaviors from end-users. Lawn water demand is directly related to weekly rainfall and evapotranspiration (ET) totals, yet regional rainfall and climate variables are seldom taken into account in water restriction strategies which generally sanction a static number of watering days per week, regardless of weather conditions. Where weekly irrigation schedules do not recognize weekly rainfall and are not connected to actual net irrigation needs, there is the potential to unintentionally promote overwatering. Ideally, to maximize water conservation, policy should be based on climate variables and conservation strategies should be synced as closely as possible to the specific hydrologic setting. In this paper, we present the results of a project that used historical rainfall and ET data to determine the typical seasonal and weekly variability of the net irrigation needs in an urbanized corridor of South Florida, USA. We identified times of the year when rainfall provides a significant amount of water on a weekly basis to meet the demand of residential lawns and landscapes and thereby identified opportunities to better align policy with regional climate. We demonstrate the benefit of using a weekly approach to analyze long-term trends in net irrigation need to identify periods or seasons when the 2 or 3 days per week allowed by typical outdoor water restriction strategies would allow a significant amount of overwatering. We propose this weekly perspective is valuable to inform efforts to better sync water restriction policies with climate.

Minimum water requirements of Japanese lawngrass for survival during prolonged drought

“…The findings of this paper can apply to both golf course roughs and home lawns because of similar management practices. Furthermore, policymakers may conserve more water during prolonged droughts by restricting irrigation of Meyer to 20–30% ET o rather than imposing traditional restrictions, especially for high irrigators (Boyer et al., 2018; Survis et al., 2017).…”

“…Water restrictions usually limit irrigation to specific hours within a day and/or days within a week (varying from 1–3 d wk −1 ; Boyer, Dukes, Duerr, & Bliznyuk, 2018). With few controls on water application amounts, restrictions can inadvertently promote overwatering (Boyer et al., 2018; Survis, Root, & Pathak, 2017). Furthermore, water restrictions do not factor in differences in water requirements among turfgrass species and cultivars, or dynamics in weather conditions that can dramatically affect the water requirements (Boyer et al., 2018; Survis et al., 2017).…”

“…With few controls on water application amounts, restrictions can inadvertently promote overwatering (Boyer et al., 2018; Survis, Root, & Pathak, 2017). Furthermore, water restrictions do not factor in differences in water requirements among turfgrass species and cultivars, or dynamics in weather conditions that can dramatically affect the water requirements (Boyer et al., 2018; Survis et al., 2017). Additionally, damage to turfgrass during long‐term water restrictions may result in a failure to recover after prolonged drought and heat stress (Hong, Bremer, & Keeley, 2020).…”

Water Conservation Benefits of Long‐Term Residential Irrigation Restrictions in Southwest Florida

“…Households had fewer irrigating events per week (mean of 1.3) than allowed under water restrictions (two), but the irrigation applied (mean of 1 in./week) exceeded the target irrigation (mean of 0.3 in./week) in 15 of the 16 weeks, indicating over‐irrigation. In a related study of Palm Beach County, Survis et al () reported that two days/week irrigation at the rates observed in Survis and Root () would have exceeded target irrigation in 99% of the weeks in the study's 20‐year historical period. Households included in the study used either public‐supplied potable water or a private well for irrigation.…”