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• Assess the capability of rainwater harvesting (RWH) to meet outdoor irrigation. • A GIS-based methodology implemented at the city scale. • Irrigation demand is largely met by RWH in 32% of the Tucson township sections. • RWH helps meet outdoor irrigation more effectively in typical residential areas. • The proposed RWH systems can lead to a total savings of 13.8 million dollars. The increased demand for water along with limited water supply and climate change has brought about water access challenges globally. Novel and sustainable water management systems are needed for addressing the imbalance between the increasing water demand and limited water resources. Rainwater as a renewable resource presents great potential to help achieve this goal. This study focuses on an important sustainable water management strategy, rainwater harvesting (RWH), and proposes a Geographic Information System (GIS) based method to assess the capability of RWH to meet outdoor irrigation demand at the city scale. High-resolution LiDAR data and orthophotos are used to delineate RWH catchment areas and identify outdoor vegetated sites. Both active and passive RWH are considered in the rainwater supply estimation. Factors including vegetation height, species, density and microclimate variables are incorporated in the outdoor irrigation demand estimation. The approach is applied to study the capacity of RWH in Tucson, Arizona, a semi-arid water stressed city in the Southwestern United States. Results show that the outdoor irrigation in 32% of the Tucson township sections can be met by RWH for more than 8 months of a wet year. The proposed RWH system deployment can lead to an overall savings of 13.8 million U.S. dollars and provides important insights into urban water management and sustainable water planning. [ABSTRACT FROM AUTHOR]

As an emerging technology, wireless communication revolutionizes the way data are shared and transferred. In particular, wireless mesh network (WMN) technology allows data transmission from one node to another without extensive cabling. In this article, spatial characteristics of maximal covering problems are explored, and a novel spatial optimization model is proposed for WMN topology planning. The model selects the optimal locations for network infrastructure to achieve the maximal coverage of spatial demand. Additionally, important WMN design requirements have been accounted for, including network topology and throughput capacity. The validity of the model is tested through a WMN deployment developed for an emergency medical service application in Tucson, Arizona. [ABSTRACT FROM AUTHOR]

• Tucson has the capacity to achieve net zero urban water with rainwater resources. • Passive systems help, but active systems are required for net zero urban water. • The median household storage required to support net zero urban water is 28.2 cubic-meters. • A roughly $10,000 investment per household is needed to reach net zero urban water. • Optimal rainwater harvesting areas do not correlate with socioeconomic status. Globally, cities are facing increased water stress with an imbalance between available water resources and projected urban water demands. Water experts have pointed to rainwater harvesting (RWH) as one answer; however, the capacity of such a solution to address deficits on an urban scale is largely untested. This study proposes a model to evaluate the necessary network of RWH systems to achieve net zero urban water, meaning a sustainable local supply capable of meeting long-term demand. This approach was applied to a water stressed city, Tucson, Arizona, in the semi-arid Southwestern United States. A daily water balance model optimized for the smallest required storage volumes to reach net zero urban water at a resolution of ten years of consecutive daily rainfall. The potential passive and active RWH network was modelled under four investment scenarios using remote sensing, localized daily rainfall, and municipal water meter data. In the most financially and physically plausible scenario, rainwater replaced imported water and a 30% demand conservation was assumed. The median required storage was 28.2 cubic-meters per 100 square-meters of roof area, or an estimated $10,000 investment. Comparatively, the median RWH household storage installation in Tucson is 5.3 cubic-meters (1395 gallons). In addition to widespread investment in large household storage, this result would require paradigm shifts across built, economic, and social systems to fully integrate the decentralized network across the urban fabric. This study shows that net zero urban water can be achieved with RWH under multiyear drought conditions with large storage volumes. [ABSTRACT FROM AUTHOR]

Access to a variety of affordable and healthy food has been a critical component in sustainable food-system planning. Research on food accessibility and food deserts (low-income areas with no or limited access to healthy food) can have important policy implications for alleviating health disparities. In the existing food access literature, supermarkets or large chain grocery stores have typically been used as the basis for measuring food access. Independent/non-chain grocers are often left out. We propose a multidimensional accessibility based assessment method to examine whether and how independent grocers help shape the food landscape and their locational strategy. A food desert elimination optimization model is formulated to evaluate the effectiveness of relying on small, full-service grocers for servicing food desert neighborhoods. The empirical study conducted in Tucson, Arizona indicates that, while full-service independent grocers fill some gaps left by chain markets, such stores are more helpful for improving food access diversity; this is reflected by the co-locating patterns of chain and non-chain stores. A few independent stores do, however, primarily serve food deserts in racially/ethnically diverse neighborhoods where higher proportions of residents rely on public assistance program and have limited mobility. Our case study suggests that small, independent grocers may have significant potential to aid in servicing areas with no or limited access to healthy food, particularly if policy incentives are provided. • We examined the role of full service independent grocery stores in shaping urban foodscape. • A spatial optimization model was developed to maximally eliminate food deserts. • Independent grocers are found to fill in the gaps left behind by chain stores in some communities while in many more add to the diversity rather than proximity. • They tend to serve more racially/ethnically diversified and dense neighborhoods. • Promoting small independent grocers in un- or underserved areas has great potential to improve regional food accessibility. [ABSTRACT FROM AUTHOR]

• Converting urban vacant land into food production sites helps increase healthy food access. • Harvested rainwater and reclaimed water can substantially enhance urban food production capability. • A new spatial optimization model is developed to optimize urban food production. • High level of community collaboration helps achieve more food production. • Urban food production has a great potential for addressing urban food deserts. Adequate access to healthy, affordable food remains a great challenge in many urban areas. Among a range of interventions, urban agriculture has been identified as an important strategy to help address urban healthy food access. While urban food production is growing in popularity, the use of potable water in traditional urban agricultural installations will exacerbate gaps in water demand and availability in water-stressed cities. This paper examines the sustainable capability of urban agriculture through an integration of alternative water resources, urban vacant land and local nutritional needs. A spatial optimization model is developed to best allocate limited resources for maximal food production to address urban food deserts. The new model is applied to test the capability of relocalized food production in Tucson, Arizona, a semi-arid region with the longest continuously farmed landscape in North America. Results highlight that urban areas with restricted water access can substantially enhance their local food production capacity in an ecologically responsible manner. [ABSTRACT FROM AUTHOR]