WATER-SMART URBAN GREENING IN ARID CITIES: A CRITICAL REVIEW OF HYDROLOGICAL, THERMAL, AND DISTRIBUTIVE TRADE-OFFS

Abstract

Arid and semi-arid cities face a structural contradiction: the vegetation that cools streets, cleans air, and supports psychological well-being depends on a resource that is chronically scarce. This paper offers a critical, theoretically grounded review of the empirical literature on "water-smart" landscaping in dryland cities, synthesizing evidence on four strategy families   climate-appropriate species selection, alternative water sourcing, irrigation optimization, and policy instruments   and evaluating each against hydrological, thermal, economic, and socio-institutional criteria drawn from socio-hydrology and urban political ecology. Rather than treating urban greening as an unconditional good, the review foregrounds the trade-offs that single-criterion assessments obscure, most notably the non-linear relationship between irrigation input and cooling benefit and the uneven distribution of both the costs and the amenities of desert landscape transitions. Drawing on verified empirical studies from Riyadh, Jeddah, Phoenix, coastal California, Jordan, Kuwait, Nevada, and Australia, the review shows that water savings of 60-90 percent are achievable at the plant and parcel scale, but that these savings do not translate automatically into either thermal benefit or equitable outcomes at the municipal scale. The paper argues that sustainability assessment of arid urban greening must be multi-criterion and multi-scalar, and it closes with implications for landscape ordinances, tariff design, and the governance capacities that determine whether technically proven strategies are actually adopted.