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Abstract Urbanization introduces new and alters the existing hydrological processes. Projecting the direction and magnitude of change of evapotranspiration (ET), often a large existing process, in humid subtropical climates is difficult due to the lack of land‐cover specific estimates of ET. This research aims to improve our fundamental understanding of ET in urban areas by focusing on ET specific to land‐cover classes of the National Land Cover Database (NLCD). Using multiple physically based models along with ET from reference watersheds, this study estimates ET—within the Atlanta, GA, USA region—for NLCD classes. ET also is estimated for urban watersheds—both in the Atlanta region and in areas with humid subtropical climate types—for which published ET estimates exist. There are major differences in land cover among the four developed classes: high‐intensity developed land is 92% impervious surfaces, while open‐space developed land—the least intensively developed land—is only 8% impervious surfaces. Consequently, open‐space developed land has an ET total that is over four times that of high‐intensity developed land. Due to a high percentage of impervious cover and substantial evaporation of water from impervious surfaces throughout the year, there is little intra‐annual variation in ET for the high‐intensity developed class. The land‐cover ET totals aggregate to reliable estimates for urban watersheds. The largest source of uncertainty for ET estimates in urban areas is likely the evaporation magnitude associated with impervious surfaces; therefore, more work is needed in determining those magnitudes for humid subtropical climates. 

Abstract Defects in sanitary‐sewer infrastructure enable exchange of large volumes of fluids to and from the environment. The intrusion of rainfall and groundwater into sanitary sewers is called inflow and infiltration (I&I). Though long recognized in the assessment of sewers, the impacts of I&I on streamflow within urban watersheds are unknown. We quantified rainfall‐derived I&I (RDI&I), groundwater infiltration (GI), and total I&I using measured flows within sanitary‐sewer pipes serving four watersheds near Atlanta, Georgia, USA. Flows were monitored in pipes that parallel local stream channels and compared with streamflow measured at nearby gauging sites. Freshwater diverted into the sewer system due to I&I ranged from 24% to 36% of the flow measured within individual pipes. The RDI&I was the smaller component of I&I, ranging from 4.2 to 9.8 mm per year among watersheds. The GI was typically an order of magnitude greater than RDI&I, ranging from 24 to 41 mm per year among watersheds with annual stream discharge of approximately 500 mm. The I&I occurring at specific moments in time commonly represented 0%–20% of the flow measured in the adjacent stream. The enhancement of low flows in streams that could be achievable if I&I were abated ranges from as much as 6%–36% across watersheds. Our discussion presents explanations for the seasonality of I&I and associated impacts on streamflow in urban watersheds, while identifying important sources of remaining uncertainty. Our results support the conclusion that I&I substantially reduces flows in urban streams, especially low flows during dry weather. 

Globally, rapid population growth in cities, regulatory and governance failures, poor infrastructure, inadequate funding for urban water systems, and the impacts of climate change are each rapidly reconfiguring regional hydrosocial relations. In the United States, these hydrosocial reconfigurations tend to reinforce racial inequalities tied to infrastructure, exacerbating environmental injustices. More generally, according to a framework of racial capitalism, infrastructural regions and hydrosocial relations are always already racialized and structured simultaneously by capitalism and racism. In this paper, we integrate hydrosocial and racial justice perspectives with the literature on infrastructural regionalism to examine Atlanta’s position in the so-called tri-state water wars between Alabama, Georgia and Florida. Combining analysis of academic, policy, and legal documents, journalistic accounts, and semi-structured interviews with water conservationists and managers working in Atlanta, we examine conflicts over water use in the infrastructural region of the Apalachicola–Chattahoochee–Flint (ACF) river system. We emphasize that the ACF conflict reworks regional hydrosocial relations through territorializations of racial capitalism. We demonstrate how particular discourses that reify Atlanta as a monolith overly simplify the regional dimensions of the crisis, diminishing the views, roles and interventions of diverse actors in the ACF region. We argue that work on infrastructure regionalism and water governance can be deepened through attention to the hydro-racial fix.