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While long‐term rainfall trends and related atmospheric dynamics have been researched over the past several decades across equatorial Africa, little is known about rainfall in western Uganda, a transition zone in the middle of the continent. Using satellite‐derived rainfall and reanalysis data from 1983 to 2017, this study examines atmospheric characteristics of seasons and multidecadal trends in rainfall. Most of the region has a biannual rainfall regime (i.e., the first rains within March–May and the second rains during August–November). Ascending (descending) air and increased (decreased) specific humidity are observed over western Uganda during the rainy (dry) seasons. Southeasterly air‐parcel back trajectories are common throughout western Uganda at all times except for the first dry season (i.e., December–February). For all seasons, wet days in western Uganda are characterized by increases in ascending air and specific humidity in addition to westerly flow anomalies. Wet days in most seasons also have a disproportionately high frequency of westerly back trajectories extending over the Congo Basin. These Congo westerlies are associated with more vertical ascent and a more humid middle troposphere compared to the other trajectories. Rainy seasons, especially the first rains, have gotten longer and wetter throughout western Uganda. The duration of the first rains increased by about 1 month over the 35 years; in turn, the rainfall total increased by approximately 70%. Rainfall also has increased for climatological seasons, with the exception being December–February. Increases in middle‐troposphere specific humidity and vertical ascent over time provide support for the wetting trends derived from the satellite‐derived rainfall data. The two rainy seasons have gotten longer and wetter, with significant increases in duration and rainfall total for the first rainsRainfall increased in all seasons, except DJF, throughout the region, and southwestern Uganda had the largest increase in annual rainfallCongo westerlies contribute substantially to rainfall, especially during JJA and SON, but were not responsible for the wetting trends

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. Evapotranspiration (ET) varies greatly among developed land‐cover classes in a humid subtropical climateET totals specific to land‐cover classes aggregate to reliable estimates for urban watershedsThe largest source of uncertainty for urban ET estimates is likely the magnitude of evaporation from impervious surfaces Evapotranspiration (ET) varies greatly among developed land‐cover classes in a humid subtropical climate ET totals specific to land‐cover classes aggregate to reliable estimates for urban watersheds The largest source of uncertainty for urban ET estimates is likely the magnitude of evaporation from impervious surfaces

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. Water infrastructure degrades over time, allowing for the movement of large volumes of fluids to and from the environment. Inflow is the flow of precipitation into sanitary‐sewer pipes through, for example, leaky manholes and gutter downspouts. Infiltration is the flow of groundwater into the same pipes through fractures, leaky joints, and other defects. They cause overflows of untreated sewage that endanger humans and ecosystems. Inflow and infiltration also represent large diversions of fresh water away from local streams. We examined rates of flow in four sanitary‐sewer pipes and quantified the inflow and infiltration. We compared these estimates to the rates of flow in nearby streams. We find that inflow and infiltration of fresh water into sanitary‐sewer pipes commonly represent 20%–40% of the flow in the pipes. Most of that water emanates from aquifers with a smaller fraction supplied by precipitation. If the inflow and infiltration were abated, and that fresh water instead flowed to stream channels, then the flows in those channels during dry periods could be enhanced by as much as 6%–36%. This is important in urban watersheds, where streamflow during dry weather is already diminished. Inflow and infiltration represent infrastructure‐mediated flow pathways that substantially alter the water cycle in urban watersheds. Large volumes of precipitation and ground water flow into sanitary‐sewer pipesThis undesirable diversion of water substantially reduces flow in urban streamsAbatement of this problem could enhance low flows in urban streams by 6%–36% Large volumes of precipitation and ground water flow into sanitary‐sewer pipes This undesirable diversion of water substantially reduces flow in urban streams Abatement of this problem could enhance low flows in urban streams by 6%–36%