Alteration of land use and climate change are among the main variables affecting watershed hydrology. Characterizing the impacts of climate variation and land use alteration on water resources is essential in managing watersheds. Thus, in this research, streamflow and baseflow responses to climate and land use variation were modeled in two watersheds, the Upper West Branch DuPage River (UWBDR) watershed in Illinois and Walzem Creek watershed in Texas. The variations in streamflow and baseflow were evaluated using the Soil and Water Assessment Tool (SWAT) hydrological model. The alteration in land use between 1992 and 2011 was evaluated using transition matrix analysis. The non-parametric Mann–Kendall test was adopted to investigate changes in meteorological data for 1980–2017. Our results indicate that the baseflow accounted for almost 55.3% and 33.3% of the annual streamflow in the UWBDR and Walzem Creek watersheds, respectively. The contribution of both land use alteration and climate variability on the flow variation is higher in the UWBDR watershed. In Walzem Creek, the alteration in streamflow and baseflow appears to be driven by the effect of urbanization more than that of climate variability. The results reported herein are compared with results reported in recent work by the authors in order to provide necessary information for water resources management planning, as well as soil and water conservation, and to broaden the current understanding of hydrological components variation in different climate regions.

The change in both streamflow and baseflow in urban catchments has received significant attention in recent decades as a result of their drastic variability. In this research, effects of climate variation and dynamics of land use are measured separately and in combination with streamflow and baseflow in the Little Eagle Creek (LEC) watershed (Indianapolis, Indiana). These effects are examined using land-use maps, statistical tests, and hydrological modeling. Transition matrix analysis was used to investigate the change in land use between 1992 and 2011. Temporal trends and changes in meteorological data were evaluated from 1980–2017 using the Mann–Kendall test. Changes in streamflow and baseflow were assessed using the Soil and Water Assessment Tool (SWAT) hydrological model using multiple scenarios that varied in land use and climate change. Evaluation of the model outputs showed streamflow and baseflow in LEC are well represented using SWAT. During 1992–2011, roughly 30% of the watershed experienced change, typically cultivated agricultural areas became urbanized. Baseflow is significantly affected by the observed urbanization; however, the combination of land and climate variability has a larger effect on the baseflow in LEC. Generally, the variability in the baseflow and streamflow appears to be heavily driven by the response to climate change in comparison to variability due to altered land use. The results reported herein expand the current understanding of variation in hydrological components, and provide useful information for management planning regarding water resources, as well as water and soil conservation in urban watersheds in Indiana and beyond.

High levels of nutrient loads in a catchment indicate the presence of pollution sources that must be identified and quantified. These loads in surface and groundwater have been a major concern that impacts water quality in the Midwestern US, including the Great Lakes Basin. In this study, we use the Soil and Water Assessment Tool (SWAT) to assess the impact of land use changes on hydrology, nutrients, and sediment loads for the St. Joseph River Basin (SJRB), which drains an area of 12,200 km² in Southwest Michigan/Northwest Indiana and is a primary source of pollutant to Lake Michigan. The SWAT models were developed to simulate streamflow, baseflow, total suspended solids (TSS), total phosphorous (TP), dissolved reactive phosphate (DRP), total nitrogen (TN), and nitrate (NO₃-N), using data from two stream gauges. The calibrated models accurately simulated the studied variables across the SJRB. The simulated average annual baseflow for Niles and Paw Paw subwatersheds were 153 and 190 mm, respectively. The impacts of land use change on variables from the SJRB were also explored. The impact of land use change on water quality over time was statistically significant but trends were not linear. Hydrology, sediments and nutrients were also quantified at the subbasin level. Subbasins with heavy urbanization or agricultural drainage infrastructure, showed more substantial increases in sediment and nutrient loads as well as decreased groundwater recharge. This study will aid in the evaluation of historical and future water resources for Midwestern rivers, enabling stakeholders to prepare for future impacts, and to execute conservation and management to sustain the SJRB.

Reliable datasets evaluating average and extreme precipitation are crucial for assessing water-sector vulnerabilities and adaptive capacity in global cities. However, conventional meteorological station data is often insufficient for consistent global analysis. In this study, we piloted and refined a publicly accessible decision-support tool (Global Urban Climate Assessment-GUCA) on 12 global cities using the ERA5-Land reanalysis precipitation dataset from the European Centre for Medium-Range Weather Forecasts (ECMWF). We analyzed data from water years 1981 to 2023 to assess flood exposure by examining trends in annual peak daily precipitation, transformed using the Standardized Precipitation Index (SPI) (z scores) and an estimate of 25-year return period precipitation. We also analyzed changes in water availability by analyzing linear trends in annual average precipitation z scores, and in untransformed annual averages. To evaluate water security in the 12 pilot cities, we combined average annual precipitation, standardized precipitation trends, freshwater withdrawal data, and population change. Our results show that several cities are experiencing significant precipitation changes. For instance, Panama City and Shenzhen showed increased flooding vulnerability over the past 20 years (71–83%), while Mogadishu, Amman, and Abuja were more susceptible to reduced water availability and intensifying droughts (23–32%). These findings demonstrate that innovative use of ERA5 reanalysis data can provide a comprehensive and self-consistent global resource for conducting analyses of different aspects of water security, offering policymakers and urban planners actionable insights for more informed decision-making across a broader range of cities worldwide. Graphical Abstract This study developed a decision-support tool to assess water-sector vulnerabilities in 12 global cities using the ERA5-Land reanalysis precipitation dataset (1981–2023) from the European Centre for Medium-Range Weather Forecasts (ECMWF). The research analyzed trends in flood exposure (using annual peak precipitation and 25-year return period estimates) and water availability (using annual average precipitation trends and the Standardized Precipitation Index). Key findings revealed increased flooding vulnerability in cities like Panama City and Shenzhen, while Mogadishu, Amman, and Abuja faced heightened drought risks. The study highlights the utility of ERA5-Land data for creating a consistent global resource to evaluate water security and climate resilience. The results are integrated into the Global Urban Climate Assessment (GUCA), an ArcGIS-based platform providing actionable insights for urban climate adaptation and investment prioritization.