Journal of The American Water Resources Association最新文献

History matching of large hydrologic models is challenging due to data sparsity and non-unique process combinations (and associated parameters) that can produce similar model predictions. We develop an ensemble-based history matching (and uncertainty quantification) approach using an iterative ensemble smoother (iES) method for three cutouts of the National Hydrologic Model (NHM) and qualitatively compare the results and performance to the stepwise history matching approach. In the latter approach, subsets of parameters and observations were sequentially calibrated to a diverse range of observations to mitigate non-uniqueness and local minima. In iES, localization simulates the same causal connections between parameters and observations without the need (and computational cost) of sequential history matching steps. iES uses a weighted sum-of-squared-errors objective function which allows differential weighting of multiple data sources. Formal adoption of range observation also pushes results to within ranges of observation values rather than discrete values. Overall, the ensemble approach performs similarly to the stepwise approach. Both approaches performed poorly for the cutout representing a snowmelt-dominated watershed, indicating a structural issue in the process representation of the model. The main advantage of iES is quantification of uncertainty in both the history matching and the predictions of interest.

The freshwater resource of the Ottawa River basin (ORB) is vital for ecological services and economic activities in the region. With climate change impacts becoming more evident, sustainable management is imperative. As a first step, it is important to assess impacts on hydro-climatology. A coupled hydrological model (WATFLOOD-RAVEN) was set up, calibrated, and validated, with all principal reservoirs implemented using the DZTR principle. The coupled model was forced with high-resolution, bias-corrected future climate projections. Ensemble results show a warmer and wetter future. Under RCP 4.5, which recent studies suggest as the more likely pathway, mean annual precipitation and temperature may increase as much as 8.6% and 3.2°C, respectively. Seasonal and monthly changes are more sporadic. Snowpack is expected to decrease substantially, while actual evapotranspiration increases moderately. Annual streamflow may rise by 7%–10%, but spring freshet streamflow is projected to shift earlier (1.1 days/decade) with a lower (12%) peak. Other indicators, such as time to center of mass and spring pulse onset, also point to earlier shifts. Results further indicate more frequent extreme high (Q10) and low (Q90) flow conditions. Substantial increases in winter reservoir inflows are likely to raise reservoir depths and reduce capacity to store the spring freshet. Better quantification of climate change impacts will aid in developing coordinated responses to climate-related challenges.

Historic rice-field watersheds in Georgetown County, South Carolina, experience climate-driven hydrologic changes threatening waterfowl habitat. The reproducible GIS–Python workflow combines HUC-scale delineation with ArcGIS Pro processing and MACA-v2 downscaled climate analysis through grouped cross-validation to measure and explain stream exposure. We used GroupKFold leave-one-tributary-out mixed-effects modeling and Boruta-screened random forest/gradient boosting with permutation importance and partial dependence for explainable machine learning. The mid-century (2030–2059) stream flow patterns increased before showing a slight decrease at the end of the century (2070–2099). The Waccamaw River experienced a discharge increase from 26,851.52 to 30,802.87 m³ s⁻¹ before its flow decreased to 30,179.38 m³ s⁻¹, while the Black River showed the most significant percentage increase at +18.63%. The Coastal Carolina region received its highest precipitation amount of 55.71 ± 2.54 mm. The mixed-effects model showed that precipitation positively correlates with discharge (β = 0.136, p = 0.042). The Waccamaw–Atlantic Intracoastal Waterway complex emerged as the most affected area with 28.21% of its stream length classified as affected. The research supports the implementation of riparian buffers, land-cover management, and adaptive operations, which provide decision-ready diagnostics to protect water quality and maintain waterfowl benefits during late-century conditions.

The Earth's climate, including that of North America, is changing rapidly and the corresponding changes in temperature, precipitation, extreme weather, and other effects are accelerating. This changing climate is affecting the region around the Great Lakes and the physical behavior of the Great Lakes themselves, presenting new challenges to humans, their infrastructure, and to natural resources, including other life in the region. Temperature in the Great Lakes continues to increase, with the greatest increases occurring in the deeper water. Winter ice cover on the Great Lakes is decreasing. In the future, Great Lakes water levels will likely exhibit greater variability and dispersion from the long-term average, with more tendency for higher lake levels, potentially impacting coastal communities and infrastructure. The increasing precipitation coming as larger events, the overall increase in precipitation in winter and spring, less as snow (except in lake-effect snow areas), along with the overall warmer temperatures resulting in increasing evaporative demand and somewhat dryer summers, are all changing the hydrology of the region. The aim of this commentary was to summarize what is happening and projected to happen to the Great Lakes and the Great Lakes region. Continuing to update and assess the changes occurring and projected to change is crucial to understanding climate change and its impacts, and to planning and policy making to adapt and achieve resiliency.

Arizona, located in the Desert Southwest of the U.S., faces chronic water scarcity and has been strongly affected by the multidecadal Millennium Drought. As the state increasingly turns to water augmentation strategies, accurate, high-resolution estimates of water balance components are essenctial. To support these efforts, this study evaluates the skill of version 3.0 of the NOAA National Water Model (NWM) 1-km retrospective hydrologic simulations across Arizona for the period 2003–2022. Model skill was assessed against streamflow at 124 daily and 98 hourly gauges, daily evapotranspiration (ET) at nine eddy covariance towers, and daily snow water equivalent (SWE) at 19 stations. Results show that the NWM performs better for high flows than low flows, particularly during winter in snow-dominated basins in central and northern Arizona. Lower skill for summer high flows is linked to precipitation forcing deficiencies, while poor baseflow simulation likely reflects the model's inability to represent channel transmission losses. ET daily variability is generally captured, though modest seasonal biases remain. SWE seasonality is represented, but magnitudes are consistently underestimated, likely due to biases in solid precipitation forcings. This study provides guidance on the regions and seasons in Arizona where NWM-derived water balance components can be used with confidence and identifies where bias correction may be needed to support water management and augmentation planning.

Across the United States, policymakers are busy developing incentive programs and mandatory policies to speed up adoption of consolidations and reduce the number of regulated water systems. Little attention, however, has been paid to why water system managers themselves, whose cooperation, if not leadership, is often required, pursue consolidation and how they characterize the benefits. Here we leverage novel, representative data from the California Water System Consolidation Survey to shed light on these questions. We find that consolidation is motivated by a diverse array of concerns within and among projects. In 80% of cases, managers reported benefits pertaining to their motivations, suggesting an overall high level of effectiveness. One exception is motivations related to technical, managerial, and financial capacity for which respondents reported fewer related benefits. Many also reported additional benefits beyond those specifically related to their motivations. We identify several factors that are associated with increased consolidation effectiveness and with specific benefits including geographic isolation of the systems, previous relationships between water systems, and water system initiation of consolidation. The results highlight opportunities to advance beneficial, community-driven projects as well as challenges meriting scholarly and policy attention, including the need to align consolidation rhetoric with the priorities and experiences of managers themselves.