Journal of The American Water Resources Association最新文献

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.

The agriculture sector is a significant consumer of water, and sustainable water use begins with monitoring irrigated land. Delineating irrigated land supports decision-makers and promotes the sustainable use of this crucial resource. This study focuses on the Nubian Sandstone Aquifer System (NSAS), the largest aquifer in the world, which spans Egypt, Sudan, Libya, and Chad. Built upon long-term satellite remote sensing observations, the study aims to: (1) quantify the increase in irrigated hectares (both pivot and non-pivot) during the last decade; (2) identify major irrigated crop types and their water requirements; and (3) quantify the increase in crop water use from the NSAS from 2000 to 2024. The findings indicate that irrigated areas fluctuate over time, but the overall irrigated area under the NSAS has increased. The total irrigated area nearly doubled from 14,635 km² in 2000 to 24,811 km² in 2024, while the area irrigated directly from the NSAS increased from 1257 to 3268 km² over the same period. Correspondingly, crops water use from the NSAS increased from an estimated 1.4 km³ in 2000 to 3.64 km³ in 2024. These results have important implications for water and land use, and policymakers in NSAS to ensure the sustainable use of these vital resources for the present and future generations.

Stream assessments are needed to inform regulatory decisions, mitigation and restoration design, and other management practices. Many methods have emerged to meet regional needs and specific management contexts. The number of available approaches creates confusion over the relative merits of methods and appropriate use cases. Furthermore, the complexity of these approaches ranges from rapid evaluations requiring minutes to complete to detailed methods needing weeks of effort. However, the level of effort associated with approaches is rarely tracked for method selection. Differences in measurement metrics and data collection create obstacles to consistent, meaningful comparisons across methods and regions. We compiled and analyzed 188 stream assessment methods, revealing four core challenges: (1) inefficient identification of methods, (2) diverse metrics for ecosystem condition, (3) a wide range of resource needs, and (4) limited comparability of results. While geomorphic (59%) and biological (46%) metrics are common, few methods (5%) comprehensively evaluate a broader set of ecosystem functions. Although many methods exist, the most pressing challenges in stream assessment are choosing appropriate methods, ensuring adaptability, and enabling comparability. Finally, we identify recommendations for improving the practice of stream assessment, including clearer guidance and standardized protocols for assessment.