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1. Increasing Alaskan river discharge during the cold season is driven by recent warming

   https://doi.org/10.1088/1748-9326/acb661  

   Blaskey, Dylan; Koch, Joshua C; Gooseff, Michael N; Newman, Andrew J; Cheng, Yifan; O’Donnell, Jonathan A; Musselman, Keith N (February 2023, Environmental Research Letters)

   Abstract Arctic hydrology is experiencing rapid changes including earlier snow melt, permafrost degradation, increasing active layer depth, and reduced river ice, all of which are expected to lead to changes in stream flow regimes. Recently, long-term (>60 years) climate reanalysis and river discharge observation data have become available. We utilized these data to assess long-term changes in discharge and their hydroclimatic drivers. River discharge during the cold season (October–April) increased by 10% per decade. The most widespread discharge increase occurred in April (15% per decade), the month of ice break-up for the majority of basins. In October, when river ice formation generally begins, average monthly discharge increased by 7% per decade. Long-term air temperature increases in October and April increased the number of days above freezing (+1.1 d per decade) resulting in increased snow ablation (20% per decade) and decreased snow water equivalent (−12% per decade). Compared to the historical period (1960–1989), mean April and October air temperature in the recent period (1990–2019) have greater correlation with monthly discharge from 0.33 to 0.68 and 0.0–0.48, respectively. This indicates that the recent increases in air temperature are directly related to these discharge changes. Ubiquitous increases in cold and shoulder-season discharge demonstrate the scale at which hydrologic and biogeochemical fluxes are being altered in the Arctic. 

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2. Recent Increases in Missouri River Streamflow Driven by Combined Effects of Climate Variability, Land‐Use Change, and Elevated CO ₂

   https://doi.org/10.1029/2024AV001432  

   Dannenberg, Matthew P; McCabe, Gregory J; Wise, Erika K; Johnston, Miriam R; Huntzinger, Deborah N; Williams, A Park (April 2025, AGU Advances)

   Abstract Missouri River streamflow increased substantially during the 20th century, with multiple large floods occurring since 1990. Using land surface models and water budget simulations, we examined the extent to which increased flow was driven by natural climate variability, anthropogenic climate trends, land‐use and land‐cover change (LULCC), and ecological effects of elevated atmospheric CO₂. Natural climate variability (arising largely from coupled ocean‐atmosphere circulation systems in both the Pacific and North Atlantic) accounted for ∼765 m³ s⁻¹of the ∼900 m³ s⁻¹increase in flow since mid‐century, while anthropogenic climate trends negatively forced flow by increasing evapotranspiration more than precipitation. LULCC and elevated CO₂further increased simulated mean streamflow by ∼550 and ∼70 m³ s⁻¹, respectively, relative to pre‐Industrial conditions and ∼100 and ∼65 m³ s⁻¹relative to mid‐20th century conditions. The LULCC effect was especially large in wet years, implying that current land cover is ill‐suited for buffering against extreme precipitation, likely in large part due to replacement of forest by cropland in the lower basin. Because increases in Missouri River flow over the past century were driven mostly by a recent (and likely transient) pluvial, our results suggest that flow in the basin could revert to a drier mean state when that pluvial ends, likely made worse by increased evaporative demand from anthropogenic warming. 

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3. Riverine heat waves on the rise, outpacing air heat waves

   https://doi.org/10.1073/pnas.2503160122  

   Sadayappan, Kayalvizhi; Li, Li (September 2025, Proceedings of the National Academy of Sciences)

   While air heat waves often grab headlines, riverine heat waves have gone quietly unnoticed because rivers are commonly perceived as cool refuges. Analysis of riverine heat waves has been hindered by fragmented datasets, despite a proliferation in water-temperature monitoring with sensors and satellites. Here, we analyze riverine heat wave events by training one single deep learning (long short-term memory) model and reconstructing consistent and continuous daily water temperatures (WT) in 1471 sites in the Contiguous United States (1980–2022). We show that riverine heat waves occur at about half the frequency (2.3 versus 4.6 events/year), a third intensity (2.6 versus 7.7 °C/event), but almost double the duration (7.2 versus 4.0 d/event) of air heat waves. Riverine heat wave events have increased at double to quadruple rates of air heat wave events, amounting to an additional 1.8 events/year in frequency, 0.43 °C/event in intensity, 3.4 d/event in duration, and 7 to 15 additional thermal stress days for aquatic ecosystems in 2022 compared to 1980. Rising riverine heat waves have outpaced those of air heat waves in 65 to 76% of the sites, particularly in regions experiencing accelerated warming (e.g., the Rockies). Riverine heat wave trends are driven predominantly by climate-induced changes such as warming and dwindling snowpacks and water flow. Human activities do play important roles: large dams elongate, whereas agriculture reduces heat waves. These results highlight anthropogenic climate change as the primary external driver, whereas human-induced structural changes as the secondary internal modulators of river response to heat disturbance. The widespread rise of riverine heat waves threatens aquatic ecosystems and water-energy-food security, underscoring the need for their global characterization and risk assessment. 

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4. Arctic hydrology: a water balance study of Imnavait Creek and Kuparuk River watersheds, Alaska

   https://doi.org/10.1139/as-2025-0033  

   Youcha, Emily K; Stuefer, Svetlana L (January 2026, Arctic Science)

   Increasing air temperatures are expected to change streamflow patterns in Arctic watersheds. However, the hydro-meteorological datasets necessary to evaluate these changes remain limited in the Arctic. We revised and updated a unique hydrologic dataset from Arctic Alaska with field measurements of continuous streamflow, precipitation, and evapotranspiration to identify changes in the hydrologic cycle. We analyzed water balance components and peak streamflow in Imnavait Creek, Upper Kuparuk River, and Kuparuk River during snowmelt and summer periods. Field measurements show that summer streamflow (mid-June to late-September) has increased in volume and magnitude. While snowmelt runoff still constitutes a sizable portion of annual runoff (28%–58%), the relative proportion of summer runoff is notably increasing. High interannual and spatial variability is observed for both rainfall and summer runoff, whereas comparatively lower interannual variability is observed for snowmelt runoff. This paper compares streamflow changes occurring at three watersheds of varying sizes and identifies reasons for observed changes using snow, rainfall, and evapotranspiration measurements. We also provide hydrologic analysis for design considerations at Arctic Alaska communities, the Dalton Highway, and the oil pipeline; as this infrastructure may be at risk of increased erosional damage due to more frequent and higher magnitude summer flow events. 

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5. The Three Colorado Rivers: Hydrologic, Infrastructural, and Economic Flows of Water in a Shared River Basin

   https://doi.org/10.1111/1752-1688.12997  

   Rushforth, R. R.; Zegre, N. P.; Ruddell, B. L. (February 2022, Journal of the American Water Resources Association)

   Rushforth, R. R.; Zegre, N. P.; Ruddell, B. L. (Ed.)

   The Colorado River Basin is a hydrologic river network that directs runoff from rain and snow falling on mountains, primarily in Colorado and Wyoming, to the Colorado River Delta in Mexico. Over the last century, in response to basin-wide water shortages, legal agreements between stakeholders in seven U.S. states and Mexico, hydrologic flows from users on the main stem of the river have been reallocated to junior water rights holders. Municipalities, businesses, farmers, and households utilize the Colorado River water to produce and trade valuable, water-derived goods and services, which effectively reallocates water through a continually adapting, boundary-free economic river network providing indirect access to "virtual" Colorado River water. We conceptualize the Colorado River Basin as a multiplex network comprised of interdependent natural flow networks, direct (infrastructural) flow networks, and indirect (virtual) flow networks. Using this reframing, we quantify the total hydrosocial impact of the Drought Contingency Plan (DCP) on Lower Basin states. For each Mm3 of water reduced through the DCP, Arizona, Nevada, and California lose an additional 0.42–0.43 Mm3, 0.33–0.51 Mm3, and 1.06–1.10 Mm3 of virtual water flow, respectively. Hence, the DCP will require Arizona, Nevada, and Southern California to restructure how they use water, relying less on direct and indirect consumption of the Colorado River water and finding more indirect water sources outside that basin. 

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