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Wildfire-induced disruptions to evapotranspiration, runoff, and water-balance closure across California's water supply watersheds

Large wildfires are reshaping California’s water-supply forests. Using 40 years of satellite and river data, we found that severe fires greatly reduce vegetation water use, sometimes increasing runoff during dry years. Recovery varies widely across basins and can take many years. The work shows that wildfire can disturb the entire water budget and highlights the need to include fire effects when planning for future water resources.

Understanding changes in Iceland's streamflow dynamics in response to climate change

Iceland relies heavily on hydropower, making it important to understand changes in streamflow. Rivers reflect a warming, wetter climate, with rainfall increasingly replacing snowfall. Annual streamflow has generally increased, most notably during the cool season, while summer flows have declined in some non-glacial rivers. Glacial rivers show increasing melt-season flows over 1973–2023 but declining trends over 1993–2023, reflecting glacier retreat and recent North Atlantic sea surface cooling.

A novel classifier-guided ensemble framework for global terrestrial evapotranspiration estimates

Existing global evapotranspiration algorithms rely on sparse local measurements and each comes with its own strengths and weaknesses. Here, we proposed an ensemble framework that employed a machine learning system to dynamically select the most appropriate algorithm to be used across spatial and temporal scales, thus fully utilizing the distinct strengths of each method. In multi-scale validations, our framework exhibited enhanced extrapolation performance, stability, and interpretability.

Technical note: High Nash–Sutcliffe Efficiencies conceal poor simulations of interannual variance in seasonal regimes

Common metrics used to evaluate hydrologic models make it relatively easy to achieve high performance scores in highly seasonal catchments. However, we analysed 18 hydrologic models and found that almost all were worse at simulating interannual variability and change in seasonal streamflow regimes. This suggests that climate change impacts on streamflow may not be accurately predicted in highly seasonal tropical, alpine, and polar regions, which are highly vulnerable to climate change.

A lesson in preparedness: assessing the effectiveness of low-cost post-wildfire flood protection measures for the catastrophic flood in Kineta, Greece

Wildfires can exacerbate flood risks, as seen in a Greek town where heavy rain caused significant damage following a recent fire. This study examined how simple, low-cost protection measures, such as Log Erosion Barriers and wooden check-dams, might have mitigated the damage. Using models and real data, we found these measures could have lowered the flood's impact by 25 % and saved millions in damage. Therefore, investing in such prevention can be cheaper than paying for repairs after disasters.

High resolution monthly precipitation isotope estimates across Australia from machine learning

We used a random forest approach to produce estimates of monthly precipitation stable isotope variability from 1962–2023, at high resolution across the entire Australian continent. Comprehensive skill and sensitivity testing shows that our random forest models skilfully predict precipitation isotope values in places and times that observations are not available. We make all outputs freely available, facilitating use in fields from ecology and hydrology to archaeology and forensic science.

Global projections of aridity index for mid and long-term future based on CMIP6 scenarios

Our study investigates global dryland dynamics and aridification under future climate scenarios. By employing the Food and Agriculture Organisation Aridity Index and an ensemble of 13 models from the 6th Coupled Model Intercomparison Project, we provide projections for dryland distribution and aridity index across three shared socio-economic pathways (2-4.5, 3-7.0, and 5-8.5) for the near-term (2030–2059) and for the long-term (2070–2099) future.

How do geological map details influence the identification of geology-streamflow relationships in large-sample hydrology studies?

We show that geological maps with varying levels of detail may influence the identification of geology–streamflow relationships across European catchments at multiple scales. At the large scale, controls varied between basins, with no map consistently superior. At the intermediate and small scales, however, higher geological detail consistently strengthened correlations, particularly for baseflow signatures, with the regional map highlighting controls more consistent with process understanding.

Assessment of source regions of the Zambezi River: implications for regional water security

This study focused on the sources of the Zambezi River, revealing new insights into its longest tributary and Angola's key role in its flow. River expeditions and earth observation data show that Angola contributed approximately 73 % of the river's flow upstream of a major floodplain during the 2023 late wet season. We highlight Angola's wetlands, which support river health and help mitigate pollution. These findings stress the need for improved monitoring and regional cooperation in the basin.

Consequences of the Aral Sea restoration for its present physical state: temperature, mixing, and oxygen regime

The Aral Sea is both an example of large-scale environmental degradation caused by human activity and a message of hope through its partial restoration. Our study shows that the restored part of the Aral Sea is now healthy in terms of vertical mixing and oxygenation. However, small perturbations of water level or transparency could significantly alter the entire ecosystem. The results contribute to understanding the consequences of large-scale lake management worldwide.

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