The intensification of precipitation extremes threatens hydro-ecological stability in topographically complex regions such as the Albertine Rift, yet global climate model (GCM) projections there are limited by structural uncertainties. We present a multi-stage framework to evaluate historical and future extreme precipitation (ten ETCCDI indices) across six agroecological zones (AEZs) of South Kivu, eastern DRC. From eight CMIP6 GCMs, we isolated regime-specialist models using Relative Importance Metrics (RIM), the Compromise Programming Index (CPI), and Jenks Optimized Classification (JOC), then apply Quantile Delta Mapping (QDM) and Bayesian Model Averaging (BMA) under SSP2–4.5, SSP3–7.0, and SSP5–8.5. Model fidelity is zone- and index-specific: MPI-ESM1–2-HR excelled for orographic intensity in high-altitude zones, while MRI-ESM2–0 in lowland and rain-shadowed zones. Several AEZs showed significant historical declines (1983–2014) in precipitation indices (e.g., decline of −4.5 mm yr−1 for PRCPTOT in the EHAZ), which reverse under high-emission pathways by the late 21st century, with PRCPTOT trends up to + 18.1 mm yr−1 and R95Ptot trends up to + 7.1 mm yr−1. The THMAZ evolved into a hotspot of hydro-climatic whiplash combining longer dry spells with intensified convective extremes. The Time of Emergence (ToE) for SDII was as early as 2024 in the EMAZ and THMAZ, and that of RX1day was ~ 2027–2029 in the EHAZ. In contrast, most intensity and volume indices showed no emergence in the high-variability lowland and transitional zones. Provincial-scale averaging masks this sub-regional vulnerabilities: the THMAZ R95pTOT trend (+7.06 mm yr⁻¹) is more than twice the provincial mean (+3.2 mm yr⁻¹). These results provide a physical baseline for infrastructure and early-warning systems in this climate-exposed region.
Study Region The study focuses on floodplain islands along a ~400 km reach of the middle Congo River between Mbandaka and Mpouya in the Democratic Republic of Congo. The study area contains approximately 800 geomorphologically stable river islands covering roughly 1040 km² and supporting vegetation ranging from early successional grasses and shrubs to mature forests, alongside small-scale fishing and agriculture. Study Focus This study investigates vegetation responses to the 2024 hydrological drought across Congo River islands and examines how hydroclimatic conditions propagated through the river-floodplain system. Hydrometeorological conditions were characterised using CHIRPS precipitation data, ERA5-Land temperature and evaporation, and HydroWeb altimetry river stage records. Drought severity was assessed using SPEI-3, consecutive dry days, and warm day frequency. Vegetation change was evaluated using spectral indices and supervised land-cover classification derived from cloud-free Sentinel-2 Level-2A imagery. New Hydrological Insights for the Region The 2024 event was characterised by persistent precipitation deficits and elevated temperatures, followed by below-average river levels consistent with reduced upstream discharge and the development of hydrological drought. Vegetation decline closely coincided with lower river stage, suggesting that reduced river–floodplain connectivity contributed to drought impacts on floodplain vegetation. Vegetation loss was greatest in shorter vegetation, suggesting that vegetation structure influences ecosystem sensitivity to water limitation.
Study region The study area is the Panj River basin, situated in the upper reaches of the Amu Darya basin. Study focus Glacier and snowmelt runoff are vital for sustaining streamflow in the Panj River Basin, a key cryospheric water source region in Central Asia. However, the impacts of glacier retreat, snow changes, and precipitation variability on long-term runoff remain unclear under global warming. This study applied the Hydrologiska Byråns Vattenbalansavdelning (HBV) model to quantify runoff components, including rainfall, snowmelt, and glacier runoff, and integrated the Budyko framework, scenario simulations, and glacier retreat experiments to assess runoff drivers and the hydrological response to glacier loss. New hydrological insights The results showed that total runoff, rainfall runoff, and snowmelt runoff exhibited significant decreasing trends during 1982–2020, whereas glacier runoff increased, reflecting a temporary compensation effect from enhanced glacier melt under climate warming. Meltwater runoff accounted for 67.9% of total runoff and played an important role in regulating streamflow, particularly during dry years. Attribution analysis revealed that runoff changes were mainly controlled by climatic factors (122.5%), with precipitation being the dominant driver, while human activities (−22.5%) partially offset the decline in runoff. Glacier retreat scenarios indicated that continued glacier loss would reduce summer meltwater supply and may alter the seasonal distribution of runoff, with potential implications for the stability of downstream water supply. The impacts of glacier change on mountain runoff processes and regional water resources provide a basis for understanding potential changes in downstream water availability in Central Asia.
Study region Hornsund, SW Spitsbergen, Svalbard – area representing the Atlantic sector of High Arctic Study focus Rapid climate warming across Svalbard is fundamentally altering high-latitude terrestrial cryospheric systems and hydrological processes. To investigate these transitions, a seasonal moving-parameter HBV modeling framework was implemented to evaluate and compare the long-term water balance dynamics of two adjacent catchments underlain by continuous permafrost: the unglaciated Fuglebekken catchment (monitored 2014–2024) and the glaciated Ariebekken catchment (monitored 2007–2024). New hydrological insights The findings suggest a structural divergence in the runoff regimes of these neighboring watersheds. While the unglaciated Fuglebekken regime is driven by seasonal snowmelt and rainfall events, the glaciated Ariebekken system benefits from a substantial glacial meltwater buffer that sustains high, steady baseflow late into the summer. Crucially, Fuglebekken shows a significant positive multi-annual storage gain over the study period (+325 mm), challenging the traditional baseline assumption of negligible annual storage changes (ΔS = 0) in continuous permafrost catchments. This net water accumulation could be consistent with localized active layer thickening and talik development. Methodologically, the integration of intra-annually shifting parameter sets allows the model to represent the non-stationary hydrogeological features of permafrost soils. Additionally, updating the model via an area-scaling glacier module accurately represents the retreat of the Ariebreen glacier, providing a physically plausible meltwater input and highlighting the transient nature of current high-discharge volumes in the deglaciating catchment.
Study region: Mongolia, an arid and semi-arid region.Study focus: Water availability (WA), calculated as precipitation minus actual evapotranspiration (AET), is difficult to estimate in drylands because the small residual can be sensitive to differences between input products. We evaluated 37 WA estimates, comprising 35 combinations of seven precipitation and five AET products and two estimates based on arithmetic average (AA) and Bayesian three-cornered hat (BTCH) fusion. We compared their temporal and spatial characteristics and evaluated their performance with observed and gridded runoff.New hydrological insights: Across the 37 estimates, the mean long-term annual WA was 39.5 ± 63.5 mm yr⁻¹ (mean ± SD), and trend slopes averaged −0.5 ± 0.8 mm yr⁻². The CV of long-term means was 160.8%, and the relative slope spread was 158.7%. Most estimates showed higher WA in northern Mongolia, although some displayed the opposite spatial gradient. Runoff agreement was weaker in southern arid basins and varied among individual combinations. ERA5_ERA5 showed comparatively strong runoff agreement, while AA and BTCH exhibited relatively consistent, intermediate performance across basins and significant correlations with gridded runoff over relatively large areas of Mongolia. Precipitation-product selection accounted for 74.5% of the combined normalized main-effect variation associated with precipitation and AET selection among the 35 individual combinations. These findings support careful input selection and regional evaluation of fusion-based WA estimates.
