ABSTRACT Storage and release of groundwater during baseflow are controlled by both topography and geology. In some geological settings, intrusive structures such as diabase dikes can affect groundwater movement by acting as either pathways or barriers to flow. While dikes can modify groundwater flow patterns, their influence on baseflow remains uncertain. Here, we evaluate how topography and diabase dikes influence the spatial distribution of specific baseflow and δ 18 O in a catchment with heterogeneous geology. We conducted synoptic campaigns to measure δ 18 O and discharge during baseflow across 26 nested subcatchments (0.02–5.33 km 2 ) of Peri Lake Experimental Catchment (20 km 2 ) in southern Brazil. All subcatchments are underlain by granite, with 12 intruded by diabase dikes. The spatial variability of δ 18 O and specific baseflow was analysed against subcatchment area, mean elevation, mean slope, and geology using Spearman correlation and multiple linear regression. The results show that in subcatchments without diabase dikes, the spatial pattern of baseflow and δ 18 O is related to topography and reflects the high storage capacity at high elevation. In contrast, in areas with diabase dikes, irregular hydraulic conductivity and fracture distribution disrupt topography‐related spatial patterns. These findings highlight that combining synoptic sampling and process‐based approaches enhances the understanding of spatial patterns of groundwater flow, particularly in small catchments in data‐limited regions.

ABSTRACTIn desert regions, precipitation is one of the significant water sources and a key driver of ecohydrological processes over a range of spatiotemporal scales. When precipitation infiltration was combined with the original soil water, the soil water and plant water use will experience significant dynamic changes, which play an important role in the stability and sustainability of the artificial vegetation. Therefore, soil water dynamics and water use strategies of Haloxylon ammodendron were studied by the hydrogen and oxygen stable isotope technique in this study. The results showed that precipitation in the desert soil was mainly in the form of piston flow, and the precipitation that led to the significant increase of infiltration and recharge was different in different precipitation events. The precipitation of 12.8 and 19.6 mm can make the surface soil water sufficient and continue to penetrate into the deep soil, and the duration of soil water response and the recharge depth were much longer and deeper than those for 4.4 and 7.8 mm events. In addition, the H. ammodendron mainly relied on stable and abundant deep soil water and groundwater. The water use source of H. ammodendron showed no significant response to 4.4 and 7.8 mm precipitation. However, a significant difference in water source proportion occurred before and after 19.6 mm of precipitation. The use proportion of shallow soil water increased from 10.7% to 24.2%, while that of groundwater decreased from 48.8% to 23.2%. Therefore, we concluded that precipitation levels have a major impact on soil water at various depths; in particular, heavy precipitation has a significant impact on deep soil water that deeply controlled the survival of the H. ammodendron plantation. These results offer an essential theoretical foundation for vegetation restoration and sustainability in arid regions.

ABSTRACT A better understanding of headwater hydrogeology in the semiarid Andes is critical because high‐elevation basins are considered water towers for the main valleys, where water demand is over‐allocated. While the body of literature generally focuses on the contribution of glaciers to streamflow, there is little information on the contribution of sparsely glacierized basins and the origins and processes of groundwater generation at high elevations. The Corrales catchment in North‐Central Chile contains both heavily and sparsely glacierized sub‐basins as well as the highest public borehole in the region, making it suitable to fill such scientific gaps. Geophysical surveys and a pumping test were carried out to obtain information on groundwater flows beneath the Tapado terminal rock glacier and a main tributary of the Elqui River. Radioactive and stable isotopes were used to characterise the hydrological connectivity and the origins of water in the headwater basins. Low electromagnetic velocities and resistivities indicate the presence of liquid water beneath the rock glacier, suggesting the upper limit of a proglacial aquifer. The downstream valley aquifer appears transmissive and dominated by old waters (several decades) that are a mix of high‐glacierized and sparsely glacierized basins. In addition, stable isotopes reveal distinct signatures for high‐glacierized and sparsely glacierized basins, which may be attributed to isotope fractionation. These results suggest that water isotopes can be used to distinguish between waters originating from high‐glacierized and sparsely glacierized basins. The study also identifies the presence of old waters in the sparsely glacierized basins, which indicates long‐term storage, slow release or slow turnover times. This finding is crucial for understanding the evolution of late‐season baseflow and streamflow in the context of climate change. As the contribution of such basins to total streamflow is significant, a better understanding of hydrological processes in sparsely glacierized regions is required.

ABSTRACTHydrologic connectivity (HC), particularly in floodplain systems, is pivotal in regulating ecosystem services by facilitating the movement of nutrients, sediments, chemicals, and biota. However, human interventions such as dam construction, levee installation, water management practices, and alterations in vegetation have significantly disrupted natural HC patterns globally. To provide a structured entry into the growing body of HC research, we conducted a systematic literature review of 1920 studies, analysing diverse definitions, influencing factors, quantification approaches, spatial and temporal scales, and management strategies. In addition to traditional review methods, our approach integrates keyword and cluster analysis to elucidate dominant research themes and trends across the literature. Our review reveals that the literature is heavily skewed towards research in North America and Europe (accounting for 72% of studies) and predominantly utilises field investigations, simulation modelling, and remote sensing integrated with geographic information systems. Although these methodologies have advanced our understanding, most studies focus on restricted spatial scales such as individual hillslopes, catchments, or stream networks and short temporal intervals, including single precipitation events or seasonal cycles. A narrow focus becomes a limitation when such studies do not contribute to broader efforts aimed at scaling insights across larger domains. These limitations highlight the potential benefits of innovative conceptual frameworks and quantification methods to better capture HC across broader environments and extended temporal scales. We conclude by discussing challenges in defining and quantifying floodplain HC and outlining potential future research directions to advance connectivity science and management, particularly in floodplain systems characterised by frequent hydrologic fluctuations, such as seasonal inundation and changing flow paths.

ABSTRACTThis study aims to assess and quantify soil erosion risk by integrating the Revised Universal Soil Loss Equation (RUSLE) with the Analytical Hierarchy Process (AHP) within a Geographic Information System (GIS) environment. The RUSLE model evaluates soil loss by combining five key factors: rainfall erosivity (R), soil erodibility (K), length of slope (LS), cover‐management factor (C), and support practices factor (P). In parallel, the AHP framework incorporates nine geo‐environmental parameters to refine the erosion hazard assessment through multi‐criteria decision analysis. The integrated approach enables the generation of spatially explicit erosion risk maps, helping to identify vulnerable zones within the watershed. A primary focus of the study is the Dam, where sedimentation due to upstream erosion poses a critical threat. The outcomes of this research aim to inform soil conservation strategies and contribute to the sustainable management of a vital non‐renewable resource, aligning with broader sustainable development goals (SDGs). The sediment delivery ratio (SDR) calculated shows that much soil will reach the basin and contribute to dam siltation. The final soil loss map established by the RUSLE model shows a maximum soil loss rate of 556.1 t ha−1 year−1 contributed over the entire watershed and an average of 49.77 t ha−1 year−1. The sediment delivery ratio is 0.53. A cross‐section of different geo‐environmental parameters shows that 37.51% of the watershed area is high to very highly vulnerable to erosion. The most dominant factors that take the maximum weight in the AHP matrix are the rainfall erosivity factor, the soil texture factor, the vegetation cover factor, and the slope.

ABSTRACT Peatlands are important habitats that provide a range of ecosystem services, one of which is hydrological regulation. Depending on landscape position, healthy peatlands can reduce flood risk and provide resilience to drought, while degraded peatlands can exacerbate these hydrological disturbances. There is, however, a lack of clear scientific communication, particularly in the media, and misguided public perceptions of the underlying processes that control peatland hydrological regulation. The ‘sponge analogy’, which compares peatlands to sponges which soak up water during rainfall and release it slowly later, contributes to this miscommunication by often oversimplifying the hydrological processes. In this paper we aim to understand why and how the sponge analogy is used, and to offer alternatives for clearer scientific communication. We present an analysis of media articles covering peatland hydrology, and the results of a UK survey of peatland practitioners, with a particular emphasis on the use of the sponge analogy and more descriptive alternatives. We show that the sponge analogy is widely used as a convenient explanation even when it is known to be inaccurate by practitioners. To more clearly communicate the hydrological processes in popular media, we suggest the alternative phrases ‘slow the flow’ and ‘dampen the droughts’ as more accurate descriptions of flood‐ limiting and drought‐ reducing peatland hydrological processes.

ABSTRACTSurface mining in the Athabasca Oil Sands Region (AOSR) of western Canada disrupts natural landscapes and permanently alters their hydrological functions. Wetlands cover ~55% of the region, primarily fen peatlands, and although provincial regulations require companies to restore disturbed ecosystems to a functional state, fens remain difficult to construct due to their complex hydrology and dependence on water exchange with surrounding uplands. Evapotranspiration (ET), a key component of the water balance, is particularly important in the sub‐humid AOSR, where increasing reclamation activity demands accurate quantification of vertical water loss, as it influences ecohydrological feedbacks and long‐term wetland sustainability. This study evaluates ET and energy dynamics in a constructed fen, built atop ~80 m deposit of composite tailings and capped with 10 m of tailings sand, using eddy covariance (EC) measurements and vegetation surveys conducted across five non‐consecutive years between 2015 and 2023. Mean ET from April 1 to October 31 was 250 ± 49.9 mm, aligning with values from natural and constructed boreal peatlands. On average, ET was 15% higher in warmer and drier years. While intra‐annual ET variability was mainly influenced by vapour pressure deficit and net radiation, a long‐term decline in ET coincided with Typha latifolia expansion, whose canopy reduced water loss by sheltering the open water. Flux partitioning revealed that transpiration exceeded evaporation by up to 70%, highlighting the role of Typha in reducing energy input and limiting turbulent mixing over the ponded water surface. Despite declining ET, latent heat flux remained the dominant component of the energy balance, suggesting functional similarity to natural fens. With rainfall exceeding ET in 80% of the years, the study site did not experience any prolonged drought periods. These findings enhance understanding of surface‐atmosphere interactions and inform wetland reclamation strategies, particularly the role of vegetation change.

ABSTRACT This study aims to evaluate the spatiotemporal dynamics of water quality in the Chongqing section of Yangtze River (YRCQ) under the implementation of Yangtze River Protection Strategy (YRPS). Leveraging daily records for nine indices from 15 monitoring stations during the hydrological years from 2020 to 2024, multivariate statistical analyses were employed to identify the dominant pollutants and elucidate the driving mechanisms. The results demonstrated that the proportion of Classes I–III complying with the Chinese Environmental Quality Standards for Surface Water (GB3838−2002, abbreviated as ‘Chinese Standard’), remained above 95% over the study period. The water quality index ( WQI ) indicated an overall ‘good’ water quality, with no ‘poor’ or ‘very poor’ classifications. Seasonal variations were evident for indices, with pH, dissolved oxygen (DO) and electrical conductivity (EC) higher in the dry season, and water temperature (WT), permanganate index (COD Mn ) and total phosphorus (TP) elevated in the wet season. Generally, water quality was markedly superior in the dry season compared to the wet season. The WQI trends indicated by the Mann–Kendall test divulged a positive trend in water quality at most upstream and midstream stations, whereas a slight deterioration was observed at most downstream stations. Water quality characteristics exhibited significant spatial heterogeneity. Based on the temporal patterns of WQI , stations were classified into four distinct categories: superior, good, fair and poor. Principal component analysis (PCA) pinpointed TP and total nitrogen (TN) as primary drivers of water quality variations, predominantly linked to urban domestic sewage and agricultural runoff. Air temperature and precipitation amount tremendously influenced water quality temporally. An increased rate of surface runoff generation from urban development and nonpoint source pollution from cropland exerted negative effects on water quality. This study underscores critical water environmental challenges in the YRCQ, providing robust theoretical and practical insights for regional water protection and sustainable management.

ABSTRACTInundation dynamics in lowland rivers are an outcome of a complex interaction between hydrologic and geomorphic factors. The co‐occurrence of river flow and tidal surge in coastal regions further complicates these interactions. The extent to which these factors mediate inundation mechanisms in regulated lowland river reaches remains challenging and has been poorly understood. This study presents a novel framework that examines the combined effect of flood drivers (riverine and high tide) and geomorphic factors in determining the inundation mechanism along the Lower Tapi Basin (LTB) in western India through an integration of hydrological, tidal, hydrodynamic, and geomorphic datasets. Using variable infiltration capacity (VIC) and Hydrologic Engineering Center River Analysis System (2D HEC‐RAS) with geomorphic characteristics of river channels, we explore how spatial inundation dynamics vary across different valley settings under different flood return periods. Our integrated modelling framework accurately simulates daily streamflow and flood inundation. Incorporation of multidisciplinary data through the integrated modelling framework has advanced our understanding of flood inundation dynamics in lowland rivers. We have further shown that the model uncertainty can be reduced by incorporating field data, bathymetric measurements and rule curve of reservoir operation in the model domain. Although this modelling framework has been developed on a specific lowland reaches of the Tapi River, it can be further extended to any lowland rivers in similar settings. Such multidisciplinary models will help to analyse river response to future projected climate and sea level change.