Hydrological Processes最新文献

Analysis of PRISM and SNOTEL station data paired with USGS streamflow gage data in the western United States shows that, in snow-dominated mountainous watersheds, streamflow regimes differ between watersheds with karst geology and their non-karst neighbours. These carbonate aquifers exhibit a spectrum of flow paths encompassing karst conduits, including large fractures or voids that transmit water readily to springs and other surface waters, and matrix flow paths through soils, highly fractured bedrock, or porous media bedrock grains. A well-connected karst aquifer will discharge a large portion of its accumulated precipitation to surface water via springs and other groundwater flow paths on an annual scale, exhibiting a lagged response to precipitation presenting as a “memory effect” in hydrograph time series. These patterns were observed in the hydrologic records of gaged watersheds with exposed or near-surface carbonate layers accounting for > 30% of their drainage area. In western snow-dominated watersheds, where paired streamflow and SNOTEL data are available, analysis of the precipitation and flow time series shows low-flow volume is strongly related to karst aquifer conditions and winter precipitation when compared to low-flow volumes present in non-karst watersheds, which have a complex relationship to multiple driving metrics. Analysis of normalised streamflow and cumulative precipitation in karst watersheds show that low-flow conditions are highly dependent on the preceding winter precipitation and streamflow in both wet and dry periods. In non-karst watersheds, increased precipitation primarily impacts high-flow, spring runoff volumes with no clear relationship to low-flow periods. When comparing cumulative streamflow and precipitation volumes within each water year and over longer timescales, karst watersheds show the potential filling and draining of large amounts of karst storage, whereas non-karst watersheds demonstrate a more stable storage regime. Communities in many western US watersheds are dependent on snow-dominated karst watersheds for their water supply. This analysis, using widely available hydrologic data, can provide insight into the recharge and storage processes within these watersheds, improve our ability to assess current flow regimes, anticipate the impacts of climate change on water availability, and help manage water supplies.

Lateral terrestrial water flow in the Weather Research and Forecasting (WRF) Model and its hydrologically enhanced version, WRF-Hydro, is calculated on a routing grid based on infiltration excess in Land Surface Model (LSM) grid disaggregates to the routing grids. However, this design neglects the lateral terrestrial water flow within LSM grids and does not resolve water lateral transport in LSM. In this study, we develop a lateral terrestrial water flow scheme in the Noah with multiparameterization (Noah-MP) of WRF-Hydro grids to address this knowledge gap and evaluate its influence on land surface hydrological processes. Our results indicate that lateral terrestrial water flow leads to 62.3% of grid surface water outflow, resulting in a decrease in accumulated water depth by 123.88 mm. In urban areas, the accumulated water depth further reduces by 21.11 mm when considering the pipe discharge scheme. Compared to the default WRF-Hydro simulation, the lateral terrestrial water flow combined with pipe discharge can effectively advance the calibrated WRF-Hydro modelling capability and reproduce the water depth reasonably compared to the observation in urban areas. Further, our analysis indicates that the decreasing lateral terrestrial water flow in LSM primarily reduces overland flow and increases streamflow in routing grids, mainly through redistributing water from the steep slopes towards the lower elevations and ultimately converting it to streamflow in the channel network.

Aquatic vegetation is an important component of natural river ecosystem, usually growing in riverine, marsh, and coastal areas, interacting with water flow to form complex flow structure, which has an important impact on bank slope stability and flood discharge capacity of river channels. Four sets of indoor flume vegetation-flow experiments were conducted using a typical beach trough structure in the lower section of the Yangtze River. The compound channel was divided into the main channel, side slope and side beach zones, and simulated vegetation such as reeds, sedges and dwarf grass were used. The emphasis was on the hydrodynamic properties under semi-covered emergent rigid vegetation and semi-covered non-submerged rigid vegetation. In this study, the Shiono and Knight equation (SKM model) was used to elucidate the distribution characteristics of ‘the depth-averaged velocity U_d’ and ‘equivalent diameter D’ of vegetation in water gradient, and the Taylor method was used to demonstrate that the proposed ‘equivalent diameter D’ of vegetation has a certain level of accuracy within a reasonable threshold range. In addition, a new secondary flow model was proposed using a genetic algorithm that considers many hydraulic and vegetation parameters. Further, a new secondary flow model was proposed using a genetic algorithm that considers many hydraulic and vegetation parameters. Finally, ‘the depth-averaged velocity U_d’ of the compound channel was accurately predicted by combining the experimental data with the new SKM model. In this study, we investigated the water-blocking ability of gradient vegetation in river water. A method in which the secondary flow law and formula are difficult to determine was solved, which could provide technical support for the design of complex vegetated rivers and the evaluation of the flood discharge capacity of rivers.

Anthropogenic climate change leads to increased precipitation intensity and exacerbated droughts in California, challenging the reliability and drought resiliency of water supply. Storing floodwater underground via managed aquifer recharge can mitigate these effects through direct infiltration or streambed infiltration. Seasonally dry streams (arroyos) already play an important part in managing groundwater recharge to the Livermore basin (CA). Understanding how, when and where stormwater and arroyo water infiltrate is critical to effectively utilise this strategy. To track water from recent storms (water year 2022–2023, WY23) into the Livermore Valley Groundwater Basin, we analysed stable water isotopes (δ¹⁸O and δ²H) in combination with naturally occurring radioactive isotopic tracers, sulphur-35 (³⁵S, t½ = 87 days) and tritium (³H, t½ = 12.3 years). By comparing measurements of δ¹⁸O, ³⁵S and ³H in arroyos to precipitation and groundwater, we classified the relative age and identified source of recharge to 16 wells near two arroyos. Two wells contained water with recent recharge (from WY23) from local precipitation. One well had recent recharge from variable (precipitation and imported water) sources. One well contained imported water recharge. Three wells contained water from mixed recent and older (pre-WY23) waters, from local precipitation sources. Two wells contained recent recharge from local mine settling ponds. Seven wells had older recharge from local precipitation sources. This combination of isotopes allows us to delineate where local and imported water recharges in this highly managed basin and identify locations where managed aquifer recharge is contributing to rapid groundwater infiltration. Our combined interpretation of isotopic water ages and sources in the context of land use shows that local infiltration of precipitation in open spaces is an important recharge mechanism, in addition to the managed arroyo recharge. A broader familiarity with ³⁵S will enable more extensive research on the infiltration of urban floodwaters.

Sap flow dynamics are critical for understanding how vegetation consumes water and adapts to environmental stress. The response of sap flow in boreal birch secondary forests to rainfall variations during the rainy season, however, has been inadequately explored. Our study indicated that photosynthetically active radiation (PAR) and vapour pressure deficit (VPD) are the primary drivers of sap flow density in birch trees across different diameter classes (F_ds: small trees, F_dm: medium-sized trees, F_dl: large trees). Soil water content (SWC) significantly reduces sap flow when it falls below the 0.18 cm³/cm³. Sap flow density increased with PAR and initially with VPD but plateaued at higher VPD levels due to saturation. A hierarchy of sap flow density was observed, with F_dl > F_dm > F_ds, each responding differently to PAR, VPD and SWC. With decreasing rainfall across rainy seasons, the influence of PAR on F_ds and F_dm weakened, while the influence of VPD strengthened. For F_dl, the impact of VPD peaked and then declined, while the influence of PAR showed an inverse pattern. In the dry season, F_dl was primarily driven by PAR and influenced by VPD and SWC, whereas F_ds was mainly controlled by VPD, with minimal effects from PAR and SWC. The response of F_dm to SWC was similar to that of F_dl, but it mirrored the response of F_ds to PAR and VPD. These findings suggest that sap flow in boreal birch forests may become increasingly susceptible to SWC stress as global climate change intensifies.

Glacier meltwater runoff during extreme heat waves is crucial for overall runoff replenishment; however, studies on the characteristics and mechanisms of extreme meltwater runoff on the Tibetan Plateau (TP) are relatively scarce. In this study, we combine field observations (hydrological, meteorological, and glaciological) with a precipitation runoff modelling system and glacier model (PRMSglacier) to investigate the characteristics of extreme glacier meltwater runoff and the associated energy balance and hydrological processes from October 2018 to September 2022 in the Sangqu Basin on the central TP. Good agreement was shown between observed and modelled total runoff and glacier-wide mass balance, with a mean Nash–Sutcliffe efficiency (NSE) of 0.74 and root-mean-square error (RMSE) of 22 mm w.e. The mean glacial meltwater runoff contributed 14% of the total runoff and snowmelt runoff 72.5% during the study period. Contributions of 21.3% and 59% for glacier meltwater and snowmelt runoff, respectively, during a heatwave from June to September 2022 thus indicated anomalously high glacial meltwater and snowmelt runoff in association with hot and dry meteorological conditions. Basin-scale energy balance results suggest that extremely low albedo and extremely high surface temperatures control the net shortwave and longwave radiation, leading to anomalously high melting of glaciers and snow. The hot and dry meteorological conditions from June to September 2022 primarily affected the source regions of the Yangtze River and Selincuo in Geladandong. This study highlights the importance of extreme glacial meltwater runoff to terrestrial water resources in association with frequent extreme heat waves.

Oxbow lakes are iconic fluvial landforms found in the floodplains of meandering rivers around the world. Their formation is associated with meander cutoff, a process that excises sections of river channel to optimise the downstream transmission of water and sediment. Overbank floods and conveyance through tie channels maintain some hydrological connectivity, but lakes are generally considered to passively infill until they are terrestrialised. Here, a suite of 64 lakes across two meandering rivers in the Bolivian Amazon Basin are used to demonstrate the hydrological dynamism of oxbow lakes by quantifying interannual variations in lake water surface area (WSA), using the modified Normalised Difference Water Index (mNDWI) on an archive of Landsat images, and evaluating the mechanisms controlling these changes using remotely sensed rainfall data and geospatial analysis. The majority of lakes (75%) decreased in size over the study period, while 25% increased in size. The results suggest that WSA variations are controlled by proximity to the active channel, with the magnitude of these variations being set by mechanisms of connectivity. Lakes connected by tie channels experienced WSA changes up to 3.9 times larger than lakes with no visible connection mechanisms. Incursion lakes displayed similar WSA changes to those with tie channels, while isolated lakes were found furthest from the mainstem and had the smallest range of WSAs. Chute lakes experienced a wider range of WSA change (−95% to +281%) and were more strongly controlled by mainstem proximity than neck lakes. Connectivity between the river and oxbow lakes is essential for governing lake hydrodynamics, and tie channels provide the critical conduit by which water can be transmitted deep into the floodplain.