首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 656 毫秒
1.
The role of hummocky terrain in governing runoff routing and focussing groundwater recharge in the Northern Prairies of North America is widely recognised. However, most hydrological studies in the region have not effectively utilised information on the surficial geology and associated landforms in large-scale hydrological characterization. The present study uses an automated digital elevation model (DEM) analysis of a 6500-km2 area in the Northern Prairies to quantify hydrologically relevant terrain parameters for the common types of terrains in the prairies with different surficial deposits widespread in the prairies, namely, moraines and glaciolacustrine deposits. Runoff retention (and storage) capacity within depressions varies greatly between different surficial deposits and is comparable in magnitude with a typical amount of seasonal snowmelt runoff generation. The terrain constraint on potential runoff retention varies from a few millimetres in areas classified as moraine to tens of millimetres in areas classified as stagnant ice moraine deposits. Fluted moraine and glaciolacustrine deposits have intermediate storage capacity values. The study also identified the probability density function describing a number of immediate upstream neighbours for each depression in a fill-and-spill network. A relationship between depression parameters and surficial deposits, as well as identified depression network structure, allows parametrisation of hydrologic models outside of the high-resolution DEM coverage, which can still account for terrain variation in the Prairies.  相似文献   

2.
  相似文献   

3.
Extended severe dry and wet periods are frequently observed in the northern continental climate of the Canadian Prairies. Prairie streamflow is mainly driven by spring snowmelt of the winter snowpack, whilst summer rainfall is an important control on evapotranspiration and thus seasonality affects the hydrological response to drought and wet periods in complex ways. A field‐tested physically based model was used to investigate the influences of climatic variability on hydrological processes in this region. The model was set up to resolve agricultural fields and to include key cold regions processes. It was parameterized from local and regional measurements without calibration and run for the South Tobacco Creek basin in southern Manitoba, Canada. The model was tested against snow depth and streamflow observations at multiple scales and performed well enough to explore the impacts of wet and dry periods on hydrological processes governing the basin scale hydrological response. Four hydro‐climatic patterns with distinctive climatic seasonality and runoff responses were identified from differing combinations of wet/dry winter and summer seasons. Water balance analyses of these patterns identified substantive multiyear subsurface soil moisture storage depletion during drought (2001–2005) and recharge during a subsequent wet period (2009–2011). The fractional percentage of heavy rainfall days was a useful metric to explain the contrasting runoff volumes between dry and wet summers. Finally, a comparison of modeling approaches highlights the importance of antecedent fall soil moisture, ice lens formation during the snowmelt period, and peak snow water equivalent in simulating snowmelt runoff.  相似文献   

4.
Abstract

The dominant source of streamflow in many mountainous watersheds is snowmelt recharge through shallow groundwater systems. The hydrological response of these watersheds is controlled by basin structure and spatially distributed snowmelt. The purpose of this series of two papers is to simulate spatially varying snowmelt and groundwater response in a small mountainous watershed. This paper examines the spatially and temporally variable snowmelt to be used as input to the groundwater flow modelling described in the second paper. Snowmelt simulation by the Simultaneous Heat and Water (SHAW) model (a detailed process model of the interrelated heat, water and solute movement through vegetative cover, snow, residue and soil) was validated by applying the model to two years of data at three sites ranging from shallow transient snow cover on a west-facing slope to a deep snow drift on a north-facing slope. The simulated energy balances for several melt periods are presented. Snow depth, density, and the magnitude and timing of snow cover outflow were simulated well for all sites.  相似文献   

5.
Studies on hydrological processes are often emphasized in resource and environmental studies. This paper identifies the hydrological processes in different landscape zones during the wet season based on the isotopic and hydrochemical analysis of glacier, snow, frozen soil, groundwater and other water sources in the headwater catchment of alpine cold regions. Hydrochemical tracers indicated that the chemical compositions of the water are typically characterized by: (1) Ca? HCO3 type in glacier snow zone, (2) Mg? Ca? SO4 type for surface runoff and Ca? Mg? HCO3 type for groundwater in alpine desert zone, (3) Ca? Mg? SO4 type for surface water and Ca? Mg? HCO3 type for groundwater in alpine shrub zone, and (4) Ca? Na? SO4 type in surface runoff in the alpine grassland zone. The End‐Members Mixing Analysis (EMMA) was employed for hydrograph separation. The results showed that the Mafengou River in the wet season was mainly recharged by groundwater in alpine cold desert zones and shrub zones (52%), which came from the infiltration and transformation of precipitation, thawed frozen soil water and glacier‐snow meltwater. Surface runoff in the glacier‐snow zone accounted for 11%, surface runoff in alpine cold desert zones and alpine shrub meadow zones accounted for 20%, thawed frozen soil water in alpine grassland zones accounted for 9% of recharge and precipitation directly into the river channel (8%). This study suggested that the whole catchment precipitation did not produce significant surface runoff directly, but mostly transformed into groundwater or interflow, and finally arrived in the river channel. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

6.
The Oak Ridges Moraine (ORM) is a key hydrogeologic feature in southern Ontario. Previous research has emphasized the importance of depression‐focused recharge (DFR) for the timing and location of water recharge to the ORM's aquifers. However, the significance of DFR has not been empirically demonstrated, and the ORM's permeable surficial deposits imply that rainfall and snowmelt will largely recharge vertically rather than move laterally to topographic depressions. The exception may be during winter and spring, when concrete soil frost limits infiltration and encourages overland flow. The potential for DFR was examined for closed depressions under forest and agricultural land covers with similar soils and surficial geology. Air temperatures, precipitation, snow depth and water equivalent, soil water contents, soil freezing, and depression surface‐water levels were monitored during the winter and spring of 2012–2013 and 2013–2014. Recharge (R) was estimated at the crest and base of each depression using a 1‐dimensional water balance approach and surface‐applied Br? tracing. Both forest and agricultural land covers experienced soil freezing; however, forest soils did not develop concrete frost. Conversely, agricultural fields saw concrete frost, overland flow, episodic ponding, and subsequent drainage of rain‐on‐snow and snowmelt inputs in open depressions. Recharge at the base of open depressions exceeded that in surrounding areas by an order of magnitude, suggesting that DFR is a significant hydrologic process during winter and spring under agricultural land cover on the ORM. Closed topographic depressions under agricultural land cover on the ORM crest may serve as critical recharge “hot spots” during winter and spring, and the ability of the unsaturated zone beneath these depressions to modify the chemistry of recharging water deserves further attention.  相似文献   

7.
S. Pohl  P. Marsh 《水文研究》2006,20(8):1773-1792
Arctic spring landscapes are usually characterized by a mosaic of coexisting snow‐covered and bare ground patches. This phenomenon has major implications for hydrological processes, including meltwater production and runoff. Furthermore, as indicated by aircraft observations, it affects land‐surface–atmosphere exchanges, leading to a high degree of variability in surface energy terms during melt. The heterogeneity and related differences when certain parts of the landscape become snow free also affects the length of the growing season and the carbon cycle. Small‐scale variability in arctic snowmelt is addressed here by combining a spatially distributed end‐of‐winter snow cover with simulations of variable snowmelt energy balance factors for the small arctic catchment of Trail Valley Creek (63 km2). Throughout the winter, snow in arctic tundra basins is redistributed by frequent blowing snow events. Areas of above‐ or below‐average end‐of‐winter snow water equivalents were determined from land‐cover classifications, topography, land‐cover‐based snow surveys, and distributed surface wind‐field simulations. Topographic influences on major snowmelt energy balance factors (solar radiation and turbulent fluxes of sensible and latent heat) were modelled on a small‐scale (40 m) basis. A spatially variable complete snowmelt energy balance was subsequently computed and applied to the distributed snow cover, allowing the simulation of the progress of melt throughout the basin. The emerging patterns compared very well visually to snow cover observations from satellite images and aerial photographs. Results show the relative importance of variable end‐of‐winter snow cover, spatially distributed melt energy fluxes, and local advection processes for the development of a patchy snow cover. This illustrates that the consideration of these processes is crucial for an accurate determination of snow‐covered areas, as well as the location, timing, and amount of meltwater release from arctic catchments, and should, therefore, be included in hydrological models. Furthermore, the study shows the need for a subgrid parameterization of these factors in the land surface schemes of larger scale climate models. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

8.
Reliable estimates of groundwater recharge are required for the sustainable management of surface and ground water resources in semi‐arid regions particularly in irrigated regions. In this study, groundwater recharge was estimated for an irrigated catchment in southeast Australia using a semi‐distributed hydrological model (SWAT). The model was calibrated under the dry climatic conditions for the period from August 2002 to July 2003 using flow and remotely sensed evapotranspiration (ET). The model was able to simulate observed monthly drain flow and spatially distributed remotely sensed ET. Recharge tended to be higher for irrigated land covers, such as perennial pasture, than for non‐irrigated land. On average, the estimated annual catchment recharge ranged between 147 and 289 mm which represented about 40% of the total rainfall and irrigation inputs. The optimized soil parameters indirectly reflected flow bypassing the soil matrix that could be responsible for this substantial amount of recharge. Overall, the estimated recharge was much more than that previously estimated for the wetter years. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

9.
Climate change threatens water resources in snowmelt‐dependent regions by altering the fraction of snow and rain and spurring an earlier snowmelt season. The bulk of hydrological research has focused on forecasting response in streamflow volumes and timing to a shrinking snowpack; however, the degree to which subsurface storage offsets the loss of snow storage in various alpine geologic settings, i.e. the hydrogeologic buffering capacity, is still largely unknown. We address this research need by assessing the affects of climate change on storage and runoff generation for two distinct hydrogeologic settings present in alpine systems: a low storage granitic and a greater storage volcanic hillslope. We use a physically based integrated hydrologic model fully coupled to a land surface model to run a base scenario and then three progressive warming scenarios, and account for the shifts in each component of the water budget. For hillslopes with greater water retention, the larger storage volcanic hillslope buffered streamflow volumes and timing, but at the cost of greater reductions in groundwater storage relative to the low storage granite hillslope. We found that the results were highly sensitive to the unsaturated zone retention parameters, which in the case of alpine systems can be a mix of matrix or fracture flow. The presence of fractures and thus less retention in the unsaturated zone significantly decreased the reduction in recharge and runoff for the volcanic hillslope in climate warming scenarios. This approach highlights the importance of incorporating physically based subsurface flow in to alpine hydrology models, and our findings provide ways forward to arrive at a conceptual model that is both consistent with geology and hydrologic principles. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

10.
Snowmelt is an important source of runoff in high mountain catchments. Snowmelt modelling for alpine regions remains challenging with scarce gauges. This study simulates the snowmelt in the Karuxung River catchment in the south Tibetan Plateau using an altitude zone based temperature‐index model, calibrates the snow cover area and runoff simulation during 2003–2005 and validates the model performance via snow cover area and runoff simulation in 2006. In the snowmelt and runoff modelling, temperature and precipitation are the two most important inputs. Relevant parameters, such as critical snow fall temperature, temperature lapse rate and precipitation gradient, determine the form and amount of precipitation and distribution of temperature and precipitation in hydrological modelling of the sparsely gauged catchment. Sensitivity analyses show that accurate estimation of these parameters would greatly help in improving the snowmelt simulation accuracy, better describing the snow‐hydrological behaviours and dealing with the data scarcity at higher elevations. Specifically, correlation between the critical snow fall temperature and relative humidity and seasonal patterns of both the temperature lapse rate and the precipitation gradient should be considered in the modelling studies when precipitation form is not logged and meteorological observations are only available at low elevation. More accurate simulation of runoff involving snowmelt, glacier melt and rainfall runoff will improve our understanding of hydrological processes and help assess runoff impacts from a changing climate in high mountain catchments. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

11.
Using hydro-meteorological time series of 50 years and in situ measurements, the dominant runoff processes in perennial Andean headwater catchments in Chile were determined using the hydrological model HBV light. First, cluster analysis was used to identify dry, wet and intermediate years. From these, sub-periods were identified with contrasting seasonal climatic influences on streamflow. By calibrating the model across different periods, impacts on model performance, parameter sensitivity and identifiability were investigated, providing insights into differences in hydrological processes. The modelling approach suggested that, independently of a dry or wet period of calibration, the streamflow response is mostly consistent with flux from groundwater storage, while only a small fraction comes from direct routing of snowmelt. The variation of model parameters, such as the groundwater rate coefficient, was found to be consistent with differing recharge in wet and dry years. The resulting snowmelt–groundwater model is a realistic hypothesis of the hydrological operation of such complex, data scarce and semi-arid Andean catchments. This model may also be a useful tool for predictions of seasonal water availability and a basis for further field studies.  相似文献   

12.
Numerical models are frequently used for the regional quantification of groundwater recharge. However there is a wide range of potential models available that represent the land surface with varying degrees of complexity, but which are rarely tested against observations at the field scale. We compared four models that simulate potential recharge at four intensively monitored sites with different vegetation and soil types in two adjacent catchments. These models were: Penman–Grindley, UN Food and Agricultural Organization, SPAtial Distributed Evaporation and Joint UK Land Environment Simulator. Standardized, unoptimized land surface datasets and pertinent literature were used for parameterization to reflect practice in regional water resource management and planning in the UK. The models were validated against soil moisture observations at all sites, as well as observed transpiration and interception and calculated total evaporation over a year at a woodland site. Soil moisture observations were generally reproduced well, but there were significant differences in how the models apportioned precipitation through the hydrological cycle. This demonstrates that soil moisture data alone are not a good diagnostic for groundwater recharge models. Significant differences in potential recharge were produced by models at both grassland sites, although simulated average annual potential recharge varied by only 15% at the grassland site on permeable soil. At the woodland sites, soil moisture contents were reproduced least accurately, and there were large differences in potential recharge at both woodland sites. This predominantly resulted from varied and inaccurate simulation of evaporation, particularly in the form of interception losses where this was explicitly represented in models. Differences in model structure, such as runoff representation, and parameter selection also influenced all results. Hydrological Processes © 2013 John Wiley & Sons, Ltd.  相似文献   

13.
Climate warming is having profound effects on the hydrological cycle by increasing atmospheric demand, changing water availability, and snow seasonality. Europe suffered three distinct heat waves in 2019, and 11 of the 12 hottest years ever recorded took place in the past two decades, which will potentially change seasonal streamflow patterns and long-term trends. Central Europe exhibited six dry years in a row since 2014. This study uses data from a well-documented headwater catchment in Central Europe (Lysina) to explore hydrological responses to a warming climate. We applied a lumped parameter hydrologic model Brook90 and a distributed model Penn State Integrated Hydrologic Model (PIHM) to simulate long-term hydrological change under future climate scenarios. Both models performed well on historic streamflow and in agreement with each other according to the catchment water budget. In addition, PIHM was able to simulate lateral groundwater redistribution within the catchment validated by the groundwater table dynamics. The long-term trends in runoff and low flow were captured by PIHM only. We applied different EURO-CORDEX models with two emission scenarios (Representative Concentration Pathways RCP 4.5, 8.5) and found significant impacts on runoff and evapotranspiration (ET) for the period of 2071–2100. Results from both models suggested reduced runoff and increased ET, while the monthly distribution of runoff was different. We used this catchment study to understand the importance of subsurface processes in projection of hydrologic response to a warming climate.  相似文献   

14.
Hydrological processes in mountain headwater basins are changing as climate and vegetation change. Interactions between hydrological processes and subalpine forest ecological function are important to mountain water supplies due to their control on evapotranspiration (ET). Improved understanding of the sensitivity of these interactions to seasonal and interannual changes in snowmelt and summer rainfall is needed as these interactions can impact forest growth, succession, health, and susceptibility to wildfire. To better understand this sensitivity, this research examined ET for a sub-alpine forest in the Canadian Rockies over two contrasting growing seasons and quantified the contribution of transpiration (T) from the younger tree population to overall stand ET. The younger population was focused on to permit examination of trees that have grown under the effect of recent climate change and will contribute to treeline migration, and subalpine forest densification and succession. Research sites were located at Fortress Mountain Research Basin, Kananaskis, Alberta, where the subalpine forest examined is composed of Abies lasiocarpa (Subalpine fir) and Picea engelmannii (Engelmann spruce). Seasonal changes in water availability from snowmelt, precipitation, soil moisture reserves yielded stark differences in T and ET between 2016 and 2017. ET was higher in the drier year (2017), which had late snowmelt and lower summer rainfall than in the wetter year (2016) that had lower snowmelt and a rainy summer, highlighting the importance of spring snowmelt recharge of soil moisture. However, stand T of the younger trees (73% of forest population) was greater (64 mm) in 2016 (275 mm summer rainfall) than 2017 (39 mm T, 147 mm summer rainfall), and appears to be sensitive to soil moisture decreases in fall, which are largely a function of summer period rainfall. Relationships between subalpine forest water use and different growing season and antecedent (snowmelt period) hydrological conditions clarify the interactions between forest water use and alpine hydrology, which can lead to better anticipation of the hydrological response of subalpine forest-dominated basins to climate variability and change.  相似文献   

15.
Identifying aquifer vulnerability to climate change is of vital importance in the Sierra Nevada and other snow‐dominated basins where groundwater systems are essential to water supply and ecosystem health. Quantifying the component of new (current year's) snowmelt in groundwater and surface water is useful in evaluating aquifer vulnerability because significant annual recharge may indicate that streamflow will respond rapidly to annual variability in precipitation, followed by more gradual decreases in recharge as recharge declines over decades. Hydrologic models and field‐based studies have indicated that young (<1 year) water is an important component of streamflow. The goal of this study was to utilize the short‐lived, naturally occurring cosmogenic isotope sulfur‐35 (35S) to quantify new snowmelt contribution to groundwater and surface waters in Sagehen Creek Basin (SCB) and Martis Valley Groundwater Basin (MVGB) located within the Tertiary volcanics of the central Sierra Nevada, CA. Activities of 35S were measured in dissolved sulfate (35SO42?) in SCB and MVGB snowpack, groundwater, springs, and streamflow. The percent of new snowmelt (PNS) in SCB streamflow ranged from 0.2 ± 6.6% during baseflow conditions to 14.0 ± 3.4% during high‐flow periods of snowmelt. Similar to SCB, the PNS in MVGB groundwater and streamflow was typically <30% with the largest fractions occurring in late spring or early summer following peak streamflow. The consistently low PNS suggests that a significant fraction of annual snowmelt in SCB and MVGB recharges groundwater, and groundwater contributions to streamflow in these systems have the potential to mitigate climate change impacts on runoff.  相似文献   

16.
Modelling nutrient transport during snowmelt in cold regions remains a major scientific challenge. A key limitation of existing nutrient models for application in cold regions is the inadequate representation of snowmelt, including hydrological and biogeochemical processes. This brief period can account for more than 80% of the total annual surface runoff in the Canadian Prairies and Northern Canada and processes such as atmospheric deposition, overwinter redistribution of snow, ion exclusion from snow crystals, frozen soils, and snow‐covered area depletion during melt influence the distribution and release of snow and soil nutrients, thus affecting the timing and magnitude of snowmelt runoff nutrient concentrations. Research in cold regions suggests that nitrate (NO3) runoff at the field‐scale can be divided into 5 phases during snowmelt. In the first phase, water and ions originating from ion‐rich snow layers travel and diffuse through the snowpack. This process causes ion concentrations in runoff to gradually increase. The second phase occurs when this snow ion meltwater front has reached the bottom of the snowpack and forms runoff to the edge‐of‐the‐field. During the third and fourth phases, the main source of NO3 transitions from the snowpack to the soil. Finally, the fifth and last phase occurs when the snow has completely melted, and the thawing soil becomes the main source of NO3 to the stream. In this research, a process‐based model was developed to simulate hourly export based on this 5‐phase approach. Results from an application in the Red River Basin of southern Manitoba, Canada, shows that the model can adequately capture the dynamics and rapid changes of NO3 concentrations during this period at relevant temporal resolutions. This is a significant achievement to advance the current nutrient modelling paradigm in cold climates, which is generally limited to satisfactory results at monthly or annual resolutions. The approach can inform catchment‐scale nutrient models to improve simulation of this critical snowmelt period.  相似文献   

17.
The Badain Jaran Desert exhibits the greatest difference in altitude of all of the world’s deserts. On the slopes of megadunes in the desert, there are physical and chemical deposits produced by surface runoff. In addition, we have observed rarely-seen infiltration-excess surface runoff in the megadune depressions as well as spring streams at the base of megadunes. We used electron microscopy, energy spectrum analysis, infiltration experiments, moisture content determinations and grain-size analysis to study the mineral and chemical composition of the runoff precipitates, and grain-size of the deposits associated with the runoff, together with the hydrological balance in the megadune area, and the atmospheric precipitation mechanism responsible for groundwater recharge and for supplying water to lakes. The observations of shallow runoff and infiltration-excess surface runoff indicate the occurrence of strong and effective precipitation in summer, which would provide an important source for groundwater recharge. Several lines of evidence, such as the physical and chemical deposits resulting from shallow subsurface runoff, spring streams, infiltration-excess runoff, and gravity capillary water with a moisture content of 3–6%, demonstrate that precipitation reaches the base of the megadunes through infiltration and subsequently becomes groundwater. The chemical deposits, such as newly-formed calcite and gypsum, and gray-black physical deposits, as well as different stages in the development of fan-shaped landforms resulting from shallow subsurface runoff, indicate that groundwater recharge in the area is the result of long-term precipitation, rather than intermittent individual major rainfall events. Fine sand layers with a low infiltration capacity lead to subsurface runoff emerging at the ground surface. Five factors play an important role in maintaining a positive water balance and in replenishing groundwater via rainfall: effective rainfall as a water source, the high infiltration capacity of the sands enabling rainfall to rapidly become capillary water in the dunes, low evapotranspiration rates due to the sparse vegetation, the fact that the depth of the sand layer influenced by evaporation is shallow enough to maximize the deep infiltration of rainfall, and rapidly-moving gravity capillary water in the sandy dunes. These five factors together constitute a mechanism for groundwater recharge from rainfall, and explain the origin of the groundwater and lakes in the area. Our findings represent a significant advance in research on the hydrological cycle, including groundwater recharge conditions and recharge mechanisms, in this desert region.  相似文献   

18.
Snowmelt drives a large portion of streamflow in many mountain areas of the world. However, the water paths from snowmelt to the arrival of the water in the streams are still largely unknown. This work analyzes for first time the influence of snowmelt on spring streamflow with different snow accumulation and duration, in an alpine catchment of the central Spanish Pyrenees. This study presents the water balance of the main melting months (May and June). Piezometric values, water temperature, electrical conductivity and isotope data (δ18O) allow a better understanding of the hydrological functioning of the basin during these months. Results of the water balance calculations showed that snow represented on average 73% of the water available for streamflow in May and June while precipitation during these months accounted for only 27%. However, rainfall during the melting period was important to determine the shape of the spring hydrographs. On average, 78% of the sum of both the snow water equivalent (SWE) accumulated at the beginning of May and the precipitation in May and June converted into runoff during the May–June melting period. The average evaporation-sublimation during the 2 months corresponded to 8.4% of the accumulated SWE and rainfall, so that only a small part of the water input was ultimately available for soil and groundwater storage. When snow cover disappeared from the catchment, soil water storage and streamflow showed a sharp decline. Consequently, streamflow electrical conductivity, temperature and δ18O showed a marked tipping point towards higher values. The fast hydrological response of the catchment to snow and meteorological fluctuations, as well as the marked diel fluctuations of streamflow δ18O during the melting period, strongly suggests short meltwater transit times. As a consequence of this hydrological behaviour, independently of the amount of snow accumulated and of melting date, summer streamflow remained always low, with only small runoff peaks driven by rainfall events.  相似文献   

19.
A study was undertaken during the winter of 1990–1991 in a small (3.7 ha) Canadian Shield catchment to examine the hydrological and hydrochemical response during rain-on-snow events. The results are presented of two large (37.9 and 34.6 mm) rain-on-snow events occurring in early and late March 1991. Peak and total runoff and the groundwater response from the two events are significantly different. Hydrological data indicate that these differences can be attributed to a combination of meteorological (temperature) and physical conditions (antecedent snowpack ripeness, soil moisture and groundwater levels). An immature snowpack (low temperature and density) combined with low antecedent soil moisture conditions significantly reduced the magnitude of the net hydrological input and runoff from the catchment during the early March event, whereas a more mature snowpack and high antecedent soil moisture conditions led to a large runoff event during late March. During both rain-on-snow events a significant portion of the pre-event snowpack chemical load was lost. Based on the maximum snowpack chemical load measured before the events, the two large rain-on-snow events and a brief mid-March warm period during which there were two much smaller rain-on-snow events removed 78% of the hydrogen ion and 63% of the sulphate and nitrate load from the snowpack, while only reducing snowpack water equivalence by 7%. A two-component (rain and snowmelt) isotopic (δ18O SMOW %0) separation of snowmelt lysimeter water during the two events indicated that snowmelt was an important (50 and 65%, respectively) water source available for infiltration and runoff at the snow-soil interface. Considering the high hydrogen ion loadings to the catchment during these two events (3.3 and 3.0 mequiv.m?2, respectively) streamflow pH was not significantly reduced due to an increase in the discharge of well-buffered groundwater. A two-component isotopic hydrograph separation of peak stream discharge during the 2–3 March event indicated that 75% of the total flow was groundwater. In mid-latitude acid-sensitive catchments, winter rain-on-snow events are an important hydrological occurrence due to their ability to elute much of the chemical load (H+, SO4, NO3) from the snowpack before the onset of spring melt when the maximum annual hydrological input typically occurs.  相似文献   

20.
Snowmelt water is a vital freshwater resource in the Altai Mountains of northwestern China. Yet its seasonal hydrological cycle characteristics could change under a warming climate and more rapid spring snowmelt. Here, we simulated snowmelt runoff dynamics in the Kayiertesi River catchment, from 2000 to 2016, by using an improved hydrological distribution model that relied on high-resolution meteorological data acquired from the National Centers for Environmental Prediction (Fnl-NCEP) that were downscaled using the Weather Research Forecasting model. Its predictions were compared to observed runoff data, which confirmed the simulations' reliability. Our results show the model performed well, in general, given its daily validation Nash–Sutcliffe efficiency (NSE) of 0.62 (from 2013 to 2015) and a monthly NSE score of 0.68 (from 2000 to 2010) for the studied river basin of the Altai Mountains. In this river basin catchment, snowfall accounted for 64.1% of its precipitation and snow evaporation for 49.8% of its total evaporation, while snowmelt runoff constituted 29.3% of the annual runoff volume. Snowmelt's contribution to runoff in the Altai Mountains can extend into non-snow days because of the snowmelt water retained in soils. From 2000 to 2016, the snow-to-rain ratio decreased rapidly, however, the snowmelt contribution remained relatively stable in the study region. Our findings provide a sound basis for making snowmelt runoff predictions, which could be used prevent snowmelt-induced flooding, as well as a generalizable approach applicable to other remote, high-elevation locations where high-density, long-term observational data are currently lacking. How snowmelt contributes to water dynamics and resources in cold regions is garnering greater attention. Our proposed model is thus timely perhaps, enabling more comprehensive assessments of snowmelt contributions to hydrological processes in those alpine regions characterized by seasonal snow cover.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号