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1.
The thermal regimes of alpine streams remain understudied and have important implications for cold‐water fish habitat, which is expected to decline due to climatic warming. Previous research has focused on the effects of distributed energy fluxes and meltwater from snowpacks and glaciers on the temperature of mountain streams. This study presents the effects of the groundwater spring discharge from an inactive rock glacier containing little ground ice on the temperature of an alpine stream. Rock glaciers are coarse blocky landforms that are ubiquitous in alpine environments and typically exhibit low groundwater discharge temperatures and resilience to climatic warming. Water temperature data indicate that the rock glacier spring cools the stream by an average of 3 °C during July and August and reduces maximum daily temperatures by an average of 5 °C during the peak temperature period of the first two weeks in August, producing a cold‐water refuge downstream of the spring. The distributed stream surface and streambed energy fluxes are calculated for the reach along the toe of the rock glacier, and solar radiation dominates the distributed stream energy budget. The lateral advective heat flux generated by the rock glacier spring is compared to the distributed energy fluxes over the study reach, and the spring advective heat flux is the dominant control on stream temperature at the reach scale. This study highlights the potential for coarse blocky landforms to generate climatically resilient cold‐water refuges in alpine streams.  相似文献   

2.
The active rock glacier “Innere Ölgrube” and its catchment area (Ötztal Alps, Austria) are assessed using various hydro(geo)logical tools to provide a thorough catchment characterization and to quantify temporal variations in recharge and discharge components. During the period from June 2014 to July 2018, an average contribution derived from snowmelt, ice melt and rainfall of 35.8%, 27.6% and 36.6%, respectively, is modelled for the catchment using a rainfall-runoff model. Discharge components of the rock glacier springs are distinguished using isotopic data as well as other natural and artificial tracer data, when considering the potential sources rainfall, snowmelt, ice melt and longer stored groundwater. Seasonal as well as diurnal variations in runoff are quantified and the importance of shallow groundwater within this rock glacier-influenced catchment is emphasized. Water derived from ice melt is suggested to be provided mainly by melting of two small cirque glaciers within the catchment and subordinately by melting of permafrost ice of the rock glacier. The active rock glacier is characterized by a layered internal structure with an unfrozen base layer responsible for groundwater storage and retarded runoff, a main permafrost body contributing little to the discharge (at the moment) by permafrost thaw and an active layer responsible for fast lateral flow on top of the permafrost body. Snowmelt contributes at least 1/3rd of the annual recharge. During droughts, meltwater derived from two cirque glaciers provides runoff with diurnal runoff variations; however, this discharge pattern will change as these cirque glaciers will ultimately disappear in the future. The storage-discharge characteristics of the investigated active rock glacier catchment are an example of a shallow groundwater aquifer in alpine catchments that ought to be considered when analysing (future) river runoff characteristics in alpine catchments as these provide retarded runoff during periods with little or no recharge.  相似文献   

3.
Groundwater flow through coarse blocky landforms contributes to streamflow in mountain watersheds, yet its role in the alpine hydrologic cycle has received relatively little attention. This study examines the internal structure and hydrogeological characteristics of an inactive rock glacier in the Canadian Rockies using geophysical imaging techniques, analysis of the discharge hydrograph of the spring draining the rock glacier, and chemical and stable isotopic compositions of source waters. The results show that the coarse blocky sediments forming the rock glacier allow the rapid infiltration of snowmelt and rain water to an unconfined aquifer above the bedrock surface. The water flowing through the aquifer is eventually routed via an internal channel parallel to the front of the rock glacier to a spring, which provides baseflow to a headwater stream designated as a critical habitat for an at‐risk cold‐water fish species. Discharge from the rock glacier spring contributes up to 50% of basin streamflow during summer baseflow periods and up to 100% of basin streamflow over winter, despite draining less than 20% of the watershed area. The rock glacier contains patches of ground ice even though it may have been inactive for thousands of years, suggesting the resiliency of the ground thermal regime under a warming climate.  相似文献   

4.
Despite the significant influence of temperature upon alpine stream benthic communities, thermal regimes of the water column and hyporheic zone of these mountain streams have received limited attention. This paper reports upon a detailed spatio‐temporal study of water column and streambed temperatures undertaken within the Taillon–Gabiétous catchment, French Pyrénées, that aims: (1) to characterize the nature and dynamics of alpine stream water column and streambed thermal patterns; (2) to investigate stream thermal variability under a range of hydroclimatological conditions; and (3) to consider the implications of (1) and (2) for alpine stream benthic communities. The catchment contains four highly dynamic hydrological sources and pathways: (1) two cirque glaciers (Taillon and Gabiétous); (2) seasonal snowpacks; (3) a karst groundwater system; and (4) hillslope aquifers. Water column temperatures were monitored continuously at four sites located along the Taillon glacial stream and at three groundwater springs (two karstic and one hillslope) over the 2002 summer melt season. An eighth site (Tourettes) was established on a predominantly groundwater‐fed stream with limited meltwater input. Bed temperatures (0·05, 0·20 and 0·40 m depth) and river discharge were measured at three sites: (1) the Taillon stream; (2) the Tourettes stream; and (3) below the confluence of (1) and (2). Air temperatures, incoming short‐wave radiation and precipitation were recorded to characterize atmospheric conditions. Glacial stream water column temperatures increased downstream, although groundwater tributaries punctuated longitudinal patterns. Karstic groundwater streams were cooler and more thermally stable than the glacial stream (except at the glacier snout). Hillslope groundwater stream temperatures were most variable and, on average, the warmest of all sites. Streambed temperatures in the glacial stream were coldest and most variable whilst the warmest and least variable streambed temperatures were recorded in an adjacent groundwater tributary. Temperature variability was strongly related to: (1) dynamic water source and pathway contributions; (2) proximity to source; and (3) prevailing hydroclimatological conditions. The high thermal heterogeneity within this catchment may sustain relatively diverse benthic communities, including some endemic Pyrénéan macroinvertebrate taxa. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

5.
Water temperature dynamics in High Arctic river basins   总被引：2，自引：0，他引：2  
Despite the high sensitivity of polar regions to climate change and the strong influence of temperature upon ecosystem processes, contemporary understanding of water temperature dynamics in Arctic river systems is limited. This research gap was addressed by exploring high‐resolution water column thermal regimes for glacier‐fed and non‐glacial rivers at eight sites across Svalbard during the 2010 melt season. Mean water column temperatures in glacier‐fed rivers (0.3–3.2 °C) were lowest and least variable near the glacier terminus but increased downstream (0.7–2.3 °C km–1). Non‐glacial rivers, where discharge was sourced primarily from snowmelt runoff, were warmer (mean: 2.9–5.7 °C) and more variable, indicating increased water residence times in shallow alluvial zones and increased potential for atmospheric influence. Mean summer water temperature and the magnitude of daily thermal variation were similar to those of some Alaskan Arctic rivers but low at all sites when compared with alpine glacierized environments at lower latitudes. Thermal regimes were correlated strongly (p < 0.01) with incoming short‐wave radiation, air temperature, and river discharge. Principal drivers of thermal variability were inferred to be (i) water source (i.e. glacier melt, snowmelt, groundwater); (ii) exposure time to the atmosphere; (iii) prevailing meteorological conditions; (iv) river discharge; (v) runoff interaction with permafrost and buried ice; and (vi) basin‐specific geomorphological features (e.g. channel morphology). These results provide insight into the potential changes in high‐latitude river systems in the context of projected warming in polar regions. We hypothesize that warmer and more variable temperature regimes may prevail in the future as the proportion of bulk discharge sourced from glacial meltwater declines and rivers undergo a progressive shift towards snow water and groundwater sources. Importantly, such changes could have implications for aquatic species diversity and abundance and influence rates of ecosystem functioning in high‐latitude river systems. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

6.
We analysed contributions to run‐off using hourly stream water samples from seven individual melt‐induced run‐off events (plus one rainfall event) during 2011, 2012 and 2013 in two nested glacierized catchments in the Eastern Italian Alps. Electrical conductivity and stable isotopes of water were used for mixing analysis and two‐component and three‐component hydrograph separation. High‐elevation snowmelt, glacier melt and autumn groundwater were identified as major end‐members. Discharge and tracers in the stream followed the diurnal variations of air temperature but markedly reacted to rainfall inputs. Hysteresis patterns between discharge and electrical conductivity during the melt‐induced run‐off events revealed contrasting loop directions at the two monitored stream sections. Snowmelt contribution to run‐off was highest in June and July (up to 33%), whereas the maximum contribution of glacier melt was reached in August (up to 65%). The maximum groundwater and rainfall contributions were 62% and 11%, respectively. Run‐off events were generally characterized by decreasing snowmelt and increasing glacier melt fractions from the beginning to the end of the summer 2012, while run‐off events in 2013 showed less variable snowmelt and lower glacier melt contributions than in 2012. The results provided essential insights into the complex dynamics of melt‐induced run‐off events and may be of further use in the context of water resource management in alpine catchments. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

7.
We have analysed a series of surface samples from the alpine glaciers of Taylor Valley, Southern Victoria Land, Antarctica for their geochemical composition. This was done to better establish the role of glaciochemical variation on the chemical composition of meltwater streams emanating from the glaciers. The chemistry of the snow and ice changes with proximity to the ocean and with elevation of the glacier surface. The aeolian transport of dry valley dust, as indicated by both chemical and particulate matter variations, is a major process affecting the overall glacier chemistry and the chemistry of the meltwaters. Streams originating on the western edges of the glaciers are more impacted by the aeolian input as they are in the direct path of the major regional wind direction. Our data strongly suggest that the variation in stream geochemistry in Taylor Valley is a result in part of the differences in chemical composition of glacier melt. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

8.
Groundwater discharge in alpine headwaters sustains baseflow in rivers originating in mountain ranges of the world, which is critically important for aquatic habitats, run-of-river hydropower generation, and downstream water supply. Groundwater storage in alpine watersheds was long considered negligible, but recent field-based studies have shown that aquifers are ubiquitous in the alpine zone with no soil and vegetation. Talus, moraine, and rock glacier aquifers are common in many alpine regions of the world, although bedrock aquifers occur in some geological settings. Alpine aquifers consisting of coarse sediments have a fast recession of discharge after the recharge season (e.g., snowmelt) or rainfall events, followed by a slow recession that sustains discharge over a long period. The two-phase recession is likely controlled by the internal structure of the aquifers. Spatial extent and distribution of individual aquifers determine the groundwater storage-discharge characteristics in first- and second-order watersheds in the alpine zone, which in turn govern baseflow characteristics in major rivers. Similar alpine landforms appear to have similar hydrogeological characteristics in many mountain ranges across the world, suggesting that a common conceptual framework can be used to understand alpine aquifers based on geological and geomorphological settings. Such a framework will be useful for parameterizing storage-discharge characteristics in large river hydrological models.  相似文献   

9.
The Wind River Range (WRR) of Wyoming has the largest concentration of alpine glaciers in the American Rockies and contributes to several major river systems in the western United States. Declines in the areal extent and volume of these glaciers are well documented, and eventual loss of alpine glaciers will reduce the amount of water available for agricultural and domestic use. The contribution of glacial melt to streamflow remains largely unquantified in Wyoming. We used isotope measurements and Bayesian modeling to estimate the fractional contribution of glacier meltwater to Dinwoody Creek (DC) in the WRR on bi‐weekly and seasonal (spring, summer, and fall) time scales over 2 years. In 2007 and 2008, we made temporally intensive measurements of the stable isotope composition of water from the DC watershed. Samples of the primary sources of streamflow (snowmelt, glacier melt, rain, and baseflow) were collected during field campaigns, and automated collection of stream samples occurred over the melt season. Isotope data (D and 18O) were analyzed within a hierarchical Bayesian framework that incorporated temporal and spatial correlations. Glacial melt contributed a significant proportion (～53–59%) to streamflow in a low‐flow year (2007) or when streamflow was low during a high‐flow year (2008). In 2008, a large and persistent snowpack contributed significantly (～0·42–51%) to streamflow in mid‐summer. The large contribution of glacial melt to streamflow suggests that the loss of glaciers may impact riparian ecosystems and human water supplies in the late summer and in years with low snowpack. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

10.
Solute and runoff fluxes from two adjacent alpine streams (one glacial and one non‐glacial) were investigated to determine how the inorganic solute chemistry of runoff responded to seasonal and interannual changes in runoff sources and volume, and to differences in physical catchment properties. Intercatchment differences in solute composition were primarily controlled by differences in catchment geology and the presence of soils, whereas differences in total solute fluxes were largely dependent on specific discharge. The glacial stream catchment had higher chemical denudation rates due to the high rates of flushing (higher specific discharge). The non‐glacial Bow River had higher overall concentrations of solutes despite the greater prevalence of more resistant lithologies in this catchment. This is likely the result of both longer average water–rock contact times, and a greater supply of protons from organic soils and/or pyrite oxidation. Increases in snowpack depth/snowmelt runoff reduced the retention of nitrate in the Bow River catchment (i.e. increased nitrate export), probably by reducing net biological uptake, or by reducing the proportion of runoff that had contact with biologically active soil horizons that tend to remove nitrate. The two streams exhibited opposite solute flux responses to climate perturbations over three melt seasons (1998, 1999, and 2000). The 1998 El Niño event resulted in an unusually thin winter snowpack, and increased runoff and solute fluxes from the glacial catchment, but decreased fluxes from the Bow River catchment. Solute fluxes in the Bow River increased proportionally to discharge, indicating that increased snowmelt runoff in this catchment resulted in a proportional increase in weathering rates. In contrast, the proportional variation in solute flux in the glacial stream was only ∼70–80% of the variation in water flux. This suggests that increased ablation of glacier ice and the development of subglacial channels during the 1998 El Niño year apparently reduced the average water–rock contact time in the glacial catchment relative to seasons when the subglacial drainage system was primarily distributed in character. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

11.
Proglacial stream development was studied in coastal British Columbia and Washington, focusing on reaches exposed by post‐Little Ice Age (LIA) glacier retreat, to address three principal questions: (i) Does the legacy of LIA glaciation influence the evolution of channel morphology? (ii) How long does it take for riparian forest to establish following glacier retreat? (iii) Can newly exposed proglacial streams provide suitable fish habitat? Channel morphologies were identified by field surveys of 69 reaches in 10 catchments. Riparian forest development and potential fish habitat were characterized in those reaches and an additional 22 catchments using GIS analysis. The landscape template imposed by the Quaternary glaciation appears to override most of the modern effects of the LIA in controlling channel‐reach morphology. Binary logistic regression analysis identified elevation and time since deglaciation as primary controls on the presence of riparian forest. At higher elevations, establishment of morphologically functional riparian forest could take several centuries, prolonged by channel instability associated with post‐LIA sediment inputs. Of the recently deglaciated streams included in this analysis, the majority (86%) of the total length was of suitable gradient for fish and could be accessed either by downstream populations or from adjacent lakes. Predicted maximum weekly average stream temperature (MWAT) indicated that the post‐LIA study streams were thermally suitable for cold‐water fish. A future scenario of glacier loss would cause a 14% decline in accessible cold‐water thermal habitat in post‐LIA streams. Decreased summer flows due to glacier retreat could further limit usable habitat by reducing stream depths and wetted perimeters. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

12.
Water source and lake landscape position can strongly influence the physico‐chemical characteristics of flowing waters over space and time. We examined the physico‐chemical heterogeneity in surface waters of an alpine stream‐lake network (>2600 m a.s.l.) in Switzerland. The catchment comprises two basins interspersed with 26 cirque lakes. The larger lakes in each basin are interconnected by streams that converge in a lowermost lake with an outlet stream. The north basin is primarily fed by precipitation and groundwater, whereas the south basin is fed mostly by glacial melt from rock glaciers. Surface flow of the entire channel network contracted by ～60% in early autumn, when snowmelt runoff ceased and cold temperatures reduced glacial outputs, particularly in the south basin. Average water temperatures were ～4 °C cooler in the south basin, and temperatures increased by about 4–6 °C along the longitudinal gradient within each basin. Although overall water conductivity was low (<27 µS cm?1) because of bedrock geology (ortho‐gneiss), the south basin had two times higher conductivity values than the north basin. Phosphate‐phosphorus levels were below analytical detection limits, but particulate phosphorus was about four times higher in the north basin (seasonal average: 9 µg l?1) than in the south basin (seasonal average: 2 µg l?1). Dissolved nitrogen constituents were around two times higher in the south basin than in the north basin, with highest values averaging > 300 µg l?1 (nitrite + nitrate‐nitrogen), whereas particulate nitrogen was approximately nine times greater in the north basin (seasonal average: 97 µg l?1) than in the south basin (seasonal average: 12 µg l?1). Total inorganic carbon was low (usually <0·8 mg l?1), silica was sufficient for algal growth, and particulate organic carbon was 4·5 times higher in the north basin (average: 0·9 mg l?1) than in the south basin (average: 0·2 mg l?1). North‐basin streams showed strong seasonality in turbidity, particulate‐nitrogen and ‐phosphorus, and particulate organic carbon, whereas strong seasonality in south‐basin streams was observed in conductivity and dissolved nitrogen. Lake position influenced the seasonal dynamics in stream temperatures and nutrients, particularly in the groundwater/precipitation‐fed north‐basin network. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

13.
In many mountain regions, large land areas with heterogeneous soils have become ice‐free with the ongoing glacier retreat. On these recently formed proglacial fields, the melt of the remaining glaciers typically drives pronounced diurnal stream level fluctuations that propagate into the riparian zone. This behaviour was measured on the Damma glacier forefield in central Switzerland with stage recorders in the stream and groundwater monitoring wells along four transects. In spite of the large groundwater stage variations, radon measurements in the near‐stream riparian zone indicate that there is little mixing between stream water and groundwater on daily time scales. At all four transects, including both losing and gaining reaches, the groundwater level fluctuations lagged the stream stage variations and were often damped with distance from the stream. Similar behaviours have been modelled using the diffusion equation in coastal regions influenced by tidal sea level variations. We thus tested the ability of such a model to predict groundwater level fluctuations in proglacial fields. The model reproduced several key features of the observed fluctuations at three of four locations, although discrepancies also arise due to non representative input data and model simplifications. Nevertheless, calibration of the model for the individual transects yielded realistic estimates of hydraulic diffusivities between the stream and groundwater monitoring wells. We conclude that studying diurnal groundwater fluctuations can provide important information about the subsurface hydrology of alpine watersheds dominated by glacier melt. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

14.
We measured stream temperature continuously during the 2011 summer run‐off season (May through October) in nine watersheds of Southeast Alaska that provide spawning habitat for Pacific salmon. The nine watersheds have glacier coverage ranging from 0% to 63%. Our goal was to determine how air temperature and watershed land cover, particularly glacier coverage, influence stream temperature across the seasonal glacial meltwater hydrograph. Multiple linear regression models identified mean watershed elevation (related to glacier extent) and watershed lake coverage (%) as the strongest landscape controls on mean monthly stream temperature, with the weakest (May) and strongest (July) models explaining 86% and 97% of the temperature variability, respectively. Mean weekly stream temperature was significantly correlated with mean weekly air temperature in seven streams; however, the relationships were weak to non‐significant in the streams influenced by glacial run‐off. Streams with >30% glacier coverage showed decreasing stream temperatures with rising summer air temperatures, whereas those with <30% glacier coverage exhibited summertime warming. Glaciers also had a cooling effect on monthly mean stream temperature during the summer (July through September) equivalent to a decrease of 1.1 °C for each 10% increase in glacier coverage. The maximum weekly average temperature (an index of thermal suitability for salmon) in the six glacial streams was substantially below the lower threshold for optimum salmon growth. This finding suggests that although glaciers are important for moderating summer stream temperatures, future reductions in glacier run‐off may actually improve the thermal suitability of some glacially dominated streams in Southeast Alaska for salmon. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

15.
Glacier‐fed river thermal regimes vary markedly in space and time; however, knowledge is limited on the fundamental processes controlling alpine stream temperature dynamics. To address the research gap, this study quantified heat exchanges at the water surface and bed of the Taillon glacier‐fed stream, French Pyrénées. Hydro‐meteorological observations were recorded at 15‐min intervals across two summer melt seasons (2010 and 2011), and energy balance components were measured or estimated based on site‐specific data. Averaged over both seasons, net radiation was the largest heat source (~80% of total flux); sensible heat (~13%) and friction (~3%) were also sources, while heat exchange across the channel–streambed interface was negligible (<1%). Latent heat displayed distinct interannual variability and contributed 5% in 2010 compared with 0.03% in 2011. At the sub‐seasonal scale, latent heat shifted from source to sink, possibly linked to the retreating valley snowline that changed temperature and humidity gradients. These findings represent the first, multiyear study of the heat exchange processes operating in a glacier‐fed stream, providing fundamental process understanding; the research highlights the direct control antecedent (winter) conditions that have on energy exchange and stream temperature during summer months. In particular, the timing and volume of snowfall/snowmelt can drive thermal dynamics by the following: (1) altering the length of the stream network exposed to the atmosphere and (2) controlling the volume and timing of cold water advection downstream. Finally, this study highlights the need to develop long‐term hydro‐meteorological monitoring stations to improve the understanding of these highly dynamic, climatically sensitive systems. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

16.
A myriad of downstream communities and industries rely on streams fed by both groundwater discharge and glacier meltwater draining the Cordillera Blanca, Northern Peruvian Andes, which contains the highest density of glaciers in the tropics. During the dry season, approximately half the discharge in the region's proglacial streams comes from groundwater. However, because of the remote and difficult access to the region, there are few field methods that are effective at the reach scale to identify the spatial distribution of groundwater discharge. An energy balance model, Rhodamine WT dye tracing, and high‐definition kite‐borne imagery were used to determine gross and net groundwater inputs to a 4‐km reach of the Quilcay River in Huascaran National Park, Peru. The HFLUX computer programme ( http://hydrology.syr.edu/hflux.html ) was used to simulate the Quilcay River's energy balance using stream temperature observations, meteorological measurements, and kite‐borne areal photography. Inference from the model indicates 29% of stream discharge at the reach outlet was contributed by groundwater discharge over the study section. Rhodamine WT dye tracing results, coupled with the energy balance, show that approximately 49% of stream water is exchanged (no net gain) with the subsurface as gross gains and losses. The results suggest that gross gains from groundwater are largest in a moraine subreach but because of large gross losses, net gains are larger in the meadow subreaches. These insights into pathways of groundwater–surface water interaction can be applied to improve hydrological modelling in proglacial catchments throughout South America. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

17.
Critical zone influences on hydrologic partitioning, subsurface flow paths and reactions along these flow paths dictate the timing and magnitude of groundwater and solute flux to streams. To isolate first‐order controls on seasonal streamflow generation within highly heterogeneous, snow‐dominated basins of the Colorado River, we employ a multivariate statistical approach of end‐member mixing analysis using a suite of daily chemical and isotopic observations. Mixing models are developed across 11 nested basins (0.4 to 85 km2) spanning a gradient of climatological, physical, and geological characteristics. Hydrograph separation using rain, snow, and groundwater as end‐members indicates that seasonal contributions of groundwater to streams is significant. Mean annual groundwater flux ranges from 12% to 33% whereas maximum groundwater contributions of 17% to 50% occur during baseflow. The direct relationship between snow water equivalent and groundwater flux to streams is scale dependent with a trend toward self‐similarity when basins exceed 5.5 km2. We find groundwater recharge increases in basins of high relief and within the upper subalpine where maximum snow accumulation is coincident with reduced conifer cover and lower canopy densities. The mixing model developed for the furthest downstream site did not transfer to upstream basins. The resulting error in predicted stream concentrations points toward weathering reactions as a function of source rock and seasonal shifts in flow path. Additionally, the potential for microbial sulfate reduction in floodplain sediments along a low‐gradient, meandering portion of the river is sufficient to modify hillslope contributions and alter mixing ratios in the analysis. Soil flushing in response to snowmelt is not included as an end‐member but is identified as an important mechanism for release of solutes from these mountainous watersheds. End‐member mixing analysis used in combination with high‐frequency observations reveals important aspects of catchment hydrodynamics across scale.  相似文献   

18.
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   

19.
Cushion plant dominated peatlands are key ecosystems in tropical alpine regions of the Andes in South America. The cushion plants have formed peat bodies over thousands of years that fill many valley bottoms, and the forage produced by the plants is critical for native and nonnative domesticated mammals. The sources and flow paths of water supporting these peatlands remain largely unknown. Some studies have suggested that glacier meltwater streams support some peatlands, and that the ongoing loss of glaciers and their meltwaters could lead to the loss or diminishment of peatlands. We analysed the hydrologic regime of 10 peatlands in four mountain regions of Bolivia and Peru using groundwater monitoring. Groundwater levels in peatlands were relatively stable and within 20 cm of the ground surface during the rainy season, and many sites had water tables 40–90 cm below the ground surface in the dry season. Topographic and groundwater elevations in the peatlands demonstrated that the water source of all 10 peatlands was hillslope groundwater flowing from lateral moraines, talus, colluvium, or bedrock aquifers into the peatlands. There was little to no input from streams, whether derived from glacier melt or other sources, and glacier melt could not have recharged the hillslope aquifers supporting peatlands. We measured the stable water isotopes in water samples taken during different seasons, distributed throughout the catchments, and the values are consistent with this interpretation. Our findings indicate that peatlands in the study region are recharged by hillslope groundwater discharge rather than stream water and may not be as vulnerable to glacial decline as other studies have indicated. However, both glaciers and peatlands are susceptible to changing thermal and precipitation regimes that could affect the persistence of peatlands.  相似文献   

20.
In glacier‐fed rivers, melting of glacier ice sustains streamflow during the driest times of the year, especially during drought years. Anthropogenic and ecologic systems that rely on this glacial buffering of low flows are vulnerable to glacier recession as temperatures rise. We demonstrate the evolution of glacier melt contribution in watershed hydrology over the course of a 184‐year period from 1916 to 2099 through the application of a coupled hydrological and glacier dynamics model to the Hood River basin in Northwest Oregon, USA. We performed continuous simulations of glaciological processes (mass accumulation and ablation, lateral flow of ice and heat conduction through supra‐glacial debris), which are directly linked with seasonal snow dynamics as well as other key hydrologic processes (e.g. evapotranspiration and subsurface flow). Our simulations show that historically, the contribution of glacier melt to basin water supply was up to 79% at upland water management locations. We also show that supraglacial debris cover on the Hood River glaciers modulates the rate of glacier recession and progression of dry season flow at upland stream locations with debris‐covered glaciers. Our model results indicate that dry season (July to September) discharge sourced from glacier melt started to decline early in the 21st century following glacier recession that started early in the 20th century. Changes in climate over the course of the current century will lead to 14–63% (18–78%) reductions in dry season discharge across the basin for IPCC emission pathway RCP4.5 (RCP8.5). The largest losses will be at upland drainage locations of water diversions that were dominated historically by glacier melt and seasonal snowmelt. The contribution of glacier melt varies greatly not only in space but also in time. It displays a strong decadal scale fluctuations that are super‐imposed on the effects of a long‐term climatic warming trend. This decadal variability results in reversals in trends in glacier melt, which underscore the importance of long‐time series of glacio‐hydrologic analyses for evaluating the hydrological response to glacier recession. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

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