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1.
Joshua C. Koch 《水文研究》2016,30(21):3918-3931
Arctic thaw lakes are an important source of water for aquatic ecosystems, wildlife, and humans. Many recent studies have observed changes in Arctic surface waters related to climate warming and permafrost thaw; however, explaining the trends and predicting future responses to warming is difficult without a stronger fundamental understanding of Arctic lake water budgets. By measuring and simulating surface and subsurface hydrologic fluxes, this work quantified the water budgets of three lakes with varying levels of seasonal drainage, and tested the hypothesis that lateral and subsurface flows are a major component of the post‐snowmelt water budgets. A water budget focused only on post‐snowmelt surface water fluxes (stream discharge, precipitation, and evaporation) could not close the budget for two of three lakes, even when uncertainty in input parameters was rigorously considered using a Monte Carlo approach. The water budgets indicated large, positive residuals, consistent with up to 70% of mid‐summer inflows entering lakes from lateral fluxes. Lateral inflows and outflows were simulated based on three processes; supra‐permafrost subsurface inflows from basin‐edge polygonal ground, and exchange between seasonally drained lakes and their drained margins through runoff and evapotranspiration. Measurements and simulations indicate that rapid subsurface flow through highly conductive flowpaths in the polygonal ground can explain the majority of the inflow. Drained lakes were hydrologically connected to marshy areas on the lake margins, receiving water from runoff following precipitation and losing up to 38% of lake efflux to drained margin evapotranspiration. Lateral fluxes can be a major part of Arctic thaw lake water budgets and a major control on summertime lake water levels. Incorporating these dynamics into models will improve our ability to predict lake volume changes, solute fluxes, and habitat availability in the changing Arctic. Published 2016. This article is a U.S. Government work and is in the public domain in the USA.  相似文献   

2.
Rainfall takes many flowpaths to reach a stream, and the success of riparian buffers in water quality management is significantly influenced by riparian hydrology. This paper presents results from hydrometric monitoring of riparian buffer hydrology in a pasture catchment. Runoff processes and riparian flowpaths were investigated on two planar hillslopes with regenerating grass and E. globulus buffers. Surface runoff and subsurface flows (A‐ and B‐horizons) were measured for 3 years using surface runoff collectors, subsurface troughs and piezometers. Water volumes moving through the riparian buffers via the measured flowpaths were ranked B‐horizon ? surface runoff ≈ A‐horizon. Runoff volumes through the B‐horizon troughs were an order of magnitude greater than those recorded for the most productive surface runoff plots or the A‐horizon troughs. Subsurface runoff and saturation‐excess overland flow (SOF) were limited to the winter months, whereas infiltration‐excess overland flow (IEOF) can occur all year round during intense storms. Surface runoff was recorded on 33 occasions, mostly during winter (late May–early October), and total annual surface runoff volumes collected by the 20 unconfined (2 m wide) runoff plots varied between > 80 and < 20 m3. Subsurface flow only occurred in winter, and the 6 m wide B‐horizon subsurface troughs flowed above 1 l s?1 continuously, whereas the A‐horizon troughs flowed infrequently (<6 days per year). In summer, surface runoff occurred as IEOF during intense storms in the E. globulus buffer, but not in the grass buffer. Observations suggest that surface crusting reduced the soil's infiltration capacity in the E. globulus buffer. During winter, SOF and seepage were observed in both buffers, but subsurface flow through the B‐horizon was the dominant flowpath. Key hydrologic differences between the grass and tree buffers are the generation of IEOF in the E. globulus buffer during intense summer storms, and the smaller subsurface runoff volumes and fewer flow days in the E. globulus buffer. Low surface runoff volumes are likely to limit the potential of these buffers to filter pollutants from surface runoff. High subsurface flow volumes and saturated conductivities are also likely to limit the residence time of water in the subsurface domain. Based on their hydrologic performance, the key roles of riparian buffers in this landscape are likely to be displacing sediment and nutrient‐generating activities away from streams and stabilizing channel morphology. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

3.
李祖忠  张旭东  江聪  杜涛  曾凌 《湖泊科学》2023,35(5):1822-1831
三峡水库蓄水引起库区水位抬升,水面面积显著增加,对区域水文循环过程产生了一定影响。为揭示三峡水库蓄水前后水面面积及蒸发损失变化规律,选取三峡库区坝前至寸滩区间作为研究区,利用Landsat影像数据提取1982—2021年水面面积,分区建立水位与面积关系曲线,进而推求库区逐日水面面积。在估计三峡库区水面面积的基础上,结合站点潜在蒸发资料推求水面蒸发损失量。研究结果表明:2010年三峡水库全面运行后,坝前至寸滩库区平均水面面积由蓄水前的372.96km2,增加到761.31km2,较蓄水前增加了1.04倍。同时,三峡水库的蓄泄调节改变了库区河段原有的水文节律,使得库区水面面积的季节性变化特征较蓄水前发生了显著变化。蓄水后,冬季水面面积最大,平均为843.81km2,较蓄水前增加了1.89倍;秋季、春季次之,水面面积分别为818.73和735.28km2,较蓄水前分别增加了97.17%和1.28倍;夏季水面面积最小,为653.03km2,较蓄水前仅增加了39.06%。水库全面运行后,...  相似文献   

4.
Spring snow melt run‐off in high latitude and snow‐dominated drainage basins is generally the most significant annual hydrological event. Melt timing, duration, and flow magnitude are highly variable and influence regional climate, geomorphology, and hydrology. Arctic and sub‐arctic regions have sparse long‐term ground observations and these snow‐dominated hydrologic regimes are sensitive to the rapidly warming climate trends that characterize much of the northern latitudes. Passive microwave brightness temperatures are sensitive to changes in the liquid water content of the snow pack and make it possible to detect incipient melt, diurnal melt‐refreeze cycles, and the approximate end of snow cover on the ground over large regions. Special Sensor Microwave Imager (SSM/I) and Advanced Microwave Scanning Radiometer for EOS (AMSR‐E) passive microwave brightness temperatures (Tb) and diurnal amplitude variations (DAV) are used to investigate the spatial variability of snowmelt onset timing (in two stages, ‘DAV onset’ and ‘melt onset’) and duration for a complex sub‐arctic landscape during 2005. The satellites are sensitive to small percentages of liquid water, and therefore represent ‘incipient melt’, a condition somewhat earlier than a traditional definition of a melting snowpack. Incipient melt dates and duration are compared to topography, land cover, and hydrology to investigate the strength and significance of melt timing in heterogeneous landscapes in the Pelly River, a major tributary to the Yukon River. Microwave‐derived melt onset in this region in 2005 occurred from late February to late April. Upland areas melt 1–2 weeks later than lowland areas and have shorter transition periods. Melt timing and duration appear to be influenced by pixel elevation, aspect, and uniformity as well as other factors such as weather and snow mass distribution. The end of the transition season is uniform across sensors and across the basin in spite of a wide variety of pixel characteristics. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

5.
The current generation of landscape evolution models use a digital elevation model for landscape representation. These programs also contain a hydrological model that defines overland flow with the drainage network routed to an outlet. One of the issues with landscape evolution modelling is the hydrological correctness of the digital elevation model used for the simulations. Despite the wide use and increased quality of digital elevation models, data pits and depressions in the elevation data are a common feature and their removal will remain a necessary step for many data sets. This study examines whether a digital elevation model can be hydrologically correct (i.e. all depressions removed so that all water can run downslope) before use in a landscape evolution model and what effect depression removal has on long‐term geomorphology and hydrology. The impact on sediment transport rates is also examined. The study was conducted using a field catchment and a proposed landform for a post‐mining landscape. The results show that there is little difference in catchment geomorphology and hydrology for the non‐depression removed and depression removed data sets. The non‐depression removed and depression removed digital elevation models were also evaluated as input to a landscape evolution model for a 50 000 year simulation period. The results show that after 1000 years there is little difference between the data sets, although sediment transport rates did vary considerably early on in the simulation. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

6.
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7.
Identification of temporal changes in hydrological regimes of river basins is an important topic in contemporary hydrology because of the potential impacts of climate change on river flow regimes.For this purpose,long-term historical records of rainfall(P),runoff(Q)and other climatic factors were used to investigate hydrological variability and trends in the Tajan River Basin over the period 1969e1998.Actual evaporation(E),rainfall variability index(d),evaporation ratio(CE)and runoff ratio(CQ)were estimated from the available hydroclimatological records.Mann-Kendall trend analysis and nonparametric Sen's slope estimates were performed on the respective time series variables to detect monotonic trend direction and magnitude of change over time.Rainfall variability index showed that 1973 was the wettest year(δ=+2.039)while 1985 was the driest(δ=-1.584).Also,decades 69e78 and 89e98 were recognized as the wettest and driest decades respectively.The gradient of variation of climatological parameters showed that during the study period,all three parameters of rainfall,evaporation and runoff have decreased and the variations of rainfall and evaporation were significant at the 95%level.Investigation of hydrological changes due of dam construction(1999)showed that the amount and annual distribution of discharge were completely different pre and post-dam construction.Discharge decreased in high water months and increased in low water months to meet water supply demands,especially for agriculture.The relationship between temperature and rainfall trends is compared for three stations in Mazandaran Province(Gorgan,Babolsar and Ramsar)from 1956 to 2003 and nine other stations with different statistical periods of 19e36 years,relating trends to northern hemisphere and global trends.Decreases in temperature were accompanied by decreases in rainfall,and vice versa.These trends were not observed in northern hemisphere and world scales,where temperature increases are accompanied by decreases in rainfall.These variations of hydroclimatological parameters show undesirable water resources situations during the statistical periods if the trend continues severe water resource crises.  相似文献   

8.
A quantitative, process relevant analysis of ten mesoscale (ca 10–90 km2) catchments in the Cairngorm mountains, Scotland was carried out using 10‐m digital terrain models (DTMs). This analysis produced a range of topographic indices that described differences in the landscape organisation of the catchments in a way that helped explain contrasts in their hydrology. Mean transit time (MTT)—derived from isotopic tracer data—was used as a metric that characterised differences in the hydrological function of the ten catchments. Some topographic indices exhibited significant correlations with MTT. Most notably, the ratio of the median flow path length to the median flow path gradient was negatively correlated with MTT, whilst the median upslope area was positively correlated. However, the relationships exhibited significant scatter which precluded their use as a predictive tool that could be applied to ungauged basins in this region. In contrast, maps of soil hydrological properties could be used to differentiate hydrologically responsive soils (which are dominated by overland flow and shallow sub‐surface storm flow) from free draining soils (that facilitate deeper sub‐surface flows). MTT was negatively correlated with the coverage of responsive soils in catchments. This relationship provided a much better basis for predicting MTT in ungauged catchments in this geomorphic province. In the Cairngorms, the extensive cover of various glacial drift deposits appears to be a first order control on soil distributions and strongly influences the porosity and permeability of the sub‐surface. These catchment characteristics result in soil cover being a much more discerning indicator of hydrological function than topography alone. The study highlights the potential of quantitative landscape analysis in catchment comparison and the need for caution in extrapolating relationships between landscape controls and metrics of hydrological function beyond specific geomorphic provinces. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

9.
The Arctic has experienced substantial warming during the past century with models projecting continued warming accompanied by increases in summer precipitation for most regions. A key impact of increasing air surface temperatures is the deepening of the active layer, which is expected to alter hydrological processes and pathways. The aim of this study was to determine how one of the warmest and wettest summers in the past decade at a High Arctic watershed impacted water infiltration and storage in deeply thawed soil and solute concentrations in stream runoff during the thaw period. In June and July 2012 at the Cape Bounty Watershed Observatory, we combined active layer measurements with major ion concentrations and stable isotopes in surface waters to characterize the movement of different runoff sources: snowmelt, rainfall, and soil water. Results indicate that deep ground thaw enhanced the storage of infiltrated water following rainfall. Soil water from infiltrated rainfall flowed through the thawed transient layer and upper permafrost, which likely solubilized ions previously stored at depth. Subsequent rainfall events acted as a hydrological flushing mechanism, mobilizing solutes from the subsurface to the surface. This solute flushing substantially increased ion concentrations in stream runoff throughout mid to late July. Results further suggest the importance of rainfall and soil water as sources of runoff in a High Arctic catchment during mid to late summer as infiltrated snowmelt is drained from soil following baseflow. Although there was some evaporation of surface water, our study indicates that flushing from solute stores in the transient layer was the primary driver of increased ion concentrations in stream runoff and not evaporative concentration of surface water. With warmer and wetter summers projected for the Arctic, ion concentrations in runoff (especially in the late thaw season), will likely increase due to the deep storage and subsurface flow of infiltrated water and subsequent flushing of previously frozen solutes to the surface.  相似文献   

10.
水文周期对纳帕海高原湿地草甸土壤碳素的影响   总被引：4，自引：0，他引：4  
综合降水量、蒸发能力、周边高山冰雪融水以及地下水资源的季节性变化特点分析了纳帕海湿地草甸水文周期特征,采用野外采样和室内分析相结合的方法,研究了水文周期对草甸土壤有机质变化的影响.结果表明,纳帕海湿地水文特征中草甸水位的周期性变化显著,并且水文周期对纳帕海湿地的草甸土壤有机质影响显著,其有机质变化表现为在0-20 cm土层呈不规则的"W"型多峰曲线变化,而在20-40 cm土层有机质的变化则为不规则的"N"型.水文周期变化对草甸土壤有机质的驱动过程可采用高斯多峰模型模拟,且拟合效果较为理想.  相似文献   

11.
Digital elevation models (DEMs) at different resolutions (180, 360, and 720 m) are used to examine the impact of different levels of landscape representation on the hydrological response of a 690‐km2 catchment in southern Quebec. Frequency distributions of local slope, plan curvature, and drainage area are calculated for each grid size resolution. This landscape analysis reveals that DEM grid size significantly affects computed topographic attributes, which in turn explains some of the differences in the hydrological simulations. The simulations that are then carried out, using a coupled, process‐based model of surface and subsurface flow, examine the effects of grid size on both the integrated response of the catchment (discharge at the main outlet and at two internal points) and the distributed response (water table depth, surface saturation, and soil water storage). The results indicate that discharge volumes increase as the DEM is coarsened, and that coarser DEMs are also wetter overall in terms of water table depth and soil water storage. The reasons for these trends include an increase in the total drainage area of the catchment for larger DEM cell sizes, due to aggregation effects at the boundary cells of the catchment, and to a decrease in local slope and plan curvature variations, which in turn limits the capacity of the watershed to transmit water downslope and laterally. The results obtained also show that grid resolution effects are less pronounced during dry periods when soil moisture dynamics are mostly controlled by vertical fluxes of evaporation and percolation. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

12.
Remote sensing data and digital elevation models were utilized to extract the catchment hydrological parameters and to delineate storage areas for the Ugandan Equatorial Lakes region. Available rainfall/discharge data are integrated with these morphometric data to construct a hydrological model that simulates the water balance of the different interconnected basins and enables the impact of potential management options to be examined. The total annual discharges of the basins are generally very low (less than 7% of the total annual rainfall). The basin of the shallow (5 m deep) Lake Kioga makes only a minor hydrological contribution compared with other Equatorial Lakes, because most of the overflow from Lake Victoria basin into Lake Kioga is lost by evaporation and evapotranspiration. The discharge from Lake Kioga could be significantly increased by draining the swamps through dredging and deepening certain channel reaches. Development of hydropower dams on the Equatorial Lakes will have an adverse impact on the annual water discharge downstream, including the occasional reduction of flow required for filling up to designed storage capacities and permanently increasing the surface areas of water that is exposed to evaporation. On the basis of modelling studies, alternative sites are proposed for hydropower development and water storage schemes. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

13.
The mid‐ to high‐boreal forest in Canada occupies the discontinuous permafrost zone, and is often underlain by glaciolacustrine sediments mantled by a highly porous organic mat. The result is a poorly drained landscape dominated by wetlands. Frost‐table dynamics and surface storage conditions help to control runoff contributions from various landscape elements, hydrological linkages between these elements, and basin streamflow during spring snowmelt. Runoff components and pathways in a forested peatland basin were assessed during two spring snowmelts with contrasting input and basin conditions. Runoff from relatively intense melt (up to 16 mm day?1) on slopes with limited soil thawing combined with large pre‐melt storage in surface depressions to produce high flows composed primarily of meltwater (78% of the 0·29 m3 s?1 peak discharge) routed over wetland surfaces and through permeable upper peat layers. Melt intensity was less in the subsequent year (maximum of 10 mm day?1) and active layer development was relatively greater (0·2 m deeper at the end of spring melt), resulting in less slope runoff. Coupling of reduced slope contributions with lower storage levels in basin wetlands led to relatively subdued streamflows dominated by older water (73% of the 0·09 m3 s?1 peak discharge) routed through less‐permeable deeper peat layers and mineral soil. Interannual differences in runoff conditions provide important insight for the development of distributed hydrological models for boreal forest basins and into potential influences on biogeochemical cycling in this landscape under a warming climate. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献   

14.
Abstract

The impact of fire on daily discharges from two mountainous basins located in the permafrost region of Eastern Siberia, the Vitimkan (969 km2) and Vitim (18 200 km2) rivers, affected by fire over 78% and 49% of their areas, respectively, in 2003, was investigated. The results of hydrological and meteorological data analysis suggest that the Vitimkan River basin had a rapid and profound hydrological response to wildfire in 2003 expressed through a 41% (133 mm) increase of summer flow. Conversely, the larger Vitim River basin showed no significant changes in discharge after the fire. The parameters of the process-based hydrological model Hydrograph were estimated for pre-fire conditions. The results of runoff simulations conducted for the continuous pre-fire periods of 1966–2002 and 1970–2002 for the Vitimkan and Vitim river basins, respectively, on a daily time step, showed satisfactory agreement with the observed flow series of both basins. Significant underestimation of precipitation and its poor representativeness for mountainous watersheds was revealed as the main cause of observed and simulated flow discrepancies, especially for high flood events. The set of dynamic parameters was developed based on data analysis and post-fire landscape changes as derived from a literature review. The model was applied to investigate the processes in the soil column and their effect on runoff formation during the post-fire period. The new set of model parameters implied the intensification of soil thaw, reduction of infiltration rate and evapotranspiration, and increase of upper subsurface flow fraction in summer flood events following the fire. According to modelling results, the post-fire thaw depth exceeded the pre-fire thaw depth by 0.4–0.7 m. Total evapotranspiration reduced by 40% in summer months, while surface flow increased almost 2.5 times during maximum flood events.  相似文献   

15.
This paper analyses measured data from two small tropical watersheds: one in a semiarid (Aiuaba, Brazil, 12·0 km2, 5 years of measurements) and another in a humid environment (Jaruco, Cuba, 43·5 km2, 21 years of measurements). The watersheds are similar with respect to catchment area (tens of km2), potential evaporation (2·1–2·6 m year?1), temperature (22–30 °C) and relief (mild hillslope steepness); but show considerable hydrological discrepancies: average precipitation in the humid watershed is two times higher; average river discharge (mm year?1) is five times higher; and surface water availability (mm year?1) is 14 times higher than in the semiarid watershed. Long‐term operation of hypothetical surface reservoirs in both basins is simulated. The analysis shows that 73% of the average river discharge are available (with 90% annual reliability) in the humid watershed, against only 28% in the semiarid. The main cause of this difference is the excess evaporation, which consumes 55% of the stored water in the semiarid reservoir, but only 12% in the humid one. The research concludes that: (1) although precipitation indicators are higher in the humid area, they are of the same order of magnitude as in the semiarid; and (2) fluvial‐regime and water‐availability variables are more than one order of magnitude higher in the humid basin, which shows a multiplication effect of these hydrological processes. Such major hydrological differences, despite the similarities between the two tropical watersheds, show the importance of further investigations in the field of comparative hydrology. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

16.
Climate change and thawing permafrost in the Arctic will significantly alter landscape hydro‐geomorphology and the distribution of soil moisture, which will have cascading effects on climate feedbacks (CO2 and CH4) and plant and microbial communities. Fundamental processes critical to predicting active layer hydrology are not well understood. This study applied water stable isotope techniques (δ2H and δ18O) to infer sources and mixing of active layer waters in a polygonal tundra landscape in Barrow, Alaska (USA), in August and September of 2012. Results suggested that winter precipitation did not contribute substantially to surface waters or subsurface active layer pore waters measured in August and September. Summer rain was the main source of water to the active layer, with seasonal ice melt contributing to deeper pore waters later in the season. Surface water evaporation was evident in August from a characteristic isotopic fractionation slope (δ2H vs δ18O). Freeze‐out isotopic fractionation effects in frozen active layer samples and textural permafrost were indistinguishable from evaporation fractionation, emphasizing the importance of considering the most likely processes in water isotope studies, in systems where both evaporation and freeze‐out occur in close proximity. The fractionation observed in frozen active layer ice was not observed in liquid active layer pore waters. Such a discrepancy between frozen and liquid active layer samples suggests mixing of meltwater, likely due to slow melting of seasonal ice. This research provides insight into fundamental processes relating to sources and mixing of active layer waters, which should be considered in process‐based fine‐scale and intermediate‐scale hydrologic models. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

17.
Two large neighbouring watersheds, the Bowron (3420 km2) and Willow (2860 km2) situated in the central interior of British Columbia, Canada, were used to compare their hydrological responses to forest harvesting in snow‐dominant environment. Both watersheds had experienced significant, comparative forest harvesting level. The long‐term hydrometric and timber harvesting data (>50 years of records) were analysed using time series analysis to examine the hydrological impacts of forest harvesting. The hydrological variables including mean, peak and low flows over annual and seasonal scales (spring snowmelt, summer rain and winter base flow) were tested separately. Results showed that forest harvesting in the Willow watershed significantly increased annual and spring mean flows as well as annual and spring peak flows, whereas it caused an insignificant change on those hydrological variables in the Bowron watershed. The contrasted differences in hydrological responses are due to the differences in topography, spatial heterogeneity, forest harvesting characteristics and climate between two watersheds. The relative uniform topography and climate in the Willow watershed may promote hydrological synchronization effects, whereas larger variation in elevations, together with forest harvesting that occurred at lower elevations, may cause hydrological de‐synchronization effect in the Bowron watershed. The contrasted results demonstrate that the effects of forest harvesting on hydrology in large watersheds are likely watershed specific, and any attempt to generalize hydrological responses to forest harvesting must be carried out with caution. A landscape ecological perspective is critically needed for future forest hydrology studies, particularly for large watersheds. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

18.
This study analyzes the stable isotopic compositions of hydrogen and oxygen (δ2H, δ18O) in montane meteoric waters including precipitation and stream water of central Taiwan to identify hydrological processes in montane catchments. Results of precipitation demonstrate that monsoon and altitude effects are two principal processes affecting δ and deuterium excess (dE) values of inland precipitation in central Taiwan. Furthermore, slope and intercept values of summer and winter local meteoric water line are modified by secondary evaporation effects such as moisture recycling and raindrop evaporation. Additionally, stream water's results indicate that differences in δ values among stream waters reflect isotopic altitude effect whereby lower values are more evident in stream water originating from high‐elevation catchments than low‐elevation catchments. Comparison of the isotopic results between precipitation and stream water indicates that summer precipitation containing recycled moisture is the most important water source for the studied stream waters and indicates that catchment effect and base flow contribution are the two major hydrological processes affecting mountain stream hydrology. The hydrological processes identified by the isotopic study re‐stress the important role of forests in mountain hydrology. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

19.
The hydrology of near‐surface glacier ice remains a neglected aspect of glacier hydrology despite its role in modulating meltwater delivery to downstream environments. To elucidate the hydrological characteristics of this near‐surface glacial weathering crust, we describe the design and operation of a capacitance‐based piezometer that enables rapid, economical deployment across multiple sites and provides an accurate, high‐resolution record of near‐surface water‐level fluctuations. Piezometers were employed at 10 northern hemisphere glaciers, and through the application of standard bail–recharge techniques, we derive hydraulic conductivity (K) values from 0.003 to 3.519 m day?1, with a mean of 0.185 ± 0.019 m day?1. These results are comparable to those obtained in other discrete studies of glacier near‐surface ice, and for firn, and indicate that the weathering crust represents a hydrologically inefficient aquifer. Hydraulic conductivity correlated positively with water table height but negatively with altitude and cumulative short‐wave radiation since the last synoptic period of either negative air temperatures or turbulent energy flux dominance. The large range of K observed suggests complex interactions between meteorological influences and differences arising from variability in ice structure and crystallography. Our data demonstrate a greater complexity of near‐surface ice hydrology than hitherto appreciated and support the notion that the weathering crust can regulate the supraglacial discharge response to melt production. The conductivities reported here, coupled with typical supraglacial channel spacing, suggest that meltwater can be retained within the weathering crust for at least several days. Not only does this have implications for the accuracy of predictive meltwater run‐off models, but we also argue for biogeochemical processes and transfers that are strongly conditioned by water residence time and the efficacy of the cascade of sediments, impurities, microbes, and nutrients to downstream ecosystems. Because continued atmospheric warming will incur rising snowline elevations and glacier thinning, the supraglacial hydrological system may assume greater importance in many mountainous regions, and consequently, detailing weathering crust hydraulics represents a research priority because the flow path it represents remains poorly constrained.  相似文献   

20.
Clarifying the distribution and dynamics of soil moisture during the freeze–thaw process is crucial for surface ecology and is an objective requirement to investigate the mechanism of changes during the groundwater recharge process in a freeze–thaw zone. Based on the monitoring data of soil moisture and temperature in the Changbai Mountain area, the freeze–thaw process is classified into four periods. This study investigates the hydrothermal migration processes during different periods. The simultaneous heat and water model is used to simulate and analyse the infiltration of soil moisture into groundwater under five precipitation insurance rates. The results are as follows: (1) The smaller the soil depth, the stronger is the correlation between soil temperature and air temperature during the freeze–thaw process. (2) The redistribution of soil moisture before and after freeze–thaw is significantly affected by the soil texture, and soil permeability affects the recharge of soil moisture from the upper region to the lower region during the thawing period. (3) Groundwater receives vertical infiltration recharge mainly during non-freezing and is supplied by freezing and snowmelt recharge during the stable thawing period. The percentage of soil water infiltration during the stable thawing period in the total annual infiltration increases gradually with the precipitation insurance rate.  相似文献   

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