Infiltration Of Snowmelt Water Research Articles

Treatment efficiency of package plants for on-site wastewater treatment in cold climates

Package plants (PP) are implemented around the world to provide on-site sanitation in areas not connected to a sewage network. The efficiency of PP has not been comprehensively studied at full scale, and the limited number of available studies have shown that their performance varies greatly. Their performance under cold climate conditions and the occurrence of micropollutants in PP effluents have not been sufficiently explored. PP are exposed to environmental factors such as low temperature, especially in cold regions with low winter temperatures and deep frost penetration, that can adversely influence the biochemical processes. The aim of this study was to investigate the treatment efficiency and possible effects of cold temperatures on PP performance, with focus on traditional contaminants (organics, solids, nutrients and indicator bacteria) and an additional assessment of micropollutants on two PP. Eleven PP hosting different treatment processes were monitored. Removal of biological oxygen demand (BOD) was high in all plants (>91%). Six out of the 11 PP provided good phosphorus removal (>71%). Small degrees of nitrification were observed in almost all the facilities, despite the low temperatures, while denitrification was only observed in two plants which achieved the highest nitrification rates (>51%) and had sludge recirculation. No strong correlation between wastewater temperature and BOD, nutrients and indicator bacteria concentration in the effluents was found. The high data variability and the effects of other process parameters as well as snow-melt water infiltration are suggested as possible reasons for the lack of correlation. However, weak negative relations between effluent concentrations and wastewater temperatures were detected in specific plants, indicating that temperature does have effects. When managed adequately, package plants can provide high BOD and phosphorus removal, but nitrogen and bacteria removal remain challenging, especially at low temperatures. Pharmaceutical compounds were detected in the effluents at concentrations within or above ranges reported for large treatment plants while phthalate ester concentrations were below commonly reported effluent concentrations.

Mechanism of snowmelt infiltration coupled with salt transport in soil amended with carbon-based materials in seasonally frozen areas

In midlatitude seasonally frozen areas, the freeze–thaw cycle affects the movement of soil water, which increases the uncertainty in salt transport and aggravates the risk of soil salinization. Based on this, a two-year field study was established on the Songnen Plain, a seasonally frozen area in northern China. Four treatments were set up: (i) control, (ii) corn stover, (iii) biochar, and (iv) combined (joint application of biochar and corn stover). The modified soil underwent seasonal freeze–thaw cycling, accompanied by the evaporation and infiltration of snowmelt water, and the soil salt migration and diffusion characteristics were determined. Both biochar and corn stover regulated the pore structure of the soil and enhanced the infiltration capacity of snowmelt water; notably, the maximum soil moisture contents in the corn stover, biochar and combined treatments increased by 9.33%, 22.12% and 16.37%, respectively, compared with that in the control group. However, biochar with abundant functional groups increased the cation exchange capacity and promoted the migration of salt ions (i.e., Na+, K+ and Cl−), and the surface soil salt content in the biochar treatment was 0.12–0.53 g/kg lower than that for the other three modes during the infiltration period. Additionally, soil water evaporation carried salts upwards, which greatly increased the salt content of the surface soil. Conversely, biochar presented a strong water-holding capacity, which reduced the ineffective evaporation of soil water, while stover acted as a barrier to hinder the return of salt. Among the treatments, the synergistic transport ability of soil salt and water was the lowest in the combined treatment. Overall, the combination of biochar and corn stover had advantages in terms of soil salt leaching and offered a healthy, effective strategy for soil salinization control in cold areas.

Earlier snowmelt predominates advanced spring vegetation greenup in Alaska

Snow is considered a vital component in the northern climate system, however, our understanding of the impacts of snowmelt on spring phenological shifts is still limited for high-latitude ecosystems. In this study, we analyzed the start of growing season (SOS) and its response to the process of snowmelt over 2000–2019 using multiple ground observations, satellite data products, and climate datasets in Alaska and part of Canada Yukon among five ecoregions. We found that the earlier snowmelt resulting from warming spring dominates the advanced spring vegetation phenology in the region. Spring vegetation greenup follows the start of snowmelt (SOM). During 2000–2019, the SOM and SOS advanced in a similar spatial pattern across the ecoregions, and SOS experienced further advancement than SOM. On average, SOS advanced about 0.49 days per day of SOM advancement. The impacts of snowmelt on vegetation phenology are largely driven by the snowmelt-induced synergistic changes in soil temperature and soil water content. As snowmelt starts, the infiltration of snowmelt water and insulation of the remaining snow cover stimulate the vegetation activities below the snow. The responses of SOS to the snowmelt phenology varied among the different ecoregions are associated with the varied climate backgrounds and vegetation types. Greater SOS and SOM advancements were found in the taiga-tundra ecotone, while lower changes were detected over the tundra. This study suggests that the snow cover and snowmelt phenology should be considered to better understand the vegetation seasonality under climate change in the high latitudes.

Estimation of Infiltration Volumes and Rates in Seasonally Water-Filled Topographic Depressions Based on Remote-Sensing Time Series.

In semi-arid ecoregions of temperate zones, focused snowmelt water infiltration in topographic depressions is a key, but imperfectly understood, groundwater recharge mechanism. Routine monitoring is precluded by the abundance of depressions. We have used remote-sensing data to construct mass balances and estimate volumes of temporary ponds in the Tambov area of Russia. First, small water bodies were automatically recognized in each of a time series of high-resolution Planet Labs images taken in April and May 2021 by object-oriented supervised classification. A training set of water pixels defined in one of the latest images using a small unmanned aerial vehicle enabled high-confidence predictions of water pixels in the earlier images (Cohen’s Κ = 0.99). A digital elevation model was used to estimate the ponds’ water volumes, which decreased with time following a negative exponential equation. The power of the exponent did not systematically depend on the pond size. With adjustment for estimates of daily Penman evaporation, function-based interpolation of the water bodies’ areas and volumes allowed calculation of daily infiltration into the depression beds. The infiltration was maximal (5–40 mm/day) at onset of spring and decreased with time during the study period. Use of the spatially variable infiltration rates improved steady-state shallow groundwater simulations.

Impact of heat advection on the thermal regime of roads built on permafrost

AbstractIn northern regions, transportation infrastructure can experience severe structural damages due to permafrost degradation. Water infiltration and subsurface water flow under an embankment affect the energy balance of roadways and underlying permafrost. However, the quantification of the processes controlling these changes and a detailed investigation of their thermal impacts remain largely unknown due to a lack of available long‐term embankment temperature data in permafrost regions. Here, we report observations of heat advection linked to surface water infiltration and subsurface flow based on a 9‐year (from 2009 to 2017) thermal monitoring at an experimental road test site built on ice‐rich permafrost conditions in southwestern Yukon, Canada. Our results show that snowmelt water infiltration in the spring rapidly increases temperature in the upper portion of the embankment. The earlier disappearance of snow deposited at the embankment slope increases the thawing period and the temperature gradient in the embankment compared with the natural ground. Infiltrated summer rainfall water lowered the near‐surface temperatures and subsequently warmed embankment fill materials down to 3.6‐m depth. Heat advection caused by the flow of subsurface water produced warming rates at depth in the embankment subgrade up to two orders of magnitude faster than by atmospheric warming (heat conduction). Subsurface water flow promoted permafrost thawing under the road embankment and led to an increase in active layer thickness. We conclude that the thermal stability of roadways along the Alaska Highway corridor is not maintainable in situations where water is flowing under the infrastructure unless mitigation techniques are used. Severe structural damages to the highway embankment are expected to occur in the next decade.

天山北坡积雪消融对不同冻融阶段土壤温湿度的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 天山北坡积雪消融对不同冻融阶段土壤温湿度的影响 DOI: 10.5846/stxb201901040044 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 自治区重点实验室课题（2018D04024）；国家自然科学基金项目（U1603342，41961002） The influence of snowmelt on soil temperature and moisture in different freezing-thawing stages on the north slope of Tianshan mountain Author: Affiliation: Fund Project: The National Natural Science Foundation of China (General Program, Key Program, Major Research Plan) 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:积雪作为一种特殊的覆被，直接影响着土壤温度、土壤水分分布及其冻结深度、冻结速率等，影响当地的生态水文过程。利用2017年11月1日至2018年3月31日天山北坡伊犁阿热都拜流域的土壤含水率资料，划分土壤不同冻融阶段，结合积雪不同阶段，进而分析积雪消融对季节性冻土温湿度的影响。结果表明：在整个土壤冻融期间，土壤温湿度的变化取决于积雪深度、大气温度和雪面温度的高低，且与其稳定性有关。土壤冻结阶段，土壤温湿度持续下降，表层土壤温湿度受气温影响较大，且波动明显，而深层土壤的温湿度变化平缓；土壤完全冻结时，有稳定积雪覆盖，由于积雪的高反射性、低导热性，影响着地气之间的热量传递，因此土壤的温湿度变化较为平稳，积雪有一定的保温作用；冻土消融阶段，气温回升，积雪消融，地表出露，各层土壤温度随气温变化而变化，且越靠近地表，土壤温度越高，变幅越大，与冻结期完全相反。由于融雪水的下渗，土壤湿度快速增加。进一步分析积雪与土壤温湿度的相关性得出，积雪对土壤温湿度的影响分不同时期，对土壤温度的影响主要在积雪覆盖时，对土壤湿度的影响主要是在积雪消融时期，这对于研究该地生态水文循环及后续融雪性洪水的模拟与预报具有一定的参考价值。 Abstract:As a special cover, snow cover directly affects soil temperature, soil moisture distribution, freezing depth and freezing rate, and affects the local eco-hydrological processes. The existence of snow can affect the frozen soil, the interaction of surface-atmosphere, and change the energy exchange and temperature transfer between the soil and the atmosphere. The freezing-thawing process of soil has an important impact on soil water content. It is of great significance for the effective utilization of frozen soil resources, the guidance of irrigation water, the study of soil evaporation, groundwater recharge and local eco-hydrological cycle. In this paper, meteorological data, soil temperature and moisture data and snow cover data were used to analyze the characteristics of seasonal frozen soil temperature and moisture changes in the study area. Based on the data of soil water content from November 1, 2017 to March 31, 2018 in the Alatobe Basin, Ili, on the northern slope of Tianshan Mountains, the different freezing-thawing stages of soil were divided, and the effects of snow melting on the temperature and moisture of seasonal frozen soil were analyzed. The results show that snow melting has a great influence on the temperature and moisture of seasonal frozen soil. The soil was frozen beginning in November in Alatobe Basin, and the soil freezing time lagged with the increase of soil depth. The soil freezing process is one-way, starting from the surface, while the melting process is two-way, starting from both the surface and the bottom. During the whole freezing-thawing period, the change of soil temperature and moisture depends on the depth of snow cover, atmospheric temperature and snow surface temperature. And it mainly affects the surface soil temperature. The deeper the soil depth is, the more slightly the change of soil temperature and moisture is. During the soil freezing stage, the soil temperature and moisture continued to decline, the surface soil temperature and moisture were greatly affected by temperature, and the fluctuation was obvious, while the deep soil temperature and moisture changed slightly. When the soil was completely frozen, there was stable snow cover. Because the high reflectivity and low thermal conductivity of snow affected the heat transfer of surface-atmosphere, the change of soil temperature and moisture was relatively stable, and the snow cover had a certain degree. During the thawing stage, the temperature rises, the snow melts and the surface exposes. The soil temperature varies with the change of temperature. The closer to the surface, the higher the soil temperature, the larger the change range, which is completely contrary to the freezing period. Soil moisture increases rapidly due to the infiltration of snowmelt water. Further analysis of the correlation between snow cover and soil temperature and moisture shows that the influence of snow cover on soil temperature and moisture can be divided into different periods. The influence on soil temperature is mainly in snow cover, and the influence on soil moisture is mainly in snow melting period, which has a certain reference value for the study of the eco-hydrology cycle and the simulation and prediction of subsequent snowmelt flood in this area. 参考文献 相似文献 引证文献

Risk assessment of snowmelt-induced landslides based on GIS and an effective snowmelt model

In early 2008, southern China experienced a severe freezing snow event, causing many geological disasters (such as landslides). Based on combining the infinite slope model and the snowmelt effect, an effective snowmelt model (ESM) is proposed to calculate the stability of landslides. The geological mechanics model of snowmelt-induced landslides is established with the Enshi area as a case study. The landslide susceptibility in the Enshi area is evaluated based on the set pair analysis and analytical hierarchy process. Then, the hazard grade of snowmelt-induced landslides is predicted and classified by the calculation results of ESM. And the warning grade of Enshi is determined based on the landslide susceptibility and the hazard grade. The results indicate the following: (1) High-susceptibility areas in Enshi are mainly concentrated in the regions of Badong County and Lichuan County. (2) The snowmelt hazard in the rock group with a high susceptibility is considered a medium-level hazard and the other areas are low-level hazards. (3) A total of 94.73% of the study region is a no-warning area, and the levels 3 and 4 warning zones account for 1.04% and 4.23%, respectively. (4) The increases in the slope gradient α and the slip zone depth Z lead to a decreasing initial stability and decreased influence of snowmelt water infiltration. (5) The snowmelt threshold can be calculated by the ESM model, and different snowmelt risk levels can be classified according to the relationship between the snowmelt threshold and the slope gradient.

Effect of snow-straw collocation on the complexity of soil water and heat variation in the Songnen Plain, China

The goal of this study was to explore the effect of the collocation coverage of snow and straw on the complexity variation of soil water and heat and its appropriate evaluation method during freeze-thaw periods in the Songnen Plain of China. Based on field trials, the characteristics of the spatial variability in soil water and heat and the correlation between the water/heat in snow and in soil were analyzed under conditions of bare land (BL), natural snow (FB0), natural snow plus 5-cm-thick straw (FB5) and natural snow plus 10-cm-thick straw (FB10). Additionally, a spectral entropy algorithm based on Fourier transform was used to calculate the spectral entropy of the soil water and heat sequences, and the spatial variation law of soil water and heat complexity in vertical section was explored; furthermore, the positive effect of straw on the soil water and heat environment was revealed. (1) During the freezing period (i.e., the rapid freezing period and stable freezing period), the collocation coverage of straw and snow weakened the differences between the surface soil and the deeper soil; furthermore, the presence of straw hindered the energy exchange between snow and soil, and as the amount of straw coverage increased, the difference between snow water/heat and that in soil increased. During the melting period, the infiltration of snowmelt water affected the variation of soil water and heat, whereas the straw, due to its water storage characteristics, absorbed large amounts of snowmelt water and provided a stable water supply to the soil. With the increase of straw coverage, the correlation between snow water/heat and that in soil was increased under the FB5 and FB10 treatments. (2) The spectral entropy algorithm evaluation values were in good agreement with the classical statistical analysis, demonstrating that the algorithm can be used to efficiently and accurately evaluate the complexity of soil water and heat time series. The spectral entropy of soil water and heat in the 10-cm soil layer under the treatments of FB0, FB5 and FB10 was less than the corresponding entropy under the BL treatment during rapid freezing and stable freezing periods. As the soil depth increased, the spectral entropy decreased under the different treatments. Affected by the maximum freezing depth, the soil water and heat spectral entropy values peaked in the vertical section during the stable freezing period; as the amount of straw coverage increased, the position of the peak value gradually increased. However, during the melting period, the complexity of soil water and heat under the three snow cover conditions increased significantly relative to that under the BL treatment. As the straw coverage increased, the complexity of soil water and heat decreased. The complexity evaluation method of the spectral entropy algorithm is reliable, and the measurement accuracy meets the evaluation requirements. The algorithm has application value for the evaluation of soil water and heat variation in cold regions.

Optimum soil frost depth to alleviate climate change effects in cold region agriculture

On-farm soil frost control has been used for the management of volunteer potatoes (Solanum tuberosum L.), a serious weed problem caused by climate change, in northern Japan. Deep soil frost penetration is necessary for the effective eradication of unharvested small potato tubers; however, this process can delay soil thaw and increase soil wetting in spring, thereby delaying agricultural activity initiation and increasing nitrous oxide emissions from soil. Conversely, shallow soil frost development helps over-wintering of unharvested potato tubers and nitrate leaching from surface soil owing to the periodic infiltration of snowmelt water. In this study, we synthesised on-farm snow cover manipulation experiments to determine the optimum soil frost depth that can eradicate unharvested potato tubers without affecting agricultural activity initiation while minimising N pollution from agricultural soil. The optimum soil frost depth was estimated to be 0.28–0.33 m on the basis of the annual maximum soil frost depth. Soil frost control is a promising practice to alleviate climate change effects on agriculture in cold regions, which was initiated by local farmers and further promoted by national and local research institutes.

Stability assessment approach for soil slopes in seasonal cold regions

In Hokkaido Japan, soil slope failures along some of the national highways are reported frequently in recent years. A stability assessment method which can consider the impact of seasonal changes like freeze-thaw action, snowmelt water infiltration etc. is of utmost importance and considered to be an immediate requirement for geotechnical practitioners, in order to properly predict the slope stability. In this study, a slope stability assessment approach based on two-dimensional numerical modelling is recommended which considers the water content changes of the soil induced by the seasonal climatic effects i.e. freeze-thaw action, snowmelt water infiltration etc. Two case studies of slope failures in Hokkaido have been studied using the recommended approach. In order to visualise the climatic parameters of most influence on slope stability, parametric studies have been performed through which many useful results in view of the soil slope stability in seasonal cold regions have been obtained. It is found that the freeze-thaw action has a considerable impact on the soil water content and slope stability. On the other hand, the snowmelt water infiltration has a very significant impact on soil slope stability. The recommended numerical modelling approach is found to be very useful in analysing the soil slope stability in seasonal cold regions.

A Case Study of a Cut Slope Failure Influenced by Snowmelt and Rainfall

In cold regions, frequent incidents of soil slope failures occur due to snowmelt and rainfall. These failures are triggered by an increase in the degree of saturation of soil due to infiltration of water derived from rainfall and snowmelt. This study investigates a soil slope failure occurred on November 27, 2015 at a cut slope of an expressway in Hokkaido, Japan. The soil slope failure is investigated using a recommended stability assessment approach considering non-isothermal coupled seepage flow simulation followed by a limit equilibrium slope stability analysis. It is concluded that at the thawing period, the slope stability is affected by rainfall and snowmelt water infiltration and later in November the failure happened due to overflow of water from a drainage ditch.

Snowmelt and the hydrological interaction of forest-grassland ecosystems in Central Yakutia, eastern Siberia

In the last two decades the major focus of study in forest water and carbon balances in eastern Siberia has been on the effect of rain during the growing season. Little attention has been paid to the contribution of snowmelt water. The results of the present study indicate that weather conditions during the snowmelt period as well as the soil moisture conditions carried from the previous year's growing season strongly determined the water availability for the forest ecosystem at the beginning of the next growing season. In the forest–grassland intermingled ecosystem of lowland Central Yakutia, gradual snowmelt water flow from the forest into the adjacent grassland depressions increased when soil moisture was high and air temperature was low, whereas low soil moisture and high air temperatures accelerated soil thawing and consequently snowmelt water infiltration into the forest soil. We found that snow depth did not determine the volume of snowmelt water moving to the grassland depression since the thermokarst lake water level in the adjacent grassland was about 25 cm lower in 2005 than in May 2006, even though maximum snow depth reached 57 cm and 43 cm in the winter of 2004–05 and 2005–06, respectively. The contribution of snowmelt water to forest growth as well as the flow of water from the forest to the grasslands showed a strong annual variability. We conclude that warmer springs and high variability in precipitation regimes as a result of climate change will result in more snowmelt water infiltration into the forest soil when the previous year's precipitation is low while more snowmelt water will flow into the thermokarst lake when the previous year's precipitation is high. Copyright © 2015 John Wiley & Sons, Ltd.

Preface "Hillslope hydrological modelling for landslides prediction"

Looking at natural hazards and risks, such as landslides, debris flow and floods, we see a broad range of science fields involved: from earth science to engineering science, to management, policy and social science. Although research on natural hazards and risks contains mono-disciplinary aspects, it is best characterized by its multi-disciplinary nature. Moreover, the link to society has always been a very important driver in natural hazards research, pushed by the need for reliable prediction models to be implemented into early warning systems as well as by the required complete understanding of the physical mechanisms for the design of mitigation works. If we focus on landslide and debris flows as in this special issue of HESS, we will see impressive progress in the geotechnical and slope stability modelling needed for hazard analysis. Similarly, the risk management aspects, such as hazard mapping and risk assessment, have received much attention. Hydrology is an important aspect of landslide and debris flow assessment. Precipitation and snowmelt water infiltration, leading to local pore water pressure increase and/or matric suction decrease, is amongst the most common triggers of landslides. Fundamental knowledge about underlying processes affecting this infiltration process, such as macropore and fissure flow, water repellency, soil structure, soil–plant–atmosphere interactions as well as the effects of land use practices (e.g. deforestation, terracing, grazing), has strongly improved in the last decade or so, with a clear focus on more detailed knowledge of hydrological process dynamics. The hydrological process understanding progressed rapidly under pressure of societal needs such as prediction of discharge generation and contaminant transport, to name a few. Although hydrology research is very strongly linked to natural hazards, such as landslides and debris flows, this improved hydrological knowledge has found its way into the landslide community rather modestly. In particular, the incorporation of hydrological processes into large-scale models is still incomplete and their application to landslide prediction limited. Landslide research tends to be more focused on novel methods to include spatial data and on the practical applicability of, e.g. landslide triggering modelling and statistical analyses for regional hazard and risk assessment. However, without stating that these fields have been fully exploited, we see that in our quantitative landslide and debris flow modelling the inclusion of increased process knowledge seems to lag behind. This in depth process understanding needs to be incorporated in our technical predictions in order to improve the reliability of early warning systems, mitigation works and landslide zonation. This special issue aims to present innovative hydrological research applied to landslide studies to improve the understanding of the spatio-temporal patterns of slope movement mechanisms induced by precipitation. The initiative struck a sympathetic note, as many colleagues were facing these challenges. The topic of hydrology and landslides is finding more and more space in hydrological research, as witnessed by the number of relevant papers published, in special issues, e.g. on hydrology of unstable clay shales (Bogaard et al., 2012) and through the organization of workshops and special conference sessions, such as six EGU sessions on hydrology and landslides, three editions of the Italian Workshop on Landslides mainly dedicated to landslide hydrology (www.iwl.unina2.it), and special sessions at IAEG2014. Therefore, this Special Issue discusses the representation of

Soil moisture and temperature variation under different types of tundra vegetation during the growing season: A case study from the Fuglebekken catchment, SW Spitsbergen

The main objective of this paper is to discuss the range of temperature and moisture differences and variability in tundra vegetation and Arctic soils in the context of weather changes during the growing season. Research was carried out in Wedel Jarlsberg Land (SW Spitsbergen) in a small non-glaciated catchment in the vicinity of the Polish Polar Station in Hornsund. Measurements of air and soil temperature and changes in volumetric soil water content were carried out between June 24 and September 9 of 2008. The studied sites represented: (1) Turbic Cryosol, poorly covered by vegetation and exhibiting evidences of strong cryogenic processes; (2) Hyperskeletic Cryosol covered by a community of wet moss tundra vegetation with variable moisture which evolves under the influence of water flowing from the adjacent mountain slopes occupied by Little Auk colonies; and (3) Haplic Cryosol covered by lichen–herb–heath tundra vegetation, located on a raised marine terrace. Hyperskeletic Cryosol is the wettest of all the soil profiles studied. This profile shows the largest fluctuations in water content, related to the rate of snow melting on mountain slopes and the outflow of ablation water. The volumetric soil water content in Hyperskeletic Cryosol varies from 29% to 71%, with an average value of 49%. The mean volumetric soil water content in the driest Haplic Cryosol is 6% and ranges from 3% to 10% throughout the growing season. This is related to its sandy texture and a large number of stones, which leads to fast infiltration of snowmelt water and rainfall. Turbic Cryosol shows an intermediate volumetric water content ranging from 21% to 38%, with a mean value of 30%. The thermal regimes of the soils studied are also variable. The warmest soil was the driest Haplic Cryosol, as no influence of cold thawing water was observed. During the measurement period, the mean soil temperature at a depth of 10cm in Haplic Cryosol was 6.3°C. Turbic Cryosol was ca. 1.2°C–1.5°C colder than Haplic Cryosol. Hyperskeletic Cryosol was the coldest in comparison with the other soils studied because of the moss cover having insulating capacity. The temperatures recorded in this profile at a depth of 10cm reached a mean value of 3.2°C. The results indicate that cold water inflow from melting snow cover greatly affects soil temperature in the first part of summer (ablation season). This is related to an increase in solar radiation and air temperature leading to more intensive snow melting. This relationship is particularly evident in the first ten days of July. The highest soil surface temperatures (>20°C) were recorded in the beginning of July under intense solar radiation (25–27MJ/m2d−1). In the second part of August, thermal gradients were weaker and soil temperatures in all the pedons studied were almost the same, ranging between +3°C and +6°C. This was due to limited solar energy inflow and heat migration into the soil transported with rainfall.

The Cold Vadose Zone: Hydrological and Ecological Significance of Frozen‐Soil Processes

Approximately 50% of soils in the Northern Hemisphere experience seasonal freezing and thawing, which influences physical, chemical, and biological processes in the vadose zone. Soil freeze–thaw drives mechanical processes, including frost heave and soil aggregate formation and breakdown, and controls snowmelt infiltration and runoff. These hydrologic processes determine the soil moisture conditions, which affect plant mortality and growth, soil microbial activities, and nutrient (e.g., C and N) cycles. Nutrients leached from the thawed soil, often with rapid infiltration of snowmelt water, may affect the quality of the groundwater and surface water, in combination with enhanced erosion and sediment load due to freeze–thaw. Nutrients released as greenhouse gases may contribute to climate feedback. With recent climate warming and changes in the extent and depth of frozen soil and permafrost, it is important to understand frozen‐soil processes and their interaction with the environment. The objective of this review is to highlight important aspects of soil freeze–thaw and related processes and to point out research challenges and opportunities in the cold vadose zone.

Run-off formation in a humid, temperate headwater catchment using a combined hydrological, hydrochemical and isotopic approach (Jizera Mountains, Czech Republic)

The formation of baseflow and stormflow was examined in the 1.18 km2 part of the headwater catchment Uhlířská, Jizera Mountains, Czech Republic, over the period 2007–2011, by means of run-off data and environmental tracers 18O and SiO2. The baseflow, computed using the digital filter approach BFLOW, contributes 67% to total streamflow and has a mean residence time of 12.3 months. It is formed by groundwater discharge from the valley deluviofluvial granitic sediments, in combination with soil water in weathered layers on hillslopes during rainfall and snowmelt periods. The prevailing source of the groundwater is the infiltration of snowmelt water. Analysis of 20 run-off events and their hysteretic patterns demonstrated that the stormflow water has a residence time of about 4 months and is generated by preferential flow on hillslopes combined by soil matrix drainage. Because of slower flow in the soil matrix, the enrichment of pore water in SiO2 is more pronounced. The stormflow and snowmelt water flowing via preferential pathways of upslope minerals soils pushes the pre-event groundwater through the pathways in wetlands to the stream, and the wetland can be therefore considered as groundwater supplied. This mechanism has been found to be typical for the groundwater-supplied headwater catchments of the Jizera Mountains and can be also assumed in other mountainous headwaters of the granitic massif in Central Europe. The main methodological contribution of this study are the residence time calculations stratified by baseflow and event flow, identifying run-off components of different travel times to streams and linking them with geochemical run-off sources. This achievement was possible because of a comprehensive dataset on hydrology, stable isotopes and silica hydrochemistry in all relevant run-off generation components. This concept indicates that a possible long-term change in snowmelt may affect the run-off regime of headwater catchments to climate or land-use changes. Copyright © 2013 John Wiley & Sons, Ltd.

Conditions of the formation of ice barriers in eroded chernozems of Western Siberia

It is shown that the water content in the upper part of chernozems in Western Siberia in the late fall period exceeds the field capacity. An ice-rich barrier is formed in the humus horizon of these soils at temperatures below zero in the cold period. This barrier has both negative and positive effects. Being impermeable for snowmelt water, it favors the development of erosion processes. At the same time, it prevents infiltration of snowmelt water beyond the soil profile with the formation of a percolative water regime (favoring soil leaching) in the chernozems.

A comparison between the effects of snow albedo and infiltration of melting water of Eurasian snow on East Asian summer monsoon rainfall

The effect of Eurasian spring snow amount on East Asian summer monsoon (EASM) rainfall has previously been studied on the basis of both observations and numerical simulations. The results indicate that information on the Eurasian spring snow amount could be important for seasonal prediction of EASM rainfall. Although previous studies identified the effects of snow albedo and melting water of Eurasian snow on global climate, their individual contributions to the prolonged snow effect on early summer regional climate have not been evaluated quantitatively. In this study, the relative importance of the effects of snow albedo and snowmelt water over the Tibetan Plateau on the simulated EASM rainfall is investigated using a regional climate model. Three ensemble simulations were conducted. The first ensemble simulation considers the actual snow cover in the initial condition. The second ensemble simulation ignores the snow effect on the surface albedo in the radiation budget. The third ensemble simulation ignores the infiltration of snowmelt water. A detailed comparison of these simulations indicates that the albedo effect is significant and its effect on rainfall amount over the Yangtze River basin is about three times that of the effect of snowmelt water from May to June. The albedo effect decreased from July to August, while the effect of snowmelt water increased. Eventually, the difference between the two effects became insignificant. Overall, the snow albedo effect over the central and western Tibet appears to dominate the observed relationship between the spring snow anomaly and the EASM rainfall anomaly.

Hydrothermal pattern of frozen soil in Nam Co lake basin, the Tibetan Plateau

Hydrothermal processes and the regimes of frozen soil formed in alpine regions with glaciers and lake area are complex and important for ecological environment but have not been studied in Tibet. Based on soil temperature and moisture data from October 2005 to September 2006 collected in the Nam Co lake basin, Tibetan Plateau (TP), those questions were discussed. The mean annual air temperature was −3.4°C with 8 months below 0°C. Air and soil temperature varied between −25.3~13.1°C and −10.3~8.8°C, respectively. Soil moisture variations in the active layer were small with the minimum value of 1.4%, but were influenced greatly by snowmelt, rainfall and evaporation, varying up to 53.8%. The active layer froze later, thawed earlier and was thinner, however, the lower altitude limit of permafrost is higher than that in most areas of TP. The effects of soil moisture (unfrozen water content) on soil temperature, which were estimated through proposed models, were more significant near ground surface than the other layers. The surface soil temperature decreased with snowcover, the effect of cold snow meltwater infiltration on soil thermal conditions was negligible, however, the effect of rainfall infiltration was evident causing thermal disruptions.

Seasonal Recharge and Replenishment of Sulfate Associated with Biodegradation of a Hydrocarbon Plume

AbstractThe downward flux of sulfate in a weathered clayey aquitard to a hydrocarbon plume in ground water was investigated at a gas well site in Alberta, Canada. The dissolved hydrocarbon plume includes monoaromatic BTEX compounds and extends less than 20 m downgradient from a natural gas condensate source in silt‐ and clay‐rich deposits. The vadose zone at the site has high concentrations of water soluble sulfate, which is apparently derived from pyrite oxidation. Seasonal infiltration of snowmelt water, most notably during the “wet” spring of 2003 and also in 2004, was focused in an excavation and recharged the water table. This recharge replenished the contaminated zone with sulfate that was flushed downward from the vadose zone. Recharge in 2003 resulted in episodic increases in sulfate concentrations in the ground water condensate plume of up to 1000 mg/L. After episodic increases in sulfate concentrations within the core of the contaminant plume associated with recharge, concentrations then decreased to less than 1 mg/L, accompanied by isotopic enrichment of the residual sulfate in 34S. The monitoring data provide strong field evidence that bacterial sulfate reduction is a dominant terminal electron‐accepting process in the natural attenuation of the hydrocarbon plume in the ground water. This result suggests that engineered infiltration and replenishment of sulfate to petroleum hydrocarbon plumes in ground water might enhance biodegradation of these plumes.