Snowmelt Flow Research Articles

Particle size distribution of total suspended sediments in urban stormwater runoff: Effect of land uses, precipitation conditions, and seasonal variations

Understanding particle size distribution (PSD) of total suspended sediments in urban runoff is essential for pollutant fate and designing effective stormwater treatment measures. However, the PSDs from different land uses under different weather conditions have yet to be sufficiently studied. This research conducted a six-year water sampling program in 15 study sites to analyze the PSD of total suspended sediments in runoff. The results revealed that the median particle size decreased in the order: paved residential, commercial, gravel lane residential, mixed land use, industrial, and roads. Fine particles less than 125 μm are the dominant particles (over 75%) of total suspended sediments in runoff in Calgary, Alberta, Canada. Roads have the largest percentage of particles finer than 32 μm (49%). Gravel lane residential areas have finer particle sizes than paved residential areas. The results of PSD were compared with previous literature to provide more comprehensive information about PSD from different land uses. The impact of rainfall event types can vary depending on land use types. A long antecedent dry period tends to result in the accumulation of fine particles on urban surfaces. High rainfall intensity and long duration can wash off more coarse particles. The PSD in spring exhibits the finest particles, while fall has the largest percentage of coarse particles. Snowmelt particles are finer for the same land use than that during rainfall events because the rainfall-runoff flows are usually larger than the snowmelt flows.

Hydrological response of the largest inland tectonic basin in Japan

The Itoigawa-Shizuoka tectonic line formed the largest inland tectonic basin in Japan. Taking advantage of the characteristics of the large tectonic basin, this study aims to clarify the hydrological response related to groundwater recharge and discharge in this area from field measurements such as monthly spring discharge measurements in the spring belt, infiltration measurements of irrigation recharge in rice paddy fields and analysis of stable isotopic ratios of oxygen and hydrogen. Volumetric water flow measurements in the tectonic basin demonstrate that the hydrological response function (HRF) is expressed as a linear equation. Despite the complex topography and geology of the mountain catchment and artificial recharge within the basin, this HRF is maintained, except for forced artificial irrigation in August when the natural water supply is significantly reduced, and except in March and April when snowmelt flows into the river. This study clarifies that monthly fluctuations in total groundwater flow within a basin can be estimated by applying HRF to monitoring data of total surface flow at the farthest downstream. The field measurements demonstrate that the rainfall in the mountain catchment area and artificial irrigation recharge in the basin greatly influence the fluctuation of groundwater flow rate, especially on the fluctuation of the spring water in the spring belt. Field data inferred that the frequent depletion of the springs in the inland tectonic basin, where all groundwater emerges at the most downstream, depends on the rapid decline in annual rainfall in mountain catchment areas. These observations suggest that the total groundwater resource in this region was affected not only by reduced irrigation recharge due to the historical paddy acreage reduction program implemented in Japan from 1971 to 2018, and by excessive groundwater extraction, but also by rapid decline in annual rainfall in mountain catchments that occurs non-periodically.

Compound erosion effect of snowmelt, wind, and rainfall on sloping farmlands of Chinese typical Mollisol region.

Research on the processes and mechanisms of compound soil erosion by multiple forces can provide scientific guidance for precisely controlling cropland soil erosion. Based on the seasonal alternation of freezing-thawing, snowmelt, wind, and rainfall erosion forces on sloping farmlands under natural conditions from November to next October of each year, we used a set of indoor simulation experiments of multi-force superimpositions to analyze the compound soil erosion processes of snowmelt (1 and 2 L·min-1), wind (12 m·s-1), and rainfall (100 mm·h-1). We further discussed the erosion effects of multi-force superimpositions. The results showed that, under single snowmelt erosion, an increase in snowmelt flow had a greater effect on sloping snowmelt erosion intensity than that of sloping runoff rate. When sloping snowmelt flow increased from 1 L·min-1 to 2 L·min-1, sloping runoff rate and erosion intensity increased by 2.7 and 4.0 times, respectively. Under snowmelt-wind superimposition erosion, previous sloping snowmelt erosion inhibited late wind erosion occurrence. As sloping snowmelt flow increased from 1 L·min-1 to 2 L·min-1, the inhibiting action subsequently increased and wind erosion intensity caused by previous snowmelt reduced by more than 50%. Both wind erosion and snowmelt-wind superimposed erosion intensified late rainfall erosion. The early wind erosion increased rainfall erosion by 24.5%. The snowmelt-wind superimposed effect increased the later slope rainfall erosion by 132.8% and 465.4% under 1 and 2 L·min-1 snowmelt runoff rates, respectively. The compound soil erosion amount driven by multiple force superimposition was not the sum of the corresponding erosion amount caused by single erosion force, with promoting or inhibiting effects of erosion force superimposition. The erosion effect of snowmelt-wind superposition was negative, but that of wind-rainfall superposition and snowmelt-wind-rainfall superpositions were positive.

Low-cost mitigation strategies for community resilience in the Trans-Himalaya to address food and water scarcity in changing environment.

Food and water scarcity in high altitudes of the Trans-Himalayan landscape are being seen as impacts of climate change, which is characterized by prolonged winters with sub-zero temperatures for a longer period. Average daily temperature from Oct to Mar (2020-21) ranged from - 6.73 ± 1.55 to 6.85 ± 1.93°C; however, fluctuates between - 10.5°C (minimum) and 4.6°C (maximum) on a typical day. With minimal rainfall, agriculture is limited to one season in these cold deserts thus limiting the land productivity. The changing scenario affects water availability for agriculture and otherwise in the villages located at further high altitudes dependent on snowmelt flow in nearby streams. This study explores the potential of extended cultivation during winters using low-cost inputs by comparing different technological options for temperature retention for vegetable cultivation. It further demonstrates the role of peoples' participation in developing zero-energy artificial ice reservoirs (water harvesting technology through capturing and storing water in the form of ice) in winters to make water available in the following growing season. With site-specific modifications, an artificial ice reservoir was created by the villagers in2020-21 which provided additional water for irrigation and was timely available (14days in advance). Using this additional water, a barren area was brought under the plantation to meet futuristic wood and fodder requirements. Confidence building (knowledge gathered, interventions to solve the major problem of water scarcity) through locally adaptable solutions (portable polyhouse, ice reservoir, increased plant productivity) motivated high altitude villagers in Trans-Himalayan to combat threats of climate change.

Response of runoff components to climate change in the source‐region of the Yellow River on the Tibetan plateau

AbstractClimate change will likely increase the total streamflow in most headwaters on the Tibetan Plateau in the next decades, yet the response of runoff components to climate change and permafrost thaw remain largely uncertain. Here, we investigate the changes in runoff components under a changing climate, based on a high‐resolution cryosphere‐hydrology model (Spatial Processes in Hydrology model, SPHY) and multi‐decadal streamflow observations at the upstream (Jimai) and downstream stations (Maqu and Tangnaihai) in the source‐region of the Yellow River (SYR). We find that rainfall flow dominates the runoff regime in SYR (contributions of 48%–56%), followed by snowmelt flow (contributions of 26%/23% at Maqu/Tangnaihai). Baseflow is more important at Jimai (32%) than at the the downstream stations (21%–23%). Glacier meltwater from the Anyê Maqên and Bayankala Mountains contributes negligibly to the downstream total runoff. With increasing temperature and precipitation, the increase in total runoff is smaller in the warm and wet downstream stations than in the cold and dry upstream station. This is because of a higher increase in evapotranspiration and a larger reduction in snowmelt flow in the downstream region in response to a warming climate. With temperature increase, there is less increase in rainfall flow in the downstream region due to increased water loss through evapotranspiration. Meanwhile, the decline in snowmelt flow is larger further downstream, which can negatively impact the spring irrigation for the whole Yellow River basin that supports the livelihoods of 140 million people. Importantly, we find that baseflow plays an increasingly important role in the permafrost‐dominated upstream region with atmospheric warming and permafrost thaw, accompanied by decreased surface flow. These findings improve our current understanding of how different hydrological processes respond to climate change and provide insights for optimizing hydropower and irrigation systems in the entire Yellow River basin under a rapidly changing climate.

Forest leaf litter nutrient discharge patterns in snowmelt surface runoff and watershed scale remote sensed simulation

The leaf litter decomposition is the important chain for the nutrient cycle in forest ecosystem, but its degradation dynamics and pulse discharge patterns in freeze-thawing watershed needed complete understanding. By integrating field observations and MODIS data, the temporal-spatial distributions of snow coverage and forest leaf litter biomass were analyzed. The critical period for snowmelt runoff under warming temperature and the relatively slow degradation patterns were identified. The on-site observations snowmelt runoff showed discharge concentration and fraction dynamics of typical forest leaf litter nutrients (carbon, nitrogen, and phosphorus) in thawing period. The snowmelt runoff flow and nutrient flux observed the linear regressions with the increased temperature from −8 °C to 6 °C (r2 = 0.443–0.987). The concentration of TOC, TN, and TP reached summit value around 50.0, 6.0, and 0.5 mg L−1 in the snowmelt runoff, respectively. The fraction analysis proved that the much high composition of dissolved organic fraction and the biggest organic phosphorus percentage was 94%. The comparison experiments of forest soil with or without leaf litter cover demonstrated that the leaf litter caused a lower discharge load in the snowmelt flow, and the leaf litter cover can decease the potential transport capability of the snowmelt runoff. Coupled with remote sensing data, the watershed leaf litter nutrient discharge model was developed with snowmelt hydrological process mode. The watershed averaged discharge of TOC, TN, and TP from deciduous broad-leaved forest leaf litter was around 851.99, 75.05, and 9.78 mg·m−2, respectively. The yearly simulation showed the spatial distribution variance of the nutrient discharge loads were held by different forest types, elevations, and slopes. The critical loss area identification provided new mitigations solution. The findings suggested that seasonal discharge of forest leaf litter nutrient in thawing period acted as a key contributor to watershed water pollution.

Таац голын усны горимын судалгаа

Surface water resources and flow regime of the river are dependent on climate, physical geography, soil condition, geology and hydrogeological conditions of the basin. These factors vary spatially and temporally and affect the runoff. To study the flow regime of the river including snowmelt and rainfall flow is crucial information for flood mitigation, control, water harvesting, hydro construction planning, dam and other hydrologic systems, etc. Therefore, we attempted to investigate the flow regime and its changes of the Taats river which is located in the Asian internal drainage basin in this study. The study was conducted using the daily runoff, precipitation and air temperature data for the period of 1975-2019. In addition, the Mann-Kendall test was applied to detect trend analysis for the annual runoff and maximum flow of the snowmelt and rainfall events. The probability of the maximum runoff of the snowmelt was estimated through the Gringorten method. The results show that the mean annual runoff and snowmelt flow decreased and rainfall flow has increased insignificantly in the study period. However, it was observed the changes in the timing of the snowmelt runoff shifted toward later in the year 1975-1990, earlier in the year 1991-2003 and on average in the period of 2004-2019. The maximum runoff of the snowmelt and rainfall is estimated at 13.2 m3/s and 275 м3/c, respectively in the 100 years.

Impacts of seepage flow and soil thaw depth on hillslope snowmelt erosion in Chinese Mollisol region

Snowmelt erosion is an important way of soil loss in Chinese Mollisol region. However, little is known about the effects of seepage flow and soil thaw depth on hillslope snowmelt runoff erosion. An indoor simulated experiment was conducted to analyze the impacts of seepage flow and soil thaw depth on hillslope snowmelt erosion. There were two snowmelt flow rates (1 and 4 L·min-1), two soil thaw depths (5 and 10 cm), and two near-surface hydrological conditions (with and without seepage flow). The results showed that hillslope runoff depth and soil erosion amount in the treatment with seepage flow were 1.1 to 1.2 times and 1.3 to 1.9 times of those in the treatment without seepage flow, respectively. Under two snowmelt flow rates, when soil thaw depth increased from 5 cm to 10 cm, hillslope runoff depth and soil erosion amount increased by 10.0% to 13.5% and 15.4% to 37.1% in the treatment without seepage flow, respectively. In the treatment with seepage flow, when soil thaw depth shifted from 5 cm to 10 cm, hillslope runoff depth increased by 6.5% to 8.5%, and soil erosion amount remained stable. Moreover, hillslope rill development was comprehensively influenced by seepage flow, soil thaw depth, and snowmelt flow rate, with rill erosion amount occupying more than 72% of hillslope snowmelt erosion amount. Compared with the treatment without seepage flow, flow velocity and shear stress under the treatment with seepage flow increased by 20.3% to 23.2% and 37.0% to 51.3%, respectively; but Darcy-Weisbach friction coefficient reduced by 9.0% to 21.4%, which caused an increase of hillslope snowmelt erosion. In addition, seepage flow enhanced rill development, which caused rill erosion amount to increase by 43.6% to 69.9% compared with the treatment without seepage flow, and it further resulted in the increase of hillslope snowmelt erosion amount. The main reason for soil thaw depth enhancing hillslope snowmelt erosion amount under the treatment without seepage flow was that both sloping runoff erosivity and erodible materials increased with increasing soil thaw depth. Furthermore, soil thaw depth had a significant impact on hillslope rill morphology development under the treatment with seepage flow. Rill widening process was dominated when soil thaw depth was 5 cm, whereas rill incision process was dominant when soil thaw depth was 10 cm. This study could improve the understanding of hillslope snowmelt erosion mechanism in Chinese Mollisol region and provide theoretical guidance for the development of water erosion model.

Field Study of Mass Balance, and Hydrology of the West Khangri Nup Glacier (Khumbu, Everest)

The depiction of glaciers’ dynamics in the high altitudes of Himalaya and the hydrological fluxes therein is often limited. Although sparse seasonal (snow/ice) melt data may be available, dense precipitation networks are not available everywhere, and especially in the highest area, and the assessment of accumulation processes and mass balance may be difficult. Hydrological fluxes are little measured in the high altitudes, and few studies are available covering flow modeling and flow partitioning. Here, we investigate the snow accumulation, ice melt, and mass balance of West Khangri Nup (WKN) glacier (0.23 km2, mean altitude 5494 m asl), which is a part of the Khumbu glacier in the Everest region, where information of precipitation and hydro-glaciological dynamics in the highest altitudes was made available recently in fulfillment of several research projects. Weather, glaciological, snow pits, hydrologic, and isotopic data gathered during field campaigns (2010–2014) on the glacier and at the EVK2CNR Pyramid site were used to (i) set up the Poli-Hydro glacio-hydrological model to describe ice and snow melt and hydrological flows from the glacier, and (ii) investigate seasonal snow dynamics on this high region of the glacier. Coupling ice ablation data and Poli-Hydro simulation for ca. 5 years (January 2010–June 2014), we estimate that the WKN depleted ca. −10.46 m of ice water equivalent per year m IWE year−1 (i.e., annually ca. −2.32 meter of water equivalent per year m WE year−1). Then, using snowpack density and isotopic (δ18O) profiles on the WKN, we demonstrate that the local snowpack is recent (Fall–Winter 2013–2014) and that significant snow accumulation did not occur recently, so this area has not been a significant one of accumulation recently. Analysis of recent snow cover from LANDSAT images also confirms snow dynamics as depicted. Our study presents original data and results, and it complements present studies covering glaciers’ mass balance as well as an investigation of accumulation zones in the Everest region and the Himalayas, which is also potentially helpful in the assessment of future dynamics under ongoing climate change.

Tracing Snowmelt Paths in an Integrated Hydrological Model for Understanding Seasonal Snowmelt Contribution at Basin Scale

AbstractSnowmelt contributions to water resources in cold regions are receiving increasing attention. However, there are clear challenges to accurately distinguish the snowmelt contributions to different hydrological processes in seasonal snow regions. Here, we present an improved method to evaluate snowmelt contributions by tracing the snowmelt flow paths in different media based on a distributed geomorphology‐based ecohydrological model coupled with a physically based snow module. The calculated snowmelt contribution is not limited to river discharge but is also applicable to evaporation and soil storage. The study region, the upstream Heihe River (UHR) basin, is located in the northeastern Tibetan Plateau. Our results indicate that snowmelt can continuously contribute to hydrological processes throughout the year because most of the snowmelt remains in soil voids, even on snow‐free days. In UHR, the snowmelt contribution to total runoff on snow days accounts for a minor part of the total snowmelt contribution, and the snowmelt contribution on snow‐free days accounts for a major part of the total. There is notable snowmelt retention in the soil in each year, which continues to supply discharge into next year. Our results also indicate that the role of snowmelt contribution to annual discharge could be gradually weakened if rainfall more greatly increases the summer discharge in the UHR basin. The improved evaluation method will contribute to a more comprehensive assessment of snowmelt contributions to hydrological processes in seasonal snow regions.

Recent evolution of glaciers in Western Asia in response to global warming: the case study of Mount Ararat, Turkey

We here investigated the recent (1976–2014) evolution of the Ararat mountain glaciers, paradigmatic of the evolution of ice bodies in Western Asia and the Caucasus. We gathered ice cover maps, including debris cover from different sources, to depict glaciers’ extension, and its variation under recent climate patterns. We then gathered data of (daily/monthly) weather variables (temperature, precipitation, snow cover depth) from two local stations managed by Turkish State Meteorological Service, which we subsequently analyzed to assess the presence of significant trends. We used the recently developed, weather-driven glaciological model Poly-Ice, able to mimic distributed ice and snow melt, mass budget, and gravity-driven ice flow of glaciers, to reproduce recent evolution of the Ararat ice bodies. We found a measurable decrease of the area (− 2.38 km2, − 30% of the initial area, − 0.06 km2 year−1) of the Ararat glaciers, including loss of ice under debris covered tongue (− 1.99 km2, − 70% of the initial area), driven by significantly increasing temperature especially in spring (+ 0.05 °C year−1). Using our Poly-Ice model, we could (i) mechanistically reproduce the response of the glaciers to the changing climate patterns, (ii) confirm faster downwasting ever since the 1990s under increasing temperature, and (iii) highlight decreased winter snow cover at thaw at the highest altitudes ever since the 1990s, further driving ice melt. Such physically based tool will further allow to project forward the dynamics of these glaciers under future climate. Our results are fully consistent with the present know how of glaciers’ retreat from Europe to Caucasus, and Central and Southern Asia, and contribute to the ongoing discussion about retreating glaciers worldwide.

Modeling the impacts of changing climatic extremes on streamflow and sediment yield in a northeastern US watershed

Study regionWe investigate the impacts of local temperature and precipitation trends on discharge and sediment loading by applying the model to a watershed in the northeastern US, where trends in increasing precipitation exceed those of other regions in North America. Study focusIn this study we simulate the response of watershed sediment loading to changing frequencies and magnitudes of extreme precipitation events using a coupled model that explicitly simulates streambank erosion and failure within a distributed watershed model. To drive the model, we use meteorological inputs from general circulation models (GCMs) as well as from a statistical weather generator (WG). New hydrological insights for the regionChanges in the timing and magnitude of snow melt and spring flows, as well as associated sediment mobilization, resulted from increases in temperature. Increases in discharge and sediment load resulted from increases in precipitation events exceeding the 95th percentile. In runs driven by WG weather data, positive trends were evident in peak (as well as annual) discharge and suspended sediment yields over the years modeled. No clear trends were seen in GCM-driven runs, which do not capture historically-observed trends in extreme precipitation. This work is consistent with other studies in that it shows important changes in discharge and sediment yields from a watershed resulting from ongoing changes in climate.

On the Direct Calculation of Snow Water Balances Using Snow Cover Information

We present a novel method for the direct determination of the snowmelt coefficient of widely used degree-day models, using only cumulated temperature and precipitation over the days of snow cover. We develop a proof of concept using (1) local measurements of precipitation, temperature and snow water equivalent (SWE) at a set of well-monitored sites in the US, and (2) available time series of snow cover from satellite and gridded daily precipitation and daily average temperature for the study region of South Tyrol, in the Italian Alps. We demonstrate how the method can reproduce the snow water balance to an acceptable extent, critically depending on the accuracy of input precipitation and temperature, highlighting the importance of a reliable representation of weather forcing if the estimate has to be robust and representative. Although not always accurate at a point, our approach yields a SWE reasonably consistent with observations, and snowmelt flows compatible with measured streamflow. At the same time, the model allows an interpretation of discrepancies between observations and simulations to detect inconsistencies between snow cover and weather forcing. This method is in principle applicable for large-scale hydrological assessments thanks to the increasing global coverage of snow cover, precipitation and temperature data. As the only other type of observation available to calibrate models is often streamflow, the direct calibration of the snow component of a model using snow cover and weather forcing reduces the number of model processes and parameters to be calibrated with streamflow, and is expected to increase model robustness.

Perceived Resource Quality as a Framework to Analyze Impacts of Climate Change on Adventure Tourism: Snow, Surf, Wind, and Whitewater

Surf, snow, wind, and whitewater provide natural resources for adventure tourism. Both the resources themselves, and access for tourism, are dependent on weather and hence are affected by climate change. For some adventure tourism subsectors (e.g., skiing and snowboarding) the industry has already responded to climate change, along with other pressures, by changing its geography and business models. In most subsectors, commercial tour operators perceive themselves as affected by short-term extreme weather events, and climate change models are not yet precise enough to predict how these will change over the short time horizons of tourism business planning. Some particular subsectors, however, can provide early warning indicators of industry responses to climate change. These include: heliskiing and heliboarding; professional big-wave surfing; and whitewater rafting and kayaking on snow melt, monsoon rainfall, or dam-release water flows. These responses may be detected through multiparameter models of visitor numbers and the geography of preferred sites or, more immediately, from the perceptions of commercial tourism operators involved in these subsectors.

Modelling capillary hysteresis effects on preferential flow through melting and cold layered snowpacks

Accurate estimation of the amount and timing of water flux through melting snowpacks is important for runoff prediction in cold regions. Most existing snowmelt models only account for one-dimensional matrix flow and neglect to simulate the formation of preferential flow paths. Consideration of lateral and preferential flows has proven critical to improve the performance of soil and groundwater porous media flow models. A two-dimensional physically-based snowpack model that simulates snowmelt, refreezing of meltwater, heat and water flows, and preferential flow paths is presented. The model assumes thermal equilibrium between solid and liquid phases and uses recent snow physics advances to estimate snowpack hydraulic and thermal properties. For the first time, capillary hysteresis is accounted in a snowmelt model. A finite volume method is applied to solve for the 2D coupled heat and mass transfer equations. The model with capillary hysteresis provided better simulations of water suction at the wet to dry snow interface in a wetting snow sample than did a model that only accounted for the boundary drying curve. Capillary hysteresis also improved simulations of preferential flow path dynamics and the snowpack discharge hydrograph. Simulating preferential flow in a subfreezing snowpack allowed the model to generate ice layers, and increased the vertical exchange of energy, thus modelling a faster warming of the snowpack than would be possible without preferential flow. The model is thus capable of simulating many attributes of heterogeneous natural melting snowpacks. These features not only qualitatively improve water flow simulations, but improve the understanding of snowmelt flow processes for both level and sloping terrain, and illuminate how uncertainty in snowmelt-derived runoff calculations might be reduced through the inclusion of more realistic preferential flow through snowpacks.

Climate change impact assessment on flow regime by incorporating spatial correlation and scenario uncertainty

Flooding risk is increasing in many parts of the world and may worsen under climate change conditions. The accuracy of predicting flooding risk relies on reasonable projection of meteorological data (especially rainfall) at the local scale. The current statistical downscaling approaches face the difficulty of projecting multi-site climate information for future conditions while conserving spatial information. This study presents a combined Long Ashton Research Station Weather Generator (LARS-WG) stochastic weather generator and multi-site rainfall simulator RainSim (CLWRS) approach to investigate flow regimes under future conditions in the Kootenay Watershed, Canada. To understand the uncertainty effect stemming from different scenarios, the climate output is fed into a hydrologic model. The results showed different variation trends of annual peak flows (in 2080–2099) based on different climate change scenarios and demonstrated that the hydrological impact would be driven by the interaction between snowmelt and peak flows. The proposed CLWRS approach is useful where there is a need for projection of potential climate change scenarios.

Performance and Uncertainty Evaluation of Snow Models on Snowmelt Flow Simulations over a Nordic Catchment (Mistassibi, Canada)

An analysis of hydrological response to a multi-model approach based on an ensemble of seven snow models (SM; degree-day and mixed degree-day/energy balance models) coupled with three hydrological models (HM) is presented for a snowmelt-dominated basin in Canada. The present study aims to compare the performance and the reliability of different types of SM-HM combinations at simulating snowmelt flows over the 1961–2000 historical period. The multi-model approach also allows evaluating the uncertainties associated with the structure of the SM-HM ensemble to better predict river flows in Nordic environments. The 20-year calibration shows a satisfactory performance of the ensemble of 21 SM-HM combinations at simulating daily discharges and snow water equivalents (SWEs), with low streamflow volume biases. The validation of the ensemble of 21 SM-HM combinations is conducted over a 20-year period. Performances are similar to the calibration in simulating the daily discharges and SWEs, again with low model biases for streamflow. The spring-snowmelt-generated peak flow is captured only in timing by the ensemble of 21 SM-HM combinations. The results of specific hydrologic indicators show that the uncertainty related to the choice of the given HM in the SM-HM combinations cannot be neglected in a more quantitative manner in simulating snowmelt flows. The selection of the SM plays a larger role than the choice of the SM approach (degree-day versus mixed degree-day/energy balance) in simulating spring flows. Overall, the snow models provide a low degree of uncertainty to the total uncertainty in hydrological modeling for snow hydrology studies.

Trends in the hydrologic regime of Alpine rivers

Summary This paper describes a trend analysis performed on 177 streamflow time series collected over the Alps in Central Europe. The analysis covers several facets of the Alpine hydrologic regimes, including winter droughts and spring snowmelt flows, both in terms of severity and timing of occurrence. Statistical trend tests are applied at a local scale (i.e. on a site-by-site basis) and at a regional scale (seeking a common trend for sites within the same hydro-climatic region). The overall results indicate a trend toward less severe winter droughts, and consistent changes in the timing of snowmelt flows. However, a more in-depth analysis at the scale of hydro-climatic regimes reveals more contrasted changes. While most glacial- and snowmelt-dominated regimes show a decreasing trend in the severity of winter droughts, contrasted trends are found for mixed snowmelt–rainfall regimes in the Southeastern Alps. Changes in the timing of snowmelt flows (earlier start and increased duration of the snowmelt season) mostly affect glacial- and snowmelt-dominated regimes. Lastly, glacial regimes show an increase in the volume and the peak of snowmelt flows.

Polychlorinated Biphenyls in Whole-Body Field Mice Collected Upgradient and Downgradient of a Sediment Retention Structure in Los Alamos Canyon, Los Alamos National Laboratory, New Mexico, USA

Polychlorinated biphenyl (PCBs) congeners were measured in (unwashed) whole-body field (deer) mice (Peromyscus maniculaltus) collected directly upgradient from a sediment retention structure (weir) within Los Alamos Canyon (LAC), Los Alamos National Laboratory (LANL), New Mexico, USA, from 2007 through 2013. Samples were also collected approximately 8 km downgradient of the retention structure in 2009 and 2013. LAC, a major drainage that crosses LANL lands, contains legacy waste, including PCBs, and occasionally discharges storm water and snowmelt flows to the Rio Grande approximately 8.8 km away from the weir. The Rio Grande is the major waterway that flows southward across the state. The weir was constructed across the channel on the northeastern boundary of LANL in late 2000 to help contain sediments mobilized by floodwaters as a result of a large wildfire in early 2000 that burned forest lands west and adjacent to LANL. Total PCBs in field mice directly upgradient of the sediment retention structure from 2007 through 2012 were significantly greater (p 0.05) than in field mice collected from background locations but decreased in concentration over time; by 2013 the levels were statistically similar (p > 0.05) to background. The highest mean total PCB concentration in field mice was below the levels that may negatively impact field mice population attributes. Total PCBs in field mice collected 8 km below the sediment retention structure in 2009 were lower than field mice collected from behind the weir and decreased over time; also by 2013, the amount of PCBs in field mice 8 km below the sediment retention structure were not significantly different (p > 0.05) from background. The rank order of concentrations of ICES 7 PCB congeners in upgradient and downgradient field mice were: No. 153 > 180 > 138 > 118 > 28 > 101 > 52 and No. 153 > 180 > 138 > 52 > 101 > 118 > 28, respectively. Based on the PCB homolog distribution, the major formulation detected in field mice was Aroclor-1260. Overall, the reduction of PCBs in whole-body field mice from both sites over time was attributed, in part, to sediment control practices.

Springtime Snowmelt and Streamflow Predictions in the Himalayan Mountains

AbstractPerennial rivers (i.e., the Indus, the Ganges, the Brahamputra) originating from the Himalayas are fed by temperature-induced snowmelt, rainfall, and base flow. Daily, weekly, or monthly streamflows of non-monsoon periods are critical for about a billion people living in these perennial river basins for water supply, irrigation, hydropower, and other water needs. The streamflow in snow and glacier dominated watersheds are affected mainly by solar energy and temperature. The existing models for streamflow and snow depth estimation are tedious and lack reliability. The impact of climate change has further enhanced the uncertainty. The springtime streamflow for the study area has increased by 2% yearly due to changes in climate during the last 25 years. The paper describes a nomogram, which combines the effect of climate change, temperature, and melting snow depth to estimate the daily average flow/discharge during spring time for a subbasin in the Himalayas. The concept is simple and uses location-s...