bluuebunny/crossref_metadata_2025_split huggingface dataset:
Preferential Flow and Melt Water Retention in Cold Snow Packs in West-Greenland
Authors: Bøggild Carl Egede 
Published: May 2018

Runoff from seasonal snow covers in Greenland provides the major source of stream flow in the non-glacierized catchments, and has gained interest in relation to hydropower potentials and water supply. During a two-month period the seasonal snow cover is melted and the discharge generated constitutes a major part of the annual runoff.
Motivated by discrepancies between modelled and observed hydrographs during the early melt period in the Tasersuaq basin, we have performed tracer experiments in several pits and at different levels below the snow surface, to improve our understanding of water flow and storage in cold snow. It is observed that vertical percolation more readily occurs the deeper in the snow pack the tracer is sprinkled. At places where preferential vertical flow is established, we believe the water will eventually reach the bottom of the snow pack once it has passed the wind crusts on the top of the snow pack.
From observations a parameterization of melt-water retention in the cold snow is suggested. We propose a time dependent term for the thermal and the gravity component, respectively, of storage in the snow pack. This time dependent term describes the fraction of snow which is exposed to melt water at the time when the water reaches the base of the snow. Incorporating such a term in hydrological models would improve them by providing an explanation of the observed fast hydrological response in the early melt period and by limiting the magnitude of the modeled peak flow.
Modelling Mountainous Water Systems Between Learning and Speculating Looking for Challenges
Authors: Burlando Paolo , Pellicciotti Francesca , Strasser Ulrich 
Published: May 2018

For many years considerable efforts have been put into investigating and modelling hydrological processes of mountainous catchments. On the one hand, the complexity and intrinsically high variability of the involved processes as well as insufficient knowledge of the underlying physical mechanisms still induce large uncertainties in understanding observed phenomena and predicting the behaviour of the system. On the other hand, the demand for models that are able to simulate mountainous water resource systems is increasing because of the needs related to both water exploitation and water conservation, which clearly call for an integrated vision and modelling of these systems.
Accordingly, this paper moves from a brief survey of the most significant achievements in mountain hydrology to discuss what could be future challenging issues related to the broader spectrum of questions, which hydrologic modelling of mountainous river systems may face in the next decades. Firstly, reference is made to existing methodologies for modelling alpine water systems, focussing on some specific aspects that provide a basis for the discussion of the weaknesses and perspectives of present simulation tools. The future is thus discussed, delineating some of the research challenges that may foster a comprehensive and integrated vision of water related issues in mountainous regions.
Comparison of Ground-Based and Airborne Snow Depth Measurements with Georadar Systems, Case Study
Authors: Marchand Wolf-Dietrich , Killingtveit Ånund , Wilén Peter , Wikström Per 
Published: May 2018

Snow depth measurements with the help of georadar (Ground Penetrating Radar, GPR) were investigated for almost two decades in Scandinavia. For the first tests in the early 1980s, results were of poor quality. Later, data quality improved when different systems were developed. In Norway, emphasis was put on ground-based snow measurements of scientific character; few attempts for operational use were undertaken. In Sweden, airborne, operational snow measurements with georadar were performed since 1986. A helicopter, flying near to the ground, was used as platform.
The objective of the presented study was to compare results from ground-based and airborne snow measurements. The radar control units used were comparable, but the antenna configuration and frequencies differed. Also radar data interpretation and the conversion of radar signal travel time into snow depth values varied. Measurements were made at common snow courses.
The comparison showed in general high correlation between radar results from both methods. Differing results were found for shallow snow and bare areas. Here, the ground-based method indicated zero or close-to-zero snow depth, whereas the airborne method rarely detected zero snow depth. This phenomenon seemed to be connected to the bigger footprint size of the airborne radar and to the different radar data interpretation methods. On average, the airborne measurements indicated shallower snow depths than ground-based measurements, 4% less in open terrain and 7% less in forest. Comparing snow depth as grid cell values, the best agreement, less than 1% difference, was obtained for the 10 m resolution.
Seasonal changes in meltwater storage and drainage characteristics of the Dokriani Glacier, Garhwal Himalayas (India)
Authors: Singh Pratap , Haritashya Umesh K. , Kumar Naresh 
Published: May 2018

Storage and drainage characteristics of the Dokriani Glacier (9.66 km2) located in the Garhwal Himalayas have been studied. In order to understand these characteristics, clear weather (non-rainy) days data for three ablation seasons (1996–1998) are used because discharge is melt-driven on such days. Moreover, diurnal variations in the discharge on clear days represent the true picture of glacier response to streamflow. Results indicate that meltwater storage characteristics of the glacier lead to high discharges in the stream during the night. Consequently, night-time discharges are comparable with those observed during daytime throughout the melt season. Meltwater storage characteristics of the glacier are much stronger in the early part of the melt season and they weaken as the melt season progresses.
Diurnal variations in the discharge are observed to be clearer with advancement of the melt season providing variations in the timing of peak flow. Maximum discharge for different years was observed between 1700 and 1900 hours, showing a lag of 2 hours in the timing of maximum flow over the ablation period. The time to peak flow varied from 8.5 to 11 hours. For all the years, a strong seasonal trend towards increasing diurnal amplitude in discharge until August and thereafter a decreasing trend, was observed. The time lag between Qmax and Tmax varied from 3–6 hours over the ablation season and recession of melt water became faster with time. The time lag is higher at the beginning of the melt season and reduces as the melt season progresses. Recession trends of the hydrographs with time suggested a similar hydrological response of the glacier in June and September. The basin behaved like a single conceptual linear reservoir for these two months, while for July and August it behaved like two conceptual linear reservoirs, namely, accumulation and ablation reservoirs.
Statistical properties of spatial snowcover in mountainous catchments in Norway
Authors: Marchand Wolf-Dietrich , Killingtveit Ånund 
Published: May 2018

The spatial distribution of snowcover in a catchment is determined by complex interactions between meteorological and physiographical factors, integrated over time. The snowcover shows variability over scales ranging from centimeters up to hundreds of kilometers.
An important and necessary decision for modelers is to determine spatial resolution in a distributed model. Since the spatial variability in snowcover may be quite large, even within a few meters, it is difficult to use modeling units small enough so that the snow can be assumed evenly distributed within the unit. A possible method to compensate for this is to use larger units, and describe the snow distribution within each unit by a statistical model (e.g. normal, log-normal, gamma, etc). This technique requires information about spatial statistical properties of snowcover within a unit.
As many of the distributed hydrological models operate on a grid basis, it would be desirable to find a statistical distribution on a sub-grid scale. However, as an initial approach, the study presented here was done on a catchment scale. The catchment scale presented the possibility of incorporating data from several historical snow surveys. These surveys were taken at the time of maximum snow accumulation in various mountainous catchments in Norway. Comparing empirical distribution functions with different theoretical distribution functions, it was shown that a mixed distribution combining two separate log-normal distributions clearly gave the best fit in most of the catchments. This seems to indicate that a mixture of at least two different populations of SWE values exists.
Evapotranspiration from a riparian fen wetland
Authors: Andersen H.E. , Hansen S. , Jensen H. E. 
Published: May 2018

Evapotranspiration rates were measured in a riparian fen wetland dominated by vascular vegetation and surrounded by open agricultural areas and forests. The wetland is situated on a floodplain in central Denmark. Measurements were taken throughout the growing season (April–September) of 1999.
Evapotranspiration rates were higher than those published for most other wetland types, with an average of 3.6 mm d−1 during the growing season and a peak rate of 5.6 mm d−1. Daily average evapotranspiration was 110% of Penman's potential open water evaporation.
Evapotranspiration was the dominant sink in the energy balance of the wetland studied. During the day, evapotranspiration accounted for 82% of the available radiant energy, Rn. Due to the presence of deposited fine-grained sediments, soil-water availability was kept high at all times which resulted in moderate canopy resistances, rc (overall mean =32 s m−1). Evapotranspiration was controlled by a combination of driving forces: Rn, saturation vapour pressure deficit, D, and rc.
It is hypothesized that the results presented in this study are conditioned by the proximity of the wetland to drier upland areas. During periods with high evaporative demand and low precipitation, warm, dry air is formed over the upland areas and wetland evapotranspiration rates are enhanced by local advection. Indicative evidence for the hypothesis is presented. Although the absolute magnitude of the results reported is only directly relevant to similar sites in Denmark, the processes and controls described are considered to be representative of riparian wetlands subjected to frequent flooding and/or with a high groundwater table, with vascular vegetation, and which are narrow corridors in open agricultural landscapes.
Expected changes in water resources availability and water quality with respect to climate change in the Elbe River basin (Germany)
Authors: Krysanova Valentina , Hattermann Fred , Habeck Anja 
Published: May 2018

Reliable modelling of climate–water interactions at the river basin and regional scale requires development of advanced modelling approaches at scales relevant for assessing the potential effects of climate change on the hydrological cycle. These approaches should represent the atmospheric, surface and subsurface hydrological processes and take into account their characteristic temporal and spatial scales of occurrence. The paper presents a climate change impact assessment performed for the Elbe River basin in Germany (about 100 000 km2). The method used for the study combines:
(a) a statistical downscaling method driven by GCM-predicted temperature trend for producing climate scenarios, and
(b) a simulation technique based on an ecohydrological semi-distributed river basin model, which was thoroughly validated in advance.
The overall result of the climate impact study for the basin is that the mean water discharge and the mean groundwater recharge in the Elbe basin will be most likely decreased under the expected climate change and diffuse source pollution will be diminished. Our study confirms that the uncertainty in hydrological and water quality responses to changing climate is generally higher than the uncertainty in climate input. The method is transferable to other basins in the temperate zone.
The silent revolution in groundwater intensive use and its influence in Spain
Authors: Fornés Juan M. , Hera África la , Llamas M. Ramón 
Published: May 2018

In the last half-century in most semi-arid or arid developed and developing countries, many aquifers have become intensively used. This means that the hydrogeological conditions may have changed, with groundwater storage being modified significantly. This intensive use has been performed mainly by millions of modest farmers with scarce public or governmental planning. This silent revolution has been market driven. The cost of groundwater abstraction is usually a small fraction of the value of the irrigated crop obtained. The benefits have been clear and important in most cases. In poor countries groundwater development has provided reliable drinking water supply and increased food security through irrigation, and consequently groundwater as become a relevant means of eradicating poverty. The impact of this groundwater development in developed countries is also significant but not yet well recognised. But sometimes, there are other associated negative effects. These sometimes have been utilised by certain lobbies to expand the hydro-myth of the unreliability (or fragility) of groundwater development, in order to continue to promote the construction of large hydraulic infrastructures.
In Spain, groundwater irrigation accounts for more than 50% of the total economic value of irrigated agricultural production, while it only consumes about 20% of the total volume of water. In spite of its benefits, groundwater has not been a significant part of Spanish water policy.
Artificial mixing to reduce growth of the blue-green alga Microcystis in Lake Nieuwe Meer, Amsterdam: an evaluation of 7 years of experience
Authors: Jungo E. , Visser Petra M. , Stroom Jasper , Mur Luuc R. 
Published: May 2018

The problem of Lake Nieuwe Meer (area = 1.3 km2, max. depth 30 m, Ptot = 500 mg/m3) was extensive growth of Microcystis with disturbing scum forming. Since 1993 the lake has been artificially mixed in summer by a bubble plume installation. The result is quite successful since the mass of Microcystis is up to 20 times lower than in the years before mixing and no scum is present any more. The study in Lake Nieuwe Meer showed a shift from cyanobacterial dominance (mainly Microcystis) to flagellates, green-algae and diatoms when artificial mixing was applied. Total phosphorus and nitrogen concentrations did not change as a result of mixing and had apparently no effect on the shift in the phytoplankton composition. The chlorophyll-a concentration was much lower in the mixed lake as a result of dilution. The total algae biomass decreased. The transparency did not improve. The total heat energy of the lake is slightly higher than before mixing but still remains in the range of annual fluctuation. The temperature on the surface is approximately 2°C lower. In the whole water-body oxygen was always higher than 5 mg/l. Living space for fish is therefore wider.
The installation in Lake Nieuwe Meer consists of flexible pipes near the sediment, built in a way to prevent sediment erosion and transport into the water. There are no constructions in the water-body. All mechanical parts are on land. The layout of the installation is shown in Fig. 1. Installed compressor energy is 85 kW. This is equivalent to an upper middle-class motor-car. The design was made specifically for this problem. It is based on the physical data of the algae and the plant.
It would be beneficial to use this 7 year's experience for further applications e.g. elimination of toxic algae in drinking-water reservoirs.
Evaluation of the effectivity of selected filter beds for iron and manganese removal
Authors: Olańczuk-Neyman K. , Częścik P. , Łasińska E. , Bray R. 
Published: May 2018

The results of experiments concerning iron and manganese removal from groundwater at a treatment facility in the first and second stage of filtration through pressure experimental filters with different filter beds are presented. Research was carried out on three parallel filters with the following filter beds: quartz sand+Hydrolit-Mn, quartz sand+pyrolusite and single medium mature quartz sand.
It was revealed that the effectiveness of iron and manganese removal from groundwater at the Sieradzka facility in Gdynia can be increased by one-stage filtering through oxidation beds of mature quartz sand or two-layered quartz sand+pyrolusite. As a result of filtration, the concentrations of both elements decreased from the average level in untreated water of 1.10 mg Fe/dm3 and 0.14 mg Mn/dm3 to below 0.2 mg Fe/dm3 and 0.05 mg Mn/dm3 in the outflow. These levels meet both the current Polish and European Union standards.
Using a comprehensive model to identify the major mechanisms of chloramine decay in distribution systems
Authors: Woolschlager J. , Rittmann B. , Piriou P. , Kiene L. , Schwartz B. 
Published: May 2018

The principle mechanisms of chloramine residual decay in drinking water distribution systems is examined using a comprehensive model of chloramine reactions calibrated to distribution system data. The results reveal that four principle chloramine decay mechanisms must be considered, including:
reactions with hypochlorous acid/ion (HOCl/OCl-); an auto- catalytic reaction in which chloramines spontaneously decay in the absence of other reactants; oxidation reactions with reduced forms of organics and iron; and biologically-catalyzed reactions, such as the reactions with nitrite produced by nitrifiers as well as the direct cometabolism of chloramines by nitrifiers. The chloramine reaction model fits the distribution system data best when all of these reactions, including cometabolism of chloramines by nitrifiers, are included in the model.
UV/H2O2-treatment: the ultimate solution for pesticide control and disinfection
Authors: Kruithof J.C. , Kamp P.C. , Belosevic M. 
Published: May 2018

Because of high contents of pesticides and micro-organisms in IJssel Lake water N.V. PWN Water Supply Company North Holland (PWN) was compelled to implement multiple barriers against these contaminants at their surface water treatment plants at Heemskerk and Andijk. For degradation of pesticides advanced oxidation was pursued. After thorough studies O3/H2O2-treatment was rejected in view of bromate formation. Subsequently application of UV/H2O2-treatment was pursued.
UV-photolysis shows a selective pesticide degradation. Conversion using an electric energy of 1 kWh/m3 varies from 18% for trichloroacetic acid to 70% for atrazine. UV/H2O2-treatment gives a much more aselective pesticide degradation. For a combination of an electric energy of 1 kWh/m3 and 15 g/m3 H2O2 most pesticides can be degraded by more than 80%. Formation of harmful by-products proved to be insignificant. In the range of 0.1-2.5 kWh/m3 electric energy and 0-25 g/m3 H2O2 bromate formation is absent, while metabolite formation is insignificant. AOC-formation is found up to 140 μg/l. Therefore AOC and residual H2O2 must be removed in a following treatment step. GAC-filtration showed very reliable results.
Application of UV/H2O2-treatment for pesticide control with an electric energy of 1 kWh/m3 goes together with an average UV-dose of 2,000 mJ/cm2. This dose is about 50 times as high as applied in conventional UV-disinfection. As expected E. coli and (after spiking) spores of sulphite reducing Clostridia are inactivated completely. In addition orientating experiments have been carried out with an UV-dose of 100 mJ/cm2. Inactivation of MS-2 phages amounted to 2.7 log, Bacillus spores inactivation to 3.4 log, while Cryptosporidium inactivation was complete (&gt;3 log). Additional data are gathered together with the University of Alberta.
In view of the very promising results, application of UV/H2O2-treatment will be pursued for full scale application at both the Heemskerk plant for organic contaminant control and the Andijk plant for both organic contaminant control and disinfection.
Long term capacity of biological activated carbon filtration for organics removal
Authors: Bonné P.A.C. , Hofman J.A.M.H. , van der Hoek J.P. 
Published: May 2018

Since March 1995 Amsterdam Water Supply has applied biological activated carbon filtration (BACF) in the treatment process of the Leiduin plant. In this plant (capacity 70 × 106 m3/y) pretreated River Rhine water is infiltrated in the dune area, west of Amsterdam, for artificial recharge. Post treatment comprises rapid sand filtration, ozonation, hardness removal, biological activated carbon filtration and slow sand filtration. At the start the carbon reactivation frequency was set at 18 months, based on removal efficiencies for AOX (adsorbable organic halogens), DOC, pesticides and micropollutants. After four years of operation of a pilot plant (10 m3/hour) in parallel with the full-scale plant, the remaining removal capacity and the break-through profile of the carbon filters was investigated. In contrast to the full-scale plant, no carbon reactivation was applied in the pilot plant during the operation of 4 years.
Spiking experiments were carried out after ozonation, in the influent of the biological activated carbon filtration with a cocktail of different pesticides after 1.5, 3 and 4 years. Influent concentrations varied between 2 to 10 μg/l. Without carbon reactivation the filter effluent still complies with the Dutch drinking water standards and guide lines, as well as with the Amsterdam Water Supply standards: DOC is less than 2 mg/l (actually 1.2 mg/l) and AOX remains below 5 μg/l.
After four years, with spiking concentrations of 2 μg/l still no pesticide break-through was observed in the two-stage biological activated carbon filtration process. It can be concluded that a running time of 3 years between two reactivations in the two stage biological active carbon filtration is achievable, without negatively affecting the finished water quality. Average DOC concentrations will increase up to 1.2 mg/l, from 1 mg/l with running times of 2 years. After four years or 100,000 bedvolumes the AOC content is equal to or lower than 10 μg/l after biological activated carbon filtration. With slow sand filtration at the end and as polishing step AOC will be less than 10-5 μg/l. With every extension of six months duration time a saving of Euro 305,000 on reactivation costs is possible. With every 6 month extension of the running time of the carbon filters a saving of €610,000 is realised on the reactivation costs of the Leiduin treatment plant.