bluuebunny/crossref_metadata_2025 huggingface dataset:
Improved Measurements and Analysis of Spatial Snow Cover by Combining a Ground Based Radar System With a Differential Global Positioning System Receiver
Authors: Marchand Wolf-Dietrich , Bruland Oddbjørn , Killingtveit Ånund
Published: May 2018

The paper describes the realization of a new snow measurement system where a Ground Penetrating Radar (GPR) is connected to a Differential Global Positioning System (DGPS) receiver. A snow scooter pulled a radar antenna, a distance wheel triggered the radar pulses and the reflections were stored in a control unit. A marker was set on the radar file each time a position was logged on the DGPS receiver. Thus, each position was directly related to a snow depth measured by the GPR. The obtained accuracy of the position was in the range of 5-10 m and manual calibration measurements were used to ensure good quality of the snow depth data.

The system was tested in the Norwegian catchment Aursunden during the period of maximum snow accumulation, 12th – 23rd April 1999. Landscape features were analyzed with a Geographic Information System (GIS) and extensive snow measurements were worked out in representative areas. The obtained data on the snow cover were later used for statistical analysis.

In addition to the efficiency which makes it possible to measure large areas in a relatively short time, the major advances in the described system is that the obtained data can be used directly in a computer aided GIS. Nevertheless, further improvement is needed because of 1) the possibility for ambiguous connection between snow depth log and position log, 2) the distance between consecutive positions is not constant since it is time dependent, 3) the algorithm for automatically detection of the ground reflection from the radar log-file still needs interference from the user.
Precipitation Estimates over the Baltic Sea: Present State of the Art
Authors: Rutgersson Anna , Bumke Karl , Clemens Marco , Foltescu Valentin , Lindau Ralf , Michelson Daniel , Omstedt Anders
Published: May 2018

Precipitation is one of the main components in the water balance, and probably the component determined with the greatest uncertainties. In the present paper we focus on precipitation (mainly rain) over the Baltic Sea as a part of the BALTEX project to examine the present state of the art concerning different precipitation estimates over that area. Several methods are used, with the focus on 1) interpolation of available synoptic stations; 2) a mesoscale analysis system including synoptic, automatic, and climate stations, as well as weather radar and an atmospheric model; and 3) measurements performed on ships. The investigated time scales are monthly and yearly and also some long-term considerations are discussed. The comparison shows that the differences between most of the estimates, when averaged over an extended period and a larger area, are in the order of 10-20%, which is in the same range as the correction of the synoptic gauge measurements due to wind and evaporation losses. In all data sets using gauge data it is important to include corrections for high winds. To improve the structure of precipitation over sea more focus is to be put on the use of radar data and combinations of radar data and other data. Interpolation methods that do not consider orographic effects must treat areas with large horizontal precipitation gradients with care. Due to the large variability in precipitation in time and space, it is important to use long time periods for climate estimates of precipitation

Ship measurements are a valuable contribution to precipitation information over sea, especially for seasonal and annual time scales.
Redoximorphic Macropore Environments in an Agrudalf
Authors: Rasmussen Lars Holm , Ernstsen Vibeke , Hansen Hans Christian Bruun
Published: May 2018

Soil materials in fracture walls may strongly interact with solutes and colloidal particles during preferential flow. Wall coatings rich in metal oxides, clays, and organic matter may increase sorption capacities, whereas coatings devoid of these constituents have the opposite effect of increasing the risk of leaching of otherwise strongly sorbing solutes. The contrasting compositions between bulk horizon and fracture wall materials of a Typic Agrudalf excavated at Flakkebjerg, Denmark, were studied by using chemical and micromorphological methods. In the upper 220 cm of the profile, the predominant desiccation and shear fractures had 2-30 mm thick hypocoatings depleted of Fe-oxides with adjacent 5-20 mm thick quasi-coatings containing 5-6 times as much Fe-oxide. Thin hypocoatings covering walls of smaller voids and surfaces of sand particles and with strong enrichments of Fe- and Mn-oxides occurred throughout the profile, but were most abundant below 220 cm. Fracture walls, commonly with distinct laminas of clay, silt, and organic matter, generally had slightly coarser texture, but were enriched in smectite compared with horizon materials. Higher contents of organic C in fracture coatings were attributed to root growth and deposition of A-horizon materials. Despite removal of Fe-oxides from depletion hypocoatings, no corresponding depletion of P was observed. However, calculations demonstrated that, in the case of macropore transport only, P sorption capacity would be at least 5 times less than during piston-like matrix flow. For adequate estimations of solute leaching from macroporous soils there is a strong need to properly take into account sorption properties of macropore wall materials!
The Influence on Summer Rainfall in the Lesotho Lowlands from Indian Ocean SSTs
Authors: Hydén Lars
Published: May 2018

Lesotho is located approximately at latitude 30 degrees south in the interior of Southern Africa. The mesoscale climate is complicated and governed by various weather systems. The inter-annual rainfall variability is great, resulting in low food security, since the growing of crops in the Lesotho Lowlands is almost exclusively rain-fed. Reliable forecasts of austral summer rainfall are thus valuable. Earlier research has shown that the sea surface temperatures (SST) in the Indian Ocean to some extent govern rainfall in Southern Africa. The research presented is part of an on-going project to find suitable oceanographic and meteorological predictors, which can be used in a forecast model for summer rainfall, to be developed later. The first part of this paper investigates the correlation between the average SSTs in the Equatorial Indian Ocean, the Central Indian Ocean, and the Agulhas Gyre, respectively, and rainfall two months later in the Lesotho Lowlands during early austral summer, October until December for the period 1949-1995. No significant correlations have been found, probably because the three ocean areas are too large. In the second part of this paper the monthly SST in 132 grid squares in the Indian Ocean were investigated and found to be correlated with rainfall in the Lesotho Lowlands two months later, October until March. Significant correlations have been found between the SSTs and certain ocean areas and December, January, and February rainfall, respectively. There is significant negative correlation between December rainfall and October SST in an ocean area between Kenya and Somalia across the Indian Ocean to Sumatra. In the area where the Somali Current flows there is also significant correlation between December SST and December rainfall. January rainfall is significantly negatively correlated with November SST in an ocean area, northeast of Madagascar. February rainfall is significantly, but weakly, negatively correlated with SST in a narrow north-south corridor in the Eastern Indian Ocean from the equator down to latitude 40 degrees south.
North Atlantic Oscillation; a Climatic Indicator to Predict Hydropower Availability in Scandinavia
Authors: Uvo Cintia B. , Berndtsson Ronny
Published: May 2018

Climate variability and climate change are of great concern to economists and energy producers as well as environmentalists as both affect the precipitation and temperature in many regions of the world. Among those affected by climate variability is the Scandinavian Peninsula. Particularly, its winter precipitation and temperature are affected by the variations of the so-called North Atlantic Oscillation (NAO).

The objective of this paper is to analyze the spatial distribution of the influence of NAO over Scandinavia. This analysis is a first step to establishing a predictive model, driven by a climatic indicator such as NAO, for the available water resources of different regions in Scandinavia. Such a tool would be valuable for predicting potential of hydropower production one or more seasons in advance.
Optical Measurements of Sea Ice in the Gulf of Finland
Authors: Rasmus Kai , Ehn Jens , Granskog Mats , Kärkäs Eija , Leppäranta Matti , Lindfors Antti , Pelkonen Antti , Rasmus Sirpa , Reinart Anu
Published: May 2018

During the spring of 1998, measurements of total albedos, spectral albedos and ice transparency were made on coastal fast ice in the Gulf of Finland, Baltic Sea, to produce values for models, to compare instruments and to test a new method for measuring under ice irradiance. The broadband albedos between 400 and 700 nm varied between 0.19 and 0.76, and those between 300 and 1,100 nm were from 0.16 to 0.75. The condition of the surface, and especially the presence of liquid water or snow, was the most important factor affecting the albedos, but also the cloudcover and forest shading had an effect. The diffuse attenuation coefficient integrated over the range 400 to 700 nm was 6.8 m−1. Spectral albedos were weakly dependent on wavelength in the visible band (300-800 nm) decreasing in the longer wavelengths. The albedo results were in good agreement with earlier observations.
The Choice of Stage-Discharge Relationship for the Ganges and Brahmaputra Rivers in Bangladesh
Authors: Mirza M. Monirul Qader
Published: May 2018

The Ganges and Brahmaputra are the two largest rivers in Bangladesh. Discharge estimations of these rivers from a stage-discharge relationship or rating curve are crucial for flood warning/control/mitigation and water resources development. So far, logarithmic rating curves have been widely used in Bangladesh. The suitability of semi-logarithmic, polynomial and quadratic rating curves has not been investigated. In this study, all four recognised stage-discharge relationships were examined for the Ganges and Brahmaputra rivers. Unbiased least squares estimators were determined for the segmented logarithmic and semi-logarithmic rating curves. This enhanced their efficiency in inter-and extrapolating discharges from the given river stages. Based on detailed analysis and goodness-of-fit criteria, segmented logarithmic and third order polynomial rating curves were found to be the best for the Ganges and Brahmaputra rivers, respectively.
Water and Climate – The IPCC TAR Perspective
Authors: Kundzewicz Zbigniew W.
Published: May 2018

The aim of the present contribution, opening a session on climate change and hydrology at the 2002 Nordic Hydrological Conference in Røros, Norway, is to discuss essential water-related findings of the Third Assessment Report (TAR) of the Intergovernmental Panel on Climate Change (IPCC), with particular reference to region-specific issues of the Nordic region. Discussion of impacts of climate variability and change embraces both already observed effects and projections for the future. After review of changes in hydrological processes, climate-related impacts on extreme hydrological events – floods and droughts – are outlined. Finally, adaptation and vulnerability are dealt with, including presentation of key water-related regional concerns in various parts of the World.
Regional Climate Scenarios for use in Nordic Water Resources Studies
Authors: Rummukainen M. , Räisänen J. , Bjørge D. , Christensen J.H. , Christensen O.B. , Iversen T. , Jylhä K. , Ólafsson H. , Tuomenvirta H.
Published: May 2018

According to global climate projections, a substantial global climate change will occur during the next decades, under the assumption of continuous anthropogenic climate forcing. Global models, although fundamental in simulating the response of the climate system to anthropogenic forcing are typically geographically too coarse to well represent many regional or local features. In the Nordic region, climate studies are conducted in each of the Nordic countries to prepare regional climate projections with more detail than in global ones. Results so far indicate larger temperature changes in the Nordic region than in the global mean, regional increases and decreases in net precipitation, longer growing season, shorter snow season etc. These in turn affect runoff, snowpack, groundwater, soil frost and moisture, and thus hydropower production potential, flooding risks etc. Regional climate models do not yet fully incorporate hydrology. Water resources studies are carried out off-line using hydrological models. This requires archived meteorological output from climate models. This paper discusses Nordic regional climate scenarios for use in regional water resources studies. Potential end-users of water resources scenarios are the hydropower industry, dam safety instances and planners of other lasting infrastructure exposed to precipitation, river flows and flooding.
Snow-Distribution Modelling in the Ammassalik Region, South East Greenland
Authors: Hasholt B. , Liston G.E. , Knudsen N.T.
Published: May 2018

The Ammassalik region is characterized by a strong alpine relief, with altitudes up to 1,000 m. Glaciers are located mainly on the western side of ridges. The climate is low arctic, with annual precipitation amounts of more than 1,000 mm, which falls mainly as snow. Furthermore very strong storms occur frequently throughout the region. All together these factors support strong snow redistribution by wind, which likely explains the glacier locations, and also explains the observed regional runoff differences. The aim of this study is to apply the Liston & Sturm snow-transport model (SnowTran-3D) to elucidate the snow distribution according to the actual climatic conditions. A digital terrain model was used to determine the terrain forcing of the wind field. Precipitation data from the Ammassalik meteorological station were corrected for aerodynamic errors and orographic effects. Wind, temperature and humidity were obtained from a station located on a nunatak 515 m.a.s.l. at the equilibrium line on the Mittivakkat Glacier. The recorded winter accumulation (balance) of snow on the glacier was used for model calibration and testing. Significant snow transport from east-facing slopes to west-facing slopes was confirmed by the model. The drift accumulations were greatest at the head of the glacier, just on the lee side of the ridge east of the glacier. In some areas, as much as 10% of the precipitation was returned to the atmosphere by blowing-snow sublimation. An average snow water equivalent of 113 cm was obtained (not including some minor areas having snow depths as great as 4 m). These results compare well with glacier observations of 114 cm collected in May 1998 (during the field survey the 4 m areas are omitted because of crevasse hazards). Future work will use the model to test scenarios that include changes in wind regime.

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The use of Satellite Imagery in Investigating the Dynamics of the Ice and Snow Cover Lake Baikal
Authors: Semovski S.V. , Mogilev N. Yu
Published: May 2018

The generation and sample applications of a set of multispectral remotely sensed products for investigations of Lake Baikal's ice cover variability are described. During the period from mid-January to the end of April, the lake is completely covered with ice, and by analyzing satellite information it is possible to investigate in detail the distribution and dynamics of the main types of snow and ice cover. Different ice cover classes and unfrozen water distributions are estimated from calibrated and navigated NOAA AVHRR 1.1-km imagery of Lake Baikal for January 1994 through May 1999. The processing strategy and characteristics of the products are reviewed. The utility of this type of multiparameter dataset for modelling applications and process studies is discussed. ERS SAR and Resurs images are used for detailed representation of different ice classes distributions.
Scenarios of extreme daily precipitation for Norway under climate change
Authors: Skaugen Thomas , Astrup Marit , Roald Lars A. , Førland Eirik
Published: May 2018

Based on downscaled daily precipitation values from the global climate model of the Max Planck Institute in Hamburg, time series of 20 years have been generated to describe the current climate of 1980–1999 (control data) and the future climate of 2030–2049 (scenario data) for Norway. These time series serve as training data for the Randomised Bartlett-Lewis Rectangular Pulse Model (RBLRPM), a precipitation simulation model, and time series of 1000 years length have been generated to assess possible changes in the extreme precipitation regime due to climate change. The analysis of changes in extreme value patterns for annual and seasonal values in the scenario and control data sets shows tendencies towards increased extreme values and seasonal shifts for the scenario period. A general increase in mean and standard deviation of the extreme value sample and for values of 10 and 100 years return period is found, although the regional variability is significant. For some regions the increase is in the order of 10 to 50 % for both annual and seasonal values.
Simple water balance modelling with few data - calibration and evaluation: investigations from a Danish Sitka spruce stand with a high interception loss
Authors: Mossin Lone , Ladekarl Ulla L.
Published: May 2018

Simple evapotranspiration models with few data requirements and Penman reference evapotranspiration for grass (Eref) limiting the actual evapotranspiration are often used to estimate chemical fluxes in ecosystems. The aim of this paper is to show how much the interception loss might exceed Eref in a wind-exposed Danish Sitka spruce stand and to demonstrate the importance of the evaluation of model performance, here represented by throughfall measurements and chemical fluxes. Precipitation, throughfall, soil moisture and soil water chemistry were measured monthly for 1.5 years. Model input was daily precipitation, Eref, leaf area index, root distribution and plant available water. The model interception loss was calculated using an empirical relationship between precipitation and interception loss that was calibrated against the measured interception loss. Interception loss was found to be unusually high, on average 58% of precipitation, which was supported by measurements from two other years with interception losses from 62–68% of precipitation. Transpiration and evaporation from soil were constrained by Eref. The modelled percolation was compared to percolation calculated by a chloride mass balance based on measured values. The percolation was only about 20% of precipitation due to the exceptionally high interception loss, which exceeded Eref by almost 50%. Therefore, in wind-exposed forest stands the interception loss should be modelled separately, as done here, and be calibrated on measured values.
Modelling the snow distribution at two high arctic sites at Svalbard, Norway, and at an alpine site in central Norway
Authors: Bruland Oddbjørn , Liston Glen E. , Vonk Jorien , Sand Knut , Killingtveit Ånund
Published: May 2018

In Arctic regions snow cover has a major influence on the environment both in a hydrological and ecological context. Due to strong winds and open terrain the snow is heavily redistributed and the snow depth is quite variable. This has a significant influence on the snow cover depletion and the duration of the melting season. In many ways these are important parameters in the climate change aspect. They influence the land surface albedo, the possibilities of greenhouse gas exchange and the length of the plant-growing season, the latter also being important for the arctic terrestrial fauna. The aim of this study is to test to what degree a numerical model is able to recreate an observed snow distribution in sites located in Svalbard and Norway. Snow depth frequency distribution, a snow depth rank order test and the location of snowdrifts and erosion areas were used as criteria for the model performance. SnowTran-3D is the model used in this study. In order to allow for occasions during the winter with milder climate and temperatures above freezing, a snow strengthening calculation was included in the model. The model result was compared to extensive observation datasets for each site and the sensitivity of the main model parameters to the model result was tested. For all three sites, the modelled snow depth frequency distribution was highly correlated to the observed distribution and the snowdrifts and erosion areas were located correspondingly by the model to those observed at the sites.
Hydrological implications of spatial and altitudinal variation in temperature in the upper Indus basin
Authors: Archer David
Published: May 2018

Runoff in the upper Indus in Pakistan is primarily fed by meltwater from snow and ice. Successful modelling of runoff thus depends on knowledge of the energy inputs for melt, and temperature provides a practical index. In this study, spatial and altitudinal variations in air temperature are investigated using correlation and regression analysis. The high levels of seasonal correlation between widely separated stations and with altitude suggest that conditions over a wide surrounding area and up to the freezing level may be inferred with reasonable reliability from climate stations at the valley level. Investigation of concurrent daily rainfall, temperature and runoff in extreme monsoon incursions shows that precipitation is accompanied by a sharp fall in temperature, reduced ablation and, most frequently, a decrease in river flow. Such temperature reductions have practical implications for short term flood forecasting and for design flood estimation.
An experimental approach for determining unsaturated hydraulic properties of rock fractures
Authors: Yunjin Hu , Baoyu Su , Genhai Mao
Published: May 2018

An experimental approach for determining the unsaturated hydraulic properties (the relations between capillary pressure, saturation and unsaturated hydraulic conductivity) of rock fractures is developed and tested. Applying this approach to a single fracture, and with only water flowing, the capillary pressure–saturation and unsaturated hydraulic conductivity–capillary pressure relationships of the fracture during drainage and imbibition can be determined simultaneously. To facilitate the test of the validity of the experimental approach and to elucidate the characteristics of water flow in unsaturated fractures, an analogous fracture with parallel, connected channels of different apertures was fabricated. Experiments of unsaturated water flow in the analogous fracture were carried out. Some characteristics of water flow in unsaturated fractures (hysteresis between drainage and imbibition, etc.) were elucidated. Comparison of measured saturation values and theoretical saturation values corresponding to different apertures at the beginning of drainage and imbibition shows that the experimental approach presented in this paper is valid.
Historical trends in river-ice break-up: a review
Authors: Prowse Terry D. , Bonsal Barrie R.
Published: May 2018

Over most northern regions, break-up is primarily a spring event. Historical evidence, however, has shown that the timing of river-ice break-up has been shifting in many areas of the Northern Hemisphere and these shifts were associated with observed air temperatures during the break-up period. This paper reviews past trends in break-up from the Eurasian and North American circumpolar regions and synthesizes them into a regional and temporal context. It also evaluates various hydro-climatic explanations for these trends including associations with winter/spring air temperature variations and relationships to large-scale circulation patterns. Even more dramatic changes to break-up timing and magnitude are forecast to occur as the result of climate change. Insights toward future break-up conditions are discussed for two broad-scale regions: the North, a region forecast to experience the most pronounced warming, and the southern limit of the cold regions, a zone of particular cryospheric sensitivity to warming.
Effects of the flow field on small scale phytoplankton patchiness
Authors: Schernewski Gerald , Podsetchine Victor , Huttula Timo
Published: May 2018

We present an example of small scale (10–100 m) horizontal, subsurface patchiness of phytoplankton (Ceratium) during an intensive bloom in August 1993 and link it to the flow field. In the small Lake Belau (1.1 km2) in northern Germany large areas of the water surface are sheltered from wind, due to vegetation. Wind sheltering effects decrease with wind speed and below 2 m/s a spatially homogeneous wind field is observed. Under weak wind conditions near-surface Ceratium patches with local chlorophyll-concentrations up to 200 mg/m3 were observed in the south bay (0.3 m depth) as well as in parts of the central basin (1 m depth). Detailed flow simulations show very good agreement between location and size of current gyres and phytoplankton patches. Inside the gyres we find low flow velocities with low vertical turbulence. This allows Ceratium to form distinct vertical layers with high densities close to the water surface, according to the light gradient. Especially in the south bay flow eddies are determined by the course of the coastline and their location and intensity is, to a large degree, independent of prevailing wind directions.
Modelling of summer stratification of morphologically different lakes
Authors: Elo Aija-Riitta
Published: May 2018

The use of a one-dimensional lake temperature model was investigated using long series of meteorological input data. These data were mainly based on one station. Effects of morphology on water temperature conditions were considered over this long period.

The studied lakes are from the Finnish Lake District. Concerning their dynamics, they are small with areas ranging from 257 km2 to 0.14 km2 with the largest depth about 80 m, but typically less than 50 m. The strength of thermal stratification varies. Verification was made using test summers: for two larger lakes longer periods could be used. Summer stratification periods could finally be resolved satisfactorily, but only after adjusting with data from each lake. For some years the vertical temperature simulations are not as successful as for others, indicating the importance of local weather differences.

For lakes with a large area to depth ratio heat is absorbed freely, while when it is small heat is blocked more into the epilimnion. For very small lakes sheltering is essential. Large total volume delays cooling, when stratification prevails. Sheltering is important and also very small lakes cool slowly due to their strong stability.
A system for modelling groundwater contamination in water supply areas: chloride contamination from road de-icing as an example
Authors: Lindström Riitta
Published: May 2018

A system for modelling groundwater contamination in water supply areas is presented, consisting of the flow and transport models, MACRO for the unsaturated zone and MOC for the groundwater zone, coupled to the geographical information system, IDRISI. A graphical user interface links the different parts of the system. The system was applied to a water supply area located close to a major road south of Stockholm. Chloride was used as an indicator in determining the risk for groundwater contamination from the road. The future chloride concentration in the aquifer was predicted and the effects of different pumping rates on the chemistry of the water supply well were tested. Modelling results showed that the chloride concentration in the aquifer will increase substantially due to road de-icing and that it will take decades to lower the chloride concentration down to the original background values after an end to the use of de-icing salt. The system may serve as a valuable tool in a planning context. Potential groundwater contamination scenarios can be simulated, and alternative groundwater management strategies can be evaluated.
Methods for water quality sampling and load estimation in monitoring of Norwegian agricultural catchments
Authors: Haraldsen Trond Knapp , Stålnacke Per
Published: May 2018

Different sampling procedures are applied to monitor water quality in agricultural catchments in the Nordic countries. The need for comparing monitoring results from the Nordic countries was the incentive for establishing a project aimed at comparing estimates of nutrient losses determined using different sampling strategies. Three different sampling methods were compared in three Norwegian catchments: weekly flow-proportional composite sampling (FPCS), weekly composite sampling with temporally equidistant subsampling every second hour (TECS) and temporally equidistant weekly point sampling (PS). Differences in load estimated between the three tested sampling strategies were smaller for nitrogen than for phosphorus or suspended solids. Point sampling tended to miss some of the peaks in concentrations of phosphorus and suspended solids, particularly during flow events, causing significantly lower load estimates for phosphorus and suspended solids by point sampling compared with composite sampling strategies. Flow-proportional composite sampling gave the most reliable data for event-responsible compounds or when the predictability of peaks was low. Based on this investigation, and similar studies in the other Nordic countries, a flow-proportional sampling strategy is recommended for studies of water quality in agricultural streams.
Runoff modelling in glacierized Central Asian catchments for present-day and future climate
Authors: Hagg W. , Braun L.N. , Weber M. , Becht M.
Published: May 2018

A conceptual precipitation–runoff model was applied in five glacierized catchments in Central Asia. The model, which was first developed and applied in the Alps, works on a daily time step and yields good results in the more continental climate of the Tien Shan mountains for present-day climate conditions. Runoff scenarios for different climates (doubling of CO2) and glacierization conditions predict an increased flood risk as a first stage and a more complex picture after a complete glacier loss: a higher discharge during spring due to an earlier and more intense snowmelt is followed by a water deficiency in hot and dry summer periods. This unfavourable seasonal redistribution of the water supply has dramatic consequences for the Central Asian lowlands, which depend to a high degree on the glacier melt water for irrigation and already nowadays suffer from water shortages.
Fuzzy, ANN, and regression models to predict longitudinal dispersion coefficient in natural streams
Authors: Tayfur Gokmen
Published: May 2018

This study developed fuzzy, ANN, and regression-based models to predict longitudinal dispersion coefficient in natural streams from flow discharge data. 92 sets of field data were employed to calibrate and validate the models. 63 sets of data were used for the calibration while the remaining data were used for the validation of the models. The model-prediction results revealed the superiority of the developed models over the existing equations. The developed models predicted the measured data satisfactorily with minimum errors and maximum accuracy rates. The three models had comparable performances although the fuzzy model had the highest accuracy rate (79%) and lowest mean relative error (0.85).
Optical properties of Finnish lakes estimated with simple bio-optical models and water quality monitoring data
Authors: Kallio Kari
Published: May 2018

The aim of this study was to estimate the distributions of spectral diffuse attenuation coefficient, attenuation depth and subsurface reflectance of Finnish lakes. In addition, the optimum empirical water quality interpretation algorithms employing reflectance ratios were investigated for the needs of remote sensing. Estimations of the optical properties were based on simple optical models and measured concentrations of optically active substances (the sum of chlorophyll a and phaeophytin a, total suspended solids and coloured dissolved organic matter (CDOM)) at 1670 monitoring stations representing 1113 lakes. The models were parameterized using optical data from 10 lakes. The mean diffuse attenuation coefficient in PAR was 3.5 m−1 and the location of the maximum attenuation depth was in the range 564–714 nm. The simulated reflectance spectra showed a shift of the maximum value to longer wavelengths as trophic status changed from oligotrophic to hyper-eutrophic. High CDOM concentrations decrease the estimation accuracy of chlorophyll a from reflectance spectra using empirical algorithms, particularly in oligotrophic lakes. The models described can be used in studying light availability for photosynthesis at different depths, in the simulation of water temperatures, in estimating how different management alternatives affect light attenuation and Secchi depth, and in various remote sensing applications.
The potential for health risks from intrusion of contaminants into the distribution system from pressure transients
Authors: LeChevallier Mark W. , Gullick Richard W. , Karim Mohammad R. , Friedman Melinda , Funk James E.
Published: May 2018

The potential for public health risks associated with intrusion of contaminants into water supply distribution systems resulting from transient low or negative pressures is assessed. It is shown that transient pressure events occur in distribution systems; that during these negative pressure events pipeline leaks provide a potential portal for entry of groundwater into treated drinking water; and that faecal indicators and culturable human viruses are present in the soil and water exterior to the distribution system. To date, all observed negative pressure events have been related to power outages or other pump shutdowns. Although there are insufficient data to indicate whether pressure transients are a substantial source of risk to water quality in the distribution system, mitigation techniques can be implemented, principally the maintenance of an effective disinfectant residual throughout the distribution system, leak control, redesign of air relief venting, and more rigorous application of existing engineering standards. Use of high-speed pressure data loggers and surge modelling may have some merit, but more research is needed.
The Milwaukee Cryptosporidium outbreak: assessment of incubation time and daily attack rate
Authors: Gupta Mukul , Haas Charles N.
Published: May 2018

The time course of reported illnesses (epidemic curve) in the 1993 Milwaukee outbreak of cryptosporidiosis was analysed using a dynamic model considering time variant force of infection and incubation time distributions. Different functional forms for the force of infection and incubation time distribution were tested. The resulting model is a coupled integro-differential equation system. These models gave a good fit to the data, although depending upon the functional forms of the underlying distributions, different incubation time and force of infection curves were obtained. However there was reasonable agreement with respect to a baseline illness rate that existed. This demonstrates that useful information may be obtained in this manner, although it should be supplemented with other data (e.g. serology) for a precise assessment of dynamics of disease occurrence during waterborne epidemic conditions.
Comparison of bacteriophages for use in iodine inactivation: batch and continuous flow studies
Authors: Brion Gail M. , O'Banion N. Brennan , Marchin George L.
Published: May 2018

Inactivation rates in batch studies for four commonly used surrogate bacteriophages were measured in stable aqueous iodine solutions for the purpose of determining which was the most suited to evaluate iodine disinfection efficacy in batch and continuous flow conditions. Two types of group Leviviridae bacteriophages were used, Type I (MS2) and Type II (GA), along with group Microviridae, Phi-X174, and group Tectiviridae, PRD1. Inactivation was compared at iodine doses of 1.0–1.5 mg I2/l. MS2 was the most susceptible to iodine inactivation of the four phages tested. Inactivation of naked, icosahedral bacteriophages, MS2 and Phi-X174 demonstrated removals to below detection limits (>99.99%) in less than 10 min. Lipid-containing PRD1 and F+ssRNA GA bacteriophages demonstrated the greatest iodine resistance in batch experiments with an average of 1.82 logs of inactivation (98.5%) after 60 min and 1.05 logs of inactivation (91.1%) after 30 min respectively. Similarly, in continuous flow studies through pentaiodide quaternary ammonium strong base resin, MS2, GA and Phi-X174 were more strongly inactivated than PRD1. The lipid component of PRD1 is thought to enhance resistance to iodine over non-lipid-containing bacteriophages by protecting easily oxidized groups on the protein capsid, but further research is needed before proving this hypothesis. The results from this research may provide a surrogate standard for more rigorous and developed research into the mode of iodine disinfection and its inactivation kinetics.
Effect of alternative on-site wastewater treatment on the viability and culturability of Salmonella choleraesuis
Authors: Pundsack J. W. , Hicks R. E. , Axler R. P.
Published: May 2018

The objective of this study was to determine how alternative on-site wastewater treatment systems (i.e. subsurface flow constructed wetlands, intermittent sand filters and intermittent peat filters) affect the viability and culturability of Salmonella choleraesuis (serotype typhimurium, ATCC 23567). Influent was a high strength septic tank effluent (BOD5 240–344 mg L−1, TN ∼100 mg L−1, TP ∼ 15 mg L−1) at the Natural Resources Research Institute's (NRRI) alternative treatment system test facility in northern Minnesota. Treatment systems were inoculated with cultures of S. choleraesuis for 5–7 consecutive days in summer and winter during 1998–99. After the seeding, outflow samples were taken until Salmonella counts were sustained at background levels. In addition to culture-based enumeration, S. choleraesuis abundances were also measured using fluorescent in situ hybridization (FISH) alone and in combination with the direct viable count method (DVC) to determine if plate counts underestimated total and viable Salmonella abundances and if the Salmonella cell viability changed after passing through the treatment systems. In most cases, total and viable cell abundances in treatment system effluents were several orders of magnitude higher than cultured cell abundances. Our results indicate that the culture-based method underestimated viable concentrations of the model pathogen, S. choleraesuis. Salmonella cell viability decreased in effluents during the summer but increased during the winter. Using a culture-based enumeration method alone to determine removal efficiencies of bacterial indicators and pathogens for wastewater treatment systems may result in artificially high estimates of effective treatment.
Development and test for long-term stability of a synthetic standard for a quantitative Cryptosporidium parvum LightCycler™ PCR assay
Authors: Filkorn-Kaiser Renata , Botzenhart Konrad , Wiedenmann Albrecht
Published: May 2018

A recently described quantitative rapid cycle real time PCR (LightCycler™) assay detects Cryptosporidium parvum after in vitro excystation, which is a surrogate marker for the viability of the organisms. In the original assay the quantification standard is a dilution series of C. parvum oocysts with a microscopically determined excystation rate. The need to keep suspensions of viable oocysts in stock and to continuously monitor their excystation rate, however, renders the assay impracticable for routine application. A synthetic standard was developed to replace the in vivo standard and was calibrated using oocysts with known excystation rates. The standard consists of a 486 bp DNA segment ranging from 229 bp upstream to 79 bp downstream of the actual PCR target site. Aliquots of the standard were frozen and stored at −20 °C and at −70 °C or lyophilised and stored at room temperature in the dark. For a period of one year samples preserved with each of the three methods were restored every four or five weeks. They were amplified in the LightCycler™ and the crossing points (CP) were monitored. No significant trend in the raw CP values could be observed for any of the three storage methods. However, when the methods were compared to each other by calculating the CP ratios (−20 °C/−70 °C; −20 °C/lyophilised; −70 °C/lyophilised) at the 10 monitoring dates, the CP ratios −20 °C/−70 °C and −20 °C/lyophilised showed a highly significant positive trend (p<0.0001) while the CP ratio −70 °C/lyophilised did not differ from the null hypothesis (p=0.53). It can be concluded that the latter two preservation methods are both appropriate, while storage at −20 °C is less advisable. Calculations based on the molecular weight of the standard and on the assumption of an average yield of three sporozoites per oocyst led to the conclusion that the target sequence is probably located on a double copy gene
An estimation of the global burden of disease due to skin lesions caused by arsenic in drinking water
Authors: Fewtrell Lorna , Fuge Ron , Kay David
Published: May 2018

The global burden of disease due to skin lesions caused by arsenic in drinking water was estimated by combining country-based exposure data with selected exposure–response relationships derived from the literature. Populations were considered to be exposed to elevated arsenic levels if their drinking water contained arsenic concentrations of 50 μg l−1 or greater. Elevated arsenic concentrations in drinking water result in a significant global burden of disease, even when confining the health outcome to skin lesions. The burden of disease was particularly marked in the World Health Organization (WHO) comparative risk assessment (CRA) ‘Sear D' region, which includes Bangladesh, India and Nepal. Unsurprisingly, Bangladesh was the worst affected country with 143 disability adjusted life years (DALYs) per 1,000 population. Although this initial estimate is subject to a large degree of uncertainty, it does represent an important first step in allowing the comparison of the problem relating to elevated arsenic in drinking water to other environmental health outcomes.
An assessment of water quality and microbial risk in Rio Grande basin in the United States–Mexican border region
Authors: Ryu Hodon , Alum Absar , Abbaszadegan Morteza , Alvarez Maria , Mendoza Jose
Published: May 2018

Increased reliance of urban populations on Rio Grande water has necessitated an expanded microbial surveillance of the river to help identify and evaluate sources of human pathogens, which could pose a public health risk. The objectives of this study were to investigate microbial and chemical water quality in Rio Grande water and to perform risk assessment analyses for Cryptosporidium. No oocysts in any of the ten-litre samples were detected. However, the limit of detection in the water samples ranged between 20 and 200 oocysts/100 L. The limits of detection obtained in this study would result in one to two orders of magnitude higher risk of infection for Cryptosporidium than the U.S.EPA annual acceptable risk level of 10−4. The bacterial data showed the significance of animal farming and raw sewage as sources of fecal pollution. Male specific and somatic coliphages were detected in 52% (11/21) and 62% (24/39) of the samples, respectively. Somatic coliphages were greater by one order of magnitude, and were better correlated with total (r2=0.6801; p≤0.05) and fecal coliform bacteria (r2=0.7366; p≤0.05) than male specific coliphages. The dissolved organic carbon (DOC) and specific ultraviolet absorbance (SUVA) values ranged 2.58–5.59 mg/L and 1.23–2.29 m−1 (mg/l)−1, respectively. Low SUVA values of raw water condition make it difficult to remove DOC during physical and chemical treatment processes. The microbial and chemical data provided from this study can help drinking water utilities to maintain balance between greater microbial inactivation and reduced disinfection by-products (DBPs) formation.
Neurosensory effects of chronic exposure to arsenic via drinking water in Inner Mongolia: I. signs, symptoms and pinprick testing
Authors: Li Yanhong , Xia Yajuan , Wu Kegong , He Linlin , Ning Zhixiong , Zhao Baixiao , Le X. Chris , Kwok Richard , Schmitt Michael , Wade Timothy , Mumford Judy , Otto David
Published: May 2018

This study was designed to assess the effects of exposure to arsenic in drinking water on neurosensory function. A questionnaire including neurological signs and symptoms and a brief neurological exam consisting of pinprick testing of the arms and legs and knee-jerk test were administered to 321 residents of the Bamen region of Inner Mongolia, China. Arsenic in water was measured by hydride generation atomic fluorescence. Participants were divided into three exposure groups—low (non-detectible-20), medium (100–300) and high (400–700 μg/l) arsenic. Significant group differences were observed in pinprick scores for all four limbs. Results indicate that arsenic alters pinprick (pain) thresholds at well-water concentrations as low as 400 μg/l, well below the 1000 μg/l threshold for neurological effect specified by NRC (1999). Regression models suggest that a 50% increase in pinprick score is associated with a 71–159 ppb increase in arsenic concentration.
A study of the efficacy of various home filtration substrates in the removal of microcystin-LR from drinking water
Authors: Pawlowicz Marek B. , Evans James E. , Johnson David R. , Brooks Robert G.
Published: May 2018

This study was conducted to determine whether common water filtration and purification systems bought by consumers and used in the home would remove cyanotoxins from water. Commonly used universal filter housings and filter sizes were utilized to identify filter media that may be effective in the removal of microcystin-LR in deionized water. Results suggest that the efficacy of home filtration devices in removing microcystin-LR varies considerably with the type of device being used. Carbon filters successfully removed microcystin-LR allowing only 0.05–0.3% of the toxin load to pass through the filter. On the other hand, pleated paper and string wound filters allowed >90% of microcystin-LR present in the sample to pass through the filters. Theoretically, the use of carbon home filtration devices tested in this study may provide protection against human exposure to cyanotoxin in addition to protection provided by water treatment methodologies utilized in water treatment facilities. Further studies need to be done to assess the efficacy of home filtration devices for various cyanotoxins and for other filtering conditions such as increased toxin load, the presence of other contaminants in drinking water, and the repetitive use of the same filter over longer time intervals.