bluuebunny/crossref_metadata_2025 huggingface dataset:
Some Remarks on the Use of GIUH in the Hydrological Practice
Authors: Corradini C. , Melone F. , Singh V. P.
Published: May 2018

The geomorphologic instantaneous unit hydrograph (GIUH) as a component of rainfall-runoff models directed to the determination of design hydrographs in ungaged basins is investigated. Specifically, we first performed a sensitivity analysis of the GIUH to errors in the basin lag estimated by commonly used empirical relationships involving basin area. Then, the details required in representing the geomorphologic features in the GIUH estimate for fixed basin lag, L, were examined. Real basins located in Central Italy were selected; they range in area from 12 km2 to 4,147 km2 and are characterized by a significant variability in the drainage channel density, D. It was found that given L a minimum detail was necessary in representing basin geomorphology. Further, the estimate of L through basin area led to large errors in computing design hydrographs for a few small basins. An explicit consideration of D is suggested in order to eliminate this shortcoming.
Sediment Fabric and Anisotropy of Hydraulic Conductivity in Sandy Till, Wisconsin, U.S.A.
Authors: Rayne Todd W. , Mickelson David M.
Published: May 2018

The orientation of macroscopic and microscopic particles in silty, sandy basal till appears to have little effect on aquifer anisotropy. The orientation of 108 elongate pebble and cobble-sized particles was measured in a trench adjacent to 25 wells screened in the till. In addition, the orientation of elongate silt and sand-sized particles was measured in thin sections of five oriented samples taken from the same trench. The orientations of the macro- and microfabric measurements agree with each other and with drumlin orientations in the vicinity. There is no preferential direction of transmissivity (i.e. no horizontal anisotropy) based on analysis of pumping test data. This is most likely due to the relatively small number of elongated, and therefore oriented, particles in the matrix.
Phreatic Water Surface Profiles along Ice Jams – An Experimental Study
Authors: Saadé Raafat G. , Sarraf Semaan
Published: May 2018

In Northern Regions, the formation of ice jams along many rivers is a common phenomena. These ice jams may occur during the freeze-up and more importantly during the spring break-up period. Ice jams in general have considerable effects on the water levels because they alter the water surface profile for stretches of tens of kilometers along the rivers. As a consequence, water levels increase significantly upstream of the ice jam and result in the flooding of towns situated along the river banks. Knowledge of the water levels within an ice jam can be used to estimate many parameters that are difficult to measure and observe. Examples of such parameters are the local and global ice jam resistance to the flow, and forces acting within an ice jam.

While ice jams are notorious causes of serious problems in hydraulic engineering, very little engineering methodology exists to deal with such problems. In this paper, the results of a laboratory study aimed at investigating the development of the water surface profile along an ice jam that is lodged in place, are analyzed and presented. A rectangular flume with a horizontal bed was used for the experiments. Twelve experiments carried out under different geometrical, hydrodynamic and ice conditions, were analysed. A simulated floating ice cover was used to arrest the downstream transport of the ice floes, forming the ice jams.

The experiments indicate two types of ice jams, those that are floating and others that are lodged at one or more locations along their length. The phreatic water level along a floating ice jam is up to 0.92 the ice jam thickness. This is not true when an ice jam is lodged in place. Different experiments have shown that the water surface profile along a lodged ice jam follows similar tendencies regardless of the geometry, ice floe size distribution and hydrodynamic conditions. It was found that the phreatic water level varies linearly from the trailing edge of the ice jam up to approximately 90% of its length downstream. Towards the remaining part of the jam's length the water level follows a cubic polynomial line.
Mass Transfer Effects on Tracer Tests Conducted in a Heterogeneous Rock Fracture
Authors: Selroos Jan-Olof
Published: May 2018

A methodology based on a combination of numerical simulation of conservative transport and an analytical solution for combined matrix diffusion and surface sorption is presented for the study of tracer tests conducted under non-uniform flow conditions in heterogeneous fractures. The methodology is based on a Monte Carlo technique with multiple realizations; hence uncertainty in transport estimates can be assessed. In an illustration example, the methodology is implemented for dipole pumping conditions ( i.e. one injection borehole and one retrieval borehole) in a single fracture. The effect of experimental conditions such as pumping rate and tracer properties on matrix diffusion are investigated. Due to the kinetic character of the mass transfer process, it is shown that for high flow rates with consequent high advection velocities and short residence times relative to the mass transfer rate, matrix diffusion only develops to a minor extent. The effect of fracture heterogeneity is also exemplified. The results indicate that both heterogeneity in transmissivity and matrix diffusion may be manifested as tailing in solute arrival. Hence it is generally difficult to distinguish these processes under experimental conditions.
Predicting Sedimentgraphs for a Small Agricultural Catchment
Authors: Banasik K. , Walling D. E.
Published: May 2018

The key components of a sedimentgraph prediction procedure for small agricultural catchments are outlined in the paper. An instantaneous unit sedimentgraph (IUSG) based on the IUH and on a dimensionless sediment concentration distribution is developed, and used for transforming the sediment produced during a specified rainfall duration into a sedimentgraph. Rainfall-runoff-suspended sediment transport data from the River Dart basin, in Devon, UK, are used to evaluate several relationships for sediment yield estimation. The relationship between the lag time of the direct runoff hydrograph and the sedimentgraph is analysed, and the use of these lag times for estimating an IUSG (sediment routing) parameter is examined. The effectiveness of the proposed sedimentgraph prediction procedure is demonstrated by the successful regeneration of a measured sedimentgraph.
Mesoscale Variability of the Upper Colorado River Snowpack
Authors: Ling Chi-Hai , Josberger Edward G. , Thorndike A.S.
Published: May 2018

In the mountainous regions of the Upper Colorado River Basin, snow course observations give local measurements of snow water equivalent, which can be used to estimate regional averages of snow conditions. We develop a statistical technique to estimate the mesoscale average snow accumulation, using 8 years of snow course observations. For each of three major snow accumulation regions in the Upper Colorado River Basin – the Colorado Rocky Mountains, Colorado, the Uinta Mountains, Utah, and the Wind River Range, Wyoming – the snow course observations yield a correlation length scale of 38 km, 46 km, and 116 km respectively. This is the scale for which the snow course data at different sites are correlated with 70 per cent correlation. This correlation of snow accumulation over large distances allows for the estimation of the snow water equivalent on a mesoscale basis. With the snow course data binned into 1/4° latitude by 1/4° longitude pixels, an error analysis shows the following: for no snow course data in a given pixel, the uncertainty in the water equivalent estimate reaches 50 cm; that is, the climatological variability. However, as the number of snow courses in a pixel increases the uncertainty decreases, and approaches 5-10 cm when there are five snow courses in a pixel.
Estimating Regional Precipitation Trends Comparison of two Methods
Authors: Hanssen-Bauer I. , Førland E. J. , Tveito O.E. , Nordli P.Ø
Published: May 2018

Two different methods were applied to estimate long-term precipitation trends representative for regions in Norway. A new method, comparative trend analysis (CTA), was applied on 142 homogeneous precipitation series of 70-100 years. In this way 12 precipitation trend regions were identified. Principal component analysis (PCA) was applied on a subset of 30 series during the period 1896-1994 The results from both analyses were used to estimate precipitation trend series at several locations. The estimates based upon the PCA were of same quality as the estimates based upon the CTA. However, by CTA it is possible to visualize the trend in a distinct region by using just one trend curve, while trend curves based on PCA are composed of contributions from 5 principal components.

The resulting trend curves document that the annual precipitation level has increased by 8-14% throughout this century in most Norwegian regions. The increase occurred not simultaneously all over the country. The regional differences in precipitation trends and variability are probably connected to variations in the atmospheric circulation patterns.
Fluxes of Water and Energy from Three High Latitude Tundra Sites in Svalbard
Authors: Harding Richard J. , Lloyd Colin R.
Published: May 2018

Measurements of the surface fluxes of radiation, heat and water vapour were made at three tundra sites near Ny-Ålesund, Svalbard for the active seasons (June to September) of 1995 and 1996. In 1995 the snow melted completely in early June, in 1996 the deeper snow pack resulted in the persistence of snow until July. Thus the snow free period was 50% longer in 1995 resulting in larger cumulative evaporation and energy inputs. In this region the snow melt is dominated by radiation input, a result of the low air temperatures and possible control of the air temperature by the surrounding sea, snow and ice fields. During the snow-free period the evaporative ratio [LE/(LE+H)] varied with surface type. At two sites, where there was a continuous cover of soil, the evaporative ratio was consistently equal to 0.5, except for a few days after rainfall when it rose to unity. This latter rise was probably due to the increased evaporation from the soil, mosses and lichens after wetting by rainfall. At a third site, with a predominantly stony surface, the evaporative ratio was lower (between 0.2 and 0.3), again rising during and after rainfall. The measurements from 1995 show the summer evaporation was 160% of the summer rainfall. However there was no evidence of a reduction of evaporation during extended dry periods. In 1996 the radiation inputs and evaporation were much reduced by the shorter active season and rainfall exceeded evaporation. The timing of the snow and snowmelt and thermal condition of the surface layers is thus important to the hydrology, the surface energy balance and the carbon balance of this region.
Priestley-Taylor Evapotranspiration in HBV-Simulations
Authors: Gardelin Marie , Lindström Göran
Published: May 2018

Estimations of potential evapotranspiration as input to runoff calculations with the HBV model are usually given as monthly standard values calculated with the Penman method. Daily changes in the weather conditions can in later model versions be taken into account by the introduction of a temperature anomaly correction of the evapotranspiration. In this study daily values of potential evapotranspiration calculated with the Priestley-Taylor method were used as input to the model. The required net radiation estimations were calculated from routine weather observations including cloudiness. Potential evapotranspiration was calculated on a three hour basis over a 20-year period. Model simulations using different input data on the potential evapotranspiration were made for three drainage basins (3,500-4,300 km2) in Sweden. The Priestley-Taylor evapotranspiration generally gave small improvements of the runoff simulations. The simple temperature anomaly correction method gave improvements of the same size.
How Extreme was the Drought?
Authors: Clausen Bente , Pearson Charles P.
Published: May 2018

In 1993/94 a severe drought on the North Island of New Zealand caused water shortage in the Auckland metropolis. How extreme was the drought? This paper presents comparisons of frequencies of the 1993/94 drought in four North Island regions using different indicators of drought and including both streamflow and rainfall data. With regard to streamflow deficit volume and duration the exceedance probabilities ranged from 1 to 25%; however, the 7-day annual minimum flows in 1993/94 were less extreme with non-exceedance probabilities from 10 to 34%. With regard to rainfall the drought in the Auckland region was most extreme (on average 2% exceedance probability) when annual rainfall totals were analysed compared to seasonal totals (on average 6% exceedance probability for half-annual totals and 13-38% for three-month totals). Thus, the conclusion was that the 1993/94 drought was extreme because of its duration rather than its magnitude.
Long-term Variation in the Stability of the Meromictic Lake Nordbytjernet Caused by Groundwater Fluctuations
Authors: Hongve Dag
Published: May 2018

A zone with permanent anoxic conditions prevailed in the deep waters of Nordbytjernet before 1978 due to a significant depth gradient in dissolved substances. High concentrations of manganese and bicarbonate in the deep waters were most important for the lake's stability. The electrolyte concentrations in the mixed layer increased between 1978 and 1991, wiping out the depth gradient. A subsequent study showed a major variation in the solute concentration in the most important surface tributary that depends on fluctuations in the elevation of the groundwater table. A rising groundwater table seems to enhance oxidation of iron sulphides and dissolution of carbonates. Increasing solute concentrations in the mixed zone contributes to a weakening of the density gradient and reduced stability. Mineralised stream water may also intrude into the anoxic zone when the lake is not thermally stratified and cause precipitation of iron and manganese. Thus, a temporary rise of the groundwater table seems to be the reason why the lake changed from meromixis to holomixis. Lately the stream water concentrations have decreased and the lake has returned to meromixis. This periodic shift may be normal for this kind of lake.
The Impact of Climate Change on Storage-Yield Curves for Multi-Reservoir Systems
Authors: Nawaz N. R. , Adeloye A. J. , Montaseri M.
Published: May 2018

In this paper, we report on the results of an investigation into the impacts of climate change on the storage-yield relationships for two multiple-reservoir systems, one in England and the other in Iran. The impact study uses established protocol and obtains perturbed monthly inflow series using a simple runoff coefficient approach which accounts for non-evaporative losses in the catchment, and a number of recently published GCM-based scenarios. The multi-reservoir analysis is based on the sequent-peak algorithm which has been modified to analyse multiple reservoirs and to accommodate explicitly performance norms and reservoir surface fluxes, i.e. evaporation and rainfall. As a consequence, it was also possible to assess the effect of including reservoir surface fluxes on the storage-yield functions. The results showed that, under baseline conditions, consideration of net evaporation will require lower storages for the English system and higher storages for the Iranian system. However, with perturbed hydroclimatology different impacts were obtained depending on the systems' yield and reliability. Possible explanations are offered for the observed behaviours.
Multivariate Technique for Validating Historical Hydrometric Data with Redundant Measurements
Authors: Bennis Saad , Kang Narut
Published: May 2018

The aim of this research was to develop an automated methodology for validating chronological series of natural inflows to reservoirs. Theoretically, gauges located on the same reservoir should indicate the same reading. However, under the influence of meteorological and hydraulic factors, or simply because of failed measuring equipment, there may be large deviations between the various measurements. Since the calculation of historical natural inflows is directly linked to the measurement of reservoir level by the water balance equation, there will be as many series of natural inflows as there are of reservoir levels. A multivariate filtering technique is used to validate the historical natural inflow computed by each water level variation. The multi filter methodology has the advantage of balancing the water volume of natural inflows to the reservoir when applied over a relatively long period of time. As a result, the validated flood peaks are not systematically overestimated or underestimated and the validated natural inflows are nearly identical for all the gauges. The proposed technique has been incorporated into a software program called ValiDeb, which has been successfully tested on-site on the Gatineau River in Quebec.
Simulation of Snowmelt in a Subarctic Spruce Woodland: Scale Considerations
Authors: Woo Ming-ko , Giesbrecht Mark A.
Published: May 2018

Subarctic woodlands comprise stands of spruce trees with varying degrees of openness, giving rise to large contrasts in melt rates within the forest. The spatial variability of the changing snow depth during a melt season was investigated at three scales (2,4 and 16 m), using an example from a site in Yukon, Canada, where the computation of snowmelt takes into account the differential rates within the woodland. During the melt period, the mean daily snow depth decreases but the variability increases as continued ablation leads to greater unevenness of the snow cover. At the three scales of representation, increasing the grid size results in a reduction in the standard deviation and the skewness of depth distribution. The blurring of snow cover pattern at the larger scales is due to a loss in information, considered as the absolute value of the difference in snow depth calculated at two scales for the same location. This loss increases as the snow depth becomes more variable during the melt season. Knowledge of the scale-induced information loss is relevant to the modelling of snowmelt that exhibits large spatial variations.
A Bivariate Extreme Value Distribution Applied to Flood Frequency Analysis
Authors: Yue Sheng
Published: May 2018

This article presents a procedure for use of the Gumbel logistic model to represent the joint distribution of two correlated extreme events. Parameters of the distribution are estimated using the method of moments. On the basis of marginal distributions, the joint distribution, the conditional distributions, and the associated return periods can be deduced. The applicability of the model is demonstrated by using multiple episodic flood events of the Harricana River basin in the province of Quebec, Canada. It is concluded that the model is useful for describing joint probabilistic behavior of multivariate flood events.
Solar-Climatic Relationship and Implications for Hydrology
Authors: Berndtsson Ronny , Uvo Cintia , Matsumoto Minoru , Jinno Kenji , Kawamura Akira , Xu Shiguo , Olsson Jonas
Published: May 2018

Research during the latest years has indicated a significant connection between climate and solar activity. Specifically, a relationship between Northern Hemisphere air temperature and sunspot cycle length (SCL) has been shown. By using monthly SCL and land air temperature from 1753-1990 (238 years) we show that this relationship also holds for a single observation point in south of Sweden. Using data after 1850 yields a statistically significant linear correlation of 0.54 between SCL and mean temperature. Furthermore, we show that there are indications of a low-dimensional chaotic component in both SCL and the interconnected mean land air temperature. This has important implications for hydrology and water resources applications. By pure definition of chaos this means that it is virtually impossible to make long-term predictions of mean temperature. Similarly, because of the strong connection between temperature and many hydrological components, it is probable that also long-term water balance constituents may follow chaotic trajectories. Long-term projections of water resources availability may therefore be impossible. Repeated short-term predictions may however, still be viable. We exemplify this by showing a technique to predict interpolated mean temperature 6 and 12 months ahead in real time with encouraging results. Improving the technique further may be possible by including information on the SCL attractor. To summarize, research into the possible existence of chaotic components in hydrological processes should be an important task for the next years to come.
Modeling Long-term Streamwater Chemistry in the Berg Catchment, Southwestern Sweden
Authors: Krám Pavel , Bishop Kevin , Moldan Filip
Published: May 2018

The geochemical model MAGIC (5.01) was applied to the Berg – Pipbäcken Nedre catchment in southwestern Sweden for the period 1846-2020. The major objective was to reconstruct historical acidification trends and predict the surface water and soil response to declining atmospheric deposition in the future based on the Gothenburg Protocol signed in 1999. Another task was to test the usefulness of Sweden's long-term small catchment monitoring program for a validation of the long-term acidification model. Berg has been one of fifteen catchments monitored very intensively by the Swedish Environmental Protection Agency during 1986-1993 and less intensively later by the Swedish University of Agricultural Sciences Department of Environmental Assessment. Anthropogenic atmospheric deposition was the dominant factor causing a decline of streamwater pH and especially soil base saturation. A scenario of future atmospheric deposition based on the emission reductions of S and N compounds agreed under the 1999 Gothenburg Protocol to the UNECE CLRTAP was modeled. This scenario stopped further acidification of soils, but recovery of streamwater pH and soil base saturation was slow and limited. Without further reductions from the deposition levels in 1995-1997, soil acidification would continue.
Solar Radiation Estimation using Temperature-based, Stochastic and Artificial Neural Networks Approaches
Authors: Morid S. , Gosain A. K. , Keshari Ashok K.
Published: May 2018

Radiation is a variable that governs many hydrological and phenological processes, but its measurements are not made routinely. To overcome this problem, continuous hydrological models that include evapotranspiration, snowmelt (using solar radiation data) and plant growth modules have applied different strategies to generate daily radiation data. In this paper, artificial neural networks (ANNs), temperature-based (TB) and stochastic (ST) approaches for estimation of solar radiation have been used and compared. These three approaches have been applied to the Ammameh Catchment, an alpine subcatchment of the Jadjroud River, in Iran. Results reveal better performance for ANNs than for TB and ST. However, the TB method because of its capability to generalize results and to be easily linked with hydrological models appears to be a good candidate to be applied in the catchments where the climatological data are limited.
Digital Elevation Hydrological Modelling in a Small Catchment in South Australia
Authors: Sun H. , Cornish P. S. , Daniell T. M.
Published: May 2018

A rainfall runoff model based on a digital elevation model (DEM) was applied to a small catchment in Happy Valley, South Australia to predict catchment storm runoff. The DEM was used to partition the catchment into several thousand irregular shaped elements. These elements, with an average size of 825 m2 each, form an interconnected one-dimensional flow network for runoff routing. The rainfall runoff model is a kinematic flow model which combines the solving of flow continuity equation and the Manning's equation to generate surface and subsurface runoff. This study improves on the existing rainfall runoff model in several areas. It adds spatial rainfall averaging methods to derive spatial rainfalls for catchment modelling; and it improves the catchment soil moisture representation by developing a boundary wetness index, and relates this index to antecedent catchment flow to derive spatial catchment moisture distribution. Improved runoff predictions were obtained as a result of the improvement in spatial data input and spatial soil moisture representation. The study identifies these improvements as the key areas for better runoff prediction. It demonstrates that where prediction results showed larger than expected variance, it is frequently caused by the inability to derive good spatially distributed input data rather than parameter estimation errors.
Evaluation of Annual Loads of Nutrients and Suspended Solids in Baltic Rivers
Authors: Kauppila Pirkko , Koskiaho Jari
Published: May 2018

Estimation of pollutant fluxes through river systems calls for accurate and precise load estimation. However, considerable uncertainty is associated with these estimates due to diffuse loading, which sets high requirements not only on sampling frequencies but also on calculation methods. The aim was to examine the variation in load calculations and the reliability of the load estimates of total phosphorus, total nitrogen and suspended solids in 24 Baltic rivers varying in size and land-use characteristics. Reliability of the load estimates was tested by simulation experiments in the river Paimionjoki using a Monte Carlo procedure.

The estimates calculated by the most reliable method were compared to the loads estimated by five other methods. The general reliability (RMSE) for P and SS was best by the correlation method and for N by the periodic method. Load calculations varied greatly depending both on the characteristics of the rivers and the calculation method. The flow-stratified method overestimated the P and SS loads by about 20% in large low-lake rivers. In small low-lake rivers, the overestimation was 10% and over 14% for P and SS, respectively. By contrast, the averaging method underestimated P and SS loads by 10% and 21% in small agricultural low-lake rivers. All the methods produced rather similar results for N in each of the river types.
Interpolation of Daily Temperature in Finland
Authors: Taskinen Antti , Sirviö Hannu , Vehviläinen Bertel
Published: May 2018

The present approach for daily temperature interpolation of the Watershed Simulation and Forecasting System of the Finnish Environment Institute is based on the inverse distance weighted interpolation. In order to improve the calculation, three alternative methods were tested: 1) modified inverse distance weighted model, 2) regression with dummy variables for taking into account time and 3) regression equation calibrated for each day. The regression model calibrated for each day proved to be the most promising model. By average, the difference between the accuracy of it and the inverse distance weighted methods wasn't big but some indication was found that in single cases it can make a difference. The estimated parameters were found to have realistic physical meanings.
Naturalization of Drainage Channels in Lithuania and Possibilities of Their Maintenance as Water Recipients
Authors: Rimkus Alfonsas , Lamsodis Romanas , Vaikasas Saulius
Published: May 2018

In the process of high expansion of drainage systems and land cultivation, most natural watercourses in Lithuania were converted into drainage channels. They were deprived of all natural riparian vegetation and abiotic conditions that kept up biodiversity, diminished erosion and deflation, induced self-purification of water etc. Thus the re-naturalization of drainage channels is essential. Consequently, to determine the possibilities to combine re-naturalization processes in channels with their function-ability it was examined the tendencies of woody vegetation (WV) spreading and the hydraulic calculation formulas estimating the performance of overgrown channels as water recipients were suggested.

As the study results showed, self-restoration of WV was most progressive in forest and outskirt channels. In the field channels WV expansion takes place as well. However, it depends on the distance from a forest, i.e. WV density decreases sharply from 1.17 stems m−2 to background level (c. 0.26 stems m−2) within the space of 300 m. In the paper there is some positive influence of WV cover in view to drainage channel maintenance discussed referring to the results of former studies as well as the publications of other authors. It includes the prevention of bottom silting as well as slope erosion and slide. The formulas estimating conductivity of overgrown channels are based on the balance of forces occurring on the boundaries of overgrown strips of a stream: resistance of tree stems, friction on the slopes, shear stresses that appear when two streams with different velocities are in contact and the horizontal component of the gravity force causing water movement. Some methods of WV cover abundance control are discussed when having assumed self- or artificial restoration of WV in channels to be maintained as recipients is projected.
Regional Variations of Snow Accumulation on Spitsbergen, Svalbard, 1997-99
Authors: Sand Knut , Winther Jan-Gunnar , Maréchal David , Bruland Oddbjørn , Melvold Kjetil
Published: May 2018

End-of-winter snow accumulation has been measured over large areas on Spitsbergen, Svalbard, using Ground Penetrating Radar (GPR) in the years of 1997, 1998, and 1999. Measuring transects following different latitudes reveal west-to-east and south-to-north gradients of snow accumulation. Generally, the east coast receives over 40% more snow (in water equivalent) than the west coast. A continental effect with lower accumulation rates can be seen in central parts of Spitsbergen at middle and northern latitudes. In the southern part of Spitsbergen accumulation rates are approximately twice as high as in the north. Elevation gradients of snow accumulation vary considerably, from –9 mm per 100 metre increase of elevation in the north-east to 258 mm/100 m in the central south. In average, the accumulation increases with 97 mm/100 m. Finally, accumulation rates close to the summit of Austfonna ice cap range from about 200 mm to 800 mm, i.e., with a factor of 4, over a few tens of kilometres. The average snow accumulation for all glacier localities measured on Spitsbergen (i.e., Austfonna excluded) for all three years is 590 mm.
Seasonal Variability of Thermal Regime in a Shallow Ice Covered Lake
Authors: Maher Osama A. , Malm Joakim
Published: May 2018

A systematic study was conducted over six years (1994-1999) on a shallow ice covered lake in the Russian Republic of Karelia with the aim of developing better understanding of some physical processes occurring in shallow ice-covered lakes. The average ice-covered period was 182 days while the longest ice-covered period was 193 days. The average lake water temperature at ice formation was 0.5-1.0°C, while the average water temperature just before ice break-up was close to 4°C. The heat flux from water to ice was low during early winter but could increase above 5 Wm-2 (daily average) during the last month before ice break-up. The heat flux from sediment to water was the main source of heat to the water body during early to mid winter being about 2-6 W·m-2 during early winter but decreasing to about 1-2 Wm-2 during early spring.
On the application of storage coefficient determination by quasi-steady-state flow
Authors: Birpinar Mehmet E. , Gazioglu Ayhan
Published: May 2018

A simple analytical method has been used for estimating the storage coefficient provided that transmissivity of the aquifer is known at the quasi-steady-state condition in confined or unconfined aquifers. The application of the method has been performed for unconfined and confined aquifer test data in Chaj Doab, Pakistan with observation wells and compared with conventional methods in the groundwater flow literature dealing with pumping tests. The results from the methodology presented in this paper conform well in practice with the results obtained from the traditional methods on the basis of order of magnitude.
Application of a degree-day snow depth model to a Swiss glacierised catchment to improve neural network discharge forecasts
Authors: Schumann G. , Lauener G.
Published: May 2018

A trained soft artificial neural network (SANN) model was applied to the Gornera catchment (Valais Alps, Switzerland) over the melt season May to September 2001 to predict hourly discharge up to five days ahead A SANN discharge forecast for three days ahead has previously been performed on this catchment using only past discharge and past and forecast air temperature as model training inputs. In this study, present zonal snow depth was included as a model input, which was predicted for five altitudinal catchment zones using an empirical degree-day model. Hourly discharge values for up to five days ahead were reconstructed using SANN predicted daily discharge parameters along with a normalised long-term moving average model (MAHM). The efficiency criterion R2 gives a model performance of 0.927 for a 24-hour-ahead forecast and 0.824 for a 120-hour-ahead forecast. Compared to previous work, adding the snow model to the SANN model inputs considerably increases the forecast accuracy, in particular during days of progressive discharge increase and thunderstorms. The SANN model yields excellent results on days marked by stable weather conditions, with an R2 value between 0.913 and 0.995. However, the model is unable to reliably predict low frequency, high magnitude events, e.g. release of stored water from a glacial lake.
Vertical motion of ground water in bed rock induced by earth tide and its influence on a repository for burnt nuclear fuel: a theoretical calculation
Authors: Rehbinder G.
Published: May 2018

Earth tide induced by the Moon and the Sun makes the volume of pores or the apertures of fractures of the bed rock vary, which in turn makes the ground water move. The flow equation of ground water, complete with the tide effect, and its solution, shows that the diffusive propagation of pore pressure is decisive for the response of the perturbation of gravity. Moreover the solution shows that diffusive flow dominates in the Fennoscandian Precambrian rock. The analysis shows that a constitutive coefficient relating the varying perturbation gravity and porosity of bed rock can be determined by field measurements of the level of water in boreholes. Water in a cavity in the bed rock is exposed to an oscillatory interaction with the surrounding pore water. If the cavity is a repository for nuclear waste, this interaction deserves attention. The analysis shows that the magnitude of the oscillatory motion of water between a repository for nuclear waste and its. surrounding groundwater is much less than the vertical motion of the phreatic surface.
A simple method to include vertical resolution in a river model, and results from an implementation
Authors: Jakobsen Flemming , Olesen Kim Wium , Madsen Mads
Published: May 2018

A simple method to include vertical resolution in a one-dimensional river model is outlined. The equations on which the method is based are the width-averaged continuity, momentum and transport equations. Some details are given on how to formulate the bed friction in a river model with vertical resolution. The equations are transformed to be in sigma coordinates. The numerical techniques, which make maximum use of an already implemented numerical solution technique in an existing river model, are described. The method is used to implement vertical resolution in the existing river model, MIKE 11. The implementation is tested on the following cases: logarithmic velocity profile, wind driven velocity profile, rapid accelerated flow, lock exchange and finally wind-forced entrainment. All test cases showed good agreement.
Atmospheric response to different sea surface temperatures in the Baltic Sea: coupled versus uncoupled regional climate model experiments
Authors: Kjellström Erik , Döscher Ralf , Meier H.E. Markus
Published: May 2018

A climate change experiment with a fully coupled high resolution regional atmosphere–ocean model for the Baltic Sea is compared to an experiment with a stand-alone regional atmospheric model. Both experiments simulate 30-yr periods with boundary data from the same global climate model system. This particular global model system simulates very high sea surface temperatures during summer for the Baltic Sea at the end of this century under the investigated emission scenario. We show that the sea surface temperatures are less warm in the coupled regional model compared to the global model system and that this difference is dependent on the atmospheric circulation. In summers with a high NAO index and thereby relatively strong westerly flow over the North Atlantic the differences between the two models are small, while in summers with a weaker, more northerly flow over the Baltic Sea the differences are very large. The higher sea surface temperatures in the uncoupled experiment lead to an intensified hydrological cycle over the Baltic Sea, with more than 30% additional precipitation in summer taken as an average over the full 30-yr period and over the entire Baltic Sea. The differences are mostly local, over the sea, but there are differences in surrounding land areas.
Spatial–temporal variability in solar radiation during spring snowmelt
Authors: Pohl S. , Marsh P. , Pietroniro A.
Published: May 2018

Much of the spring landscape of arctic regions is dominated by a patchy snow cover with implications for both spring melt runoff and atmospheric fluxes. In addition to a variable end-of-winter snowpack, spatial differences in snowmelt energy terms play an important role in the development of this patchy snow cover. This paper focuses specifically on the influence of solar radiation on snowmelt by using a model to simulate the small-scale variability of solar radiation incident on the ground surface due to topographic influences over a small arctic catchment. The model only requires a digital elevation model (DEM) and measured global radiation.

Despite the relatively low relief (average slope 3°) of the study area, the results showed solar radiation differences of up to 10% of the area-wide mean over the melt period. This would result in differences in snowmelt amounts of up to 50 mm, a value similar in magnitude to the overall mean end-of-winter snow water equivalent in the study region. An analysis of the effects of changing model scale showed that the simulated variability decreased substantially for larger grid sizes.

The results show that the small-scale variability of solar radiation contributes greatly to the mosaic patterns in melting snow covers of arctic regions, affects the timing and amount of meltwater release and influences the surface energy balance of these areas considerably.
Seasonal groundwater turnover
Authors: Engström Maria , Nordell Bo
Published: May 2018

Seasonal air temperature variations and corresponding changes in groundwater temperature cause convective movements in groundwater similar to the seasonal turnover in lakes. Numerical simulations were performed to investigate the natural conditions for thermally driven groundwater convection to take place. Thermally driven convection could be triggered by a horizontal groundwater flow. Convection then starts at a considerably lower Rayleigh number (Ra) than the general critical Rayleigh number (Rac) assuming that 10°C groundwater is cooled to 4°C, i.e. heated from below convection in porous media. This study supports the hypothesis that seasonal temperature variations, under certain conditions, initiate and drive thermal convection.
Groundwater vulnerability assessment using GIS-based DRASTIC method in the irrigated and coastal region of Sindh province, Pakistan
Authors: Shahab Asfandyar , Shihua Qi , Rad Saeed , Keita Souleymane , Khan Majid , Adnan Syed
Published: May 2018

This study aims to evaluate the vulnerability of shallow aquifer in irrigated and coastal regions of Sindh province, Pakistan by applying DRASTIC method in geographical information system (GIS) environment. Vulnerability index values ranging from 119 to 200 were categorized into three contamination risk zones. Results illustrated that 28.03% of the total area that was distributed in the upper northern and southernmost coastal area of the province was very highly vulnerable to contamination, 56.76% of the area was highly vulnerable, while the remaining 15.21% area was in medium vulnerable zone. Single and multi-parameter sensitivity analysis evaluated the relative importance of each DRASTIC parameter and illustrated that depth to water table and net recharge caused the highest variation in the vulnerability index. Two water quality indicators parameters, i.e., electrical conductivity (EC) and nitrate ion (NO3−) were used to validate the DRASTIC index. The spatial distribution map of both parameters showed a certain level of similarity with the vulnerability map and both parameters illustrated significant correlation with the DRASTIC vulnerability index (p < 0.01). This signified that vulnerable zones are particularly more prone to EC and NO3− contamination. Findings of this study will assist local authorities in contamination prevention in the groundwater of the lower Indus Plain.
Nontuberculous mycobacteria in hospital water systems: application of HPLC for identification of environmental mycobacteria
Authors: Galassi L. , Donato R. , Tortoli E. , Burrini D. , Santianni D. , Dei R.
Published: May 2018

Nontuberculous mycobacteria (NTM), ubiquitous in water environments, are increasingly recognized as nosocomial pathogens. Our study reports a one-year survey of the water system of two hospitals, A and B, in a small town near Florence, Italy. NTM were found throughout the study period in both settings, but B showed a significantly higher mycobacterial load. Mycobacterium gordonae and Mycobacterium fortuitum were the most frequent species isolated. Identification was carried out by conventional techniques and by high performance liquid chromatography (HPLC) analysis of cell wall mycolic acids. HPLC profiling could be used as a first-choice method for identification of environmental mycobacteria.
Cyanobacterial blooms and the presence of cyanotoxins in small high altitude tropical headwater reservoirs in Kenya
Authors: Mwaura Francis , Koyo Anderson O. , Zech Ben
Published: May 2018

The phytoplankton community in three small (0.065–0.249 km2) reservoirs in the stepped plateau landscape in the Kinangop area above the Rift Valley floor in Kenya were studied between 1998 and 2000. Approximately 70 species of phytoplankton were identified. The community was dominated by chlorophytes, cyanobacteria and chrysophytes. Diatoms were rare. The phytoplankton assemblage was frequently dominated by cyanobacteria in the dry season. The phytoplankton assemblage transformed to a mixture of cyanobacteria, chlorophytes and chrysophytes at the onset of the long rains, and mixture of cyanobacteria and chlorophytes after the long rains. Thereafter the phytoplankton assemblage consisted mainly of a mix of cyanobacteria and chrysophytes until the onset of the short rains when cyanobacterial dominance re-emerged. The most common phytoplankton species included Microcystis spp., Botryococcus braunii, Ceratium hirundinella, Anabaena spp. and Euglena viridis. The dry season cyanobacterial blooms produced cyanotoxins that included microcystin and endotoxins. The concentrations were well above the recommended safe limits for drinking water. The patterns of cyanotoxin production showed that the growth of the toxin-producing cyanobacteria was regulated by water temperature, pH and nutrients. The appearance of cyanotoxins in the small reservoirs is a serious public health issue in rural Kenya because such reservoirs are key sources of water for humans, livestock and wildlife.
Optimal reconstruction of historical water supply to a distribution system: A. Methodology
Authors: Aral M. M. , Guan J. , Maslia M. L. , Sautner J. B. , Gillig R. E. , Reyes J. J. , Williams R. C.
Published: May 2018

The New Jersey Department of Health and Senior Services (NJDHSS), with support from the Agency for Toxic Substances and Disease Registry (ATSDR) conducted an epidemiological study of childhood leukaemia and nervous system cancers that occurred in the period 1979 through 1996 in Dover Township, Ocean County, New Jersey. The epidemiological study explored a wide variety of possible risk factors, including environmental exposures. ATSDR and NJDHSS determined that completed human exposure pathways to groundwater contaminants occurred in the past through private and community water supplies (i.e. the water distribution system serving the area). To investigate this exposure, a model of the water distribution system was developed and calibrated through an extensive field investigation. The components of this water distribution system, such as number of pipes, number of tanks, and number of supply wells in the network, changed significantly over a 35-year period (1962–1996), the time frame established for the epidemiological study. Data on the historical management of this system was limited. Thus, it was necessary to investigate alternative ways to reconstruct the operation of the system and test the sensitivity of the system to various alternative operations. Manual reconstruction of the historical water supply to the system in order to provide this sensitivity analysis was time-consuming and labour intensive, given the complexity of the system and the time constraints imposed on the study. To address these issues, the problem was formulated as an optimization problem, where it was assumed that the water distribution system was operated in an optimum manner at all times to satisfy the constraints in the system. The solution to the optimization problem provided the historical water supply strategy in a consistent manner for each month of the study period. The non-uniqueness of the selected historical water supply strategy was addressed by the formulation of a second model, which was based on the first solution. Numerous other sensitivity analyses were also conducted using these two models. Both models are solved using a two-stage progressive optimality algorithm along with genetic algorithms (GAs) and the EPANET2 water distribution network solver. This process reduced the required solution time and generated a historically consistent water supply strategy for the water distribution system.
The prominence of health in donor policy for water supply and sanitation: a review
Authors: Clark Rebecca , Gundry Stephen W.
Published: May 2018

Improved water supply, sanitation and hygiene used in combination are effective at achieving better health for poor people in developing countries. However, donor policy has been dominated by interventions in water supply, at the expense of achieving the potential health benefits of improved sanitation and hygiene. Commitments recently made by the international community require greater emphasis on improved sanitation and hygiene and their impacts on health. This review assesses whether such a shift in emphasis is apparent in donor policy. It examines the prominence given to achieving better health in water supply and sanitation policies of three donors: the World Bank, the European Union and the Department for International Development of the British Government. It finds that health benefits are explicit and integral in recently updated policy documentation concerning water supply and sanitation. This has taken place in an environment focused on poverty reduction and demand-led, financially sustainable interventions. Mechanisms that have enabled donors to prioritise the health impacts in this environment are discussed, including adoption of an asset-based conceptualisation of poverty and a cross-sectoral approach.