bluuebunny/crossref_metadata_2025_split huggingface dataset:
Groundwater in Norwegian River Plains
Authors: Stang Ole 
Published: May 2018

Existing conflicts or problems concerning groundwater in Norwegian river plains are outlined. Emphasis is placed on the effects of river regulation. Two methods of determining aquifer diffusivity are proposed. The methods require continuous recordings of river stage and groundwater level at the time of a flood peak or during periodic fluctuations of river stage.
The methods are applied to data from two Norwegian river plain aquifers and consistent results for aquifer diffusivity are obtained.
It is concluded that the proposed solutions represent a feasible and competitive way of obtaining aquifer parameters in Norwegian river plains.
The Paths of the Suspended Particulate Inorganic and Organic Matter in a Small Urban Estuary: The Aarhus Harbour Estuary
Authors: Kronvang K. B. , Christiansen C. 
Published: May 2018

The nverine supply of suspended inorganic and organic sediment, its temporal and spatial distribution and its exchange with the bay, were estimated for an urban estuary (Aarhus Harbour Estuary, Denmark) during 1983-84. The river supplies high levels of particulate matter to the estuary. Export from the estuary averages one fifth of the river introduced particulate matter resulting in the accumulation of terrigenous material in the estuary.
River discharge determines whether the high depletion of particulate matter in the upper estuary follows an exponential(flocculation) or a lineary curve (dilution). Preferential deposition of organic as opposed to inorganic matter in the upper estuary depletes the particulate matter of organic matter and associated pollutants.
The estuary is divided into three depositional zones identified on the basis of sediment activity, grain-size and organic content. A sediment budget is precented for the estuary. Good agreement is shown between the actually dredged sediment quantity and the mass to sedimentation from the budget.
Laboratory Experiments on Solute Transport in Non-Homogeneous Porous Media
Authors: Refsgaard Anders 
Published: May 2018

Solute transport in groundwater is a process which has become of major importance during the last decades due to increasing contamination of ground water. This process usually occurs in a medium heterogeneous with respect to hydraulic conductivity and porosity, properties that affect the dispersion of the solutes.
The present paper describes an experimental investigation of the solute transport process in heterogeneous porous media, especially the connection between the statistical properties of their hydraulic conductivity distributions and the dispersion parameters governing the spreading of the solutes. The experimental results are compared to theoretical solutions derived for the same case of a solute pulse in an average uniform flow through a heterogeneous porous medium. Generally there is good agreement between the theory and the experiments.
In field applications this means that the dispersion parameters can be more readily determined from the soil properties. Furthermore, the deviations between dispersivities determined in laboratory columns and dispersitivies found under field conditions can be explained quantitatively by the differencies in the length scales and in the variances of the hydraulic conductivity distributions.
WATBAL
Authors: Knudsen J. , Thomsen A. , Refsgaard J. Chr 
Published: May 2018

A semi-distributed, physically based hydrological modelling system, WATBAL, which accounts for the entire land phase of the hydrological cycle is described. As compared to the two alternative hydrological model types, i.e. the traditional lumped, conceptual rainfall runoff models (STANFORD model type) and the complex, fully distributed, physically based model (SHE model type) WATBAL represents an intermediate approach.
In the model, primary attention is given to the hydrological processes at the root zone level through a distributed, physically based approach whereas the groundwater processes are simulated in less details by use of a lumped, conceptual approach. This approach allows WATBAL to utilize spatially distributed input data to account for the spatial and temporal variability of meteorological conditions, vegetation and soil properties. Thus WATBAL can e.g. utilize digital satellite information as input data.
WATBAL has primarily been designed as a tool for predicting the runoff from ungauged catchments and for assessing the hydrological effects of land use changes. The capability of the model for simulating ungauged catchments is tested using results from a recent feasibility study for medium size dams in Zimbabwe.
Proposed Swedish Spillway Design Floods in Relation to Observations and Frequency Analysis
Authors: Bergström S. , Lindström G. , Sanner H. 
Published: May 2018

Proposed guidelines for the computation of spillway design floods in Sweden are described. The guidelines are based on the transformation of extreme hydrological conditions to floods by use of conceptual hydrological models.
Floods computed according to the guidelines are compared to observations for both autumn conditions when rainfall dominates and for snowmelt conditions in spring. The highest floods are in the order of 60% of the proposed guidelines.
Comparisons with frequency analysis show that the computed floods are well beyond the 10,000 year flood according to the Gumbel and Lognormal 2 distribution functions, while the results according to Lognormal 3 are more uncertain.
A Net Radiation Model for Calculating Daily Snowmelt in Open Environments
Authors: Granger R. J. , Gray D. M. 
Published: May 2018

Climatological data from three stations in western Canada are used to develop a model for estimating daily net radiation from station latitude, station altitude and cloud cover. Expressions describing: a) the seasonal variation in atmospheric transmissivity; b) the interaction between direct-beam and diffuse short-wave radiation and c) the effect of cloud cover on these components are presented.
The seasonal decrease in albedo of a shallow snowcover is approximated by three line segments. Albedo decreases at an average rate of 0.0061/day during premelt; at an average rate of about 0.071/day during melt and takes on a reasonably constant value of 0.17 when the ground is snowfree.
The exchange of long-wave radiation dominates the radiation balance of a complete snowcover. During these periods it is recommended that the net flux be calculated from observations of ambient air temperature and vapor pressure in standard expressions.
Hydrological Model for the Tude Å Catchment
Authors: Christensen Steen 
Published: May 2018

A numerical hydrological model has been developed for a 450 km2 Danish catchment using comprehensive field data. The model integrates a simple evapotranspiration model, a lumped flow model for a phreatic aquifer found in till, and a traditional two-dimensional groundwater model for a confined fluvio-glacial aquifer. A minimal but adequate number of model parameters were calibrated by trial and error to make the model fit 29-year time series of hydraulic head and stream runoff data.
By simulating a “semi-natural” hydrological situation unaffected by withdrawals it is demonstrated that groundwater development can change the water balance considerably. In the actual case withdrawals induce a 25% increase in leakage from the phreatic to the confined aquifer, and reduce stream base flow by up to 30% in normal years, and up to 35% in dry years. On the other hand the reduction in base flow is considerably smaller for the upper stream catchments.
On Currents and Vertical Mixing in Lake Ontario during Summer Stratification
Authors: Omstedt A. , Murthy C.R. 
Published: May 2018

Currents and vertical mixing characteristics were investigated on the basis of time series of current meter and temperature data from a summer-stratified period in Lake Ontario. The experimental set up consisted of seven current meters distributed in one vertical line from 12 m below the surface to 1 m above the lake bottom at a total depth of 143 m. The period considered for the analysis was from June to September, 1991.
The currents showed pronounced oscillations with two significant kinetic energy peaks, one at about 17 hours due to inertial motions, and one at 10 days, probably due to meteorological forcing. The current shear in the hypolimnion was strong enough to overcome stability and generate turbulence (Richardson numbers below 0.25) and there was probably turbulence enough available to keep the matter (almost neutral buoyant particles) in the whole Nepheloid bottom layer in suspension. In the thermocline region the turbulence was mainly damped (Richardson numbers above 1), but some events with lower Richardson numbers were also calculated indicating increased mixing during these events. By analysing filtered and unfiltered current meter data it was found that the shear-generated turbulence in the hypolimnion was mainly due to the meteorologically forced currents. In the thermocline region, however, the vertical shear associated with the inertial oscillation had a greater impact on the mixing.
Statistical Estimates of PMP Values
Authors: Elíasson Jónas 
Published: May 2018

The article discusses two statistical methods to estimate PMP values, the Hershfield and the NERC methods. Neither method offers any explanation why the PMP values can be calculated by the use of unbounded statistical distributions, but both methods include the use of envelope curves that are not independent of the region. Bounded data that fits an unbounded distribution must deviate from the distribution for high return periods and tend to a limiting value, and then there exists, a limiting reduced variate that can be used to find the PMP value. When the distribution is EV1, the limiting reduced variate can be defined by a mapping transformation, or by cutting off the distribution. It is shown that when Hershfield or NERC methods are used, the limiting reduced variate is included in the PMP values and can be separated from regional parameters. It is suggested that the limiting reduced variate, that depends solely on return period, may more easily be transferred between regions than the other parameters. This may be a great help in finding PMP values in regions where observations are not extensive enough to define limiting return periods with necessary certainty.
A case study with data from Iceland demonstrates, that using the limiting reduced variate, similarities emerge in the Icelandic data and the NERC PMP that justify the acceptance of the NERC method.
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.
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.
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.
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.
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.
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

Abstract
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 &lt; 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.
Making regulatory mechanisms work: lessons from cases of Private Sector Participation
Authors: Frade T. , Sohail M. 
Published: May 2018

This paper is about the regulation of private sector participation (PSP) in public water utilities. Using case studies from Argentina, Chile and the United Kingdom, it identifies and discusses the regulatory mechanisms that have been introduced and the issues surrounding information access, price and service quality regulation. The paper also analyzes what measures have been implemented in these three cases in order to achieve regulatory accountability, independence and an adequate level of financial and human resources.
The method adopted was case survey including the analysis of official regulatory documents and other relevant material and validation by an expert panel. It investigates the conditions that are necessary for regulatory mechanisms to be implemented and operated effectively in each context, and draws out some general conclusions for areas of improvement.
Prediction of breakthrough of pesticides in GAC-filters and breakthrough of colour in ion-exchange-filters
Authors: Heijman S.G.J. , Siegers W. , Sterk R. , Hopman R. 
Published: May 2018

Adsorption columns are widely used in drinking water treatment to improve a number of water quality parameters. Granular activated carbon filtration (GAC) can be used to decrease the concentration of DOC, colour, taste, odour and pesticides. Columns filled with ion-exchange resins are used to remove colour, nitrate and DOC. The regeneration frequency of these types of filters depends strongly on the natural water quality. Especially the DOC-concentration and DOC-composition determines the efficiency of the processes. Because pilot-plant experiments with realistic contact-times will last for more than a year (for GAC) there is a need for a prediction of breakthrough based on shorter and less expensive laboratory experiments. The available models are not accurate enough because the exact parameters are not available. In batch experiments with natural water, with realistic (low) pesticide concentrations and the full grain size of the adsorbent the adsorption parameters are measured in an independent experiment. With the parameters obtained with these experiments an accurate prediction of the breakthrough curve is possible.
With the same parameters predictions of breakthrough curves are calculated under different process conditions. The possibilities of process optimisation can reduce the investment costs for new full-scale plants.