bluuebunny/crossref_metadata_2025 huggingface dataset:
Hydrologic Regions in the Nordic Countries
Authors: Gottschalk Lars , Jensen Jørgen Lundager , Lundquist Dan , Solantie Reijo , Tollan Arne
Published: May 2018

A reviewed report of a Nordic working group on Hydrologic regions is presented in this paper. The emphasis is mainly put on runoff regime patterns in the Nordic countries. Maps over runoff regimes, annual runoff and variations coefficient of runoff are presented. For Finland a more detailed regime map is given also.
Hydrogeology of Crystalline Rocks: Case Studies of Two Areas in India
Authors: Uhl Vincent W. , Nagabhushanam K. , Johansson John Olaf
Published: May 2018

Two-thirds of India is underlain by consolidated rocks and approximately one-half of this hard rock area is composed of Precambrian crystalline rocks. Many rural areas in India are dependent on ground water for drinking and irrigation water supply. Population growth and increasing demands for food and water have resulted in increased withdrawals of ground water in some areas and a decline in water levels. In contrast, the lack of technical expertise and seed money has inhibited the development of ground-water resources in other areas.

In this paper, the ground-water resources of two crystalline rock areas are described. The recent drilling of over 600 wells in these areas by the Evangelical Lutheran Church (E.L.C.) Water Development Project provided the data base. The geology, occurrence of ground water, and types of ground-water flow systems in these areas are discussed.

Well data such as yield, depth and thickness of overburden, aquifer depth, and well depth were analyzed statistically for both areas. The results helped to quantify the occurrence of ground water with depth and the distribution of well yields and expected well yields in different rock types and topographic settings.

Both step-drawdown and constant-rate pumping tests were conducted on 150 production wells. Aquifer transmissivity ranges from approximately 1 to 400 m2/day (meters squared per day) in both areas. Specific capacity results are also presented.
Nitrogen in Soil Water
Authors: Lind Anne-Margrethe
Published: May 2018

This review comprises a general description of nitrogen in soil water and the use of nitrogen fertilizer. The following investigations on nitrogen leaching and transformations are described: Investigations on drainage water. Losses of nutrients by leaching in agricultural production. Influence of nitrogen fertilizer on nitrate nitrogen content in drainage water.

Nitrate reduction in the subsoil.

Water balance and nitrogen balance by optimum plant production.

The main conclusions are that the leaching of nitrogen as nitrate mainly occurs in the autumn and winter periods as a result of biological degradation of plant residues. Increased plant covering of the soil will decrease the nitrate leaching.
Note on Random Raindrops and Sampling Error
Authors: Bardsley W. E.
Published: May 2018

A number of variables of interest in precipitation studies can be interpreted as sums of random numbers of random variables, where the summed quantity is a power transformation of raindrop diameter. Included in this category are raingauge measurements and radar reflectivity. A general expression is given for the coefficient of variation of such variables when the number of terms per sum and the transformed variable follow any specified probability distribution. Some simple expressions are obtained for the special case of an exponential distribution of raindrop diameters.
Parametrization of Contaminant Transport through an Anisotropic Unconfined Aquifer
Authors: Bobba A.G. , Bukata R.P.
Published: May 2018

A duo two-dimensional deterministic model of contaminant transport through a homogeneous and anisotropic unconfined aquifer is developed. This model is then utilized to evaluate the effects of such hydrogeologic parameters as convection, dispersion, and chemical adsorption on the build-up, steady-state, and recovery phases of the subsurface contaminant transport. Figures are presented illustrating the dependence of the subsurface transport upon principal velocity ratios, dispersivity ratios, and the adsorption coefficient. The results clearly indicate a distinct dominance of the principal velocity ratio (i.e., degree of aquifer anisotropy) on the transport of subsurface contaminants.
Spring Flood Meltwater or Groundwater?
Authors: Rodhe Allan
Published: May 2018

The environmental isotope oxygen-18 was used as a tracer to separate stream discharge into flows originating from groundwater and fresh meltwater. Two, mainly forested, watersheds (areas 6.6 and 4.0 km2) in southern Sweden were studied during snowmelt 1979. The seasonal variation of δ18O in precipitation makes the δ18O of meltwater different from that of groundwater, hence making the separation possible.

The major part of the streamflow this spring originated from groundwater. Of the total water volumes that left the areas, during the two periods of snowmelt that occurred this year, the fraction of groundwater ranged between 0.7 ± 0.2 and 0.9(±) 0.2 The volume of meltwater in the streams corresponded to the volume of snowmelt and precipitation over 10-15% of the catchments. A field survey indicated that these percentages reasonably well describe the extension of the saturated areas, i.e. the effluent areas for groundwater where no infiltration can take place.
Characteristics of Three-layer Circulation and inverse Surface Salinity Gradients in Two Small Semi-enclosed Danish Embayments
Authors: Christiansen Chr , Christoffersen H. , Lomhott S.
Published: May 2018

Inverse surface salinity gradients were measured in two small Danish embayments. Three possible mechanisms are taken into account. In Knebel Vig the circulation and salinity distribution can be generated by tidal modification of the stratification at the entrance which is maintained by external dynamics rather than by fresh water discharged into the embayment. In Egens Vig the involved mechanisms can be coastal upwelling and difference in heating between shallow waters near the coast and deeper waters in the central part of the embayment.
Assessment of »True« Variability of Small Rainfall Events in a Small Mountainous Watershed in the Summer
Authors: Nkemdirim Lawrence C. , Meller Brian D.
Published: May 2018

The standard error of mean areal rainfall was calculated for various densities of rain gauge network in a small mountainous watershed in the summer of 1978. It is shown that a) the optimum gauge density required to assess mean rainfall is about 3 gauges/km2; b) the »true« variability in the spatial distribution of rainfall decreases with increasing rainfall amount; and c) the relationship between »true« variability and rainfall volume is linear in that watershed.
Outlines of the Hydrogeological Conditions in the Suså-Area, Denmark
Authors: Kelstrup N. , Binzer K.
Published: May 2018

A pre-Quaternary greensand limestone aquifer was investigated by means of archive data and borehole logging. The aquifer is composed of layers of different lithology, i.e. clay, marl, lime sand, limestone and hardgrounds, which dip slightly towards northwest and are cut by faults. The fault zones, together with a fracture system in the top layers of the aquifer caused by ice pressure, localize zones of high hydraulic conductivity.The hydraulic negative boundaries are found in zones of low hydraulic conductivity mainly within the fault blocks. Both the hydraulic gradient and the hydraulic conductivity decrease with depth in the aquifer. Therefore the main part of the groundwater flow takes place at the upper part of the aquifer. The hydrogeology of the Quaternary aquifers was investigated by means of environmental tritium. Depth of penetration of the tritium has been found and hydraulic properties such as actual velocity, hydraulic conductivity and leakage factors have been estimated. Point values of infiltration are given for two localities to 100-150 mm/year. The groundwater recharge to the limestone aquifers underlying the Quaternary deposits are estimated to between 55-105 mm/year.
Finite Element Analysis of Square Aquifers Containing Pumped Wells and Comparison with Finite Difference Method
Authors: Aberra Tilahun
Published: May 2018

The numerical solution of the behaviour of discrete time steps in digital computer analysis of square aquifers containing pumped wells is examined by using the finite element method with a 4 node linear quadrilateral isoparametric surface element. A wide range of time steps are used in the computation. The calculations show that discrete time steps can cause errors and oscillations in the calculations particularly when wells start and stop pumping. Comparison with known results obtained by theoretical and finite difference procedures has been considered. The main objective of this paper is to demonstrate comparison of the finite element and finite difference simulation results over a regular linear 4 node quadrilateral mesh suitable to represent the two numerical schemes with a marked similarity. The dimensionless time drawdown results of the finite element method agreed well with the finite difference and analytical results for small time increment. However, for large time increments, there are from slight to significant oscillations in the results and notable discrepancies are observed in the solutions of the two numerical methods.
On the Use of Bulk Aerodynamic Formulae Over Melting Snow
Authors: Daniel Moore R.
Published: May 2018

Bulk aerodynamic formulae which relate the turbulent exchanges of sensible and latent heat over melting snow to measurements of windspeed, temperature and humidity at one level can be derived from flux-gradient relationships and assumed log-linear profiles. Recent analyses of local advection over snow and wind flow over complex terrain suggest that the bulk aerodynamic formulae should apply in non-ideal field situations. The assumption that the scaling lengths for temperature and humidity equal the roughness length is problematic, since theoretical analyses indicate they should be much less than the roughness length. However, the effect of scale length inequality on the stability correction tends to compensate for the effect on the neutral-case transfer coefficient. Field experience indicates that the bulk aerodynamic formulae are adequate for use in energy balance estimates of daily or shorter term snowmelt.
Nimbus-7 SMMR Polarization Responses to Snow Depth in the Mid-Western U.S.
Authors: Hall D.K. , Foster J.L. , Chang A.T.C.
Published: May 2018

Analysis of January and February 1979 Scanning Multichannel Microwave Radiometer (SMMR) data has revealed discrepancies in the responses of vertically and horizontally polarized brightness temperature (TB) data to snow in the state of Indiana. Ten satellite overpasses were analyzed between January 8 and February 21, 1979. In four cases, the horizontally polarized TBs correlated with snow depth significantly better than did the vertically polarized TBs. These four overpasses occurred either when the snowpack was building up or when it had metamorphosed and/or was melting. For example, on February 17, the coefficient of correlation, R, between vertically polarized TB and snow depth was R = -.46 while it was R = -.86 for the horizontally polarizedTB data. Just prior to February 17, air temperatures rose above 0°C in the study area causing melting of the snowpack. On February 17, air temperatures dropped well below 0°C and the snow and water in the snowpack froze causing a metamorphosis of the snowpack. It is concluded that horizontally polarized TB data may be more useful than vertically polarized data for analysis of snow in regions in which there are a range of snowpack conditions, or where a snowpack undergoes rapid metamorphosis. However, analysis of both polarizations may reveal information concerning the structure of a snowpack.
Urban Runoff Peak Frequency Curves
Authors: Marsalek J.
Published: May 2018

Runoff peak frequency curves were derived from runoff flows observed in an urban test catchment and from runoff flows simulated for storms selected from two rainfall records. The first record, of a shorter length, was recorded in the test catchment. The second rainfall record, of a greater length, was recorded at a station located 10.6 km west of the test catchment. Comparisons of peak frequency curves derived from observations and both sets of simulations indicated a good agreement. As the sewer system became surcharged, the rate of flow increase with the increasing return period diminished.
Time Lag Solution of the Muskingum Flood Routing Equation
Authors: Gill M. A.
Published: May 2018

Use of time lag in the Muskingum method of flood routing is explained by considering some specific examples. Time lag method removes undesirable predicted results which are obtained by the conventional method. A method is also proposed for calculating the time lag. The examples which have been considered are of floods which can be described in algebraic terms; the method is however of general application and can be adapted for numerical computation.
Modelling of Solute Transport in the Unsaturated Zone
Authors: Høgh Jensen K. , Ammentorp H.C. , Sevel Torben
Published: May 2018

A numerical model for solute transport in the unsaturated zone has been developed. The model is based on the basic equation for soil water flow in one dimension and the general convection-dispersion equation. These are solved by numerical techniques and coupled under the assumption that the flow equation can be solved independently.

Options for solute-soil reactions are included in the model comprising adsorption, ion exchange and decay. In addition the effect of immobile water may be considered in the calculations.

The model has been applied for simulating field conditions. The model calculations have been compared with measurements of moisture content and the results from a field tracer experiment.
On Soil Retention Curves and Hydrological Forecasting in Ungauged Catchments
Authors: Anderson M. G. , Howes S. , Kneale P. E. , Shen J. M.
Published: May 2018

In many physically based hydrological models, there is the requirement to specify the suction-moisture curve of the soil system. This paper shows that where the suction moisture curve is known, then a model can be derived to predict groundwater rise. Secondly, it is shown that with only mapped soils data, relationships exist that allow suction-moisture curves to be predicted. This prediction scheme is incorporated into a forecasting model for ungauged catchments and results are presented to show the potential validity of the scheme for operational forecasting.
Areal Reduction Factors from Rain Movement
Authors: Bengtsson Lars , Niemczynowicz Janusz
Published: May 2018

The relation between rain movement and areal reduction of rain intensity is investigated. An approach for calculating areal reduction factors from point hyetographs and storm speed is suggested. Very good agreement is found between moving storm derived areal reduction factors and reduction factors determined using a dense net of rain gauges. Moving areal reduction factors calculated for design storms and historical storms are shown not to differ much between different cities in the Nordic countries.
Frequency Analysis of Low Flows: Hypothetical Distribution Methods and a Physically Based Approach
Authors: Loganathan G. V. , Mattejat P. , Kuo C. Y. , Diskin M. H.
Published: May 2018

A mixed log Pearson type III distribution, a double bounded probability density function, partial duration series and a physically based approach are analyzed for frequency estimates of low flows. The mixed log Pearson III involves a point probability mass at zero for intermittent streams. The double bounded probability distribution has lower and upper bounds with a point mass at the lower bound. Two approaches are used in partial duration series i) truncation, and ii) censoring which represent curtailing of the population and the sample respectively. The parameters are estimated by maximum likelihood procedure. Considering low flows as part of the recession limb of stream flow hydrographs a physically based approach is formulated. By using the exponential decay of stream recessions and considering the initial recession flows, recession durations, and recharge due to incoming storms as statistically independent random variables, a first order random coefficient Markov model for initial recession flows is formed. The resulting steady state probability distribution for initial recession flows is combined with the probability distribution of the exponential decay to obtain the probabilities of low flow events. The methods are applied to both perennial and intermittent streams.
The Dynamic Calibration of Tipping-Bucket Raingauges
Authors: Niemczynowicz Janusz
Published: May 2018

The dynamic calibration of three types of tipping-bucket raingauges extensively used in the Nordic countries was performed. The tested and calibrated gauges were: “LTH gauge”, PLUMATIC gauge and RIMCO gauge. It was found that with regard to all tested gauges, the volume of water which tips the bucket is not a constant characteristic for the gauge; it depends on rainfall intensity. Thus, in order to avoid errors, a calculation of the rainfall intensity or of rainfall volume from tipping-bucket registrations must go through empirical, usually non-linear calibration function. The procedure involved in the dynamic calibration of the tipping-bucket raingauges is described in the paper. Examples of typical calibration curves are provided. The magnitude of errors, in respect of measured rainfall intensity, which occur when linear gauge calibration is used is stated too.
Runoff Studies in a Small Catchment
Authors: Myrabø Steinar
Published: May 2018

This paper discusses results from a field study in a small East-Norwegian catchment. The main object of the study was to separate the different runoff processes in a small catchment. Direct measurements of precipitation snowmelt, runoff and the saturated basin area were undertaken in the field together with chemical hydrograph separation.

A functional relation between saturated area and runoff was established showing that the initial runoff being a good moisture indicator for a basin. Further the hydrograph of pure saturated overlandflow (produced from rain on the saturated area) may be separated from the rest of the runoff at any moment of time.

This paper also discusses the results in view of existing methods to estimate soil moisture and to forecast runoff.

One of the main conclusions is that the dynamic response area should be taken into consideration both in field investigations and in hydrological models, – specially in humid climate.
Groundwater Modelling for Hydropower Development in Iceland
Authors: Freysteinsson S. , Helgason S.
Published: May 2018

Groundwater problems in moberg and lava formations are frequently encountered in connection with development of hydroelectric power resources in the volcanic zones in Iceland. The paper gives account of experience by VST from design work and evaluation of performance related to groundwater and seepage at some of Landsvirkjun's projects in Southwest Iceland. The major problems encountered are: leakage under dams on lava, seepage from reservoirs on lava and moberg formations, seepage from canals and dewatering of excavations. The most relevant problems are associated with dams founded on lava and seepage from reservoirs on lava. The discussion is concentrated on three such dams, at Thorisos, Hrauneyjafoss and Sultartangi. Brief description is given of the methods used for estimating seepage and comparisons between forecasts and observations after construction. In general the reservoirs and structures have performed satisfactorily.
Variations in the 87Sr/86Sr Ratio in Lake Waters from Central Sweden
Authors: Wickman F. E. , Åberg G.
Published: May 2018

The 87Sr/86Sr ratios of lake waters from eastern Central Sweden, a region consisting mainly of 1.7-2.0 × 109 years old granitoid rocks are reported and discussed. The ratios range from 0.722-0.739, and are similar to lake and stream waters in geologically similar areas.

The annual variation of the isotope ratio in two small lakes varied in the range of 0.7323-0.7339 and 0.7313-0.7325 respectively, except at ice clearing in spring when the ratio of surface water was lowered by a contribution from melting snow. Small lateral differences also exist in Lake Mälaren, probably because its complex outline hinders complete mixing of its water.

The Sr isotopic ratio variations with respect to bedrock geology suggest that a more important influence on the ratio is the mineralogic composition of the Quaternary deposits (mainly till).

The great difference between the ratios of rain water (0.709-0.710) and those of rocks in old Precambrian platforms with granitic rocks (0.720 and greater) results in waters (ground, lake and river) with ratios around 0.720-0.740. This means that the 87Sr/86Sr ratio is an excellent tool in studies of hydrologic processes, such as mixing of waters and exchange reactions between water and mineral matter.
An Indirect Method for Determination of the Parameters of Flood Plain Aquifers
Authors: Beldring Stein , Gottschalk Lars
Published: May 2018

An indirect method of determining flood plain aquifer parameters from estimated autocorrelation of groundwater table data is presented. For this purpose a stream-aquifer system is approximated by a cascade of linear reservoirs. The response of groundwater piezometric head to an arbitrarily varying flood pulse in the river is given by the convolution equation. The autocorrelation function of groundwater piezometric head is expressed as a function of the parameters of the aquifer and the autocorrelation function of the water stage in the river. Observations performed in Gaupne in western Norway are used to determine the parameters of a flood plain aquifer.
Environmental Impacts of an Old Mine Tailings Deposit – Metal Concentrations and Water Pathways
Authors: Sandén P. , Karlsson S. , Lohm U.
Published: May 2018

Variations in metal concentrations in a heavily polluted stream receiving acidic leachates from an old mine tailings deposit are analysed from a hydrological perspective. From an extensive data material, collected during three years, the variations in concentrations of four metals (copper, zinc, cadmium and lead) are discussed. The deposit is the principal source for these metals in the watershed. The variation in metal concentrations in the vicinity of the deposit can to a large extent be explained by simple dilution of contaminated water with uncontaminated water from the surrounding area. Further downstream the deposit, other processes become increasingly important for the metal concentrations in the water bodies.
Hydrological Analysis of Basin Behaviour from Soil Moisture Data
Authors: Andersson Lotta
Published: May 2018

Soil moisture dynamics in the Velen drainage basin (Sweden) were analyzed in order to assess the degree of and the reasons for spatial variation in basin behaviour. The main tool was a modified version of the soil moisture accounting routine in the conceptual runoff model HBV, optimized against neutron probe field data. Simulated soil moisture dynamics, interception and percolation rates agreed well with measurements and other calculations. Integration of simulated evapotranspiration from sites with different characteristics agreed well with water balance computations for the area. It was shown that unsaturated flow through macropores probably occurred after heavy rainstorms. During spring, evapotranspiration was limited to values below the potential (Penmans equation) even at times when no soil moisture deficit existed. Soil moisture differences between forest and grassland (including a deforested site) were, during summer, mainly attributed to differences in the root distribution with depth. The effect of interception on the total evapotranspiration rates was only significant during periods when transpiration demands were low. Soil moisture differences between forest sites were mainly attributed to topography but variations in soil characteristics and root distribution had to be considered, especially during dry periods.
Application of an Adaptive Forecast Algorithm to the River Västerdalälven
Authors: Iritz László
Published: May 2018

During the last two decades, advances in electronic engineering, hydrological modelling and systems theory have given considerable benefits to the hydrological forecast developments. Today several powerful adaptive techniques are available, which can improve the reliability of hydrological forecasting. One of these techniques is the self-tuning predictor based on an ARMA type model using direct parameter estimation by recursive least square algorithm. The selftuning predictor has been tested on the River Västerdalälven in Sweden.
Difficulties in Deducing Temporal Changes in Precipitation Chemistry from Snow and Ice Cores: The Spatial Variability Problem
Authors: Metcalf R. C. , Peck D. V.
Published: May 2018

Depth profiles of chemical impurities found in snow and ice have usually been interpreted simply in terms of temporal changes in atmospheric concentrations of the species of interest. Measurements of pH and conductivity from individual snow stratigraphic layers sampled above 2,600 metres indicate local spatial variation in these parameters is sufficiently large to potentially mask temporal changes inferred from depth profiles. Inferences concerning past climatic variation based on assumed temporal chemical variations for a given depth profile are suspect, prior to adequate measurements of a given analyte's spatial variability in the immediate area of sampling. A method is presented for calculating the number of samples of a given stratigraphic layer necessary to achieve the required precision about the mean pH in a vertical ice profile.
Modelling the Effect of Climatic Warming on the Hofsjökull Ice Cap, Central Iceland
Authors: Jóhannesson Tómas
Published: May 2018

A time-dependent cylindrically symmetric computer model of the Hofsjökull ice cap, Central Iceland, has been defined in order to investigate the time-scale of possible glacier variations. The model is forced with a set of hypothetical mass balance scenarios, chosen to span the range of plausible mass balance variations of Hofsjökull caused by greenhouse warming. For each mass balance scenario the model computes the change in the volume of the ice cap and the associated time-dependent runoff variations. The response time of the ice cap is found to be of the order of 50-100 years,˜when mass balance - elevation feedback is taken into account. The response time increases with the size of the climatic perturbation. The model indicates that increased runoff from the area now covered by Hofsjökull, caused by a possible greenhouse warming, will be significant for 100-200 years after the climate starts to change. A mass balance scenario produced by raising the equilibrium line by 200 m (corresponding roughly to a warming of 1-1.5°C) over a 50-year period leads to a maximum runoff increase of about 40 m3s−1 occurring 50 years after the equilibrium line starts to rise. This amounts to approximately 50 % of the total precipitation that falls on Hofsjökull at present and approximately 25 % of the present discharge of rivers that issue from Hofsjökull and the neighbouring area.
Base Catchment Modeling in Urban Runoff Simulation
Authors: Lyngfelt Sven
Published: May 2018

The selection of numerical model and the transformation of catchment data into ‘input data’ are two fundamental problems in urban runoff simulation. They are discussed from a general point of view. A numerical solution method for the kinematic wave equations is proposed for base catchment modeling. In connection to this solution a methodology for the generation of input data representing the individual base catchment is presented.
Hydrology of Rivers of the Cryolithic Zone in the U.S.S.R.
Authors: Sokolov B. L.
Published: May 2018

The investigations provided the possibility to obtain a considerably better knowledge of the water balance of river basins and the water exchange between rivers and aquifers. The hydrological role of seasonal glaciation under the conditions of cold climate and permafrost has been studied and a methodological base for field studies of the specific phenomena and processes developed.
Influence of Rainfall Movement on Peak Discharge in Urban Sewers
Authors: Andersen Henrik Sandgård , Jacobsen Per , Harremoës Poul
Published: May 2018

Calculations have been made in order to evaluate the effect of rainfall movement on peak discharge. The 25 extreme events have been selected from a long historical rain series from a single rain gauge. The rains have been simulated to move with the recorded speed and direction of the rain across an artificial, elongated catchment positioned in 8 different directions. A real catchment layout was also investigated. The paper investigates the effect of longitudinal movement. Laterally, the rain is assumed to be uniformly distributed.

Calculations were made with the MOUSE-program, modelling runoff using the dynamic wave approach. An additional program was developed to simulate the moving rain input. Peak discharge in the sewer system with and without rainfall movement was treated statistically in terms of return period and compared.

The movement of the rain is not important from a statistical point of view (up to 5 %), but for individual events the effect may be significant (at least up to 19 %). The result is restricted to the effect of longitudinal variation in time and space. The effect of variation lateral to the movement may be much bigger, increasing with size of catchment.

The artificial catchment with flow direction towards NE gives the greatest increase in the Qmax and vice versa with the catchment orientated towards SW. This is due to wind direction from the SW being the most frequent in Denmark. The effect of rainfall movement is smaller for the real catchment with sewers in many different directions.
Conceptual Modelling of Water Loss on Flood Plains and its Application to River Yamuna Upstream of Delhi
Authors: Asger Nielsen S. , Refsgaard J. C. , Mathur V.K.
Published: May 2018

A water loss module for the river modelling system MIKE 11 has been developed to account for water losses due to retention and infiltration on flood plains. MIKE 11 including the water loss module has been calibrated and tested on data from the Yamuna river, India. The inclusion of the water loss module has improved the water level forecasts at Delhi to a large extent.
Soil and Stream Water Chemistry During Spring Snowmelt
Authors: Hendershot W. H. , Mendes L. , Lalande H. , Courchesne F. , Savoie S.
Published: May 2018

In order to determine how water flowpath controls stream chemistry, we studied both soil and stream water during spring snowmelt, 1985. Soil solution concentrations of base cations were relatively constant over time indicating that cation exchange was controlling cation concentrations. Similarly SO4 adsorption-desorption or precipitation-dissolution reactions with the matrix were controlling its concentrations. On the other hand, NO3 appeared to be controlled by uptake by plants or microorganisms or by denitrification since their concentrations in the soil fell abruptly as snowmelt proceeded. Dissolved Al and pH varied vertically in the soil profile and their pattern in the stream indicated clearly the importance of water flowpath on stream chemistry. Although Al increased as pH decreased, the relationship does not appear to be controlled by gibbsite. The best fit of calculated dissolved inorganic Al was obtained using AlOHSO4 with a solubility less than that of pure crystalline jurbanite.
Seasonal Variations in Suspended Sediment Yield in the Baltic Sea Drainage Basin
Authors: Lajczak Adam , Jansson Margareta B.
Published: May 2018

The aim of this article is to describe the seasonal fluctuations of suspended sediment yield in the Baltic Sea drainage basin and to quantify the monthly inflow of suspended sediment to the Baltic. The seasonal fluctuations of sediment yield are controlled by rain and snow amounts and by ground thawing. The rhythm of the sediment yield shows great differences between mountainous and lowlandic areas, and also between areas with oceanic and continental climates. The seasonal fluctuations of the total suspended sediment inflow to the different sub-areas of the Baltic Sea imitate the seasonal regimes of the sediment yield within the different catchments. Most of the suspended load is supplied to the sea during snow melting. For the Baltic as a whole, the inflow reaches a maximum value in April (22.2% of the annual inflow) and a minimum value in January (3.7% of the annual inflow).
Hydrological and Environmental Effects of Agricultural and Urban Activities in a Small Swedish River Basin
Authors: Hogland William
Published: May 2018

The environmental influence of forestry, agriculture and urban activities on the hydrological conditions in a small river basin in southern Sweden and the effects on the river water quality are analyzed and quantified on different time scales. The emphasis is on the river flow fluctuations and the transport of nitrogen to the sea. Different measures for decreasing the load of nutrients are discussed. It is shown that if wetlands are re-established in rural areas and techniques for water treatment are introduced, it is possible to reduce the nitrogen transport to the sea by 60%. However, this reduction would have little influence on improving the nutrient status of coastal waters.
Annual Variability in Summer Evapotranspiration and Water Balance at a Subarctic Forest Site
Authors: Lafleur Peter M.
Published: May 2018

Evapotranspiration (ET) and precipitation were measured during five summers (1989-1993 inclusive) at a subarctic forest site near Churchill, Manitoba, Canada. Mean daily ET varied from 2.14-3.18 mm d−1 during the five summers, while mean daily precipitation (P) ranged from 1.46-3.15 mm d−1. Yearly variability in summer ET was most influenced by availability of surface moisture, then by atmospheric conditions (i.e. temperature), and least of all by net radiation. In four of the five years total summer ET exceeded P resulting in significant soil water deficits and in the other year summer ET and P were similar in magnitude.

The use of equilibrium evaporation (EE) as a predictor of ET was explored. Separate relationships between ET and EE were computed for all five years. Three statistically dissimilar groups of equations were found: 1989/1990, 1991/ 1992, and 1993. A single regression equation describing all years is presented.
Simulation of Discharge using Different Methods of Meteorological Data Distribution, Basin Discretization and Snow Modelling
Authors: Braun L.N. , Brun E. , Durand Y. , Martin E. , Tourasse P.
Published: May 2018

This contribution investigates the performance of discharge modelling when proceeding from rather simple methods of snowmelt modelling to more sophisticated, distributed approaches. In all cases, the conceptual HBV runoff model is used for the calculation of discharge from the Romanche River basin (French Alps, area = 224 km2,12.5 % glacierized), feeding the Lac de Chambon reservoir used for hydroelectric power production. The results show that when using temperature-index approaches, no gain in performance is achieved by the more detailed basin discretization. However, a clear gain is observed when the precipitation and air temperature distribution of the elaborate meteorological data analysis system “SAFRAN” is used as input to the conceptual snow model. When using the original version of the physically-based “CROCUS” snow model, a strong overestimation of discharge resulted during the main snow melt season. A revised SAFRAN model version employing a new radiation routine, and the use of a realistic distribution of snow cover in each sub-unit considered by CROCUS resulted in a discharge simulation performance which is as good as the one from the calibrated conceptual models. Sensitivity analyses of the various snow models investigating the hydrological consequences of climatic change show surprisingly similar results.
Regional Flood Relationships by Nonparametric Regression
Authors: Gringras D. , Alvo M. , Adamowski K.
Published: May 2018

Since some theoretical assumptions needed in linear regression are not always fulfilled in practical applications, nonparametric regression was investigated as an alternative method in regional flood relationship development. Simulation studies were developed to compare the bias, the variance and the root-mean-square-errors of nonparametric and parametric regressions. It was concluded that when an appropriate parametric model can be determined, parametric regression is preferred over nonparametric regression. However, where an appropriate model cannot be determined, nonparametric regression is preferred. It was found that both linear regression and nonparametric regression gave very similar regional relationships for annual maximum floods from New Brunswick, Canada. It was also found that nonparametric regression can be useful as a screening tool able to detect data deficient relationships.
Frost Heave due to Ice Lens Formation in Freezing Soils
Authors: Sheng D. , Axelsson K. , Knutsson S.
Published: May 2018

A frost heave model which simulates formation of ice lenses is developed for saturated salt-free soils. Quasi-steady state heat and mass flow is considered. Special attention is paid to the transmitted zone, i.e. the frozen fringe. The permeability of the frozen fringe is assumed to vary exponentially as a function of temperature. The rates of water flow in the frozen fringe and in the unfrozen soil are assumed to be constant in space but vary with time. The pore water pressure in the frozen fringe is integrated from the Darcy law. The ice pressure in the frozen fringe is determined by the generalized Clapeyron equation. A new ice lens is assumed to form in the frozen fringe when and where the effective stress approaches zero. The neutral stress is determined as a simple function of the unfrozen water content and porosity. The model is implemented on an personal computer. The simulated heave amounts and heaving rates are compared with experimental data, which shows that the model generally gives reasonable estimation.
Reconstructed Runoff from the High Arctic Basin Bayelva based on Mass-Balance Measurements
Authors: Hagen Jon Ove , Lefauconnier Bernard
Published: May 2018

The river Bayelva drains a catchment area of 31.5 km2 in the Kongsfjord area close to the research station Ny-Ålesund (79° N 12°E) on the northwest coast of Spitsbergen. The basin is 54% glacierized, and the studied glacier Austre Brøggerbreen is 6.1 km2 and constitutes 20% of the basin. On this glacier a mass-balance monitoring program including accumulation and ablation measurements has been carried out continuously since 1967. The winter snow accumulation shows very stable conditions with a mean accumulation of 0.71 ± 0.16 m/year in water equivalent. The runoff from the glacier in an equilibrium year should thus be 4.33 × 106 m3. The mean ablation on this glacier has been greater than the winter accumulation, 1.14 ± 0.26 m/year of water equivalent, which results in an annual runoff of 6.95 × 106 m3. That is more than 60% higher runoff from the glacier than in a year with zero net balance. The result is a mean net balance of – 0.42 m/year, or an annual runoff from the glacier due to the retreat of the glacier of 2.6 × 106 m3.

In Bayelva, a runoff station was operated from 1974-1978. In 1988 this basin was chosen as a hydrological research site, and the runoff measurements were restarted and a permanent station for water discharge and sediment transport measurements was constructed in the river. This basin is the only one in Svalbard with some years of hydrological data. The water balance discussion shows that there is good agreement between the measured runoff in the river Bayelva and the potential runoff calculated from the mass-balance measurements on Brøggerbreen. On the basis of this correlation the total annual runoff was reconstructed from the whole period of mass-balance data from 1967-1991. The runoff from the whole basin has been 30% higher than in years with an equilibrium mass-balance on the glacier.
Estimating the Uncertainty in Spatial Estimates of Areal Snow Water Equivalent
Authors: Carroll Steven S.
Published: May 2018

With the increased demand for water in the United States, particularly in the West, it is essential that water resources be accurately monitored. Consequently, the National Weather Service (NWS) maintains a set of conceptual, continuous, hydrologic simulation models used to generate extended streamflow predictions, water supply outlooks, and flood forecasts. A vital component of the hydrologic simulation models is a snow accumulation and ablation model that uses observed temperature and precipitation date to simulate snow cover conditions. The simulated model states are updated throughout the snow season using snow water equivalent estimates (estimates of the water content of snowpack) obtained from airborne and ground-based snow water equivalent data. The National Weather Service has developed a spatial geostatistical model to estimate the areal snow water equivalent in a river basin. The estimates, which are obtained for river basins throughout the West, are used to update the snow model. To facilitate accurate updating of the simulated snow water equivalent estimates generated by the snow model, it is necessary to incorporate measures of uncertainty of the areal snow water equivalent estimates. In this research, we derive the expression for the mean-squared prediction error of the areal snow water equivalent estimate and illustrate the methodology with an example from the Upper Colorado River basin.
Nested Threshold Autoregressive (NeTAR) Models for Studying Sources of Nonlinearity in Streamflows
Authors: Astatkie T. , Watt W.E. , Watts D.G.
Published: May 2018

Historical development of nonlinear stochastic modeling of streamflows is discussed. Physical considerations and graphical investigations of daily streamflows revealed that air temperature and state of basin storage are the most important sources of nonlinearity in catchments with seasonal snow accumulation. The average temperature for the preceding three days, and the flow one or two days earlier were adequate proxies for the temperature and storage conditions of a catchment. The Nested Threshold Autoregressive (NeTAR) model, which considers these sources of nonlinearity simultaneously, was applied to two years of daily flows of the Oldman River near Brocket in Alberta, Canada. A third year of daily data was used for validating the model. The final NeTAR model provided useful insights into the dynamics of this streamflow system.
Modelling Influence of River Regulation on Runoff to the Gulf of Bothnia
Authors: Carlsson Bengt , Sanner Håkan
Published: May 2018

Runoff from a land area of approximately 490,000 km2 enters the Gulf of Bothnia. This runoff is of essential importance for the flushing of the Gulf. A change in the volume of runoff effects the residence time. There are many natural as well as man made changes in the runoff, both in the form of long-term changes over many years and those occurring within one year. The most significant man made changes come from hydropower regulation. This report describes the effect on runoff from the development of the hydropower plants in Sweden and Finland by means of comparing recorded regulated runoff and simulated natural runoff. A recent time period, 1980-91, and a time period before regulation, 1925-36, were simulated. The monthly magnitudes of the redistributed flows were found to be on average 1,700 m3/s. The maximum redistributed monthly flow in May – June reached 5,000-6,000 m3/s.
Evaporation from a Small Lake in the Continental Arctic using Multiple Methods
Authors: Gibson J. J. , Prowse T.D. , Edwards T. W. D.
Published: May 2018

Daily evaporation from a small lake in the continental Low Arctic of Canada was examined using three independent experimental methods and a simplified combination model. Mean daily lake evaporation (± variability between methods) was estimated to be 3.2+0.3−0.3 mm d−1 and 2.5+0.6−0.3 mmd−1 over fifty-day periods during two consecutive summers. Based on these results and additional class-A pan data, total thaw-season evaporation estimates of 220 mm to 320 mm were obtained, equivalent to 70% to 100% of annual precipitation. These values are 15 to 70% higher than predicted by standard evaporation maps of Canada. Our results indicate that the Priestley-Taylor model provides a good approximation of the Bowen ratio energy balance model in this setting. As expected, estimates based on mass balance are highly sensitive to uncertainty in measurement of lake inflow and outflow.
The Effect of River-Ice Break-Up on Suspended Sediment and Select Trace-Element Fluxes
Authors: Milburn David , Prowse Terry D.
Published: May 2018

Ice break-up on northern rivers presents a unique research challenge because of its dynamic nature and complexity of physical, chemical and biological processes. Rapidly moving ice, ice jamming, flood levels, and enhanced flow velocities can produce significant sediment transport and trace-element fluxes. Systematic sampling for these parameters, however, is rarely conducted because of logistical difficulties. This paper discusses the magnitude and relative significance of sediment and trace-element fluxes during break-up of the Liard River in northern Canada. Historical data for the open-water and stable ice-covered periods are compared to that measured during the 1987 and 1993 break-up events. Analysis reveals that a break-up pulse occurs during this period that if not accounted, can lead to significant underestimation of suspended sediment and trace-element fluxes. More generally, any estimates of annual sediment or trace-elements for northern rivers that do not include data for the critical break-up period must be regarded as being conservative.
Evapotranspiration from a Wetland Complex on the Arctic Coastal Plain of Alaska
Authors: Mendez Johnny , Hinzman Larry D. , Kane Douglas L.
Published: May 2018

Evapotranspiration (ET) from an arctic coastal wetland near Prudhoe Bay, Alaska, was studied during the summers between 1994 and 1996. The purpose of the study was to compare different ET models and to gain a better understanding of evapotranspiration from arctic wetlands. The models used to obtain ET from the watershed were the Bowen ratio energy balance (BREB), Priestley-Taylor (PT), Penman-Monteith (PM), Penman Combination (PC), energy balance (EB), water balance (WB), and WB based on Time Domain Reflectometry (TDR). For one of the ponds, evaporation determined by the EB, PT, PC, BREB, WB, and the aerodynamic (AD) methods were also compared. ET during the summer snow-free period for the watershed averaged 1.45 mm/day obtained via the BREB model. Evaporation from all ponds after spring snowmelt averaged 3.11 mm/day (obtained via the WB). Evaporation rate from ponds was on average twice that of the tundra as a whole. Latent heat flux was the dominant energy sink in wetlands and ponds, whereas sensible heat flux dominated in the drier upland area. The PT and PM models compared well to the BREB (used as the standard of comparison for ET) for 1994 and 1995, once parameters were properly calibrated using 1996 data. The BREB compared well with independent values of ET from the water balance and eddy correlation methods. For the pond, the EB, BREB, WB, PT, and AD methods gave very similar evaporation results for the summer.
Application of Georadar for Snow Cover Surveying
Authors: Sand Knut , Bruland Oddbjørn
Published: May 2018

A commercial georadar was tested over in a Norwegian catchment in order to determine the areal mean snow water equivalent (SWE) and its spatial distribution. The methodology used and the results obtained are described. The radar was run along a number of selected snow courses, and the results were compared with manual measurements of snow depth and density. It was found that georadar is able to give accurate estimates of mean SWE with much less time spent in the field compared to conventional measurements. Georadar also gave a good description of the areal distribution of SWE.