bluuebunny/crossref_metadata_2025_split huggingface dataset:
Forecasting high waters at Venice Lagoon using chaotic time series analysis and nonlinear neural networks
Authors: Zaldívar J. M. , Gutiérrez E. , Galván I. M. , Strozzi F. , Tomasin A. 
Published: May 2018

Time series analysis using nonlinear dynamics systems theory and multilayer neural networks models have been applied to the time sequence of water level data recorded every hour at ‘Punta della Salute’ from Venice Lagoon during the years 1980–1994. The first method is based on the reconstruction of the state space attractor using time delay embedding vectors and on the characterisation of invariant properties which define its dynamics. The results suggest the existence of a low dimensional chaotic attractor with a Lyapunov dimension, DL, of around 6.6 and a predictability between 8 and 13 hours ahead. Furthermore, once the attractor has been reconstructed it is possible to make predictions by mapping local-neighbourhood to local-neighbourhood in the reconstructed phase space. To compare the prediction results with another nonlinear method, two nonlinear autoregressive models (NAR) based on multilayer feedforward neural networks have been developed.
From the study, it can be observed that nonlinear forecasting produces adequate results for the ‘normal’ dynamic behaviour of the water level of Venice Lagoon, outperforming linear algorithms, however, both methods fail to forecast the ‘high water’ phenomenon more than 2–3 hours ahead.
Bayesian-based pipe failure model
Authors: Watson T. G. , Christian C. D. , Mason A. J. , Smith M. H. , Meyer R. 
Published: May 2018

The efficient long term management of large-scale public funded assets is an area of growing importance. Ageing infrastructure, growth and limited capital all result in the need for a more robust and rigorous methodology to prioritise rehabilitation and renewal decisions and, as importantly, to forecast future expenditure requirements. The overall objective of this research is to develop a Bayesian-based decision support system that will facilitate the identification of efficient asset management policies. The Bayesian approach enables us to formally incorporate, express and update our uncertainty when determining such policies. This is particularly relevant for water utilities that have incomplete or unreliable historical failure data sets and, as a consequence, rely heavily on past engineering experience.
An object oriented discrete event simulation has been developed to analyse existing maintenance policies, test the Bayesian methodology and to develop and identify improved maintenance policies. This paper focuses on the areas of research relating to the long term management of water distribution systems and, in particular, will present: (1) an overview of the Bayesian approach, (2) development and initial results for an object oriented discrete event simulation and (3) proposed future research and development.
THE PARAMETRIC APPROACH TO WATERSHED MODELING
Authors: SNYDER WILLARD M. 
Published: May 2018

The parametric approach to watershed modeling is shown to lie between the stochastic and deterministic approaches. Essentially, the parametric approach attempts to find functional relationships between numerically defined hydrologic and physical characteristics of a drainage area.
Successful parametric modeling requires progression through sequential stages of data processing, model formulation, optimization of parameters, examination of results, association of characteristics, and conversion to prediction procedures. Selected examples of the various stages are discussed.
STATISTICAL INTERPRETATION OF HYDROMETEOROLOGICAL EXTREME VALUES
Authors: SAMUELSSON B. 
Published: May 2018

The application of Jenkinson's method to extremal distributions for low probability annual extremes of rainfall and stream flow is studied and discussed.
A statistical method devised by Jenkinson has been examined and compared with other methods of fitting extreme value distributions to observed data. The Jenkinson method, being strictly objective, has the particular advantage of taking into account the extreme part of the extreme value distribution. The author shows, by applying the Jenkinson method to extreme values which significantly belong to several different kinds of frequency distributions, that this method could be applied as a standard one. Finally, the author indicates the possibility of using the Jenkinson method to extrapolate statistical characteristics from a series of statistically unstable short-term data.
Snowmelt Estimated from Energy Budget Studies
Authors: Bengtsson Lars 
Published: May 2018

The snowmelt at a point is estimated through a simplified energy budget. From the energy equation a degree-day method is derived. The rate of snowmelt is found as a constant multiplied by the temperature excess over an equilibrium temperature which depends on solar radiation.
The snowmelt events in Kiruna (3 years) and Luleå (4 years) are analysed utilizing energy balance computations and the degree-day method. First observed and calculated day when the ground was free of snow is for all seven years in good agreement. The rate of snowmelt calculated by the proposed degree-day method is almost identical to the rate found from energy balance computations. Snowmelt rates estimated by a simple degree-day method using a constant equilibrium temperature are too fast in the beginning and too slow at the end of the melting season.
Evaporation from a Snow Cover
Authors: Bengtsson Lars 
Published: May 2018

Possible evaporation rates from a snow surface with respect to available energy and vapour pressure deficit in the air are discussed. In literature reported measurements and measurements carried out at the University of Luleå are analysed. It is found that for northern areas the total amount of evaporation during the whole snow covered season amounts only to 10–20 mm.
Different formulas for estimating the evaporation from a snow surface are discussed. It is stressed that for forecasting purposes the aerodynamic formula and the profile method should be used only together with energy balance computations. The air density stratification reduces the evaporation rate considerably. A formula for the reduced evaporation rate is suggested. Finally, evaporation is analysed as a transient process, and possibilities of developing more soundly based evaporation models are discussed.
Seasonal Fluctuations of Physical and Chemical Parameters of a Weir Basin in a Regulated West Norwegian River
Authors: Baekken T. , Fjellheim A. , Larsen R. 
Published: May 2018

Both before (1967-69) and after (1976-78) the regulation of the river Ekso in western Norway, physical and chemical analyses were made of the river water. After the regulation water samples for chemical analyses were taken at the inlet and outlet of a weir basin 375 m long which had recently been built to maintain the previous water level.
The reduced water discharges and the increased water temperatures which followed the regulation presumably increased the amount and the quality of food available to detritusfeeding animals.
The O2 content of the water was slightly reduced after the regulation. The pH was in the same range. Specific conductance (H20) and the concentrations of major ions before the regulation (Ca2+, Cl− NO3−-N, PO43−-P) and after the regulation (Ca2+, Mg2+, Cl−, SO42−, N03−-N. NH4+-N, PO43−-P) were also in the same range, but a distinct seasonal variation appeared after the regulation.
These variations were thought to have three main reasons: 1) water discharge, 2) biological production, 3) nonspecified physicochemical relationships.
Ionic fluxes through the weir basin were highest during the autumn. Only small differences were found between the inlet and outlet of the weir basin.
Regression analyses based on the concentrations of major ions and water discharge after the regulation were made separatly for the summer and the winter season. H20 and SO42−-concentrations were not correlated to water discharge, Cl−-concentrations were positively correlated, whereas Ca2+ showed a negative correlation. Mg2+ and NO3−-N were not correlated to water discharge during the summer season, but showed a significant negative correlation during the winter.
Hydrological Data-Model Work in Greenland
Authors: Thomsen Th. , Jørgensen G.H. 
Published: May 2018

The hydrological studies of the Greenland technical Organization in Greenland are being followed up at Copenhagen by hydrological data work as well as hydrological model-simulation.
The hydrological regions vary greatly in Greenland, depending on whether the drainage basin is influenced by ablation runoff. To describe a runoff time series from these areas, a hydrological model calibration is made, followed by a simulation. In drainage basins influenced by rain and snow only, a slightly modified version of the precipitation runoff model (NAM) is applied. The parameter transfer for the determination of model input is found by intensive data analysis work here between Nuuk and Kangerluarsunnguup Tasersua (KANG) for temperature and precipitation along with detailed investigations in the basin. This is to ensure that a too short calibration period in connection with the adaption of a hydrological model to the basin data is balanced in the manner that these adapt the hydrological model, and not vice versa.
In drainage basins also influenced by ablation runoff it is not possible to use a traditional precipitation runoff model but a hydrological ablation model has been developed in cooperation with The Geological Survey of Greenland. The hydrological ablation model describes the transfer of the temperature after heating and cooling factors as well as snow mobility on the ice, melting density criteria, refreezing etc. The model has been applied to the hydrological basin of Paakitsup Akuliarusersua (PAKI) at Ilulissat where 90% of the drainage basin is covered by the Ice cap.
Data evaluation work prior to hydrological model calibration thus allows for a higher degree of simulation reliability.
Nitrogen Balance in Fertilizer Application and Plant Production
Authors: Aslyng H.C. 
Published: May 2018

The investigation comprises several agricultural crops, a Karup locality (56°16' N, 9°9' E) with an average annual precipitation of 775 mm and coarse sand (soil 1), and a Tåstrup locality (55°40' N, 12°18' E) with an average precipitation of 600 mm and clay with fine sand (soil 6). Soils 1 and 6 have 5 and 8 t N/ha in organic matter, respectively, to 50 cm soil depth and an average effective root zone capacity for available water of 60 and 170 mm.
Data for soils 1 and 6 in kg N/ha as average (with great annual variation) were for spring barley found to be around the following: mineralization 75 and 135, denitrification 5 and 20, uptake in harvest 105 and 155, leaching 65 and 40, and spring storage 10 and 60, respectively. Wintering and late growing crops reduce the leaching by around 20 kg N/ha. The nitrogen leaching from sandy soil is clearly influenced by variation in fertilization whereas the leaching from clay soil is only a little affected.
Infiltration in Unsaturated Frozen Soil
Authors: Engelmark Helén 
Published: May 2018

A one-dimensional mathematical model is used to simulate the process of snow-melt infiltration in unsaturated frozen silt. Hydraulic and thermal parameters are mainly based on data given in the literature.
Field observations in a watershed (of area 1.8 km2) are compared with simulated data and consequences on snow melt run-off are discussed.
Estimation of Combined Sewer Overflow Discharge From the City of Malmö
Authors: Hogland W. , Berndtsson R. , Larson M. 
Published: May 2018

The function of combined sewer overflows (CSO) from both a quantitative and a qualitative point of view is often little known in the Nordic communities. Since large pollution loads are discharged from urban areas by CSO, it is important to consider this problem when rehabilitation plans are established.
A study aiming at the estimation of yearly volumes of CSO and yearly quantities of pollution load from CSO has been carried out in the city of Malmö, Sweden. The CSO discharges into four different types of receiving waters: the channel, the harbour, the Sege River and the Öresund. Registration of frequency, duration and water volume was made at about 30 weirs at different time periods.
Storm Water Management Model (SWMM) was used both to simulate single SCO events and for continuous simulation. The results from these simulations were compared with actual measurements.
The total pollution load was estimated from mean concentration of pollutants from more than 100 samples taken at different weirs and CSO events.
Through analysis of the occurrence of CSO in time and space, a program of priorities for the rehabilitation of the CSO-system was established.
Temperature and Flow Conditions in a Reservoir with a Submerged Outlet Tunnel During the Winter Period
Authors: Tvede Arve M. 
Published: May 2018

The reservoir Sundsbarmvatn, in Southern Norway, is used for electricity production from November to May. Sundsbarmvatn has two main basins. Water from the upper basin, Mannerosfjorden, flows into the lower basin, Gullnesfjorden. The two basins are separated by a narrow sound with a sill. The regulation interval for Sundsbarmvatn is 612-574 m a.s.l., but the sill prevents Mannerosfjorden from being lowered below 580 m a.s.l. The water intake in Gullnesfjorden is 571 m a.s.l.
The water temperature conditions has been studied during two winters when the reservoir water was released. This study shows that a marked thermocline was gradually developed at the depth of withdrawal in Gullnesfjorden. In the epilimnion layer the temperature is gradually lowered through the winter, but in the hypolimnion layer the temperature seems to stay constant through the winter. In Mannerosfjorden, however, we find no clear thermocline at the end of the winter. The remaining water was relatively warm with temperatures mainly above 3 °C.
The sill between the two basins seems to have a strong influence on which depth the water is flowing out of Mannerosfjorden and hence on the temperature and circulation pattern in Gullnesfjorden. At the end of the winter season this flow is strengthening and initiates a homogeneous flow layer in Gullnesfjorden. This layer is dipping downwards towards the outlet tunnel. For this reason the temperature of the water leaving the power station is 0.4-1.2 °C colder than the hypolimnion temperature in the reservoir at the tunnel depth.
Variations of 87Sr/86Sr in Water from Streams Discharging into the Bothnian Bay, Baltic Sea
Authors: Åberg F. , Wickman F. E. 
Published: May 2018

The 87Sr/86Sr ratio in 53 water samples were analysed, 26 from streams in Sweden, 22 from streams in Finland and 5 from the Bothnian Bay itself. The brackish seawater of the bay had the isotope ratio 0.7095, while the stream-water samples varied from 0.7177 to 0.7366. The weighted average isotope ratio with respect to discharges was 0.7313, this high ratio reflecting the dominance of granitic Proterozoic rocks in the region.
For streams with an average discharge between 1-40 m3/s the isotope ratio was within the interval 0.718-0.736, while those with discharges &gt;150 m3/s defined an interval of 0.728-0.735. The variations in isotope ratios are discussed with respect to bedrock geology of drainage basins, possible effects of seawater inundations and Postglacial uplift combined with the complex history of the Baltic Sea.
Snowmelt Runoff in Suburban Environments
Authors: Buttle J. M. , Xu F. 
Published: May 2018

While snowmelt and rain-on-snow events have received considerable attention in rural watersheds they have been largely ignored in urban hydrology, despite the fact that they may result in severe flooding. The runoff responses of two subcatchments of a small drainage basin in Peterborough, Ontario were investigated for the spring snowmelts of 1984 and 1985. One of the catchments has undergone substantial suburbanization, while the other is largely in rural land use. Measurements in each catchment included snowpack water-equivalent depths, snowmelt and precipitation, fluxes of net radiation over snowpacks, infiltration capacities of pervious surface types, and streamflow.
Suburban development appears to have produced substantial increases in spring quickflow yields from the entire basin. A comparison of the responses of the two subcatchments reveals that the suburban catchment reacts more rapidly to snowmelt and rain-on-snow inputs and generates larger initial quickflow response ratios than the rural basin as a result of the microclimatic, pedologic and hydraulic characteristics of built-up areas. However, the dynamic behaviour of the runoff contributing area of the rural catchment results in a marked increase in its quickflow yield as melt progresses. The results suggest that the distinct nature of the processes of snow accumulation, melt and runoff generation in built-up areas should be considered when modelling suburban snowmelt runoff.
The Potential of Real Time Control to reduce Combined Sewer Overflow
Authors: Broks K. , Geenen A. , Nelen F. , Jacobsen P. 
Published: May 2018

The potential of Real Time Control (RTC) to reduce the overflow volume from a combined sewer system has been investigated for a catchment in Copenhagen, named Strandvaenget. The results have been compared with the alternative of increasing the storage volume of the system. The RTC strategy has been derived using a mathematical optimization and a rule based method. As the only objective is to reduce the Combined Sewer Overflow (CSO), the developed rule based control algorithm can achieve almost the same results as the optimization method.
From the results of time series calculations, it can be concluded that the introduction of RTC appears very promising when the mean yearly CSO volume has to be reduced. In this research, the potential of RTC is investigated for an increasing amount of storage volume and for an increasing demand for reduction of CSO volume.
Temperature and Salt Content Regimes in Three Shallow Ice-Covered lakes
Authors: Malm J. , Terzhevik A. , Bengtsson L. , Boyarinov P. , Glinsky A. , Palshin N. , Petrov M. 
Published: May 2018

A field study on the temperature, salt content, and density regime in three shallow ice-covered Karelian lakes is presented. The measurements show that the heat content increases during the whole ice-covered period. At ice formation a weak stable stratification existed in the lakes, with average temperatures about 1°C. Thereafter, the stability of the stratification gradually increased, mainly due to pronounced temperature increases in the bottom layers. In mid-winter the bottom layer in the deep parts of the lakes obtained temperatures above 4°C. The density stratification in these layers was stable, however, due to higher salt contents (increasing continuously during the winter) in the vicinity of the bottom. The horizontal variations in temperature and salt content were very small, and both parameters can be considered to be horizontally homogeneous.
Under-ice convection was developed in two of the three investigated lakes during the second half of April, when heating due to penetrating solar radiation became apparent. Although no under-ice convection in the conventional sense occurred in the third lake (Uros), interior convection developed when the temperature exceeded 4°C (the temperature of maximum density) there. The absence of under-ice convection in Lake Uros is most likely due to the higher vertical temperature gradient in the lake before spring heating and smaller extinction coefficient than in the other two lakes.
Characteristics of Turbulent Cross and Alongshore Momentum Exchanges During a Thermal Bar Episode in lake Ontario
Authors: Gbah Messon B. , Murthy Raj C. 
Published: May 2018

Time series flow data obtained during the thermal bar episode of 17 April to 24 May 1990 in Lake Ontario are analyzed to provide a kinematic description of the coastal flow and cross-margin exchange characteristics. A thermal bar is a shore-parallel front which separates descending waters at or near the fresh water temperature of maximum density (4°C) during Spring and Fall seasons. Thermal bars are important because of their influence mixing, cross-shore exchanges, and the variability of biotic factors in coastal zones.
The analysis shows that cross-frontal exchange coefficients, Ky, are nearly constant and consistently smaller than along-frontal counterparts, Kx. Moreover, these exchange coefficients are several orders of magnitude smaller than typical coastal and oceanic values in the absence of the bar. The turbulent kinetic energy represents less than 6% of the total kinetic energy in the flow. These results suggest that small-scale horizontal fluctuations and cross-frontal turbulent momentum exchanges are severely inhibited in the spring during the thermal bar.
The Effects of Frozen Soils on Groundwater Recharge and Discharge in Granitic Rock Terrane of the Canadian Shield
Authors: Thorne G. A. , Laporte J. , Clarke D. 
Published: May 2018

Hydrologic measurements on groundwater flow systems of the Canadian Shield during the winter period provide insight into groundwater dynamics and can support conclusions based on measurements of the more “active” spring-to-fall, open-water period. To illustrate this, we present the results of detailed and continuous year-round measurements of parameters such as groundwater levels, air/soil temperatures, soil heat flux and soil moisture content which were made in upland recharge and wetland discharge areas of a local groundwater flow system in granitic terrane of the Canadian Shield.
Recharge to the groundwater flow system in the rocks of the study area occurs as rain or snowmelt waters infiltrate exposed vertical and/or sub-horizontal soil-infilled fractures in outcrops of the upland area. During winter, soils in the fractures of the recharge area do not normally freeze below 0.5 m depth and shallow (5-20 cm depth) soil temperatures are most often only 1-2°C below freezing. During the spring melt period the temperature of these frozen soils remains near 0°C for several weeks as the pore ice absorbs thermal energy necessary for the phase transition from ice to water. However, despite these soils being completely or partially frozen, infiltration and recharge to the groundwater flow system in the rock occurs as shown by large and rapid rises in watertable and piezometric levels.
In the groundwater discharge area of this flow system, near-surface soil temperatures (5 cm depth) reached minimums of about -12°C during the 1996 winter and freezing soils extended downward to more than 75 cm depth. During the spring melt period, as meltwaters add heat to the substrate, these shallow soil temperatures also, rise to near 0°C and remain frozen for several weeks as latent heat of fusion of ice becomes a factor. However, during the spring melt period, while ice covers ithe surface and soils are still frozen in the discharge area, groundwater level rises are recorded in both the overburden and bedrock of the discharge area. This is attributed to hydraulic pressure being rapidly transmitted to the discharge area through the low storativity groundwater flow system in the rock from the large waterlevel increases occurring in the rock of the adjacent upland recharge area.