bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of Three Gorges Reservoir (TGR) water storage in June 2003 on Yangtze River sediment entering the estuary
Authors: Chu Z. X. , Zhai S. K.
Published: April 2010

Abstract. The world-greatest water conservancy project, Three Gorges Reservoir (TGR), stored water for the first time in June 2003, which provides an excellent opportunity to examine its effects on the sediment entering the Yangtze River estuary. A daily record dataset of water discharge and suspended sediment concentration (SSC) of the Yangtze River measured at Datong (the controlling hydrological gauging station into the estuary) from May 15 to July of 2003 spanning the water storage, together with a monthly record dataset of runoff, sediment load and SSC measured at Datong from 1953 to 2003, were used to examine the effects of the TGR water storage in June 2003 on the Yangtze River sediment entering the estuary. The results show that the unnaturally clearer water due to the TGR sedimentation resulted by the water storage in June 2003 brought the Yangtze River markedly decreased SSC and sediment load entering the estuary both during the TGR water storage and in the second half year of 2003. The Yangtze River water and sediment discharges into the estuary from 15 May to 15 July in 2003 spanning the TGR water storage clearly indicated three phases: (1) pre-water storage of the TGR from 15 May to 25 May, during this phase, SSC and sediment load increased with water discharge increasing; (2) water storage of the TGR from 25 May to 10 June (including the preparation phase from 25 May to 31 May), during this phase, SSC and sediment load decreased dramatically with water discharge decreasing; and (3) post-water storage of the TGR, at the beginning, SSC, sediment load and water discharge basically remained at a relatively low value until the end of June, and since then, SSC and sediment load increased gradually with water discharge increasing. In addition, the real total sediment load was reduced by 2456.07×104 t than the estimated total sediment load during the period from 27 May to 2 July in 2003.
Simulation of spring snowmelt runoff by considering micro-topography and phase changes in soil layer
Authors: Nakayama T. , Watanabe M.
Published: April 2010

Abstract. The NICE model was extended to include the effect of the micro-topography in slope and shading characteristics and the phase changes in soil moisture on snow/frost depths and snowmelt runoff by combining the land-surface, the multi-layer runoff, and the groundwater flow models (NICE-SNOW). The model was applied to the upstream regions of shrinking Kushiro Mire in the invasion of alder, where the spring runoff affects greatly the annual sediment and nutrient transports because the spring flood continues in longer time than that in typhoon seasons. The simulation reproduced excellently the observed values of annual river discharge including snowmelt runoff with the greater time-to-peak of runoff than in snow-free period, in addition to snow depth, frost depth, soil temperature, soil moisture, and groundwater level, by conducting the quantitative assessment of goodness-of-fit and parameter sensitivity analysis. We quantified that the mechanism of spring snowmelt runoff is related to changes in micro-topography, soil structure, soil temperature, soil moisture, and groundwater flow. The model shows that the local effect of snow depth and the frost depth disappears in the snowmelt runoff discharge of catchment in the same way as some previous researches though they are very important as water resources of catchment. After the frozen soil restricts the infiltration in the coldest part of winter, the thawed soil increases the pore size in the early spring. The NICE-SNOW could explain the snowmelt flood continues a longer time than that in the typhoon period because some part of meltwater flows as an intermediate flow in the partially-thawed hillslope soil layer. This is also related to the simulation result that more than half of total soil moisture stays unfrozen at some places even in winter periods, which indicates that there is a high degree of spatial heterogeneity of frozen ground.
A parameter identifiability study of two chalk tracer tests
Authors: Mathias S. A. , Butler A. P. , Atkinson T. C. , Kachi S. , Ward R. S.
Published: April 2010

Abstract. As with most fractured rock formations, Chalk is highly heterogeneous. Therefore, meaningful estimates of model parameters must be obtained at a scale comparable with the process of concern. These are frequently obtained by calibrating an appropriate model to observed concentration-time data from radially convergent tracer tests (RCTT). Arguably, an appropriate model should consider radially convergent dispersion (RCD) and Fickian matrix diffusion. Such a model requires the estimation of at least four parameters. A question arises as to whether or not this level of model complexity is supported by the information contained within the calibration data. Generally modellers have not answered this question due to the calibration techniques employed. A dual-porosity model with RCD was calibrated to two tracer test datasets from different UK Chalk aquifers. A multivariate sensitivity analysis, which assumed only a priori upper and lower bounds for each model parameter, was undertaken. Rather than looking at measures of uncertainty, the shape of the multivariate objective function surface was used to determine whether a parameter was identifiable. Non-identifiable parameters were then removed and the procedure was repeated until all remaining parameters were identifiable. It was found that the single fracture model (SFM) (which ignores mechanical dispersion) obtained the best mass recovery, excellent model performance and best parameter identifiability in both the tests studied. However, there was no objective evidence suggesting that mechanical dispersion was negligible. Moreover, the SFM (with just two parameters) was found to be good at approximating the Single Fracture Dispersion Model SFDM (with three parameters) when different, and potentially erroneous parameters, were used. Overall, this study emphasises the importance of adequate temporal sampling of breakthrough curve data prior to peak concentrations, to ensure adequate characterisation of mechanical dispersion processes, and continued monitoring afterwards, to ensure adequate characterisation of fracture spacing (where possible), when parameterising dual-porosity solute transport models.
Experimental study of fingered flow through initially dry sand
Authors: Rezanezhad F. , Vogel H.-J. , Roth K.
Published: April 2010

Abstract. Water infiltration into coarse textured dry porous media becomes instable depending on flow conditions characterized through dimensionless quantities, i.e. the Bond number and the Capillary number. Instable infiltration fronts break into flow fingers which we investigate experimentally using Hele-Shaw cells. We further developed a light transmission method to measure the dynamics of water within flow fingers in great detail with high spatial and temporal resolution. The method was calibrated using x-ray absorption and the measured light transmission was corrected for scattering effects through deconvolution with a point spread function. Additionally we applied a dye tracer to visualize the velocity field within flow fingers. We analyzed the dynamics of water within the finger tips, along the finger core behind the tip, and within the fringe of the fingers during radial growth. Our results confirm previous findings of saturation overshoot in the finger tips and revealed a saturation minimum behind the tip as a new feature. The finger development was characterized by a gradual increase in water content within the core of the finger behind this minimum and a gradual widening of the fingers to a quasi-stable state which evolves on time scales that are orders of magnitudes longer than those of fingers' evolution. In this state, a sharp separation into a core with fast convective flow and a fringe with exceedingly slow flow was detected. All observed phenomena could by consistently explained based on the hysteretic behavior of the soil- water characteristic and on the positive pressure induced at the finger tip by the high flow velocity.
Footprints of climate in groundwater and precipitation
Authors: Liebminger A. , Haberhauer G. , Papesch W. , Heiss G.
Published: April 2010

Abstract. In the last decades, the 18O/16O signature of meteoric water became a key tracer intensively used both in hydrology and in paleoclimatology, based primarily on the correlation of the 18O/16O ratio in precipitation with temperature. This correlation with temperature is generally well understood as a result of Rayleigh processes of atmospheric vapour during the formation of precipitation. The resulting isotopic signals in precipitation are also transferred into the groundwater body since the isotopic composition of groundwater is determined by the precipitation infiltrating into the ground. However, the whole variability of the 18O/16O ratio especially in temporal data series of precipitation and groundwater can not be explained with temperature alone. Here we show for the first time that certain interactions between different climate induced changes in local parameters prevailing during precipitation events are responsible for the observed deviation. These effects are superimposed by an overall isotopic pattern representing the large scale climate input primarily based on temperature. The intense variability of isotopes due to the particular topography of Austria recorded over a time period of 40 years provides an unique possibility to uncover this hidden information contributed by relative humidity and type of precipitation. Since there is a growing need to predict the variation of climate together with its associated potential hazards like floods and dry periods the results of this work are contributing to a better overall understanding of the complex interaction of climate with the corresponding water cycle.
Temporal dynamics of hydrological threshold events
Authors: McGrath G. S. , Hinz C. , Sivapalan M.
Published: April 2010

Abstract. The episodic nature of hydrological flows such as surface runoff and preferential flow is a result of the nonlinearity of their triggering and the intermittency of rainfall. In this paper we examine the temporal dynamics of threshold processes that are triggered by either an infiltration excess (IE) mechanism when rainfall intensity exceeds a specified threshold value, or a saturation excess (SE) mechanism governed by a storage threshold. We analytically derive probabilistic measures of the time between successive events in each case, and in the case of the SE triggering, we relate the statistics of the time between events to the statistics of storage and the underlying water balance. In the case of the IE mechanism, the temporal dynamics of flow events is shown to be simply scaled statistics of rainfall timing. In the case of the SE mechanism the time between events becomes structured. With increasing climate aridity the mean and the variance of the time between SE events increases but temporal clustering, as measured by the coefficient of variation (CV) of the inter-event time, reaches a maximum in deep stores when the climatic aridity index equals 1. In very humid and also very arid climates, the temporal clustering disappears, and the pattern of triggering is similar to that seen for the IE mechanism. In addition we show that the mean and variance of the magnitude of SE events decreases but the CV increases with increasing aridity. The CV of inter-event times is found to be approximately equal to the CV of the magnitude of SE events per storm only in very humid climates with the CV of event magnitude tending to be much larger than the CV of inter-event times in arid climates. In comparison to storage the maximum temporal clustering was found to be associated with a maximum in the variance of soil moisture. The CV of the time till the first saturation excess event was found to be greatest when the initial storage was at the threshold.
Hydrologic effects of land and water management in North America and Asia: 1700–1992
Authors: Haddeland I. , Skaugen T. , Lettenmaier D. P.
Published: April 2010

Abstract. The hydrologic effects of land use changes, dams, and irrigation in North America and Asia over the past 300 years are studied using a macroscale hydrologic model. The simulation results indicate that the expansion of croplands over the last three centuries has resulted in 2.5 and 6 percent increases in annual runoff volumes for North America and Asia, respectively, and that these increases in runoff to some extent have been compensated by increased evapotranspiration caused by irrigation practices. Averaged over the year and the continental scale, the accumulated anthropogenic impacts on surface water fluxes are hence relatively minor. However, for some regions within the continents human activities have altered hydrologic regimes profoundly. Reservoir operations and irrigation practices in the western part of USA and Mexico have resulted in a 25 percent decrease in streamflow in June, and a 9 percent decrease in annual runoff volumes reaching the Pacific Ocean. In the area in South East Asia draining to the Pacific Ocean, land use changes have caused an increase in runoff volumes throughout the year, and the average annual increase in runoff is 12 percent.
Uncertainty, sensitivity analysis and the role of data based mechanistic modeling in hydrology
Authors: Ratto M. , Young P. C. , Romanowicz R. , Pappenberge F. , Saltelli A. , Pagano A.
Published: April 2010

Abstract. In this paper, we discuss the problem of calibration and uncertainty estimation for hydrologic systems from two points of view: a bottom-up, reductionist approach; and a top-down, data-based mechanistic (DBM) approach. The two approaches are applied to the modelling of the River Hodder catchment in North-West England. The bottom-up approach is developed using the TOPMODEL, whose structure is evaluated by global sensitivity analysis (GSA) in order to specify the most sensitive and important parameters; and the subsequent exercises in calibration and validation are carried out in the light of this sensitivity analysis. GSA helps to improve the calibration of hydrological models, making their properties more transparent and highlighting mis-specification problems. The DBM model provides a quick and efficient analysis of the rainfall-flow data, revealing important characteristics of the catchment-scale response, such as the nature of the effective rainfall nonlinearity and the partitioning of the effective rainfall into different flow pathways. TOPMODEL calibration takes more time and it explains the flow data a little less well than the DBM model. The main differences in the modelling results are in the nature of the models and the flow decomposition they suggest. The "quick'' (63%) and "slow'' (37%) components of the decomposed flow identified in the DBM model show a clear partitioning of the flow, with the quick component apparently accounting for the effects of surface and near surface processes; and the slow component arising from the displacement of groundwater into the river channel (base flow). On the other hand, the two output flow components in TOPMODEL have a different physical interpretation, with a single flow component (95%) accounting for both slow (subsurface) and fast (surface) dynamics, while the other, very small component (5%) is interpreted as an instantaneous surface runoff generated by rainfall falling on areas of saturated soil. The results of the exercise show that the two modelling methodologies have good synergy; combining well to produce a complete modelling approach that has the kinds of checks-and-balances required in practical data-based modelling of rainfall-flow systems. Such a combined approach also produces models that are suitable for different kinds of application. As such, the DBM model can provides an immediate vehicle for flow and flood forecasting; while TOPMODEL, suitably calibrated (and perhaps modified) in the light of the DBM and GSA results, immediately provides a simulation model with a variety of potential applications, in areas such as catchment management and planning.
Evolutionary geomorphology: thresholds and nonlinearity in landform response to environmental change
Authors: Phillips J. D.
Published: April 2010

Abstract. Geomorphic systems are typically nonlinear, owing largely to their threshold-dominated nature (but due to other factors as well). Nonlinear geomorphic systems may exhibit complex behaviors not possible in linear systems, including dynamical instability and deterministic chaos. The latter are common in geomorphology, indicating that small, short-lived changes may produce disproportionately large and long-lived results; that evidence of geomorphic change may not reflect proportionally large external forcings; and that geomorphic systems may have multiple potential response trajectories or modes of adjustment to change. Instability and chaos do not preclude predictability, but do modify the context of predictability. The presence of chaotic dynamics inhibits or excludes some forms of predicability and prediction techniques, but does not preclude, and enables, others. These dynamics also make spatial and historical contingency inevitable: geography and history matter. Geomorphic systems are thus governed by a combination of ''global'' laws, generalizations and relationships that are largely (if not wholly) independent of time and place, and ''local'' place and/or time-contingent factors. The more factors incorporated in the representation of any geomorphic system, the more singular the results or description are. Generalization is enhanced by reducing rather than increasing the number of factors considered. Prediction of geomorphic responses calls for a recursive approach whereby global laws and local contingencies are used to constrain each other. More specifically a methodology whereby local details are embedded within simple but more highly general phenomenological models is advocated. As landscapes and landforms change in response to climate and other forcings, it cannot be assumed that geomorphic systems progress along any particular pathway. Geomorphic systems are evolutionary in the sense of being path dependent, and historically and geographically contingent. Assessing and predicting geomorphic responses obliges us to engage these contingencies, which often arise from nonlinear complexities. We are obliged, then, to practice evolutionary geomorphology: an approach to the study of surface processes and landforms with recognizes multiple possible historical pathways rathen than an inexorable progression toward some equilbribrium state or along a cyclic pattern.
Effect of flow forecasting quality on benefits of reservoir operation – a case study for the Geheyan reservoir (China)
Authors: Dong X. , Dohmen-Janssen C. M. , Booij M. , Hulscher S.
Published: April 2010

Abstract. This paper presents a methodology to determine the effect of flow forecasting quality on the benefits of reservoir operation. The benefits are calculated in terms of the electricity generated, and the quality of the flow forecasting is defined in terms of lead time and accuracy of the forecasts. In order to determine such an effect, an optimization model for reservoir operation was developed which consists of two sub-models: a long-term (monthly) and a short-term (daily) optimization sub-model. A methodology was developed to couple these two sub-models, so that both short-term benefits (time span in the order of the flow forecasting lead time) and long-term benefits (one year) were considered and balanced. Both sub-models use Discretized Dynamic Programming (DDP) as their optimization algorithms. The Geheyan reservoir on the Qingjiang River in China was taken as case study. Observed (from the 1997 hydrological year) and forecasted flow series were used to calculate the benefits. Forecasted flow series were created by adding noises to the observed series. Different magnitudes of noise reflected different levels of forecasting accuracies. The results reveal, first of all, a threshold lead time of 33 days, beyond which further extension of the forecasting lead time will not lead to a significant increase in benefits. Secondly, for lead times shorter than 33 days, a longer lead time will generally lead to a higher benefit. Thirdly, a perfect inflow forecasting with a lead time of 4 days will realize 87% of the theoretical maximum electricity generated in one year. Fourthly, for a certain lead time, more accurate forecasting leads to higher benefits. For inflow forecasting with a fixed lead time of 4 days and different forecasting accuracies, the benefits can increase by 5 to 9% compared to the actual operation results. It is concluded that the definition of the appropriate lead time will depend mainly on the physical conditions of the basin and on the characteristics of the reservoir. The derived threshold lead time (33 days) gives a theoretical upper limit for the extension of forecasting lead time. Criteria for the appropriate forecasting accuracy for a specific feasible lead-time should be defined from the benefit-accuracy relationship, starting from setting a preferred benefit level, in terms of percentage of the theoretical maximum. Inflow forecasting with a higher accuracy does not always increase the benefits, because these also depend on the operation strategies of the reservoir.
Measurement and estimation of the aerodynamic resistance
Authors: Liu S. , Mao D. , Lu L.
Published: April 2010

Abstract. Using two methods of eddy correlation system and evaporation pan to measure respectively the aerodynamic resistance over bare soil surface and maize field, this paper analyses the diurnal variation of the aerodynamic resistance and its relationship with wind speed. Based on direct measurements by eddy correlation system, an evaluation of the aerodynamic resistance models is made. These models include Thom model, Verma-Ronsenberg model, Monteith-Hatfield model, XieXianqun model, Mahrt-Ek model, Choudhury-1 model and Choudhury-2 model. The results show that: the distribution of the aerodynamic resistance takes a "U" type in the daytime and inverse "V" type at night. The aerodynamic resistance is a power function of wind speed. The aerodynamic resistances measured by eddy correlation system are in agreement with those measured by evaporation pan, but big differences occur when the evaporation rate is very small at night or rainy day. Choudhury-1 model, XieXianqun model and Thom model give the better agreement with the measurements by eddy correlation system both over bare soil surface and the maize field, while Mahrt-Ek Model and Monteith-Hatfield model perform worse.
Hydrologic responses of the Zwalm catchment using the REW model: incorporating uncertainty of soil properties
Authors: El Ouazzani Taibi A. , Zhang G. P. , Elfeki A.
Published: April 2010

Abstract. The research presented in this paper focuses on an application of a newly developed physically-based watershed model approach, which is called Representative Elementary Watershed (REW) approach. The study stressed the effects of uncertainty of input parameters on the watershed responses (i.e. simulated discharges). The approach was applied to the Zwalm catchment, which is an agriculture dominated watershed with a drainage area of 114.3 km2 located in East-Flanders, Belgium. Uncertainty analysis of the model parameters is limited to the saturated hydraulic conductivity because of its high influence on the watershed hydrologic behavior. The assessment of outputs uncertainty is performed using the Monte Carlo method. The ensemble statistical watershed responses and their uncertainties are calculated and compared with the measurements. The results show that the measured discharges are falling within the 95% confidence interval of the modeled discharge.
Detection of contaminant plumes released from landfills
Authors: Yenigül N. B. , Hendsbergen A.T. , Elfeki A. M. M. , Dekking F. M.
Published: April 2010

Abstract. Contaminant leaks released from landfills are a significant threat to groundwater quality. The groundwater detection monitoring systems installed in the vicinity of such facilities are vital. In this study the detection probability of a contaminant plume released from a landfill has been investigated by means of both a simulation and an analytical model for both homogeneous and heterogeneous aquifer conditions. The results of the two models are compared for homogeneous aquifer conditions to illustrate the errors that might be encountered with the simulation model. For heterogeneous aquifer conditions contaminant transport is modelled by an analytical model using effective (macro) dispersivities. The results of the analysis show that the simulation model gives the concentration values correctly over most of the plume length for homogeneous aquifer conditions, and that the detection probability of a contaminant plume at given monitoring well locations match quite well. For heterogeneous aquifer conditions the approximating analytical model based on effective (macro) dispersivities yields the average concentration distribution satisfactorily. However, it is insufficient in monitoring system design since the discrepancy between the detection probabilities of contaminant plumes at given monitoring well locations computed by the two models is significant, particularly with high dispersivity and heterogeneity.
Technical Note: Real-time updating procedure for flood forecasting with conceptual HBV-type models
Authors: Wöhling Th. , Lennartz F. , Zappa M.
Published: April 2010

Abstract. Flood forecasting is of increasing importance as it comes to an increasing variability in global and local climates. But rainfall-runoff models are far from being perfect. In order to achieve a better prediction for emerging flood events, the model outputs have to be continuously updated. This contribution introduces a rather simple, yet effective updating procedure for the conceptual distributed rainfall-runoff model PREVAH, whose runoff generation module relies on similar algorithms as the HBV-Model. The current conditions of the system, i.e. the contents of the upper soil reservoirs, are updated by the proposed method. The testing of the updating procedure on data from two mountainous catchments in Switzerland reveals a significant increase in prediction accuracy with regards to peak flow.
Comparison of three measurement methods of saturated hydraulic condutivity
Authors: Fallico C. , Migliari E. , Troisi S.
Published: April 2010

Abstract. After pointing out the importance of the saturated hydraulic conductivity (ks) measurements and the difficulties and uncertainties that are present, and after recalling salient aspects of three well-known measurement methods of this parameter (i.e. constant-head tension infiltrometer (TI) method, constant-head pressure infiltrometer (PI) method and soil core (SC) estimates method), the results of an investigation on data which were obtained during a measurement campaign on an area of 800 m2, on a sandy loam hillslope, located in Southern Italy, were carried out again here. Three sets of values of ks, obtained with these measurement methods, were analyzed statistically, verifying that the log-normal distribution describes these better than the normal one; moreover, the more significant statistical parameters of each set were compared (average value , amplitude A, coefficient of variation CV and standard deviation SD), individualizing the more significant differences. The greatest value of hydraulic conductivity was found with method (PI), while the smallest with (SC) and the intermediate with (TI); these differences were translated into macroporosity and into the influence of the single measurement method. Moreover, referring to the possible factors affecting the results, the importance can be noted of the structure, the texture and the soil events, in terms of utilization, which can affect the measure of ks leading often to very different values even for similar soils, but with a different history, independently of the coincidence of the measurement points and they can be determining to explain the differences affecting the results obtained in analogous investigations by other researchers. Having confirmed that generalization is not possible, the need was emphasized to adopt the necessary devices relating to the specific measurement method, case by case, and to carefully explain the obtained results, in the light of the peculiarities and the limits of each situation. Finally, the results of similar statistical analysis carried out on a greater number of ks values, measured through the (TI) and (PI) methods are shown in this paper, with some statistical considerations on the increasing of the measurements number.
A conceptual model of flow to the Waikoropupu Springs, NW Nelson, New Zealand, based on hydrometric and tracer (18O, Cl,3H and CFC) evidence
Authors: Stewart M. K. , Thomas J. T.
Published: April 2010

Abstract. The Waikoropupu Springs, a large karst resurgence 4 km from the coast, are supplied by the Arthur Marble Aquifer (AMA) underlying the Takaka Valley, South Island, New Zealand. New evidence on the recharge sources in the catchment, combined with previous results, is used to establish a new recharge model for the AMA. Combined with the oxygen-18 mass balance, this yields a quantitative description of the inputs and outputs to the aquifer. It shows that the Main Spring is sourced mainly from the karst uplands (74%), with smaller contributions from the Upper Takaka River (18%) and valley rainfall (8%), while Fish Creek Spring contains mostly Upper Takaka River water (50%). In addition, much of the Upper Takaka River contribution to the aquifer (58%) bypasses the springs and is discharged offshore via submarine springs. The chemical concentrations of the Main Spring show input of 0.5% of sea water on average, which varies with flow and derives from the deep aquifer. Tritium measurements spanning 40 years, and CFC-11 measurements, give a mean residence time of 8 years for the Main Spring water using the preferred two-component model. Our conceptual flow model, based on the flow, chloride, oxygen-18 and age measurements, invokes two different flow systems with different recharge sources to explain the flow within the AMA. One system contains deeply penetrating old water with mean age 10.2 years and water volume 3 km3, recharged from the karst uplands. The other, at shallow levels below the valley floor, has much younger water, with mean age 1.2 years and water volume 0.4 km3, recharged by Upper Takaka River and valley rainfall. The flow systems contribute in different proportions to the Main Spring, Fish Creek Springs and offshore springs. Their very different behaviours, despite being in the same aquifer, are attributed to the presence of a diorite intrusive below the surface of the lower valley, which diverts the deep flow towards the Waikoropupu Springs and allows much of the shallow flow to pass over the intrusive and escape via submarine springs.
Rivers we can't bring ourselves to clean – historical insights into the pollution of the Moselle River (France), 1850–2000
Authors: Garcier R. J.
Published: April 2010

Abstract. As products of both natural and social systems, rivers are highly complex historical objects. We show in this paper that historical analysis works on two different levels: one level, which we call "structural", shows the materiality of the riverine environment as the spatial-temporal product of natural factors and human impacts (bed and course alterations, pollution, etc.). On a second level – "semiotic" – we show that river systems are also social constructs and the subjects of ancient and diverse management practices. The quality of a river will be a function of the dialectical interaction between both levels. Historical analysis can uncover the inherited constraints that bear upon current management practices. To help substantiate this analytical framework, we analyse the case of the Moselle river in eastern France by using archival sources and statistical data. Severely impaired by industrial discharges from iron, coal and salt industries between the 1875s and the early 1980s, the waters of the Moselle became the subject of a social consensus between stakeholders that prevented the implementation of efficient pollution management policies until the 1990s. The example urges caution on the pervasiveness of participatory approaches to river management: social consensus does not necessarily benefit the environment.
Comparison of data-driven methods for downscaling ensemble weather forecasts
Authors: Liu X. , Coulibaly P. , Evora N.
Published: April 2010

Abstract. This study investigates dynamically different data-driven methods, specifically a statistical downscaling model (SDSM), a time lagged feedforward neural network (TLFN), and an evolutionary polynomial regression (EPR) technique for downscaling numerical weather ensemble forecasts generated by a medium range forecast (MRF) model. Given the coarse resolution (about 200-km grid spacing) of the MRF model, an optimal use of the weather forecasts at the local or watershed scale, requires appropriate downscaling techniques. The selected methods are applied for downscaling ensemble daily precipitation and temperature series for the Chute-du-Diable basin located in northeastern Canada. The downscaling results show that the TLFN and EPR have similar performance in downscaling ensemble daily precipitation as well as daily maximum and minimum temperature series whatever the season. Both the TLFN and EPR are more efficient downscaling techniques than SDSM for both the ensemble daily precipitation and temperature.
Temporal variability of subsurface stormflow formation
Authors: Kienzler P. M. , Naef F.
Published: April 2010

Abstract. Subsurface storm flow (SSF) can play a key role for the runoff generation at hillslopes. Quantifications of SSF suffer from the limited understanding of how SSF is formed and how it varies in time and space. This study concentrates on the temporal variability of SSF formation. Controlled sprinkling experiments at three experimental slopes were replicated with varying precipitation intensity and varying antecedent precipitation. SSF characteristics were observed with hydrometric measurements and tracer experiments. SSF response was affected in different ways and to varying degree by changes of precipitation intensity and antecedent precipitation. The study showed that the influence of antecedent soil moisture on SSF response depends on the type of SSF formation. Formation of subsurface stormflow was hardly influenced by the increase of precipitation intensity. As a consequence, subsurface flow rates were not increased by higher precipitation intensity. Different soil structures determined runoff formation at different precipitation intensities. Saturation and flow formation occurred at the base of the soil, but also within the topsoil during high precipitation intensity. This implies that timing and magnitude of flow response can change substantially at different precipitation intensities.
Filter properties of seam material from paved urban soils
Authors: Nehls T. , Jozefaciuk G. , Sokolowska Z. , Hajnos M. , Wessolek G.
Published: April 2010

Abstract. We studied pavement seam material. This is the soil substrate in joints of pervious pavements in urban areas. It is mostly 1 cm thick and develops from the original seam filling by depositions of all kinds of urban residues, including anthropogenic organic substances. It was investigated, how this unique form of organic matter influences the filter properties of seam material and how the seam material influences heavy metal transport through the pavement. The seam material is characterised by a darker munsell colour, higher organic carbon content, higher surface areas, higher cation exchange capacities, but a lower fraction of high adsorption energy sites compared to the original seam filling. The deposited anthropogenic organic matter itself could be characterised as particulate and non-polar. Compared to natural soils, it has a small surface area and a low surface charge density resulting in a small cation exchange capacity of only 75 cmol(+) kg−1C. The seam material shows stronger sorption of Pb and Cd compared to the original construction sand. The retardation capacity of seam material towards Pb is similar, towards Cd it is much smaller compared to natural soils. The simulated long term displacement scenarios for a street in Berlin do not indicate an acute contamination risk for Pb. For Cd the infiltration from ponds can lead to a displacement of Cd during only one decade.
The olive tree: a paradigm for drought tolerance in Mediterranean climates
Authors: Sofo A. , Manfreda S. , Dichio B. , Fiorentino M. , Xiloyannis C.
Published: April 2010

Abstract. Olive tree (Olea europaea L.) is commonly grown in the Mediterranean basin where prolonged droughts may occur during the vegetative period. This species has developed a series of physiological mechanisms to tolerate drought stress and grow under adverse climatic conditions that can be observed in numerous plants of the Mediterranean macchia. These mechanisms have been investigated through an experimental campaign carried out over both irrigated and drought-stressed plants in order to comprehend the plant response under stressed conditions and its ability to recover. Experimental results show that olive plants subjected to water deficit lower the water content and water potentials of their tissues, establishing a particularly high potential gradient between leaves and roots, and stop canopy growth but not photosynthetic activity and transpiration. This allows the continuous production of assimilates as well as their accumulation in the various plant parts, so creating a higher root/leaf ratio if compared to well-watered plants. Active and passive osmotic adjustment due to the accumulation of sugars (in particular mannitol and glucose), proline and other osmolytes has a key role in maintaining cell turgor and leaf activities. At severe drought-stress levels, the non-stomatal component of photosynthesis is inhibited and a light-dependent inactivation of the photosystem II occurs. Finally, the activities of some antioxidant enzymes involved in the scavenging of activated oxygen species and in other biochemical pathways, increase during a period of drought. The present paper provides an overview of the driving mechanisms adopted by olive trees to face drought stress with the aim of better understand plant-soil interactions.
Impact of changing DOC concentrations on the potential distribution of acid sensitive biota in a boreal stream network
Authors: Laudon H. , Buffam I.
Published: April 2010

Abstract. DOC concentrations have increased in many surface waters in Europe and North America over the past few decades. As DOC exerts a strong influence on pH this DOC increase could have detrimental effects on acid sensitive biota in many streams and lakes. To investigate the potential implications of changes in the DOC concentration on stream water biota, we have used a mesoscale boreal stream network in northern Sweden as a case study. The network was sampled for stream water chemistry at 60 locations during both winter base flow and spring flood periods, representing the extremes experienced annually in these streams both in terms of discharge and acidity. The effect of changing DOC on pH was modeled for all sampling locations using an organic acid model, with input DOC concentrations for different scenarios adjusted by between –30% and +50% from measured present concentrations. The resulting effect on pH was then used to quantify the proportion of stream length in the catchment with pH below the acid thresholds of pH 5.5 and pH 5.0. The results suggest that a change in stream water DOC during base flow would have only a limited effect on pH and hence on the stream length with pH below the acid thresholds. During the spring flood on the other hand a change in DOC would strongly influence pH and the stream length with pH below the acid thresholds. For example an increase in DOC concentration of 30% at all sites would increase the proportion of stream length with pH below 5.5 from 37% to 65%, and the proportion of stream length with pH below 5.0 would increase from 18% to 27%. The results suggest that in poorly-buffered high DOC waters, even a marginal change in the DOC concentration could impact acid sensitive biota in a large portion of the aquatic landscape.
Modelling the impacts of European emission and climate change scenarios on acid-sensitive catchments in Finland
Authors: Posch M. , Aherne J. , Forsius M. , Fronzek S. , Veijalainen N.
Published: April 2010

Abstract. The dynamic hydro-chemical Model of Acidification of Groundwater in Catchments (MAGIC) was used to predict the response of 163 Finnish lake catchments to future acidic deposition and climatic change scenarios. Future deposition was assumed to follow current European emission reduction policies and a scenario based on maximum (technologically) feasible reductions (MFR). Future climate (temperature and precipitation) was derived from the HadAM3 and ECHAM4/OPYC3 general circulation models under two global scenarios of the Intergovernmental Panel on Climate Change (IPCC: A2 and B2). The combinations resulting in the widest range of future changes were used for simulations, i.e., the A2 scenario results from ECHAM4/OPYC3 (highest predicted change) and B2 results from HadAM3 (lowest predicted change). Future scenarios for catchment runoff were obtained from the Finnish watershed simulation and forecasting system. The potential influence of future changes in surface water organic carbon concentrations was also explored using simple empirical relationships based on temperature and sulphate deposition. Surprisingly, current emission reduction policies hardly show any future recovery; however, significant chemical recovery of soil and surface water from acidification was predicted under the MFR emission scenario. The direct influence of climate change (temperate and precipitation) on recovery was negligible, as runoff hardly changed; greater precipitation is offset by increased evapotranspiration due to higher temperatures. Predicted changes in dissolved organic carbon induced by reductions in acid deposition or increases in temperature may potentially influence the recovery of surface waters from acidification and may offset the increase in pH resulting from S deposition reductions. However, many climate-induced changes in processes are generally not incorporated in current versions of acidification models. To allow more reliable forecasts, the mechanisms by which climate changes affect key biogeochemical processes need to be incorporated directly into process-oriented models such as MAGIC.
Recovery of acidified Finnish lakes: trends, patterns and dependence of catchment characteristics
Authors: Vuorenmaa J. , Forsius M.
Published: April 2010

Abstract. The regional-scale trends (south, central and north Finland) in key acidification parameters over the period 1990–2003 were studied in lakes used for monitoring of acidification (157 lakes), and the catchment characteristics that best discriminate between lakes showing recovery (significant increase in alkalinity) and those not showing recovery (no significant increase) were determined. A significant decline in sulphate concentrations occurred in 82–98% of the lakes, depending of the region. Base cation (BC) concentrations decreased for most lakes, but to a lesser extent than those of SO4. Consequently, a significant increase in Gran alkalinity occurred in 40–92% of the lakes. The recovery from acidification has been strongest in lakes in south Finland, where both levels and decrease of S (and N) deposition have been higher compared to other regions. A significant increase in pH was detected in about 50% of the lakes in the south. Here labile aluminium concentrations also decreased in the most acidic lakes. Recovery has occurred most strongly in lakes which have SO4 as a dominant acid anion, whereas recovery has been weaker in acidified humic lakes which have organic anion as a dominant acid anion. The non-recovering lakes in south Finland have higher proportion of exposed bedrock in the catchment, and higher TOC and lower BC concentrations. In central Finland the proportion of peatland and TOC concentrations were higher and the decrease of BC concentration was steeper in non-recovering lakes than in recovering lakes. In north Finland, catchment characteristics, trend slopes and concentrations did not separate the recovering and non-recovering lakes. The non-recovering lakes were also located in regions which are acid-sensitive based on bedrock type, soil properties, weathering rate and runoff. These factors have resulted in lower concentrations and steeper downward trends for base cations.
Lacustrine wetland in an agricultural catchment: nitrogen removal and related biogeochemical processes
Authors: Balestrini R. , Arese C. , Delconte C.
Published: April 2010

Abstract. The role of specific catchment areas, such as the soil-river or lake interfaces, in removing or buffering the flux of N from terrestrial to aquatic ecosystems is globally recognized but the extreme variability of microbiological and hydrological processes make it difficult to predict the extent to which different wetlands function as buffer systems. In this paper we evaluate the degree to which biogeochemical processes in a lacustrine wetland are responsible for the nitrate removal from ground waters feeding Candia Lake (Northern Italy). A transect of 18 piezometers was installed perpendicular to the shoreline, in a sub-unit formed by 80 m of poplar plantation, close to a crop field and 30 m of reed swamp. The chemical analysis revealed a drastic NO3-N ground water depletion from the crop field to the lake, with concentrations decreasing from 15–18 mg N/l to the detection limit within the reeds. Patterns of Cl, SO4, O2, NO2-N, HCO3 and DOC suggest that the metabolic activity of bacterial communities, based on the differential use of electron donors and acceptors in redox reactions is the key function of this system. The significant inverse relationship found between NO3-N and HCO3 is a valuable indicator of the denitrification activity. The pluviometric regime, the temperature, the organic carbon availability and the hydrogeomorphic properties are the main environmental factors affecting the N transformations in the studied lacustrine ecosystem.
Floodplain sediment from a 30-year-recurrence flood in 2005 of the Ping River in northern Thailand
Authors: Wood S. H. , Ziegler A. D.
Published: April 2010

Abstract. This paper documents the nature of flood-producing storms and floodplain deposition associated with the 28 September–2 October 2005 30-year-recurrence flood on the Ping River in northern Thailand. The primary purpose of the study is to understand the extent that deposits from summer-monsoon floods can be identified in floodplain stratigraphy A secondary objective is to document the sedimentation processes/patterns associated with a large contemporary flood event on a medium-sized Asian river. Maximum sediment depths of 15 cm were found on the river levee, within 30 m of the main channel, and at 350 m thickness was 4 cm. Sediment depth generally decreased exponentially with distance away from the main channel. The extent of sediment deposition was about 1 km from the river channel. However, 72% of the sediment was deposited within an oval-shaped area 200–400 m from the main channel and centered on a tributary stream, through which sediment-laden water entered the floodplain, in addition to overtopping the levee of the main channel. Sediment concentration during the flood was estimated at 800–1500 mg L−1; and we believe the sediment was delivered by flows of well-mixed flood water occurring over a 1–2 day period. These data suggest that flood-deposited strata related to 30-year recurrence floods is only likely to be preserved in deposits located relatively close to the main river channel where fine sand and clayey coarse silt deposits have thicknesses of at least 5–10 cm. These relatively thick deposits would survive bioturbation, whereas more distal areas with thin clayey silt deposits would not.