bluuebunny/crossref_metadata_2025 huggingface dataset:
Simple sensors to achieve fine spatial resolution in continuous measurements of soil moisture and salinity
Authors: Konukcu F. , Gowing J. W. , Rose D. A.
Published: April 2010

Abstract. It is increasingly necessary to be able to measure, simultaneously, continuously and at fine spatial resolution, the salinity and water content of soil. This paper reports the design, construction, calibration and laboratory testing of two simple but robust instruments that enable this to be achieved. Salinity in solution was measured reliably, at 10-mm spacing, by multi-electrode resistivity probes up to saturation with NaCl (c. 6 mol l–1), though these probes required individual calibration and were unable to detect precipitated salt. Volumetric water content was measured with great sensitivity over a wide range, from air-dryness (0.06 m3m–3) to saturation (0.55 m3m–3) in a sandy loam, using thermal-conductivity probes that used a common calibration and were unaffected by the salinity of the soil solution, by temperature and by ageing. Keywords: soil moisture, soil salinity, thermal-conductivity moisture probe, four-electrode salinity probe
An integrated simulation method for flash-flood risk assessment: 2. Effects of changes in land-use under a historical perspective
Authors: Rosso R. , Rulli M.C.
Published: April 2010

Abstract. The influence of land use changes on flood occurrence and severity in the Bisagno River (Thyrrenian Liguria, N.W. Italy is investigated using a Monte Carlo simulation approach (Rulli and Rosso, 2002). High resolution land-use maps for the area were reconstructed and scenario simulations were made for a pre-industrial (1878), an intermediate (1930) and a current (1980) year. Land-use effects were explored to assess the consequences of distributed changes in land use due to agricultural practice and urbanisation. Hydraulic conveyance effects were considered, to assess the consequences of channel modifications associated with engineering works in the lower Bisagno River network. Flood frequency analyses of the annual flood series, retrieved from the simulations, were used to examine the effect of land-use change and river conveyance on flood regime. The impact of these effects proved to be negligible in the upper Bisagno River, moderate in the downstream river and severe in the small tributaries in the lower Bisagno valley that drain densely populated urban areas. The simulation approach is shown to be capable of incorporating historical data on landscape and river patterns into quantitative methods for risk assessment. Keywords: flood, simulation, distributed model, land-use changes, channel modifications, historical data
Hydrological application of the INCA model with varying spatial resolution and nitrogen dynamics in a northern river basin
Authors: Rankinen K. , Lepistö A. , Granlund K.
Published: April 2010

Abstract. As a first step in applying the Integrated Nitrogen model for CAtchments (INCA) to the Simojoki river basin (3160 km2), this paper focuses on calibration of the hydrological part of the model and nitrogen (N) dynamics in the river during the 1980s and 1990s. The model application utilised the GIS land-use and forest classification of Finland together with a recent forest inventory based on remote sensing. In the INCA model, the Hydrologically Effective Rainfall (HER) is used to drive the water flow and N fluxes through the catchment system. HER was derived from the Watershed Simulation and Forecast System (WSFS). The basic component of the WSFS is a conceptual hydrological model which simulates runoff using precipitation, potential evapotranspiration and temperature data as inputs. Spatially uniform, lumped input data were calculated for the whole river basin and spatially semi-distributed input data were calculated for each of the nine sub-basins. When comparing discharges simulated by the INCA model with observed values, a better fit was obtained with the semi-distributed data than with the spatially uniform data (R2 0.78 v. 0.70 at Hosionkoski and 0.88 v. 0.78 at the river outlet). The timing of flow peaks was simulated rather well with both approaches, although the semi-distributed input data gave a more realistic simulation of low flow periods and the magnitude of spring flow peaks. The river basin has a relatively closed N cycle with low input and output fluxes of inorganic N. During 1982-2000, the average total N flux to the sea was 715 tonnes yr–1, of which 6% was NH4-N, 14% NO3-N, and 80% organic N. Annual variation in river flow and the concentrations of major N fractions in river water, and factors affecting this variation are discussed. Keywords: northern river basin, nitrogen, forest management, hydrology, dynamic modelling, semi-distributed modelling
Dynamic nitrogen deposition thresholds during forest stand development in a Douglas fir forest analysed with two nitrogen models SMART2 and MERLIN
Authors: Tietema A. , Mol-Dijkstra J. P. , Kros J. , De Vries W.
Published: April 2010

Abstract. This study focuses on spatial variability of throughfall water and chemistry and forest floor water content within a Douglas fir (Pseudotsuga menziesii, Franco L.) forest plot. Spatial patterns of water and chemistry (NH4+, NO3‾, SO42-, Cl‾, Mg2+, Ca2+, Na+ and K+) were compared and tested for stability over time. The spatial coefficient of variation (CV) was between 18 and 26% for amounts of throughfall water and ions, and 17% for forest floor water content. Concentrations and amounts of all ions were correlated significantly. Ion concentrations were negatively correlated with throughfall water amounts, but, except for NH4+, there was no such relation between throughfall water and ion amounts. Spatial patterns of throughfall water fluxes and forest floor water contents were consistent over time; patterns of ion fluxes were somewhat less stable. Because of the spatial variability of forest floor thickness and drainage, it was not possible to relate patterns in throughfall water directly to patterns in water content. The spatial variability of throughfall nitrogen and forest floor water contents can cause significant variability in NO3‾ production within the plot studied. Keywords: nutrient throughfall, forest floor water, spatial variability, time-stability, nitrogen
N fluxes in two nitrogen saturated forested catchments in Germany: dynamics and modelling with INCA
Authors: Langusch J.-J. , Matzner E.
Published: April 2010

Abstract. The N cycle in forests of
the temperate zone in Europe has been changed substantially by the impact of
atmospheric N deposition. Here, the fluxes and concentrations of mineral N in
throughfall, soil solution and runoff in two German catchments, receiving high N
inputs are investigated to test the applicability of an Integrated Nitrogen
Model for European Catchments (INCA) to small forested catchments. The
Lehstenbach catchment (419 ha) is located in the German Fichtelgebirge (NO
Bavaria, 690-871 m asl.) and is stocked with Norway spruce (Picea abies (L.) Karst.) of different ages. The Steinkreuz
catchment (55 ha) with European beech (Fagus sylvatica L.) as the
dominant tree species is located in the Steigerwald (NW Bavaria, 400-460 m asl.).
The mean annual N fluxes with throughfall were slightly higher at the
Lehstenbach (24.6 kg N ha-1) than at the Steinkreuz (20.4 kg N ha-1).
In both catchments the N fluxes in the soil are dominated by NO3. At
Lehstenbach, the N output with seepage at 90 cm soil depth was similar to the N
flux with throughfall. At Steinkreuz more than 50 % of the N deposited was
retained in the upper soil horizons. In both catchments, the NO3 fluxes with runoff were lower than those with seepage. The average annual NO3
concentrations in runoff in both catchments were between 0.7 to 1.4 mg NO3-N L-1 and no temporal trend was observed. The N budgets at the catchment scale indicated similar amounts of N retention (Lehstenbach: 19 kg N ha-1yr-1 ; Steinkreuz: 17 kg N ha-1yr-1). The parameter settings of the INCA model were simplified to reduce the model
complexity. In both catchments, the NO3 concentrations and fluxes in
runoff were matched well by the model. The seasonal patterns with lower NO3 runoff concentrations in summer at the Lehstenbach catchment were replicated.
INCA underestimated the increased N3 concentrations during short
periods of rewetting in late autumn at the Steinkreuz catchment. The model will
be a helpful tool for the calculation of "critical loads" for the N
deposition in Central European forests including different hydrological regimes. Keywords: forest ecosystem, modelling, N budgets, N saturation, NO3 leaching, water quality, INCA
Long-term modelling of nitrogen turnover and critical loads in a forested catchment using the INCA model
Authors: Langusch J.-J. , Matzner E.
Published: April 2010

Abstract. Many forest ecosystems in Central Europe have reached the status of N saturation due to chronically high N deposition. In consequence, the NO3 leaching into ground- and surface waters is often substantial. Critical loads have been defined to abate the negative consequences of the NO3 leaching such as soil acidification and nutrient losses. The steady state mass balance method is normally used to calculate critical loads for N deposition in forest ecosystems. However, the steady state mass balance approach is limited because it does not take into account hydrology and the time until the steady state is reached. The aim of this study was to test the suitability of another approach: the dynamic model INCA (Integrated Nitrogen Model for European Catchments). Long-term effects of changing N deposition and critical loads for N were simulated using INCA for the Lehstenbach spruce catchment (Fichtelgebirge, NE Bavaria, Germany) under different hydrological conditions. Long-term scenarios of either increasing or decreasing N deposition indicated that, in this catchment, the response of nitrate concentrations in runoff to changing N deposition is buffered by a large groundwater reservoir. The critical load simulated by the INCA model with respect to a nitrate concentration of 0.4 mg N l–1 as threshold value in runoff was 9.7 kg N ha–1yr–1 compared to 10 kg ha–1yr–1 for the steady state model. Under conditions of lower precipitation (520 mm) the resulting critical load was 7.7 kg N ha–1yr–1 , suggesting the necessity to account for different hydrological conditions when calculating critical loads. The INCA model seems to be suitable to calculate critical loads for N in forested catchments under varying hydrological conditions e.g. as a consequence of climate change. Keywords: forest ecosystem, N saturation, critical load, modelling, long-term scenario, nitrate leaching, critical loads reduction, INCA
Nutrient concentrations and fluxes for podzolic and gley soils at Plynlimon, mid-Wales: implications for modelling inorganic nitrogen and phosphorus in upland UK environments
Authors: Neal C.
Published: April 2010

Abstract. The effect of felling on stream nitrate, ammonium and soluble reactive phosphate (SRP) concentrations is examined for acidic and acid sensitive Sitka Spruce afforested catchments with podzolic and gley soils in mid-Wales. For the streams draining the felled podzolic areas, the concentrations of nitrate can be up to an order of magnitude higher than pre-fell values and post-fell concentrations can even be lower than the pre-fell values. Felling for the podzolic soils barely leads to any changes in ammonium or SRP concentration. For the gley soils, felling results in an order of magnitude increase in nitrate, ammonium and SRP for a small drainage ditch, but the pulse is much reduced before it reaches the main Nant Tanllwyth channel. Rather, within-catchment and within-stream processes not only imbibe nitrate, ammonium and SRP fluxes generated, but in the case of nitrate, concentrations with- and post-felling are lower than pre-felling concentrations. The flux changes involved are described in terms of (a) input-output relationships and (b) "felling disruption" and "felling recovery responses". The findings are linked to issues of hydrobiological controls and forestry management. Keywords: Plynlimon, Hafren, Hore, streams, nitrate, ammonium, SRP, phosphorus, soluble reactive phosphorus, phosphate, orthophosphate, Sitka spruce, forestry, felling, podzol, gley
Hydrological processes and their seasonal controls in a small Mediterranean mountain catchment in the Pyrenees
Authors: Gallart F. , Llorens P. , Latron J. , Regüés D.
Published: April 2010

Abstract. The Vallcebre catchments are located in a middle mountain area of the Pyrenean ranges, built up by sedimentary rocks and loamy soils. The vegetation cover is pastures and forests of Pinus sylvestris, mostly occupying former agricultural terraces. Some relatively small, heavily eroded landscapes (badlands) occur in the catchments, playing a relevant hydrological and geomorphic role. Annual precipitation is 924 mm and potential (reference) evapotranspiration is about 700 mm. Rainfall interception in forests represents about 24% of precipitation; interception rates were similar throughout the seasons because of a compensation between rainfall intensities and atmospheric conditions. Soil moisture showed a temporal pattern characterised by the occurrence of marked deficit periods in summer and also, but less pronounced, in winter. During most of the year, subsurface flows on hillslopes drove the spatial organisation of soil moisture and the occurrence of saturated areas. Nevertheless, this spatial organisation was also controlled by the patterns of vegetation cover. During dry periods, subsurface flow ceased, saturated areas disappeared and the spatial patterns of soil moisture changed. Stream flow from these catchments was dominated by storm flow, and the runoff generating mechanisms showed a clear seasonal pattern, controlled mainly by the soil moisture and the extent of saturated areas. During the dry periods, runoff was produced only on impervious areas and badlands. At the end of the dry periods, some large rainfall events generated significant runoff because of the perched saturation of the shallow soil horizons. Thereafter, runoff generation was dominated by the role of saturated areas. Stream waters in catchments with badlands had very high suspended sediment concentrations. The seasonal pattern of erosion processes in badlands was characterised by physical weathering during winter, regolith breakdown and vigorous hillslope erosion during spring and summer, and efficient transport of sediments in autumn.
Multivariate synthetic streamflow generation using a hybrid model based on artificial neural networks
Authors: Ochoa-Rivera J. C. , García-Bartual R. , Andreu J.
Published: April 2010

Abstract. A model for multivariate streamflow generation is presented, based on a multilayer feedforward neural network. The structure of the model results from two components, the neural network (NN) deterministic component and a random component which is assumed to be normally distributed. It is from this second component that the model achieves the ability to incorporate effectively the uncertainty associated with hydrological processes, making it valuable as a practical tool for synthetic generation of streamflow series. The NN topology and the corresponding analytical explicit formulation of the model are described in detail. The model is calibrated with a series of monthly inflows to two reservoir sites located in the Tagus River basin (Spain), while validation is performed through estimation of a set of statistics that is relevant for water resources systems planning and management. Among others, drought and storage statistics are computed and compared for both the synthetic and historical series. The performance of the NN-based model was compared to that of a standard autoregressive AR(2) model. Results show that NN represents a promising modelling alternative for simulation purposes, with interesting potential in the context of water resources systems management and optimisation. Keywords: neural networks, perceptron multilayer, error backpropagation, hydrological scenario generation, multivariate time-series..
Internal evaluation of a physically-based distributed model using data from a Mediterranean mountain catchment
Authors: Anderton S. P. , Latron J. , White S. M. , Llorens P. , Gallart F. , Salvany C. , O’Connell P. E.
Published: April 2010

Abstract. An evaluation of the performance of a physically-based distributed model of a small Mediterranean mountain catchment is presented. This was carried out using hydrological response data, including measurements of runoff, soil moisture, phreatic surface level and actual evapotranspiration. A-priori model parameterisation was based as far as possible on property data measured in the catchment. Limited model calibration was required to identify an appropriate value for terms controlling water loss to a deeper regional aquifer. The model provided good results for an initial calibration period, when judged in terms of catchment discharge. However, model performance for runoff declined substantially when evaluated against a consecutive, rather drier, period of data. Evaluation against other catchment responses allowed identification of the problems responsible for the observed lack of model robustness in flow simulation. In particular, it was shown that an incorrect parameterisation of the soil water model was preventing adequate representation of drainage from soils during hydrograph recessions. This excess moisture was then being removed via an overestimation of evapotranspiration. It also appeared that the model underestimated canopy interception. The results presented here suggest that model evaluation against catchment scale variables summarising its water balance can be of great use in identifying problems with model parameterisation, even for distributed models. Evaluation using spatially distributed data yielded less useful information on model performance, owing to the relative sparseness of data points, and problems of mismatch of scale between the measurement and the model grid. Keywords: physically-based distributed model, SHETRAN, parameterisation, Mediterranean mountain catchment, internal evaluation, multi-response
The application of data mining techniques for the regionalisation of hydrological variables
Authors: Hall M. J. , Minns A. W. , Ashrafuzzaman A. K. M.
Published: April 2010

Abstract. Flood quantile estimation for ungauged catchment areas continues to be a routine problem faced by the practising Engineering Hydrologist, yet the hydrometric networks in many countries are reducing rather than expanding. The result is an increasing reliance on methods for regionalising hydrological variables. Among the most widely applied techniques is the Method of Residuals, an iterative method of classifying catchment areas by their geographical proximity based upon the application of Multiple Linear Regression Analysis (MLRA). Alternative classification techniques, such as cluster analysis, have also been applied but not on a routine basis. However, hydrological regionalisation can also be regarded as a problem in data mining — a search for useful knowledge and models embedded within large data sets. In particular, Artificial Neural Networks (ANNs) can be applied both to classify catchments according to their geomorphological and climatic characteristics and to relate flow quantiles to those characteristics. This approach has been applied to three data sets from the south-west of England and Wales; to England, Wales and Scotland (EWS); and to the islands of Java and Sumatra in Indonesia. The results demonstrated that hydrologically plausible clusters can be obtained under contrasting conditions of climate. The four classes of catchment found in the EWS data set were found to be compatible with the three classes identified in the earlier study of a smaller data set from south-west England and Wales. Relationships for the parameters of the at-site distribution of annual floods can be developed that are superior to those based upon MLRA in terms of root mean square errors of validation data sets. Indeed, the results from Java and Sumatra demonstrate a clear advantage in reduced root mean square error of the dependent flow variable through recognising the presence of three classes of catchment. Wider evaluation of this methodology is recommended. Keywords: regionalisation, floods, catchment characteristics, data mining, artificial neural networks
Multifractal modelling and simulation of rain fields exhibiting spatial heterogeneity
Authors: Pathirana A. , Herath S.
Published: April 2010

Abstract. Spatial multifractals are statistically homogeneous random fields. While being useful to model geophysical fields exhibiting a high degree of variability and discontinuity and including rainfall, they ignore the spatial trends embedded in the variability that are evident from large temporal aggregation of spatial fields. The modelling of rain fields using multifractals causes the information related to spatial heterogeneity, immensely important at some spatial scales, to be lost in the modelling process. A simple method to avoid this loss of the heterogeneity information is proposed. Instead of modelling rain fields directly as multifractals, a derived field M is modelled; this is the product of filtering observed rainfall snapshots with spatial heterogeneity as indicated by long term accumulations of rain fields. The validity of considering the field M as multifractal is investigated empirically. The applicability of the proposed method is demonstrated using a discrete cascade model on gauge-calibrated radar rainfall of central Japan at a daily scale. Important parameters of spatial rainfall, like the distribution of wet areas, spatial autocorrelation and rainfall intensity distributions at different geographic locations with different amounts of average rainfall, were faithfully reproduced by the proposed method. Keywords: spatial rainfall, downscaling, multifractals
Pressure head distribution during unstable flow in relation to the formation and dissipation of fingers
Authors: Cho H. , de Rooij G. H.
Published: April 2010

Abstract. Wetting front instability creates a shallow induction zone from which fingers emerge that rapidly transport water and solutes downwards. How the induction zone affects finger location and spacing is unknown. In the moist subsoil, fingers may well dissipate because the finger tips no longer have to overcome the water entry value. Both flow regions were investigated in a two-dimensional chamber with a fine-over-coarse glass bead porous medium. A capillary fringe was created by upward wetting through capillary rise. Upon ponding with dye-coloured water, fingers emerged, propagated downward and diverged when reaching the capillary fringe. Microtensiometers were installed in the induction zone, the fingers, and in the capillary fringe. In the induction zone, a lateral sinusoidal pressure head developed within minutes. Only in one of two experiments could the observed pressure head pattern be satisfactorily reproduced by a steady-state model assuming uniform induction zone properties and uniform infiltration. Later, fingers emerged below the pressure head minima. The induction zone did not affect finger properties. The pressure head in the induction zone was determined by the depth of the finger tips. The water requirement of the fingers dictated the lateral pressure head gradients. The pressure heads in the capillary fringe supported the hypothesis that the flow stabilised and dissipated there. Keywords: fingered flow, wetting front instability, unsaturated flow, microtensiometers, induction zone, capillary fringe
The Surface Energy Balance System (SEBS) for estimation of turbulent heat fluxes
Authors: Su Z.
Published: April 2010

Abstract. A Surface Energy Balance System (SEBS) is proposed for the estimation of atmospheric turbulent fluxes and evaporative fraction using satellite earth observation data, in combination with meteorological information at proper scales. SEBS consists of: a set of tools for the determination of the land surface physical parameters, such as albedo, emissivity, temperature, vegetation coverage etc., from spectral reflectance and radiance measurements; a model for the determination of the roughness length for heat transfer; and a new formulation for the determination of the evaporative fraction on the basis of energy balance at limiting cases. Four experimental data sets are used to assess the reliabilities of SEBS. Based on these case studies, SEBS has proven to be capable to estimate turbulent heat fluxes and evaporative fraction at various scales with acceptable accuracy. The uncertainties in the estimated heat fluxes are comparable to in-situ measurement uncertainties. Keywords: Surface energy balance, turbulent heat flux, evaporation, remote sensing
The water balance of two semi-arid shrubs on abandoned land in South-Eastern Spain after cold season rainfall
Authors: Archer N. , Hess T. , Quinton J.
Published: April 2010

Abstract. The inland, mountainous marginal areas (land abandoned by farming and colonised by shrubs) of the Iberian Peninsular, Spain, generally receive a higher rainfall than the coastal areas (Lazaro and Rey, 1991) and may store water after cold season (autumn and winter) rainfall. By measuring runoff, change of soil water content and rainfall, this study tests the hypothesis that two shrubs on two sites on abandoned land do not use all the water available after cold season rainfall. One site was on an upper alluvial slope dominated by Anthyllis cytisoides and the other on a lower alluvial slope dominated by Retama sphaerocarpa. The root systems of A. cytisoides and R. sphaerocarpa penetrate to 3 m and 20 m, respectively. A. cytisoides senesces during the dry season and R. sphaerocarpa is evergreen. The water balance is dominated by high actual evapotranspiration (ET), which is limited by rainfall. Reference evapotranspiration was high; runoff was low and soil water storage occurred above 2 m depth. ET and water storage were highest under A. cytisoides shrubs. Runoff was lower on the ‘Anthyllis’ site. The spatial variability of soil water is high and the problems of its measurement are discussed. The quantity of rainfall infiltrated was greater under shrubs than grass-areas, suggesting that shrub roots facilitated preferential flow. The growing season of A. cytisoides began when water was available in the upper soil layers and senescence occurred when the upper soil layers dried to less than 4% water content. A. cytisoides, therefore, relies on water from these layers. The main growth of R. sphaerocarpa occurred when the upper soil layers were relatively dry, so that R. sphaerocarpa must extract water from deeper layers. Results suggest that A. cytisoides accumulates rainfall and runoff and directs water to lower layers for later use, while R. sphaerocarpa extracts water from deeper soil layers. By mid-summer both shrubs had extracted all the available water accumulated in the upper soil layers from cold season rainfall. Keywords: water balance, neutron probe, patchy vegetation, mosaic vegetation, Spain, semi arid, Anthyllis cytisoides, Retama sphaerocarpa
Technical Note:Practical considerations on the use of down-sized time-domain reflectometry (TDR) probes
Authors: Mojid M. A.
Published: April 2010

Abstract. Nine time-domain reflectometry (TDR) probes, 2 to 10 cm long, were evaluated by comparing their measurement accuracy of TDR-pulse travel time in a sand and sandy loam soil, and electrical conductivity in NaCl solutions. TDR probes <2.5 cm in length generated trough-haped TDR waveforms with rounded corners at the points of the pulse reflection from the probe ends. The sharpness of the pulse reflection on the waveforms increased with both the increasing probe length and soil-water content. The transition time for the propagation of TDR pulse at the probe entrance increased as the soil dried up. The increased transition time caused a rightward movement of the first peak of the waveform at the probe entrance. Because of such peak movement, TDR-support software algorithm determined travel path of TDR pulse through the probe that was smaller than the actual travel path. TDR-measured pulse travel time tTDR varied erratically with the predicted pulse travel time tg (from volumetric soil-water content) for the probes <2.5 cm in length. But, for all probes ³2.5 cm in length, tTDR varied linearly with tg and followed the 1:1 line. TDR could not measure tTDR <300 ps accurately. A minimum probe length Lmin and the lowest allowable soil-water content qmin that the probe can accurately measure govern this lowest pulse travel time tmin. The mean absolute deviation between tTDR and tg was 77 ps for the 2.3 cm long probe and 1.39 ps for all probes ≥2.5 cm in length. All probes ≥2.5 cm in length measured electrical conductivity of salt solutions sTDR that compared well with the electrical conductivity measured by a conductivity meter sm. The length of the probes did not exert any noticeable influence on the accuracy of electrical conductivity measurement. Keywords: TDR probe, pulse travel time, dielectric constant, electrical conductivity
Nearshore circulation revealed by wastewater discharge from a submarine outfall, Aveiro Coast, Portugal
Authors: Figueiredo da Silva J. , Duck R. W. , Hopkins T. S. , Anderson J. M.
Published: April 2010

Abstract. The morphological and climatic conditions of the Atlantic coast of northern Portugal result in a prevailing upwelling circulation over the continental shelf. A submarine outfall releases wastewater into the ocean c. 3 km directly offshore (at ∼16 m water depth) from S. Jacinto, 5 km to the north of the inlet to the estuarine coastal lagoon system of the Ria de Aveiro. The buoyant plume has a distinctive reddish brown colour and is clearly visible at the water surface. The transport and dispersion of the plume was monitored by airborne photography and by in situ water sampling. Results revealed the surface currents present and water mass fronts in the nearshore zone of the Aveiro coast. During the spring and summer, the plume was not transported offshore in the manner expected by the upwelling shelf circulation. Instead, it was commonly observed to be transported alongshore with the prevailing southerly circulation or with an onshore component. The transport to the south caused the outfall plume to interact with the circulation associated with the tidal currents generated in the inlet channel to the Ria de Aveiro. The observations suggest that the trophic status of the Ria de Aveiro is unlikely to change because of the operation of the submarine outfall. Furthermore, this study demonstrates how simple observations of wastewater discharge from a submarine outfall can be used to improve understanding of nearshore circulation. Keywords: water circulation, upwelling, ocean outfall, remote sensing, eutrophication, Ria de Aveiro
Bioturbation, ecosystem functioning and community structure
Authors: Biles C. L. , Paterson D. M. , Ford R. B. , Solan M. , Raffaelli D. G.
Published: April 2010

Abstract. The effect of community structure on the functioning of the ecosystem is an important issue in ecology due to continuing global species loss. The influence of infaunal community structure on the functioning of marine systems is proposed here to act primarily through bioturbation of the sediment. Nutrient concentration in the water column, generated by release from the sediment, was used as a measure of ecosystem functioning. In situ and laboratory experiments showed a significant difference in nutrient concentrations with different species treatments. Bioturbation profiles showing the incorporation of tracer particles also differed between communities with different dominant species. The behavioural differences between infaunal species, generating different modes and rates of bioturbation, are therefore proposed to influence nutrient release. The presence and quantity of bioturbating infauna also influenced the amount of sediment suspended in the water column. The increase in surface area available for microbial activity may generate an increase in nutrient cycling. Abiotic influences on sediment structure, such as flow, may have a similar effect on nutrient concentration. Annular flumes used in both laboratory and in situ experiments to generate flow conditions produced a significant increase in ammonia (NH4-N) production in macrofaunal treatments. Flow may influence the behaviour of macrofaunal species, causing changes in NH4-N production through modifying bioturbation of the sediment. Keywords: bioturbation, community structure, ccosystem functioning, estuaries, flow, infauna
The O and H stable isotope composition of freshwaters in the British Isles. 1. Rainfall
Authors: Darling W. G. , Talbot J. C.
Published: April 2010

Abstract. An understanding of the hydrological cycle in stable isotopic terms requires the characterisation of rainfall. This paper reviews existing and new data for the British Isles. Rainfall at the Wallingford (Oxfordshire) collection station was collected daily from November 1979 to October 1980. Large variations in isotopic content were noted, sometimes from day to day. Winter rainfall was similar to summer in amount, and only slightly depleted isotopically. Amount and temperature correlations with δ18O were generally low, only the autumn and winter temperature relationships being significant. A 20-year monthly dataset from 1982 to 2001 for Wallingford gives the following regression: δ2H = 7.0δ18O + 1.2, a slope somewhat below the world meteoric line but consistent with the those from other long-term stations in NW Europe. The data showed uncorrelated maxima and minima for each year, but rather more consistent amount-weighted averages. Although there is only a small difference in gradient between summer and winter rainfall values, when plotted against the month of the year there are clear changes in the values of both isotopes, and the δ2H-δ18O relationship as demonstrated by the d-excess parameter. The isotope-amount correlation is low but significant, with summer months appearing to be well-correlated when considered in terms of month of the year. On this same seasonal basis temperature has a strong correlation throughout the year, giving a positive δ18O-temperature relationship of 0.25 ‰ per °C change. The Wallingford monthly record is compared with data from Keyworth (Nottinghamshire) and the Valentia station of the GNIP (IAEA-WMO Global Network for Isotopes in Precipitation) in SW Ireland. While not large, differences between the stations are broadly attributable to the balance between maritime and continental influences. Over the period September 1981 to August 1982 the maximum number of monthly collection stations was operating across the British Isles. While a comparison of the sites serves mostly to illustrate the variability of British weather in space and time, there is clear isotopic evidence for the predominance of frontal rainfall in winter and convective rainfall in summer. The effect of altitude on isotopic content was measured within a high-relief stream catchment in Scotland. The best correlations occurred during winter, when an average relationship of approximately –0.30 ‰ δ18O per 100 m increase in altitude was observed. It is well established that rainfall isotopic composition changes in response to alterations in climate. However these changes are difficult to detect isotopically in the short term, even when the changes are indexed, e.g. in the form of the NAO (North Atlantic Oscillation). The brief duration of rainfall isotope records is a further hindrance; for the British Isles proxies such as tree-ring cellulose may have some value in extending the record back. Keywords: stable isotopes, rainfall,British Isles
Modelling persistence in annual Australia point rainfall
Authors: Whiting J. P. , Lambert M. F. , Metcalfe A. V.
Published: April 2010

Abstract. Annual rainfall time series for Sydney from 1859 to 1999 is analysed. Clear evidence of nonstationarity is presented, but substantial evidence for persistence or hidden states is more elusive. A test of the hypothesis that a hidden state Markov model reduces to a mixture distribution is presented. There is strong evidence of a correlation between the annual rainfall and climate indices. Strong evidence of persistence of one of these indices, the Pacific Decadal Oscillation (PDO), is presented together with a demonstration that this is better modelled by fractional differencing than by a hidden state Markov model. It is shown that conditioning the logarithm of rainfall on PDO, the Southern Oscillation index (SOI), and their interaction provides realistic simulation of rainfall that matches observed statistics. Similar simulation models are presented for Brisbane, Melbourne and Perth. Keywords: Hydrological persistence,hidden state Markov models, fractional differencing, PDO, SOI, Australian rainfall
An easily installable groundwater lysimeter to determine waterbalance components and hydraulic properties of peat soils
Authors: Schwaerzel K. , Bohl H. P.
Published: April 2010

Abstract. A simple method for the installation of groundwater lysimeters in peat soils was developed which reduces both time and financial effort significantly. The method was applied on several sites in the Rhinluch, a fen peat land 60 km northwest of Berlin, Germany. Over a two-year period, upward capillary flow and evapotranspiration rates under grassland with different groundwater levels were measured. The installation of tensiometers and TDR probes additionally allowed the in situ determination of the soil hydraulic properties (water retention and unsaturated hydraulic conductivity). The results of the measurements of the unsaturated hydraulic conductivity demonstrate that more than one single method has to be applied if the whole range of the conductivity function from saturation to highly unsaturated is to be covered. Measuring the unsaturated conductivity can be done only in the lab for an adequately wide range of soil moisture conditions. Keywords: peat soils, soil hydraulic properties, evapotranspiration, capillary flow, root distribution, unsaturated zone
TECHNICAL NOTE: First evidence of a structured and dynamic spatial pattern of rainfall within a small humid tropical catchment
Authors: Bidin K. , Chappell N. A.
Published: April 2010

Abstract. In a study of the spatial variability of rainfall across a network of 46 raingauges in a 4 km2 rainforest catchment in the interior of northeastern Borneo, seasonal rainfall totals were correlated with raingauge separation distance, aspect and relief. A very high degree of spatial variability in seasonal totals across a very small area was found, even in comparison with other regions experiencing convective rainfall. Moreover, it shows systematic, stochastic structure in rainfall is present over scales of 10s to 100s metres; these patterns change from the southwest monsoon (May-October) to the northeast monsoon (November-April). Local associations with aspect and relief are present but the seasonal changes in rainfall pattern over the whole 4 km2 catchment must relate to more complex local topographic effects on the regional windfield. Keywords: catchment, Malaysia,monsoon, rainfall, spatial variability
Review of recent advances in index flood estimation
Authors: Bocchiola D. , De Michele C. , Rosso R.
Published: April 2010

Abstract. Index flood estimation for regional flood frequency analysis needs to be based on the information available. The most appropriate method depends on the specific application and its choice requires a problem-oriented analysis. This paper presents a simple theoretical framework to deal with index flood estimation for a specific river site. The methodological approaches available for the purpose are reviewed. For each, the information required is specified and the reliability of the estimate, particularly desirable in risk analysis and management, is discussed. Where flood observations are lacking, indirect estimation must be undertaken using scenarios including those commonly met in hydrological practice; generally, these depend on the amount and type of information available. For each scenario, the methodologies are outlined, in order of the expected degree of complexity. After a guided analysis, an investigator can adopt the method providing the best tradeoff between effort in collecting and handling data and the resultant reliability which can be expected. Keywords: direct and indirect methods, index flood estimation, reliability, scenarios.
Characterising and modelling groundwater discharge in anagricultural wetland on the French Atlantic coast
Authors: Weng Ph. , Giraud F. , Fleury P. , Chevallier C.
Published: April 2010

Abstract. Interaction between a wetland and its surrounding aquifer was studied in the Rochefort agricultural marsh (150 km2). Groundwater discharge in the marsh was measured with a network of nested piezometers. Hydrological modelling of the wetland showed that a water volume of 770,000 m3 yr–1 is discharging into the marsh, but that this water flux essentially takes place along the lateral borders of the wetland. However, this natural discharge volume represents only 20% of the artificial freshwater injected each year into the wetland to maintain the water level close to the soil surface. Understanding and quantifying the groundwater component in wetland hydrology is crucial for wetland management and conservation. Keywords: wetland, hydrology, groundwater, modelling, marsh
Predicting recovery of acidified freshwaters in Europe and Canada: an introduction
Authors: Ferrier R. C. , Wright R. F. , Jenkins A. , Barth H.
Published: April 2010

Abstract. Abstract: The RECOVER: 2010 project was designed to assess the current and future anthropogenic pressures on sensitive European freshwater ecosystems. This pan–European assessment utilised a standardised predictive modelling approach to evaluate the degree of compliance with respect to the restoration of acidified waters by 2016, as specified under the EU Water Framework Directive (WFD), and evaluated the environmental benefits of proposed UN-ECE protocols on emissions control. Between 1970 and 2000, observations and model simulations show a significant decline in acidic surface water in all regions of Europe. This demonstrated the success of policies aimed at reducing emission of acidifying compounds. The nature and extent of future regional recovery from acidification is, however, dependent upon the historical pattern of deposition, regional ecosystem characteristics and the role of confounding factors, which may delay the onset of recovery or the magnitude of response. Model predictions to 2010 and beyond emphasise the continued benefit of currently proposed reductions, as reflected by the degree of recovery of freshwater ecosystems. A key component was to link such hydrochemical recovery with ecological response, and the project aimed to evaluate this against current WFD criteria of “good status" and “reference conditions". The RECOVER: 2010 project research has also played a major role in defining the dynamic modelling outputs which will be required to support the review of the Gothenburg Protocol within the work of the UN-ECE CLRTAP Working Group on Effects (WGE), and model outputs have been made available to a range of national agencies throughout Europe. Keyword: recovery, acidification, modelling, policy, good status, reference conditions
Long-term development of acid deposition (1880–2030) in sensitive freshwater regions in Europe
Authors: Schöpp W. , Posch M. , Mylona S. , Johansson M.
Published: April 2010

Abstract. Time series of the deposition of acidifying substances are a pre-requisite for the study of the acidification and recovery of ecosystems such as surface waters. This paper reports the derivation and calculation of deposition trends of the potentially acidifying compounds SO2, NOx and NH3 in sensitive freshwater regions in Europe studied in the EU-funded RECOVER: 2010 project. The time interval covered is 151 years: from 1880, which can be considered as the pre-industrial era in most countries, to 2030, taking into account the consequences of current emission reduction agreements in Europe. The historic and predicted emissions for European countries are used to calculate the deposition development in the study areas, using meteorologically averaged atmospheric source-receptor transfer coefficients derived from the EMEP Lagrangian acid deposition model. These time series were used as driving forces for the application of the dynamic acidification model MAGIC to study the acidification and recovery of sensitive freshwater ecosystems in Europe. Keywords: acid deposition, historic depositions, sensitive lake regions, Europe
Modelling reversibility of central European mountain lakes from acidification: Part II – the Tatra Mountains
Authors: Kopácek J. , Cosby B. J. , Majer V. , Stuchlík E. , Veselý J.
Published: April 2010

Abstract. A dynamic, process-based model of surface water acidification, MAGIC7, has been applied to four representative alpine lakes in the Tatra Mountains (Slovakia and Poland). The model was calibrated for a set of 12 to 22-year experimental records of lake water composition. Surface water and soil chemistry were reconstructed from 1860 to 2002 and forecast to 2050 based on the reduction in sulphur and nitrogen emissions presupposed by the Gothenburg Protocol. Relatively small changes in the soil C:N ratios were not sufficient to simulate observed changes in NO3‾ concentrations, so an alternative empirical approach of changes in terrestrial N uptake was applied. Measured sulphate sorption isotherms did not allow calibration of the pattern of sulphate response in the lakes, indicating that other mechanisms of S release were also important. The lake water chemistry exhibited significant changes during both the acidification advance (1860 to 1980s) and retreat (1980s to 2010). An increase in lake water concentrations of strong acid anions (SAA; 104–149 μeq l–1) was balanced by a decline in HCO3‾ (13–62 μeq l–1) and an increase in base cations (BC; 42–72 μeq l–1), H+ (0-18 μeq l–1), and Alin+ (0–26 μeq l–1). The carbonate buffering system was depleted in three lakes. In contrast, lake water concentrations of SAA, BC, H+, and Alin+ decreased by 57–82, 28–42, 0–11, and 0–22 μeq l–1, respectively, the carbonate buffering system was re-established, and HCO3‾ increased by 1–21 μeq l–1 during the chemical reversal from atmospheric acidification (by 2000). The MAGIC7 model forecasts a slight continuation in this reversal for the next decade and new steady-state conditions thereafter. Gran alkalinity should come back to 1950s levels (0–71 μeq l–1) in all lakes after 2010. Partial recovery of the soil pool of exchangeable base cations can be expected in one catchment, while only conservation of the current conditions is predicted for three lakes. Even though the pre-industrial alkalinity values of 16–80 μeq l–1 will not be reached due to the insufficient recovery of soil quality, the ongoing chemical improvement of water should be sufficient for biological recovery of most alpine lakes in the Tatra Mountains. Keywords: MAGIC, atmospheric deposition, sulphate, nitrate, base cations, aluminium, alkalinity, pH