bluuebunny/crossref_metadata_2025 huggingface dataset:
Simulation of flood reduction by natural river rehabilitation using a distributed hydrological model
Authors: Liu Y. B. , Gebremeskel S. , de Smedt F. , Hoffmann L. , Pfister L.
Published: April 2010

Abstract. The effects of river rehabilitation on flood reduction in the Steinsel sub-basin of the Alzette River basin, Grand-Duchy of Luxembourg, are discussed; the rehabilitation measures include planting and changing riparian and in-stream vegetation, and re-meandering of channelised reaches, etc. in the headwater streams. To simulate flood reduction by river rehabilitation, the streams have been classified into different orders and by assessing the response of the stream channels to the resistance or obstruction of flows. Based on this assessment, the roughness to the flow in the first and second order streams is adjusted in line with the river rehabilitation while the roughness of higher order channels downstream is unchanged. The hydrological analysis utilises the WetSpa distributed model based on spatial information on topography, soil type and land use. The increased channel roughness in the headwater channels delays the flows, so that peak discharges at the outlet of the basin are reduced. The simulation indicates that, after river naturalisation, the reduction in peak flow can be as much as 14% and the time of concentration may be delayed by as much as two hours. Also, an impact analysis has assessed the possible flood reduction for a changed climate scenario. Keywords: river rehabilitation, flood reduction, distributed hydrological modelling, WetSpa
The origin of summer monsoon rainfall at New Delhi by deuterium excess
Authors: Pang Hongxi , He Yuanqing , Zhang Zhonglin , Lu Aigang , Gu Juan
Published: April 2010

Abstract. The deuterium excess in summer monsoon precipitation, determined from isotopic measurements(δ18O and
Research Note:Effects of human activities on the Yangtze River suspended sediment flux into the estuary in the last century
Authors: Yang S. L. , Shi Z. , Zhao H. Y. , Li P. , Dai S. B. , Gao A.
Published: April 2010

Abstract. The surface erosion area in the Yangtze River basin increased from 364×103 km2 in the 1950s to 707×103 km2 in 2001 due to a great increase in population. Based on the regression relationship between surface erosion area and population, the surface erosion area was predicted to be about 280×103 km2 at the beginning of the 20th century. The sediment yield, which increased by about 30% during the first six decades of the 20th century, was closely related to the surface erosion area in this river basin. The Yangtze annual suspended sediment flux into the estuary was about 395×106 t a-1 at the beginning of the century, and this gradually increased to an average of 509×106 t a-1 in the 1960s. The increase in the suspended sediment flux into the estuary was accelerated in the 1950s and the 1960s due to the rapid increase in population and land use immediately after the Second World War and the Liberation War. After the riverine suspended sediment flux reached its maximum in the 1960s, it decreased to <206×106 t a-1 in 2003. Construction of dams was found to be the principal cause for this decreasing trend because, during the same period, (a) the riverine water discharge did not show a decreasing trend, (b) water diversion was not influential and (c) sedimentation in lakes and canals of the middle and lower reaches did not increase. The total storage capacity of reservoirs has increased dramatically over the past half century. The amount of sediment trapped in reservoirs has increased to more than half a billion t a-1. As a result, the suspended sediment flux into the estuary dramatically decreased, even though the sediment yield from many areas of the basin increased in recent decades. Human activities gradually increased the suspended sediment flux into the estuary before the 1960s and then rapidly decreased it. The last century was a period when the Yangtze suspended sediment flux into the estuary was dramatically affected by human activities. Keywords: riverine sediment flux, human activities, surface erosion, dam, Yangtze (Changjiang) River
Direct measurement of the soil water retention curve using X-ray absorption
Authors: Bayer A. , Vogel H.-J. , Roth K.
Published: April 2010

Abstract. X-ray absorption measurements have been explored as a fast experimental approach to determine soil hydraulic properties and to study rapid dynamic processes. As examples, the pressure-saturation relation θ(Ψ) for a uniform sand column has been considered as has capillary rise in an initially dry sintered glass column. The θ(Ψ)-relation is in reasonable agreement with that obtained by inverting a traditional multi-step outflow experiment. Monitoring the initial phase of capillary rise reveals behaviour that deviates qualitatively from the single-phase, local-equilibrium regime described by Richards’ equation. Keywords: X-ray absorption, soil hydraulic properties, soil water dynamics, Richards’ equation
234U/238U Disequilibrium along stylolitic discontinuities in deep Mesozoic limestone formations of the Eastern Paris basin: evidence for discrete uranium mobility over the last 1–2 million years
Authors: Deschamps P. , Hillaire-Marcel C. , Michelot J.-L. , Doucelance R. , Ghaleb B. , Buschaert S.
Published: April 2010

Abstract. The (234U/238) equilibrium state of borehole core samples from the deep, low-permeability limestone formations surrounding the target argilite layer of the Meuse/Haute-Marne experimental site of the French agency for nuclear waste management -ANDRA- (Agence nationale pour la gestion des déchets radioactifs) was examined to improve understanding of naturally occurring radionuclide behaviour in such geological settings. Highly precise, accurate MC-ICP-MS measurements of the (234U/238U) activity ratio show that limestone samples characterised by pressure dissolution structures (stylolites or dissolution seams) display systematic (234U/238U) disequilibria, while the pristine carbonate samples remain in the secular equilibrium state. The systematic feature is observed throughout the zones marked by pressure dissolution structures: (i) the material within the seams shows a deficit of 234U over 238U ((234U/238U) down to 0.80) and (ii) the surrounding carbonate matrix is characterised by an activity ratio greater than unity (up to 1.05). These results highlight a centimetric-scale uranium remobilisation in the limestone formations along these sub-horizontal seams. Although their nature and modalities are not fully understood, the driving processes responsible for these disequilibria were active during the last 1–2 Ma. Keywords: uranium isotopes, multiple-collector ICP-MS, waste management, remobilisation, migration
An analysis of the long-term variation in stream water quality for three upland catchments at Loch Dee (Galloway, S.W. Scotland) under contrasting land management
Authors: Langan S. J. , Hirst D.
Published: April 2010

Abstract. A long term record of water chemistry, consisting of twenty years of weekly spot samples, from three sub-catchments draining into a loch and the loch outflow in Galloway, S.W. Scotland have been analysed. The analysis undertaken consisted of a three component statistical trend model. The technique allows the identification of long-term, seasonal and short-term trends, as well as differentiation between base flow and high flow responses. The land usage in the three sub-catchments is moorland, forest and forest plus lime. The results show that, since the mid-1980s, there has been a gradual decline in stream-water sulphate of the same order as reductions in the deposition of non-marine sulphate. Superimposed on this trend are somewhat random but considerable perturbations to this decline, caused by sea-salt deposition. There is no evidence of changes in surface water nitrate concentrations. The influence of different land management is evident in the sulphate, nitrate and pH data, whilst variations in calcium concentrations are also a product of differences in hydrological routing and the impact of sea-salt episodes. Keywords: trend analysis, acid deposition, land management, water quality, sea-salts, Galloway, S.W. Scotland
The water quality functioning of the upper River Severn, Plynlimon, mid-Wales: issues of monitoring, process understanding and forestry
Authors: Neal C.
Published: April 2010

Abstract. An overview of hydrochemical studies of the upper River Severn catchment in the Plynlimon region of mid-Wales, as linked to twenty years of research at CEH Wallingford, is presented. The work provides a bibliography of publications to date and illustrates that the water quality changes associated with felling are often small when compared with the effects of climate variability. The felling effects are manifested most clearly at the local scale and with clear as opposed to phased felling. Phased felling over several years, which is standard forestry practice, provides a much reduced response. The highly heterogeneous nature of the catchment is emphasised. This complexity makes identification and modelling of the changes very difficult to describe in terms of space and time. Long-term records (forty years or more) are needed to allow assessment of the changing water quality patterns associated with climate variability, climate change, changing pollutant deposition patterns and forestry rotation cycles. More detailed but still long-term (daily to sub-daily) records are required to examine ``fractal processes": within the fine structure is a high information content that can help unravel the dynamics of the internal workings of the catchment in a way that experiments at the plot scale cannot resolve. Keywords: nutrients, acidity, trace metals, trace elements, Plynlimon, River Severn, forestry, fractals
Riparian forestry management and adult stream insects
Authors: Briers R. A. , Gee J. H. R.
Published: April 2010

Abstract. The impacts of coniferous plantation forestry on the biology of upland streams in the UK are firmly established. Whilst benthic communities have been well studied, very little research has considered the impacts of riparian forestry management on adult stream insects, yet the essentially terrestrial adult (reproductive) phase may be important in determining the abundance and distribution of larval stages. Riparian vegetation has a potentially strong impact on survival and success of adult stages through alteration of microclimate, habitat structure and potential food sources, in addition to effects carried over from larval stages. Here, current riparian management strategies are analysed in the light of available information on the ecology of adult stream insects. On the whole, management practices appear to favour adult stream insects, although an increase in tree cover in riparian areas could be beneficial, by providing more favourable microclimatic conditions for adults. This conclusion is drawn based on rather limited information, and the need for further research into the effects of riparian forestry management on adult stream insects is highlighted. Keywords: microclimate, plantation, life history, riparian vegetation
Regional variations in diffuse nitrogen losses from agriculture in the Nordic and Baltic regions
Authors: Vagstad N. , Stålnacke P. , Andersen H.-E. , Deelstra J. , Jansons V. , Kyllmar K. , Loigu E. , Rekolainen S. , Tumas R.
Published: April 2010

Abstract. This paper describes nitrogen losses from, and the characteristics of, 35 selected catchments (12 to 2000 ha) in the Nordic and Baltic countries. Average annual losses of N in 1994–1997 ranged from 5 to 75 kg ha-1, generally highest and characterised by significant within-country and interannual variations, in Norway and the lowest losses were observed in the Baltic countries. An important finding of the study is that the average nutrient losses varied greatly among the studied catchments. The main explanations for this variability were water runoff, fertiliser use (especially the amount of manure), soil type and erosion (including stream bank erosion). However, there were several exceptions, and it was difficult to find general relationships between the individual factors. For example, there was poor correlation between nitrogen losses and surpluses. Therefore, the results suggest that the observed variability in N losses cannot have been due solely to differences in farm management practices, although the studied catchments do include a wide range of nutrient application levels, animal densities and other relevant elements. There is considerable spatial variation in the physical properties (soil, climate, hydrology, and topography) and the agricultural management of the basins, and the interaction between and relative effects of these factors has an important impact on erosion and nutrient losses. In particular, hydrological processes may have a marked effect on N losses measured in the catchment stream water. The results indicate that significant differences in hydrological pathways (e.g. the relationship between fast- and slow-flow processes) lead to major regional differences in N inputs to surface waters and therefore also in the response to changes in field management practices. Agricultural practices such as crop rotation systems, nutrient inputs and soil conservation measures obviously play a significant role in the site-specific effects, although they cannot explain the large regional differences observed in this study. The interactions between agricultural practices and basic catchment characteristics, including hydrological processes, determine the final losses of nitrogen to surface waters, hence it is necessary to understand these interactions to manage diffuse losses of agricultural nutrients efficiently. Keywords: agriculture, catchments, diffuse sources, nitrogen, losses, Baltic, Nordic
Indicators of nitrate in wetland surface and soil-waters: interactions of vegetation and environmental factors
Authors: Kennedy M. P. , Murphy K. J.
Published: April 2010

Abstract. This paper describes a new bio-indicator method for assessing wetland ecosystem health; as such, the study is particularly relevant to current legislation such as the EU Water Framework Directive, which provides a baseline of the current status of surface waters. Seven wetland sites were monitored across northern Britain, with model construction data for predicting eco-hydrological relationships collected from five sites during 1999. Two new sites and one repeat site were monitored during 2000 to provide model test data. The main growing season for the vegetation, and hence the sampling period, was May–August during both years. Seasonal mean concentrations of nitrate (NO3-) in surface and soil water samples during 1999 ranged from 0.01 to 14.07 mg N l–1, with a mean value of 1.01 mg N l–1. During 2000, concentrations ranged from trace level (<0.01 mg N l–1) to 9.43 mg N l–1, with a mean of 2.73 mg N l–-1. Surface and soil-water nitrate concentrations did not influence plant species composition significantly across representative tall herb fen and mire communities. Predictive relationships were found between nitrate concentrations and structural characteristics of the wetland vegetation, and a model was developed which predicted nitrate concentrations from measures of plant diversity, canopy structure and density of reproductive structures. Two further models, which predicted stem density and density of reproductive structures respectively, utilised nitrate concentration as one of the independent predictor variables. The models were tested where appropriate using data collected during 2000. This approach is complementary to species-based monitoring, representing a useful and simple tool to assess ecological status in target wetland systems and has potential for bio-indication purposes. Keywords: bio-indicators, surface water, water quality, wetland vegetation
A simple model for predicting soil temperature in snow-covered and seasonally frozen soil: model description and testing
Authors: Rankinen K. , Karvonen T. , Butterfield D.
Published: April 2010

Abstract. Microbial processes in soil are moisture, nutrient and temperature dependent and, consequently, accurate calculation of soil temperature is important for modelling nitrogen processes. Microbial activity in soil occurs even at sub-zero temperatures so that, in northern latitudes, a method to calculate soil temperature under snow cover and in frozen soils is required. This paper describes a new and simple model to calculate daily values for soil temperature at various depths in both frozen and unfrozen soils. The model requires four parameters: average soil thermal conductivity, specific heat capacity of soil, specific heat capacity due to freezing and thawing and an empirical snow parameter. Precipitation, air temperature and snow depth (measured or calculated) are needed as input variables. The proposed model was applied to five sites in different parts of Finland representing different climates and soil types. Observed soil temperatures at depths of 20 and 50 cm (September 1981–August 1990) were used for model calibration. The calibrated model was then tested using observed soil temperatures from September 1990 to August 2001. R2-values of the calibration period varied between 0.87 and 0.96 at a depth of 20 cm and between 0.78 and 0.97 at 50 cm. R2-values of the testing period were between 0.87 and 0.94 at a depth of 20cm, and between 0.80 and 0.98 at 50cm. Thus, despite the simplifications made, the model was able to simulate soil temperature at these study sites. This simple model simulates soil temperature well in the uppermost soil layers where most of the nitrogen processes occur. The small number of parameters required means that the model is suitable for addition to catchment scale models. Keywords: soil temperature, snow model
Calibration of the INCA model in a Mediterranean forested catchment: the effect of hydrological inter-annual variability in an intermittent stream
Authors: Bernal S. , Butturini A. , Riera J. L. , Vázquez E. , Sabater F.
Published: April 2010

Abstract. Mediterranean regions are characterised by a stream hydrology with a marked seasonal pattern and high inter-annual variability. Accordingly, soil N processes and leaching of solutes in Mediterranean regions also show a marked seasonality, occurring in pulses as soils re-wet following rain. The Integrated Nitrogen Catchment model (INCA) was applied to Fuirosos, a Mediterranean catchment located in NE Spain using hydrological data and streamwater nitrate and ammonium concentrations collected from 1999 to 2002. This study tested the model under Mediterranean climate conditions and assessed the effect of the high inter-annual variability on the ability of INCA to simulate discharge and N fluxes. The model was calibrated for the whole three-year period and the n coefficients of determinion (r2) between simulated and observed data were 0.54 and 0.1 for discharge and nitrate temporal dynamics, respectively. Ammonium dynamics were simulated poorly and the linear regression between observed and simulated data was not significant statistically. To assess the effect of inter-annual variability on INCA simulations, the calibration process was run separately for two contrasting hydrological years: a dry year with a total rainfall of 525 mm and a wet year with a total of 871 mm. The coefficients of determination for the correlation between observed and simulated discharge for these two periods were 0.67 (p<0.0001) and 0.62 (p<0.0001), respectively. Nitrate temporal dynamics were not simulated as well in the dry year (r2 = 0.13 p<0.0001) as in the wet year (r2 = 0.56 p<0.0001). Annual nitrate balances were similar to those estimated from observations. Results suggest that, in Mediterranean catchments, both hydrology and nitrate mobilisation are influenced strongly by soil moisture, which is highly variable within and between years; also, a single parameter set is insufficient to capture the inter-annual variability in Fuirosos. It is suggested that, when using INCA in semiarid systems such as those in Mediterranean regions, certain of the parameters currently fixed in INCA (e.g. base flow index or drainage area) be treated as variables dependent on soil moisture deficit. Keywords: environmental modelling, intermittent stream, Mediterranean climate, Fuirosos, hydrology, nitrate
Comparative simulation of the nitrogen dynamics using the INCA model and a neural network analysis: implications for improved nitrogen modelling
Authors: Lischeid G. , Langusch J.
Published: April 2010

Abstract. Continuing deposition of nitrogen in forested catchments affects stream and groundwater quality. However, the dependence of nitrogen dynamics on climatic and hydrological boundary conditions is still poorly understood. These dynamics have been investigated by applying the process-oriented Integrated Nitrogen in CAtchments (INCA) model and an artificial neural network to the data set from the forested Steinkreuz catchment in South Germany. The data comprise daily values of precipitation, air temperature and discharge of the catchment runoff. The INCA model simulated the mean nitrate concentration in the stream as well as seasonal fluctuations but it underestimated the short-term variance of the observed stream water nitrate concentration, especially the pronounced concentration peaks in late summer. In contrast, the artificial neural network matched the short-term dynamics using non-linear regressions with stream discharge and air temperature data. The results provide strong evidence that the short-term dynamics of stream nitrate concentration during storm-flow were generated in the riparian zone, which is less than 1% of the catchment area, and is not considered explicitly in the INCA model. The concentration peaks have little effect on the catchment’s nitrogen budget and the shallow groundwater data suggest that the short-term hydrological dynamics also govern groundwater recharge in the upland parts of the catchment. This substantial underestimate by the INCA model parameterisation is balanced by a corresponding underestimate of denitrification in clayey layers of the deeper aquifer. A better understanding of these processes is necessary to improve long-term risk assessments. Keywords: catchment, runoff, nitrogen, INCA, artificial neural network, flushing
The trends and dependencies between air and water temperatures in lakes in northern Poland in 1961–2000
Authors: Dabrowski M. , Marszelewski W. , Skowron R.
Published: April 2010

Abstract. Over 40 years, from 1961–2000, daily mean values of surface lake water temperatures at 0.4 m depth in six lakes in northern Poland were recorded with nearby mean daily air temperatures at 2 m. Air temperatures increased on average from 0.020 to 0.025°C year–1 while lake-water temperatures varied more but increased by 0.005 to 0.028°C year-1. For shorter periods (for instance, for 10 days) the pattern of trend directions and values was more complex, depending on the morphometric and trophic conditions of the lakes. It has been concluded that changes in lake water temperatures during climate warming may be documented by studies of lakes located relatively closely together (up to 300 kilometres). Keywords: physical limnology, climate changes, lake water, temperature
Simulating nitrogen budgets in complex farming systems using INCA: calibration and scenario analyses for the Kervidy catchment (W. France)
Authors: Durand P.
Published: April 2010

Abstract. The integrated nitrogen model INCA (Integrated Nitrogen in Catchments) was used to analyse the nitrogen dynamics in a small rural catchment in Western France. The agrosystem studied is very complex, with: extensive use of different organic fertilisers, a variety of crop rotations, a structural excess of nitrogen (i.e. more animal N produced by the intensive farming than the N requirements of the crops and pastures), and nitrate retention in both hydrological stores and riparian zones. The original model features were adapted here to describe this complexity. The calibration results are satisfactory, although the daily variations in stream nitrate are not simulated in detail. Different climate scenarios, based on observed climate records, were tested; all produced a worsening of the pollution in the short term. Scenarios of alternative agricultural practices (reduced fertilisation and catch crops) were also analysed, suggesting that a reduction by 40% of the fertilisation combined with the introduction of catch crops would be necessary to stop the degradation of water quality. Keywords: diffuse pollution, nitrate, climate change, model
Groundwater redox conditions and conductivity in a contaminant plume from geoelectrical investigations
Authors: Naudet V. , Revil A. , Rizzo E. , Bottero J.-Y. , Bégassat P.
Published: April 2010

Abstract. Accurate mapping of the electrical conductivity and of the redox potential of the groundwater is important in delineating the shape of a contaminant plume. A map of redox potential in an aquifer is indicative of biodegradation of organic matter and of concentrations of redox-active components; a map of electrical conductivity provides information on the mineralisation of the groundwater. Both maps can be used to optimise the position of pumping wells for remediation. The self-potential method (SP) and electrical resistivity tomography (ERT) have been applied to the contaminant plume associated with the Entressen landfill in south-east France. The self-potential depends on groundwater flow (electrokinetic contribution) and redox conditions ("electro-redox" contribution). Using the variation of the piezometric head in the aquifer, the electrokinetic contribution is removed from the SP signals. A good linear correlation (R2=0.85) is obtained between the residual SP data and the redox potential values measured in monitoring wells. This relationship is used to draw a redox potential map of the overall contaminated site. The electrical conductivity of the subsoil is obtained from 3D-ERT analysis. A good linear correlation (R2=0.91) is observed between the electrical conductivity of the aquifer determined from the 3D-ERT image and the conductivity of the groundwater measured in boreholes. This indicates that the formation factor is nearly homogeneous in the shallow aquifer at the scale of the ERT. From this correlation, a map of the pore water conductivity of the aquifer is obtained. Keywords: self-potential, redox potential, electrical resistivity tomography, fluid conductivity, contaminant plume
WANDA, a regional dynamic nitrogen model (With Aggregated Nitrogen DynAmics) for nitrate leaching from forests
Authors: Tietema A.
Published: April 2010

Abstract. Nitrate concentrations in recently infiltrated groundwater in forested areas in the Netherlands are slowly increasing towards the EU limit of 50 mg NO3 l–1. The origin of this nitrate is thought to be leaching from nitrogen (N) saturated semi-natural ecosystems in these areas. To simulate nitrate leaching on a regional scale, the empirical model WANDA (a regional nitrogen model With Aggregated Nitrogen DynAmics) is introduced. The model is built around the concept that in forests the C:N ratio of the organic layer is indicative of the amount of nitrate leaving the system in drainage. WANDA was tested on a regional dataset of an infiltration area of 10 km2. This infiltration area consisted of 350 forest stands draining to the catchment "Edese Bos" used by a drinking water company. In 75 of the 350 forest stands the C:N ratio of the organic layer was measured. In 30 of these 75 stands, the nitrate concentrations below the rooting zone were measured. A hydrological model calculated water fluxes. The C:N ratio of the 75 stands ranged from 15.7 to 31.3 g C g–1 N. Scots pine stands had the highest C:N ratios in the organic layer. Nitrate concentrations varied in the 30 stands from 0.6 to 70 mg NO3 l–1. The nitrate concentrations in the Douglas fir stands were higher, and in the beech stands lower, than those observed in the locations with other tree species. WANDA predicted nitrate concentrations well, but improvements are required to simulate nitrate fluxes. The simulation of the water fluxes in WANDA is probably where more focussed modelling effort is now required. Keywords: nitrogen, nitrate, forest, model, WANDA, C:N ratio, organic layer
Temporal variability in phosphorus transfers: classifying concentration–discharge event dynamics
Authors: Haygarth P. , Turner B.L. , Fraser A. , Jarvis S. , Harrod T. , Nash D. , Halliwell D. , Page T. , Beven K.
Published: April 2010

Abstract. The importance of temporal variability in relationships between phosphorus (P) concentration (Cp) and discharge (Q) is linked to a simple means of classifying the circumstances of Cp–Q relationships in terms of functional types of response. New experimental data at the upstream interface of grassland soil and catchment systems at a range of scales (lysimeters to headwaters) in England and Australia are used to demonstrate the potential of such an approach. Three types of event are defined as Types 1–3, depending on whether the relative change in Q exceeds the relative change in Cp (Type 1), whether Cp and Q are positively inter-related (Type 2) and whether Cp varies yet Q is unchanged (Type 3). The classification helps to characterise circumstances that can be explained mechanistically in relation to (i) the scale of the study (with a tendency towards Type 1 in small scale lysimeters), (ii) the form of P with a tendency for Type 1 for soluble (i.e., <0.45 μm P forms) and (iii) the sources of P with Type 3 dominant where P availability overrides transport controls. This simple framework provides a basis for development of a more complex and quantitative classification of Cp–Q relationships that can be developed further to contribute to future models of P transfer and delivery from slope to stream. Studies that evaluate the temporal dynamics of the transfer of P are currently grossly under-represented in comparison with models based on static/spatial factors. Keywords: phosphorus, concentration, discharge, lysimeters, temporal dynamics, overland flow
Recession-based hydrological models for estimating low flows in ungauged catchments in the Himalayas
Authors: Rees H. G. , Holmes M. G. R. , Young A. R. , Kansakar S. R.
Published: April 2010

Abstract. The Himalayan region of Nepal and northern India experiences hydrological extremes from monsoonal floods during July to September, when most of the annual precipitation falls, to periods of very low flows during the dry season (December to February). While the monsoon floods cause acute disasters such as loss of human life and property, mudslides and infrastructure damage, the lack of water during the dry season has a chronic impact on the lives of local people. The management of water resources in the region is hampered by relatively sparse hydrometerological networks and consequently, many resource assessments are required in catchments where no measurements exist. A hydrological model for estimating dry season flows in ungauged catchments, based on recession curve behaviour, has been developed to address this problem. Observed flows were fitted to a second order storage model to enable average annual recession behaviour to be examined. Regionalised models were developed, using a calibration set of 26 catchments, to predict three recession curve parameters: the storage constant; the initial recession flow and the start date of the recession. Relationships were identified between: the storage constant and catchment area; the initial recession flow and elevation (acting as a surrogate for rainfall); and the start date of the recession and geographic location. An independent set of 13 catchments was used to evaluate the robustness of the models. The regional models predicted the average volume of water in an annual recession period (1st of October to the 1st of February) with an average error of 8%, while mid-January flows were predicted to within ±50% for 79% of the catchments in the data set. Keywords: Himalaya, recession curve, water resources, ungauged catchment, regionalisation, low flows
Constraints of artificial neural networks for rainfall-runoff modelling: trade-offs in hydrological state representation and model evaluation
Authors: de Vos N. J. , Rientjes T. H. M.
Published: April 2010

Abstract. The application of Artificial Neural Networks (ANNs) in rainfall-runoff modelling needs to be researched more extensively in order to appreciate and fulfil the potential of this modelling approach. This paper reports on the application of multi-layer feedforward ANNs for rainfall-runoff modelling of the Geer catchment (Belgium) using both daily and hourly data. The daily forecast results indicate that ANNs can be considered good alternatives for traditional rainfall-runoff modelling approaches, but the simulations based on hourly data reveal timing errors as a result of a dominating autoregressive component. This component is introduced in model simulations by using previously observed runoff values as ANN model input, which is a popular method for indirectly representing the hydrological state of a catchment. Two possible solutions to this problem of lagged predictions are presented. Firstly, several alternatives for representation of the hydrological state are tested as ANN inputs: moving averages over time of observed discharges and rainfall, and the output of the simple GR4J model component for soil moisture. A combination of these hydrological state representers produces good results in terms of timing, but the overall goodness of fit is not as good as the simulations with previous runoff data. Secondly, the possibility of using multiple measures of model performance during ANN training is mentioned.
Empirical Mode Decomposition in 2-D space and time: a tool for space-time rainfall analysis and nowcasting
Authors: Sinclair S. , Pegram G. G. S.
Published: April 2010

Abstract. A data-driven method for extracting temporally persistent information, at different spatial scales, from rainfall data (as measured by radar/satellite) is described, which extends the Empirical Mode Decomposition (EMD) algorithm into two dimensions. The EMD technique is used here to decompose spatial rainfall data into a sequence of high through to low frequency components. This process is equivalent to the application of successive low-pass spatial filters, but based on the observed properties of the data rather than the predetermined basis functions used in traditional Fourier or Wavelet decompositions. It has been suggested in the literature that the lower frequency components (those with large spatial extent) of spatial rainfall data exhibit greater temporal persistence than the higher frequency ones. This idea is explored here in the context of Empirical Mode Decomposition. The paper focuses on the implementation and development of the two-dimensional extension to the EMD algorithm and it's application to radar rainfall data, as well as examining temporal persistence in the data at different spatial scales.
Variability in stream discharge and temperature: a preliminary assessment of the implications for juvenile and spawning Atlantic salmon
Authors: Tetzlaff D. , Soulsby C. , Youngson A. F. , Gibbins C. , Bacon P. J. , Malcolm I. A. , Langan S.
Published: April 2010

Abstract. This study focuses on understanding the temporal variability in hydrological and thermal conditions in a small mountain stream and its potential implication for two life stages of Atlantic salmon (Salmo salar) – stream resident juveniles and returning adult spawners. Stream discharge and temperature in the Girnock Burn, NE Scotland, were characterised over ten hydrological years (1994/1995–2003/2004). Attention was focussed on assessing variations during particular ecologically "sensitive" time periods when selected life-stages of salmon behaviour may be especially influenced by hydrological and thermal conditions. Empirical discharge data were used to derive hydraulic parameters to predict the Critical Displacement Velocity (CDV) of juvenile salmon. This is the velocity above which fish may no longer be able to hold station in the water column and thus can be used as an index of time periods where feeding behaviour might be constrained. In the Girnock Burn, strong inter- and intra-annual variability in hydrological and thermal conditions may have important implications for feeding opportunities for juvenile fish; both during important growth periods in late winter and early spring, and the emergence of fry in the late spring. Time periods when foraging behaviour of juvenile salmon may be constrained by hydraulic conditions were assessed as the percentage time when CDV for 0+ and 1+ fish were exceeded by mean daily stream velocities. Clear seasonal patterns of CDV were apparent, with higher summer values driven by higher stream temperatures and fish length. Inter-annual variability in the time when mean stream velocity exceeded CDV for 0+ fish ranged between 29.3% (1997/1998) and 44.7% (2000/2001). For 1+ fish mean stream velocity exceeded CDV between 14.5% (1997/1998) and 30.7% (2000/2001) of the time. The movement of adult spawners into the Girnock Burn in preparation for autumn spawning (late October to mid-November) exhibited a complex relationship with hydrological variability with marked inter-annual contrasts. In years when discharge in the period prior to spawning was low, fish movement was increasingly triggered by suboptimal flow increases as spawning time approached. In contrast, wet years with numerous events allowed a much more even distribution of fish entry. Elucidating links between discharge/temperature variability and foraging opportunities and upriver migration of adult Atlantic salmon have the potential to contribute to the improvement of conservation strategies in both regulated and unregulated rivers.
Orographic effects on convective precipitation and space-time rainfall variability: preliminary results
Authors: Bongioannini Cerlini P. , Emanuel K. A. , Todini E.
Published: April 2010

Abstract. In the EFFS Project, an attempt has been made to develop a general framework to study the predictability of severe convective rainfall events in the presence of orography. Convective activity is embedded in orographic rainfall and can be thought as the result of several physical mechanisms. Quantifying its variability on selected area and time scales requires choosing the best physical representation of the rainfall variability on these scales. The main goal was (i) to formulate a meaningful set of experiments to compute the oscillation of variance due to convection inside model forecasts in the presence of orography and (ii) to give a statistical measure of it that might be of value in the operational use of atmospheric data. The study has been limited to atmospheric scales that span the atmosphere from 2 to 200 km and has been focused on extreme events with deep convection. Suitable measures of the changing of convection in the presence of orography have been related to the physical properties of the rainfall environment. Preliminary results for the statistical variability of the convective field are presented.
Significance of spatial variability in precipitation for process-oriented modelling: results from two nested catchments using radar and ground station data
Authors: Tetzlaff D. , Uhlenbrook S.
Published: April 2010

Abstract. The importance of considering the spatial distribution of rainfall for process-oriented hydrological modelling is well-known. However, the application of rainfall radar data to provide such detailed spatial resolution is still under debate. In this study the process-oriented TACD (Tracer Aided Catchment model, Distributed) model had been used to investigate the effects of different spatially distributed rainfall input on simulated discharge and runoff components on an event base. TACD is fully distributed (50x50m2 raster cells) and was applied on an hourly base. As model input rainfall data from up to 7 ground stations and high resolution rainfall radar data from operational C-band radar were used. For seven rainfall events the discharge simulations were investigated in further detail for the mountainous Brugga catchment (40km2) and the St. Wilhelmer Talbach (15.2km2) sub-basin, which are located in the Southern Black Forest Mountains, south-west Germany. The significance of spatial variable precipitation data was clearly demonstrated. Dependent on event characteristics, localized rain cells were occasionally poorly captured even by a dense ground station network, and this resulted in inadequate model results. For such events, radar data can provide better input data. However, an extensive data adjustment using ground station data is required. For this purpose a method was developed that considers the temporal variability in rainfall intensity in high temporal resolution in combination with the total rainfall amount of both data sets. The use of the distributed catchment model allowed further insights into spatially variable impacts of different rainfall estimates. Impacts for discharge predictions are the largest in areas that are dominated by the production of fast runoff components. The improvements for distributed runoff simulation using high resolution rainfall radar input data are strongly dependent on the investigated scale, the event characteristics and the existing monitoring network.
Coupling meteorological and hydrological models for flood forecasting
Authors:   Bartholmes,   Todini
Published: April 2010

Abstract. This paper deals with the problem of analysing the coupling of meteorological meso-scale quantitative precipitation forecasts with distributed rainfall-runoff models to extend the forecasting horizon. Traditionally, semi-distributed rainfall-runoff models have been used for real time flood forecasting. More recently, increased computer capabilities allow the utilisation of distributed hydrological models with mesh sizes from tenths of metres to a few kilometres. On the other hand, meteorological models, providing the quantitative precipitation forecast, tend to produce average values on meshes ranging from slightly less than 10 to 200 kilometres. Therefore, to improve the quality of flood forecasts, the effects of coupling the meteorological and the hydrological models at different scales were analysed. A distributed hydrological model (TOPKAPI) was developed and calibrated using a 1x1 km mesh for the case of the river Po closed at Ponte Spessa (catchment area c. 37000 km2). The model was then coupled with several other European meteorological models ranging from the Limited Area Models (provided by DMI and DWD) with resolutions from 0.0625° * 0.0625°, to the ECMWF ensemble predictions with a resolution of 1.85° * 1.85°. Interesting results, describing the coupled model behaviour, are available for a meteorological extreme event in Northern Italy (Nov. 1994). The results demonstrate the poor reliability of the quantitative precipitation forecasts produced by meteorological models presently available; this is not resolved using the Ensemble Forecasting technique, when compared with results obtainable with measured rainfall.
Impact of phosphorus control measures on in-river phosphorus retention associated with point source pollution
Authors: Demars B. O. L. , Harper D. M. , Pitt J.-A. , Slaughter R.
Published: April 2010

Abstract. In-river phosphorus retention alters the quantity and timings of phosphorus delivery to downstream aquatic systems. Many intensive studies of in-river phosphorus retention have been carried out but generally on a short time scale (2-4 years). In this paper, monthly water quality data, collected by the Environment Agency of England and Wales over 12 years (1990-2001), were used to model daily phosphorus fluxes and monthly in-river phosphorus retention in the lowland calcareous River Wensum, Norfolk, UK. The calibrated model explained 79% and 89% of the observed variance before and after phosphorus control, respectively. A split test revealed that predicted TP loads were in good agreement with observed TP loads (r2=0.85), although TP loads were underestimated under high flow conditions. During relatively dry years, there was no net export of phosphorus from the catchment. High retention of phosphorus occurred, particularly during the summer months, which was not compensated for, by subsequent higher flow events. This was despite a relatively modest critical discharge (Q) above which net remobilisation occur. Phosphorus removal from the effluent at two major STWs (Sewage Treatment Works) reduced phosphorus retention but not the remobilisation. This may indicate that the presence of impoundments and weirs, or overbank flows may have more control on the phosphorus dynamics under high flow conditions. Further phosphorus remedial strategies will be necessary to prevent downstream risks of eutrophication occurring independently of the unpredictable variability in weather conditions. More research is also needed to quantify the impact of the weir and overbank flows on phosphorus dynamics.
National flood modelling for insurance purposes: using IFSAR for flood risk estimation in Europe
Authors: Sanders R. , Shaw F. , MacKay H. , Galy H. , Foote M.
Published: April 2010

Abstract. Flood risk poses a major problem for insurers and governments who ultimately pay the financial costs of losses resulting from flood events. Insurers therefore face the problem of how to assess their exposure to floods and how best to price the flood element of their insurance products. This paper looks at the insurance implications of recent flood events in Europe and the issues surrounding insurance of potential future events. In particular, the paper will focus on the flood risk information needs of insurers and how these can be met. The data requirements of national and regional flood models are addressed in the context of the accuracy of available data on property location. Terrain information is generally the weakest component of sophisticated flood models. Therefore, various sources of digital terrain models (DTM) are examined and discussed with consideration of the vertical and horizontal accuracy, the speed of acquisition, the costs and the comprehensiveness of the data. The NEXTMap DTM series from Intermap Technologies Inc. is proposed as a suitable DTM for flood risk identification and mapping, following its use in the UK. Its acquisition, processing and application is described and future plans discussed. Examples are included of the application of flood information to insurance property information and the potential benefits and advantages of using suitable hazard modelling data sources are detailed.
Do effective properties for unsaturated weakly layered porous media exist? An experimental study
Authors: Bayer A. , Vogel H.-J. , Ippisch O. , Roth K.
Published: April 2010

Abstract. In a multi-step outflow experiment we found that a weak heterogeneity within a sand column prevents the estimated effective hydraulic parameters from being unique. We compared vertical water content profiles calculated from these parameters with profiles measured by x-ray attenuation. A layered material model based on x-ray data was able to reproduce the outflow curve and also the water content distribution inside the column. We also calculated effective parameters for the layered model turned upside down and obtained large differences to the set of values of the original sample.