bluuebunny/crossref_metadata_2025 huggingface dataset:
Commentary on comparison of MODIS snow cover and albedo products with ground observations over the mountainous terrain of Turkey
Authors: Şorman A. Ü. , Akyürek Z. , Şensoy A. , Şorman A. A. , Tekeli A. E.
Published: April 2010

Abstract. The MODerate-resolution Imaging Spectroradiometer (MODIS) snow cover product was evaluated by Parajka and Blösch (2006) over the territory of Austria. The spatial and temporal variability of the MODIS snow product classes are analyzed, the accuracy of the MODIS snow product against numerous in situ snow depth data are examined and the main factors that may influence the MODIS classification accuracy are identified in their studies. The authors of this paper would like to provide more discussion to the scientific community on the "Validation of MODIS snow cover images" when similar methodology is applied to mountainous regions covered with abundant snow but with limited number of ground survey and automated stations. Daily snow cover maps obtained from MODIS images are compared with ground observations in mountainous terrain of Turkey for the winter season of 2002–2003 and 2003–2004 during the accumulation and ablation periods of snow. Snow depth and density values are recorded to determine snow water equivalent values at 19 points in and around the study area in Turkey. Comparison of snow maps with in situ data show good agreement with overall accuracies in between 62 to 82 percent considering a 2-day shift during cloudy days. Studies show that the snow cover extent can be used for forecasting of runoff hydrographs resulting mostly from snowmelt for a mountainous basin in Turkey. MODIS-Terra snow albedo products are also compared with ground based measurements over the ablation stage of 2004 using the automated weather operating stations (AWOS) records at fixed locations as well as from the temporally assessed measuring sites during the passage of the satellite. Temporarily assessed 20 ground measurement sites are randomly distributed around one of the AWOS stations and both MODIS and ground data were aggregated in GIS for analysis. Reduction in albedo is noticed as snow depth decreased and SWE values increased.
Influence of rainfall observation network on model calibration and application
Authors: Bárdossy A. , Das T.
Published: April 2010

Abstract. The objective in this study is to investigate the influence of the spatial resolution of the rainfall input on the model calibration and application. The analysis is carried out by varying the distribution of the raingauge network. The semi-distributed HBV model is calibrated with the precipitation interpolated from the available observed rainfall of the different raingauge networks. An automatic calibration method based on the combinatorial optimization algorithm simulated annealing is applied. Aggregated Nash-Sutcliffe coefficients at different temporal scales are adopted as objective function to estimate the model parameters. The performance of the hydrological model is analyzed as a function of the raingauge density. The calibrated model is validated using the same precipitation used for the calibration as well as interpolated precipitation based on networks of reduced and increased raingauge density. The effect of missing rainfall data is investigated by using a multiple linear regression approach for filling the missing values. The model, calibrated with the complete set of observed data, is then run in the validation period using the above described precipitation field. The simulated hydrographs obtained in the three sets of experiments are analyzed through the comparisons of the computed Nash-Sutcliffe coefficient and several goodness-of-fit indexes. The results show that the model using different raingauge networks might need recalibration of the model parameters: model calibrated on sparse information might perform well on dense information while model calibrated on dense information fails on sparse information. Also, the model calibrated with complete set of observed precipitation and run with incomplete observed data associated with the data estimated using multiple linear regressions, at the locations treated as missing measurements, performs well. A meso-scale catchment located in the south-west of Germany has been selected for this study.
A new method for determination of Most Likely Initiation Points and the evaluation of Digital Terrain Model scale in terrain stability mapping
Authors: Tarolli P. , Tarboton D. G.
Published: April 2010

Abstract. Physically-based models have been used previously to map areas of potential instability where shallow landslides may initiate. Here we introduce a new approach for determining the Most Likely Initiation Points (MLIP) for landslides. We identify the location with critical (lowest) stability index from a terrain stability model on each downslope path from ridge to valley. The SINMAP Stability Index (SI) was applied with this method. Only potential initiation points less than a threshold are considered to avoid identification of stable locations on downslope paths that do not contain any unstable locations. Mapped or observed landslides are often used to evaluate the effectiveness of model derived terrain stability maps, but a problem with these observations is that they may demarcate the entire landslide scar, including run out zones, rather than just initiation locations. Comparing such observations to SI does not provide a meaningful way to assess the effectiveness of the SI map because the demarcated area may include considerable area with stable SI values. In this paper we suggest using the relative density of MLIP locations within and outside demarcated landslide areas to assess the discriminating capability of a SI map. This approach was tested using landslides mapped from aerial photographs and airborne laser altimetry (LIDAR) derived elevation data for a small basin located in the Northeastern Region of Italy. Digital Terrain Models (DTMs) were derived from the LIDAR data for a range of grid cell sizes (from 2 to 50 m) and SI and MLIP evaluated for each. We found that the direct comparison of SI within and outside of landslides was not effective. However when MLIP was used we found appreciable differences between the density of MLIP points within and outside mapped landslides with ratios as large as three or more with the highest ratios for a DTM grid cell size of 10 m. This demonstrated the utility of the MLIP approach to quantifying the effectiveness of a terrain stability map when comparisons are to mapped landslides that include runout zones. This also suggests that in this study area, where landslides occurred in complexes that were sometimes more than 100 m wide, a DTM scale of 10 m is optimal. DTM scales larger than 10 m result in loss of resolution, while for DTM scales smaller than 10 m the physical processes responsible for triggering landslides are obscured by smaller scale DTM variability that is resolved.
Evaluation of bias-correction methods for ensemble streamflow volume forecasts
Authors: Hashino T. , Bradley A. A. , Schwartz S. S.
Published: April 2010

Abstract. Ensemble prediction systems are used operationally to make probabilistic streamflow forecasts for seasonal time scales. However, hydrological models used for ensemble streamflow prediction often have simulation biases that degrade forecast quality and limit the operational usefulness of the forecasts. This study evaluates three bias-correction methods for ensemble streamflow volume forecasts. All three adjust the ensemble traces using a transformation derived with simulated and observed flows from a historical simulation. The quality of probabilistic forecasts issued when using the three bias-correction methods is evaluated using a distributions-oriented verification approach. Comparisons are made of retrospective forecasts of monthly flow volumes for the Des Moines River, issued sequentially for each month over a 48-year record. The results show that all three bias-correction methods significantly improve forecast quality by eliminating unconditional biases and enhancing the potential skill. Still, subtle differences in the attributes of the bias-corrected forecasts have important implications for their use in operational decision-making. Diagnostic verification distinguishes these attributes in a context meaningful for decision-making, providing criteria to choose among bias-correction methods with comparable skill.
Numerical understanding of regional scale water table behavior in the Guadalupe Valley aquifer, Baja California, Mexico
Authors: Campos-Gaytan J. R. , Kretzschmar T.
Published: April 2010

Abstract. A regional groundwater flow model was developed, in order to evaluate the water table behavior in the region of the Guadalupe Valley, in Baja California, Mexico. The State of Baja California has been subject to an increment of the agricultural, urban and industrials activities, implicating a growing water-demand. However, the State is characterized by its semi-arid climate with low surface water availability; resulting in an extensive use of groundwater in local aquifer. Based on historic piezometric information of the last two decades, however, a negative evolution could be observed, resulting a negative storage volume. So far, there is not an integral hydrogeological evaluation that determine the real condition of the groundwater resource, and that permit to planning a management of the Guadalupe Valley Aquifer. A steady-state calibration model was carried out in order to obtain the best possible match to measured levels at the Guadalupe Valley Aquifer. The contours of calculated water table elevations for January 1983 were reproduced. Generally, the comparison of the observed and calculated water table configurations have a good qualitative and quantitatively adjustment. Nowadays, it is count with a hydrogeological model that can be used for simulates the groundwater flow in the region of the Guadalupe Valley.
Satellite-based evapotranspiration and crop coefficient for irrigated sorghum in the Gezira scheme, Sudan
Authors: Bashir M. A. , Hata T. , Abdelhadi A. W. , Tanakamaru H. , Tada A.
Published: April 2010

Abstract. The availability of the actual water use from agricultural crops is considered as the key factor for irrigation water management, water resources planning, and water allocation. Traditionally, evapotranspiration (ET) has been estimated in the Gezira scheme by multiplying the reference evapotranspiration (ETo) by crop coefficient (kc) which is derived from the phenomenological crop stages. Recently, advanced developed energy balance models assist to estimate ET through remotely sensed data. In this study Enhanced Thematic Mapper Plus (ETM+) images were used to estimate spatial distribution of daily, monthly and seasonal ET for irrigated sorghum in the Gezira scheme, Sudan. The daily ET maps were also used to estimate kc over time and space. Results of remotely sensed based energy balance were compared with actual measurements conducted during 2004/05 season. The daily actual ET values estimated using the energy balance model during the satellite acquisition dates (28 July, 29 August, 16 October and 17 November) were 4.7, 5.5, 7.1 and 2.7 mm/day, while the average seasonal evapotranspiration for irrigated sorghum estimated to be around 596 mm. The remotely estimated kc values in the initial, crop development, mid-season and late-season stages were 0.62, 0.85, 1.15, and 0.48 respectively. On the other hand the widely used tradition kc values during the pervious mention stages are 0.55, 0.94, 1.21 and 0.65, respectively. This research shows that remotely sensed measurements can help objectively analyzed the irrigation water requirement for different field crops on daily and seasonal time step. Moreover, the remotely sensed real-time data availability provides the system managers with information that not previously available.
A multitemporal remote sensing approach to parsimonious streamflow modeling in a southcentral Texas watershed, USA
Authors: Weissling B. P. , Xie H. , Murray K. E.
Published: April 2010

Abstract. Soil moisture condition plays a vital role in a watershed's hydrologic response to a precipitation event and is thus parameterized in most, if not all, rainfall-runoff models. Yet the soil moisture condition antecedent to an event has proven difficult to quantify both spatially and temporally. This study assesses the potential to parameterize a parsimonious streamflow prediction model solely utilizing precipitation records and multi-temporal remotely sensed biophysical variables (i.e.~from Moderate Resolution Imaging Spectroradiometer (MODIS)/Terra satellite). This study is conducted on a 1420 km2 rural watershed in the Guadalupe River basin of southcentral Texas, a basin prone to catastrophic flooding from convective precipitation events. A multiple regression model, accounting for 78% of the variance of observed streamflow for calendar year 2004, was developed based on gauged precipitation, land surface temperature, and enhanced vegetation Index (EVI), on an 8-day interval. These results compared favorably with streamflow estimations utilizing the Natural Resources Conservation Service (NRCS) curve number method and the 5-day antecedent moisture model. This approach has great potential for developing near real-time predictive models for flood forecasting and can be used as a tool for flood management in any region for which similar remotely sensed data are available.
Guidelines for depth data collection in rivers when applying interpolation techniques (kriging) for river restoration
Authors: Rivas-Casado M. , White S. , Bellamy P.
Published: April 2010

Abstract. River restoration appraisal requires the implementation of monitoring programmes that assess the river site before and after the restoration project. However, little work has yet been developed to design effective and efficient sampling strategies. Three main variables need to be considered when designing monitoring programmes: space, time and scale. The aim of this paper is to describe the methodology applied to analyse the variation of depth in space, scale and time so more comprehensive monitoring programmes can be developed. Geostatistical techniques were applied to study the spatial dimension (sampling strategy and density), spectral analysis was used to study the scale at which depth shows cyclic patterns, whilst descriptive statistics were used to assess the temporal variation. A brief set of guidelines have been summarised in the conclusion.
Riverine transport of biogenic elements to the Baltic Sea – past and possible future perspectives
Authors: Humborg C. , Mörth C.-M. , Sundbom M. , Wulff F.
Published: April 2010

Abstract. The paper reviews critical processes for the land-sea fluxes of biogenic elements (C, N, P, Si) in the Baltic Sea catchment and discusses possible future scenarios as a consequence of improved sewage treatment, agricultural practices, increased hydropower demand and global warming, i.e., changes in hydrological patterns. These most significant drivers will not only change the total amount of nutrient inputs and fluxes of organic and inorganic forms of carbon to the Baltic Sea, their ratio (C:N:P:Si) will alter as well with consequences for phytoplankton species composition in the Baltic Sea. In summary, we propose that N fluxes will increase due to higher live stock densities in those countries recently acceded to the EU, whereas P and Si fluxes will decrease due to an increase in sewage treatment in these new EU member states and with further damming and still eutrophic states of many lakes in the entire Baltic Sea catchment. This might eventually decrease cyanobacteria blooms in the Baltic but increase the potential for other nuisance blooms. Dinoflagellates will be substituting diatoms that even today grow below their optimal growth conditions due to low Si concentrations in some regions of the Baltic Sea. C fluxes will probably increase from the boreal part of the Baltic Sea catchment due to the expected higher temperatures and heavier rainfall. However, it is not clear whether both dissolved organic carbon and alkalinity, that have opposite feedbacks to global warming will increase in similar amounts, since the spring flow peak will be smoothed out in time due to higher temperatures that cause less snow cover and deeper soil infiltration.
Modelling microbiological water quality in the Seine river drainage network: past, present and future situations
Authors: Servais P. , Billen G. , Goncalves A. , Garcia-Armisen T.
Published: April 2010

Abstract. The Seine river watershed is characterized by a high population density and intense agricultural activities. Data show low microbiological water quality in the main rivers (Seine, Marne, Oise) of the watershed. Today, there is an increasing pressure from different social groups to restore microbiological water quality in order to both increase the safety of drinking water production and to restore the possible use of these rivers for bathing and rowing activities, as they were in the past. A model, appended to the hydro-ecological SENEQUE/Riverstrahler model describing the functioning of large river systems, was developed to describe the dynamics of faecal coliforms (FC), the most usual faecal contamination indicator. The model is able to calculate the distribution of FC abundance in the whole drainage network resulting from land use and wastewater management in the watershed. The model was validated by comparing calculated FC concentrations with available field data for some well-documented situations in different river stretches of the Seine drainage network. Once validated, the model was used to test various predictive scenarios, as, for example, the impact of the modifications in wastewater treatment planned at the 2012 horizon in the Seine watershed in the scope of the implementation of the European Water Framework Directive. The model was also used to investigate past situations. In particular, the variations of the microbiological water quality in the Parisian area due to population increase and modifications in wastewater management were estimated over the last century. It was shown that the present standards for bathing and other aquatic recreational activities are not met in the large tributaries upstream from Paris since the middle of the 1950's, and at least since the middle of the XIXth century in the main branch of the Seine river downstream from Paris. Efforts carried out for improving urban wastewater treatment in terms or organic matter and nutrient loading resulted in a sensible reduction of microbiological contamination, but were not specific enough toward bacteriological contamination for achieving the objective of restoring levels compatible with bathing activities in the Parisian area.
The "WFD-effect" on upstream-downstream relations in international river basins – insights from the Rhine and the Elbe basins
Authors: Moellenkamp S.
Published: April 2010

Abstract. The upstream-downstream relationship in international river basins is a traditional challenge in water management. Water use in upstream countries often has a negative impact on water use in downstream countries. This is most evident in the classical example of industrial pollution in upstream countries hindering drinking water production downstream. The European Water Framework Directive (WFD) gives new impetus to the river basin approach and to international co-operation in European catchments. It aims at transforming a mainly water quality oriented management into a more integrated approach of ecosystem management. After discussing the traditional upstream-downstream relationship, this article shows that the WFD has a balancing effect on upstream-downstream problems and that it enhances river basin solidarity in international basins. While it lifts the downstream countries to the same level as the upstream countries, it also leads to new duties for the downstream states. Following the ecosystem approach, measures taken by downstream countries become increasingly more important. For example, downstream countries need to take measures to allow for migrating fish species to reach upstream stretches of river systems. With the WFD, fish populations receive increased attention, as they are an important indicator for the ecological status. The European Commission acquires a new role of inspection and control in river basin management, which finally also leads to enhanced cooperation and solidarity among the states in a basin. In order to achieve better water quality and to mitigate upstream-downstream problems, also economic instruments can be applied and the WFD does not exclude the possibility of making use of financial compensations, if at the same time the polluter pays principle is taken into account. The results presented in this article originate from a broader study on integrated water resources management conducted at Bonn University and refer to the Rhine and Elbe basins (Moellenkamp, 2006).
The spatial variability of snow water equivalent
Authors: Skaugen T.
Published: April 2010

Abstract. The spatial distribution of snow water equivalent (SWE) is modelled as a two parameter gamma distribution. The parameters of the distribution are dynamical in that they are functions of the number of accumulation and ablation events and the temporal correlation of accumulation and ablation events. The estimated spatial variability is compared to snow course observations from the alpine catchments Norefjell and Aursunden in Southern Norway. A fixed snow course at Norefjell was measured 26 times during the snow season, which showed that the spatial coefficient of variation change during the snow season with a decreasing trend from the start of the accumulation period and a sharp increase in the ablation period. The gamma distribution with dynamical parameters reproduced the observed spatial statistical features of SWE well both at Norefjell and Aursunden. Also the shape of simulated spatial distribution of SWE agreed well with the observed at Norefjell. The temporal correlation tends to be positive for both accumulation and ablation events. However, at the start of ablation, a better fit between modelled and observed spatial standard deviation of SWE is obtained by using negative correlation between SWE and melt.
Stakeholder discourse and water management in a catchment in northern Italy
Authors: Lupo Stanghellini P. S. , Collentine D.
Published: April 2010

Abstract. The Water Framework Directive (WFD; directive 2000/60/EC) was created to ensure the sustainable use of water resources in the European Union. A central guideline included throughout the directive is a call for the participation of stakeholders in the management of these resources. Involving stakeholders is an important step to ensure that catchment management plans take into consideration local experience in the development of these plans and the impact of the plans on local interests. This paper describes and analyses the results of a series of workshops to facilitate implementation of the WFD at a catchment level based on the stakeholder participation model, CATCH. To test the usefulness of the stakeholder participation model CATCH for water management in a catchment area, a sub-catchment in an alpine valley in the north-east of Italy, the Alta Valsugana in the Province of Trento, was chosen as the setting for a series of workshops. In this valley water is fundamental for activities associated with agriculture, domestic use, energy production, sports and recreation. In the recent past the valley has had serious problems related to water quality and quantity. Implementation of water management plans under the WFD may lead to conflicts within the catchment between different stakeholder interest groups. Including stakeholders in the development of management plans not only follows the guidelines of the WFD but also could result in a more locally adapted and acceptable plan for the catchment. A new stakeholder analysis methodology was developed and implemented in order to identify the relevant stakeholders of the area and then two sets of workshops involving the key stakeholders identified were conducted in Spring 2006. The CATCH meetings were a new experience for the participants, who had to deal with both the principles of the WFD in general and the participation requirement in particular. During the meetings, the CATCH model played a very important role in structuring the participatory process. It provided a general framework consisting of a sequence of steps that helped the participants to reach the goal of the process; the identification and evaluation of measures to improve water management in the catchment. This test of the CATCH model showed it to be a dynamic and flexible tool, useful for structuring and guiding the participation process, without imposing undue restrictions on influencing the outcome of stakeholder participation in a small catchment.
Eutrophication and Phosphorous accumulation in sediments of Karlskärsviken, bay in Lake Mälaren
Authors: Olli G.
Published: April 2010

Abstract. Biogenic silica (BSi) and phosphorous (P) accumulation were investigated in sediment cores from Karlskärsviken, a bay of Lake Mälaren. The aim was to understand and quantify environmental changes since the Middle Ages, with focus on industrial times, and to evaluate anthropogenic influences on the bay's water quality. The BSi accumulation in the sediments is a better indicator of former nutrient trophy than P accumulation and for this reason a BSi inferred P content, BSi-P, is calculated. There is an increasing trend of BSi-P content in the bay since the Middle Ages, with a small decrease in the inner bay section during the last decades. In Karlskärsviken, the shallow inner section of the bay, where the water quality is dominated by loading from the bay catchment area, is less nutritious than the water in the outer section, which is influenced by the main streams in the Lake Mälaren. The P content in the water column is presently higher than in the mid nineteenth century, and the P loading to Karlskärsviken is not found to have changed since the 1960s and 1970s.
Web services for distributed and interoperable hydro-information systems
Authors: Horak J. , Orlik A. , Stromsky J.
Published: April 2010

Abstract. Web services support the integration and interoperability of Web-based applications and enable machine-to-machine interaction. The concepts of web services and open distributed architecture were applied to the development of T-DSS, the prototype customised for web based hydro-information systems. T-DSS provides mapping services, database related services and access to remote components, with special emphasis placed on output flexibility (e.g. multilingualism), where SOAP web services are mainly used for communication. The remote components are represented above all by distant data and mapping services (e.g. eteorological predictions), modelling and analytical systems (currently HEC-HMS, Modflow and additional utilities), which support decision making in water management.
Knowledge-based approaches for river basin management
Authors: Mikulecký P. , Olševičová K. , Ponce D.
Published: April 2010

Abstract. Rare attempts to use knowledge technologies and other relevant approaches are found in the river basin management. Some applications of expert systems as well as utilization of soft computing techniques (as neural networks or genetic algorithms) are known in an experimental level. Knowledge management approaches still have not been used at all. In this paper we discuss knowledge-based approaches in the river basin management as a difficult yet important direction which could be proven to be helpful. We summarize the research done in the scope of the AQUIN project, one of first Czech knowledge management projects in the river basin management. The project was initiated by the water management company in Pilsen, where dispatchers make decisions about manipulations on the reservoir Nýrsko, the strategic source of drinking water for inhabitants of Pilsen. The project aim was to support dispatchers' decision making under a high degree of uncertainty or data shortage. The research is continued in the scope of a new project AQUINpro, planned for the period of 2006 to 2008.
Development of an Open-GIS decision aid system for ecological and economical management of surface and groundwater resources in the Bistrita River Basin (Romania)
Authors: Trifu M. C. , Craciunescu V. , Rusu C. , Pandele A. , Garnier J. , Billen G. , Ledoux E.
Published: April 2010

Abstract. The Bistrita River Basin (a length of 283 km, a surface of 7039 km2, a mean discharge of 65 m3/s) is one of the most important tributary of the Siret River, which is the second major affluent of the Danube River. Heavily influenced by hydraulic management and highly polluted by agricultural and urban activities in some stretches, the Bistrita river has been studied in the framework of the Diminish Project (LIFE03 ENV/ RO/000539), funded by the Life Environment Program. The project aims to support the implementation of the EU Water Framework Directive and to combat the nutrient pollution by developing an integrated, on-line, GIS-based support system for the management of the water quality in relation with human activities, using socio-economical analysis, at the scale of the river catchments. Based on modeling approaches the decisional system allows to predict which strategy will lead to the most effective reduction of nutrient concentrations within the Bistrita hydrological network and of nutrient loads transported by the Siret River into the Danube. The consequences of the nutrient pollution are discussed for two basin areas, from two points of view: i) the effects of point and diffuse pollution for surface and groundwater, on the basis of the basin response to the changing pressures over the river catchments (industrial, rural, urban, agricultural changes), ii) the economical valuation of environmental costs and cost-effectiveness of the measures, that can be proposed from socio-economic scenarios, for reaching the "good ecological status" of this river.
Assessment of strip tillage systems for maize production in semi-arid Ethiopia: effects on grain yield and water balance
Authors: Temesgen M. , Rockstrom J. , Savenije H. H. G. , Hoogmoed W. B.
Published: April 2010

Abstract. The traditional tillage implement, the Maresha plow, and the tillage systems that require repeated and cross plowing have caused poor rainfall partitioning, land degradation and hence low water productivity in Ethiopia. Conservation tillage could alleviate these problems. However, no-till can not be feasible for smallholder farmers in semi-arid regions of Ethiopia because of difficulties in maintaining soil cover due to low rainfall and communal grazing and because of high costs of herbicides. Strip tillage systems may offer a solution. This study was initiated to test strip tillage systems using implements that were modified forms of the Maresha plow, and to evaluate the impacts of the new tillage systems on water balance and grain yields of maize (Zea mays XX). Experiments were conducted in two dry semi arid areas called Melkawoba and Wulinchity, in the central Rift Valley of Ethiopia during 2003–2005. Strip tillage systems that involved cultivating planting lines at a spacing of 0.75 m using the Maresha plow followed by subsoiling along the same lines (STS) and without subsoiling (ST) were compared with the traditional tillage system of 3 to 4 times plowing with the Maresha plow (CONV). Soil moisture was monitored to a depth of 1.8 m using Time Domain Reflectometer while surface runoff was measured using rectangular trough installed at the bottom of each plot. STS resulted in the least surface runoff (Qs=17 mm-season−1), the highest transpiration (T=196 mm-season−1), the highest grain yields (Y=2130 kg-ha−1) and the highest water productivity using total evaporation (WPET=0.67 kg-m−3) followed by ST (Qs=25 mm-season−1, T=178 mm-season−1, Y=1840 kg-ha−1, WPET=0.60 kg-m−3) and CONV (Qs=40 mm-season−1,T=158 mm-season−1, Y=1720 kg-ha−1, WPET=0.58 kg-m−3). However, when the time between the last tillage operation and planting of maize was more than 26 days, the reverse occurred. There was no statistically significant change in soil physical and chemical properties after three years of experimenting with different tillage systems.
Comparison of soil moisture fields estimated by catchment modelling and remote sensing: a case study in South Africa
Authors: Vischel T. , Pegram G. , Sinclair S. , Wagner W. , Bartsch A.
Published: April 2010

Abstract. The paper compares two independent approaches to estimate soil moisture at the regional scale over a 4625 km2 catchment (Liebenbergsvlei, South Africa). The first estimate is derived from a physically-based hydrological model (TOPKAPI). The second estimate is derived from the scatterometer on board on the European Remote Sensing satellite (ERS). Results show a very good correspondence between the modelled and remotely sensed soil moisture, illustrated over two selected seasons of 8 months by regression R2 coefficients lying between 0.78 and 0.92. Such a close similarity between these two different, independent approaches is very promising for (i) remote sensing in general (ii) the use of hydrological models to back-calculate and disaggregate the satellite soil moisture estimate and (iii) for hydrological models to assimilate the remotely sensed soil moisture.
Extreme precipitation and extreme streamflow in the Dongjiang River Basin in southern China
Authors: Wang W. , Chen X. , Shi P. , van Gelder P. H. A. J. M. , Corzo G.
Published: April 2010

Abstract. Extreme hydro-meteorological events have become the focus of more and more studies in the last decade. Due to the complexity of the spatial pattern of changes in precipitation processes, it is still hard to establish a clear view of how precipitation has changed and how it will change in the future. In the present study, changes in extreme precipitation and streamflow processes in the Dongjiang River Basin in southern China are investigated. It was shown that little change is observed in annual extreme precipitation in terms of various indices, but some significant changes are found in the precipitation processes on a monthly basis. The result indicates that when detecting climate changes, besides annual indices, seasonal variations in extreme events should be considered as well. Despite of little change in annual extreme precipitation series, significant changes are detected in several annual extreme flood flow and low-flow series, mainly at the stations along the main channel of Dongjiang River, which are affected significantly by the operation of several major reservoirs. The result highlights the importance of evaluating the impacts of human activities in assessing the changes of extreme streamflows. In addition, three non-parametric methods that are not-commonly used by hydro-meteorology community, i.e., Kolmogorov–Smirnov test, Levene's test and quantile test, are introduced and assessed by Monte Carlo simulation in the present study to test for changes in the distribution, variance and the shift of tails of different groups of dataset. Monte Carlo simulation result shows that, while all three methods work well for detecting changes in two groups of data with large data size (e.g., over 200 points in each group) and big difference in distribution parameters (e.g., over 100% increase of scale parameter in Gamma distribution), none of them are powerful enough for small data sets (e.g., less than 100 points) and small distribution parameter difference (e.g., 50% increase of scale parameter in Gamma distribution).
Region-of-influence approach to a frequency analysis of heavy precipitation in Slovakia
Authors: Gaál L. , Kyselý J. , Szolgay J.
Published: April 2010

Abstract. The L-moment-based regionalization approach developed by Hosking and Wallis (1997) is a frequently used tool in regional frequency modeling of heavy precipitation events. The method consists of the delineation of homogeneous pooling groups with a fixed structure, which may, however, lead to undesirable step-like changes in growth curves and design value estimates in the case of a transition from one pooling group to another. Unlike the standard methodology, the region-of-influence (ROI) approach does not make use of groups of sites (regions) with a fixed structure; instead, each site has its own "region", i.e. a group of sites that are sufficiently similar to the site of interest. The aim of the study is to develop a version of the ROI approach, which was originally proposed in order to overcome inconsistencies involved in flood frequency analysis, for the modeling of probabilities of heavy precipitation amounts. Various settings of the distance metric and pooled weighting factors are evaluated, and a comparison with the standard regional frequency analysis over the area of Slovakia is performed. The advantages of the ROI approach are assessed by means of simulation studies. It is demonstrated that almost any setting of parameters of the ROI method yields estimates of growth curves and design values at individual sites that are superior to the standard regional and at-site estimates.
Strong increases in flood frequency and discharge of the River Meuse over the late Holocene: impacts of long-term anthropogenic land use change and climate variability
Authors: Ward P. J. , Renssen H. , Aerts J. C. J. H. , van Balen R. T. , Vandenberghe J.
Published: April 2010

Abstract. In recent years the frequency of high-flow events on the Meuse (northwest Europe) has been relatively great, and flooding has become a major research theme. To date, research has focused on observed discharge records of the last century and simulations of the coming century. However, it is difficult to delineate changes caused by human activities (land use change and greenhouse gas emissions) and natural fluctuations on these timescales. To address this problem we coupled a climate model (ECBilt-CLIO-VECODE) and a hydrological model (STREAM) to simulate daily Meuse discharge in two time-slices: 4000–3000 BP (natural situation), and 1000–2000 AD (includes anthropogenic influence). For 4000–3000 BP the basin is assumed to be almost fully forested; for 1000–2000 AD we reconstructed land use based on historical sources. For 1000–2000 AD the simulated mean annual discharge (260.9 m³ s−1) is significantly higher than for 4000–3000 BP (244.8 m³ s−1), and the frequency of large high-flow events (discharge >3000 m³ s−1) is higher (recurrence time decreases from 77 to 65 years). On a millennial timescale almost all of this increase can be ascribed to land use changes (especially deforestation); the effects of climatic change are insignificant. For the 20th Century, the simulated mean discharge (270.0 m³ s−1) is higher than in any other century studied, and is ca. 2.5% higher than in the 19th Century (despite an increase in evapotranspiration). Furthermore, the recurrence time of large high-flow events is almost twice as short as under natural conditions (recurrence time decreases from 77 to 40 years). On this timescale climate change (strong increase in annual and winter precipitation) overwhelmed land use change as the dominant forcing mechanism.
Evaluation of 1-D tracer concentration profile in a small river by means of Multi-Layer Perceptron Neural Networks
Authors: Piotrowski A. , Wallis S. G. , Napiórkowski J. J. , Rowinski P. M.
Published: April 2010

Abstract. The prediction of temporal concentration profiles of a transported pollutant in a river is still a subject of ongoing research efforts worldwide. The present paper is aimed at studying the possibility of using Multi-Layer Perceptron Neural Networks to evaluate the whole concentration versus time profile at several cross-sections of a river under various flow conditions, using as little information about the river system as possible. In contrast with the earlier neural networks based work on longitudinal dispersion coefficients, this new approach relies more heavily on measurements of concentration collected during tracer tests over a range of flow conditions, but fewer hydraulic and morphological data are needed. The study is based upon 26 tracer experiments performed in a small river in Edinburgh, UK (Murray Burn) at various flow rates in a 540 m long reach. The only data used in this study were concentration measurements collected at 4 cross-sections, distances between the cross-sections and the injection site, time, as well as flow rate and water velocity, obtained according to the data measured at the 1st and 2nd cross-sections. The four main features of concentration versus time profiles at a particular cross-section, namely the peak concentration, the arrival time of the peak at the cross-section, and the shapes of the rising and falling limbs of the profile are modeled, and for each of them a separately designed neural network was used. There was also a variant investigated in which the conservation of the injected mass was assured by adjusting the predicted peak concentration. The neural network methods were compared with the unit peak attenuation curve concept. In general the neural networks predicted the main features of the concentration profiles satisfactorily. The predicted peak concentrations were generally better than those obtained using the unit peak attenuation method, and the method with mass-conservation assured generally performed better than the method that did not account for mass-conservation. Predictions of peak travel time were also better using the neural networks than the unit peak attenuation method. Including more data into the neural network training set clearly improved the prediction of the shapes of the concentration profiles. Similar improvements in peak concentration were less significant and the travel time prediction appeared to be largely unaffected.
Ecohydrology in Mediterranean areas: a numerical model to describe growing seasons out of phase with precipitations
Authors: Pumo D. , Viola F. , Noto L. V.
Published: April 2010

Abstract. The probabilistic description of soil moisture dynamics is a relatively new topic in hydrology. The most common ecohydrological models start from the soil water balance, a stochastic differential equation where the unknown quantity is the function of the soil moisture, depending both on spaces and time. Most of existing solutions in literature are obtained in a probabilistic framework and under steady-state condition; even if this last condition allows the analytical handling of the problem, it has considerably simplified the problem by subtracting generalities from it. The steady-state hypothesis, used in many ecohydrological works, appears perfectly applicable in arid and semiarid climatic areas like those of African's or middle American's savannas, but it seems to be no more valid in areas with Mediterranean climate, where, notoriously, the wet season foregoes the growing season, thus recharging the soil moisture. This initial condition, especially for deep rooted vegetation, has a great importance by enabling survival in absence of rainfalls during the growing season and, however, keeping the water stress low during its first period. The aim of this paper is to investigate the soil moisture dynamics using a simple non-steady numerical ecohydrological model. The numerical model is able to reproduce soil moisture probability density function, obtained analytically in previous studies for different climate and soil conditions in steady state conditions. The proposed model gives both the soil moisture time-profile and the vegetation static water stress time-profile. From the former it is possible to extract the probability density function of soil-moisture during the whole growing season, while the latter allows the estimation of the vegetation response to the water stress. Here the differences between the analytical and the numerical probability density functions are presented, showing how the numerical model is able to capture the effects of winter recharge on the soil moisture. The dynamic water stress is numerically evaluated, implicitly taking into account the soil moisture condition at the beginning of the growing season. The model proposed here is applied in the forested river basin of the Eleuterio in Sicily (Italy).
Neural network emulation of a rainfall-runoff model
Authors: Abrahart R. J. , See L. M.
Published: April 2010

Abstract. The potential of an artificial neural network to perform simple non-linear hydrological transformations is examined. Four neural network models were developed to emulate different facets of a recognised non-linear hydrological transformation equation that possessed a small number of variables and contained no temporal component. The modeling process was based on a set of uniform random distributions. The cloning operation facilitated a direct comparison with the exact equation-based relationship. It also provided broader information about the power of a neural network to emulate existing equations and model non-linear relationships. Several comparisons with least squares multiple linear regression were performed. The first experiment involved a direct emulation of the Xinanjiang Rainfall-Runoff Model. The next two experiments were designed to assess the competencies of two neural solutions that were developed on a reduced number of inputs. This involved the omission and conflation of previous inputs. The final experiment used derived variables to model intrinsic but otherwise concealed internal relationships that are of hydrological interest. Two recent studies have suggested that neural solutions offer no worthwhile improvements in comparison to traditional weighted linear transfer functions for capturing the non-linear nature of hydrological relationships. Yet such fundamental properties are intrinsic aspects of catchment processes that cannot be excluded or ignored. The results from the four experiments that are reported in this paper are used to challenge the interpretations from these two earlier studies and thus further the debate with regards to the appropriateness of neural networks for hydrological modelling.
Effects of decreasing acid deposition and climate change on acid extremes in an upland stream
Authors: Evans C. D. , Reynolds B. , Hinton C. , Hughes S. , Norris D. , Grant S. , Williams B.
Published: April 2010

Abstract. This study assesses the major chemical processes leading to acid extremes in a small, moorland stream in mid-Wales, UK, which has been monitored since 1979. Results suggest that base cation (mainly calcium) dilution, the "sea-salt effect", and elevated nitrate pulses, are the major causes of seasonal/episodic minima in acid neutralising capacity (ANC), and that the relative importance of these drivers has remained approximately constant during 25 years of decreasing acid deposition and associated long-term chemical recovery. Many of the chemical variations causing short-term reductions in stream acidity, particularly base cation dilution and organic acid increases, are closely related to changes in water-flowpath and therefore to stream discharge. Changes in the observed pH-discharge relationship over time indicate that high-flow pH has increased more rapidly than mean-flow pH, and therefore that episodes have decreased in magnitude since 1980. However a two-box application of the dynamic model MAGIC, whilst reproducing this trend, suggests that it will not persist in the long term, with mean ANC continuing to increase until 2100, but the ANC of the upper soil (the source of relatively acid water during high-flow episodes) stabilising close to zero beyond 2030. With climate change predicted to lead to an increase in maximum flows in the latter half of the century, high-flow related acid episodes may actually become more rather than less severe in the long term, although the model suggests that this effect may be small. Two other predicted climatic changes could also detrimentally impact on acid episodes: increased severity of winter "sea-salt" episodes due to higher wind speeds during winter storms; and larger sulphate pulses due to oxidation of reduced sulphur held in organic soils, during more extreme summer droughts. At the Gwy, the near-coastal location and relatively small extent of peat soils suggest that sea-salt episodes may have the greatest influence.