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Non-climatic reasons, such as station replacement and changing the measurement device and calculation method, may make climate data unrepresentative of the actual variation of the regional climate. Data quality control and homogenization tests for climate data are critical. Thus, this study aims to evaluate the quality and homogeneity level of precipitation time series in arid and semi-arid climatic zones and specify the breakpoint in the datasets. The proposed methodology has been used to conduct arid and semi-arid representative case studies comprising 40 annual precipitation series for Iraq between 1979 and 2014. A Box-Cox transformation has been used to adjust the non-normally distributed datasets. Outliers have been censored by truncating extreme values. The results of the outliers indicate that they may be caused more by climate variability than by human-induced reasons. Homogeneity adjustments have been developed by applying these four homogeneity tests: Pettitt's test, the Standard Normal Homogeneity method, Buishand's test, and von Neumann's check. Approximately 40% of the series (i.e., 16 stations out of 40) were homogeneous. Each homogeneity test was evaluated separately, and non-homogeneous stations were identified. Then, the series was classified into three groups that were assigned the labels "useful", "doubtful", and "suspect". The results indicated that twenty-one stations were associated with the class 'suspect', three of the stations belonged to the class 'doubtful', and sixteen locations were within the class 'useful'. Furthermore, the data analysis indicated no influence of the outliers on the results of the homogeneity tests. Accordingly, the study recommends further research on homogeneity tests that can be applied without considering outlier tests for similar case studies. [ABSTRACT FROM AUTHOR]

Recent climate change studies have given a lot of attention to the uncertainty that stems from general circulation models (GCM), greenhouse gas emission scenarios, hydrological models and downscaling approaches. Yet, the uncertainty that stems from the selection of the baseline period has not been studied. Accordingly, the main research question is as follows: What would be the differences and/or the similarities in the evaluation of climate change impacts between the GCM and the delta perturbation scenarios using different baseline periods? This article addresses this issue through comparison of the results of two different baseline periods, investigating the uncertainties in evaluating climate change impact on the hydrological characteristics of arid regions. The Lower Zab River Basin (Northern Iraq) has been selected as a representative case study. The research outcomes show that the considered baseline periods suggest increases and decreases in the temperature and precipitation (P), respectively, over the 2020, 2050 and 2080 periods. The two climatic scenarios are likely to lead to similar reductions in the reservoir mean monthly flows, and subsequently, their maximum discharge is approximately identical. The predicted reduction in the inflow for the 2080–2099 time period fluctuates between 31 and 49% based on SRA1B and SRA2 scenarios, respectively. The delta perturbation scenario permits the sensitivity of the climatic models to be clearly determined compared to the GCM. The former allows for a wide variety of likely climate change scenarios at the regional level and are easier to generate and apply so that they could complement the latter. [ABSTRACT FROM AUTHOR]

This paper uses an analytical framework of multi-level and multi-phase perspectives to explore low carbon transition pathways for the UK road transport system. The work draws on the impact made by the national (UK) and regional (EU) low carbon policy instruments on the UK road sector. The results show that the transformation pathway, which is at the take-off phase on a large scale, is the only fully active pathway. The transformation is mainly characterized by the adoption of biofuel blends and hybrid electric vehicles, as well as niche technologies. For the emergence of an ideal low carbon road system in the UK, it is shown that the transformation pathway is insufficient and the likely pathway sequence to full decarbonization will be transformation-substitution-de-alignment/re-alignment. However, the dynamics that can favour a smooth process of this sequence will demand a range of active niche technologies and strong government intervention. [ABSTRACT FROM PUBLISHER]

The impact of climate variability on water demand and availability in drylands is substantial. Establishing methods to analyse precipitation (P) and evapotranspiration data sets may generate useful tools that assist in drought recognition and regional variations therein. The authors developed an index that simultaneous integrates both these variables in climate variability analysis. This study proposes the alpha and normalised forms of the reconnaissance drought index (RDI) as a single climatic index for the recognition of geographical areas with differing drought characteristics and potential weather variability. The prime application is that the RDI combines in a single index both P and potential evapotranspiration. A more consistent trend of climate variability can be identified by applying time series of different durations of RDI compared to using time series of P and potential evapotranspiration separately. The researchers explore this approach using meteorological data form 24 locations representing arid, semi-arid (Mediterranean (MD), tropical (TR), continental (CN)), and humid climatic conditions. The method is then tested through application to the semi-arid Lower Zab River basin (LZRB) in Iran and Iraq. Findings show that many regions such as the LZRB will face major droughts, indicating that there is an urgent requirement to advance water management strategies. [ABSTRACT FROM AUTHOR]

Wetlands have long played an important role as natural purification systems. Textile industry processes are among the most environmentally unsustainable industrial processes, because they produce coloured effluents in large quantities polluting water resources. In this study, two different azo dyes (Acid Blue 113 (AB113) and Basic Red 46 (BR46)) have been fed as part of synthetic wastewater recipes to a laboratory-scale vertical-flow construction wetland set-up comprising wetlands with gravel media as controls and wetlands planted with Phragmites australis (Cav.) Trin. ex Steud. (Common Reed) for each dye. Two different concentrations (7 mg/l and 215 mg/l) were used for each dye at two different hydraulic retention times (48 h and 96 h). According to results for the low concentration of BR46, there is no significant ( p > 0.05) difference between wetlands (unplanted and planted) in terms of dye removal. The use of plants concerning the short contact time scenario for ammonia-nitrogen (NH 4 -N) and a low concentration of AB113 is linked to good removal. In case of low dye concentrations, the presence of plants for the long contact time scenario impacted significantly ( p < 0.05) positive on the removal efficiencies of nutrients. For chemical oxygen demand (COD), the removal percentages were 50%, 59% and 67% for the control and for the wetlands with short and long retention times, respectively. All reductions were statistically significant ( p < 0.05). For the high concentration of BR46, the removal percentages for this dye and COD were 94% and 82%, and 89% and 74% for the long and short retention times, respectively. For the low concentration of AB113, the percentage corresponding removals for the dye were 71%, 68% and 80%. The COD removals were 4%, 7% and 15% for the control, and the short and long retention times, respectively. Finally, for the high concentration of AB113, the percentage removals for the dye and COD were 71% and 73%, and 50% and 52% for the 48-h and 96-h retention times in this order. [ABSTRACT FROM AUTHOR]

A higher demand on textile materials has resulted in an increase of the number of textile factories particularly in the developing world, which consequently negatively effects the environment due to their contaminated effluents. Textile effluents are highly coloured and mixed with different chemicals and pollutants. Shallow pond systems are a promising, cheap and effective technique for the treatment of contaminated wastewater. The aim of this study is to assess the performance of pond systems vegetated by Lemna minor L. (duckweed) for textile dye removal under controlled laboratory conditions. The key objectives of this study are to assess the influence of design variables on water quality parameters, the dye and chemical oxygen demand (COD) removal of dyes, and the effect of dye accumulation as a function of the relative growth rate of L. minor . Findings indicate that the simulated shallow pond system (as a polishing step) is able to remove only Basic Red 46 (BR46) in low concentrations, and ponds containing L. minor significantly (p < 0.05) outperformed algae-dominated ponds and control ponds. The simple chemical structure, absence of sulpho-group and small molecular weight associated with neutral pH values enhanced the capacity of the uptake of BR46 molecules. Furthermore, the total dissolved solid concentrations were within the threshold set for discharge to the aquatic environment. [ABSTRACT FROM AUTHOR]

Due to water scarcity in many arid countries, there is considerable interest in recycling various wastewater streams such as treated urban wastewater for irrigation in the agricultural sector. The aim was therefore to assess if domestic wastewater treated by different wetlands can be successfully recycled to water commercially grown crops. The objectives were (i) to study the effect of irrigation on Chilli (De Cayenne; Capsicum annuum (Linnaeus) Longum Group ‘De Cayenne’) with domestic wastewater treated by wetland compared to tap water (fresh water); (ii) to assess the overall quality and particularly the microbiological contamination of Chilli fruits; and (iii) to determine the persistence of microbial contaminants in the soil irrigated by treated wastewater between September 2013 and September 2014. High yields were associated with tap water and an organic growth medium. No bacterial contamination was detected for fruits harvested from plants irrigated by wetland outflow water. In contrast, fruits harvested from those plants irrigated by preliminary treated wastewater showed high contamination by total coliforms, Streptococcus spp. and Salmonella spp. This was especially the case for fruits, which were located close to the contaminated soil surface. However, findings indicate that vegetable pots receiving wastewater treated with wetlands can be considered as safe compared to those receiving only preliminary treated wastewater. [ABSTRACT FROM AUTHOR]

This article assesses the adverse impact of upstream anthropogenic regulation of a transboundary river watershed on the natural flow regime of the downstream country, by focusing on a case study: the Diyala (Sīrvān) River watershed shared between Iraq and Iran. The article explores transboundary watershed management difficulties in a three-level system called the transboundary three-scalar framework, which helps to sustainably manage water resources. The average rates of reduction in flow between 2004 and 2013 ranged from nearly 24% in February to about 77% in September. The median of the reduction of rates between June and October was 66.4%. [ABSTRACT FROM AUTHOR]

Monitoring large-scale treatment wetlands is costly and time-consuming, but required by regulators. Some analytical results are available only after 5 days or even longer. Thus, adaptive neuro-fuzzy inference system (ANFIS) models were developed to predict the effluent concentrations of 5-day biochemical oxygen demand (BOD5) and NH4-N from a full-scale integrated constructed wetland (ICW) treating domestic wastewater. The ANFIS models were developed and validated with a 4-year data set from the ICW system. Cost-effective, quicker and easier to measure variables were selected as the possible predictors based on their goodness of correlation with the outputs. A self-organizing neural network was applied to extract the most relevant input variables from all the possible input variables. Fuzzy subtractive clustering was used to identify the architecture of the ANFIS models and to optimize fuzzy rules, overall, improving the network performance. According to the findings, ANFIS could predict the effluent quality variation quite strongly. Effluent BOD5 and NH4-N concentrations were predicted relatively accurately by other effluent water quality parameters, which can be measured within a few hours. The simulated effluent BOD5 and NH4-N concentrations well fitted the measured concentrations, which was also supported by relatively low mean squared error. Thus, ANFIS can be useful for real-time monitoring and control of ICW systems. [ABSTRACT FROM AUTHOR]

Nitrogen (N) transformations and removal in integrated constructed wetlands (ICWs) are often high, but the contributions of various pathways, including nitrification/denitrification, assimilation by plants and sediment storage, remain unclear. This study quantified the contributions of different N removal pathways in a typical multi-celled ICW system treating domestic wastewater. Findings showed near complete average total N retention of circa 95% at 102.3 g m-2 yr-1 during the 4-year period of operation. Variations in total N and NH4-N removal rates were associated with effluent flow volume rates and seasons. According to the mass balance estimation, assimilation by plants and sediment/soil storage accounted for approximately 23% and 20%, respectively, of the total N load removal. These were the major N removal route besides microbial transformations. Thus, the combination of plants with high biomass production offer valuable opportunities for improving ICW performance. The retrieval and use of sequestered N in the ICW sediment/soils require coherent management and provide innovative and valuable opportunities. [ABSTRACT FROM AUTHOR]

Summary Recent increases in human activities in shared river basins have unquestionably raised concerns about potential hydrological impacts, especially impacts of dams and large-scale water withdrawal schemes in the highlands. Anthropogenic pressures twinned with drought impacts have exacerbated water management challenges. This article assesses the cumulative consequences of upstream anthropogenic pressures and drought spells on temporal river flow regimes for the downstream country. The size and complexity of problems confronting transboundary river watersheds makes it necessary to use a representative example basin to study the problems and potential solutions. The Diyala (Sīrvān) river basin, which shares dozens of transboundary watersheds between Iraq and Iran, has been selected as a representative case study. A subset of the Indicators of Hydrologic Alteration (IHA) was utilised and climate variability was considered in assessing the combined effect of various forms of upstream human-river regulations and climatic conditions on natural flow regimes in the downstream state. Findings indicated that the anthropogenic river-regulation coupled with the impact of drought periods have noticeably modified the natural flow paradigm. The yearly average runoffs, which are no longer available for the downstream country, have soared to very high levels, particularly over the last fifteen years. More adverse impacts were detected in the non-rainy season. Findings reveal also that damming and considerable water diversion to large-scale irrigation projects in the upstream state are the main regulations affecting the management of shared water resources in the downstream country. [ABSTRACT FROM AUTHOR]

In order to observe the impact of different water compositions on sludge dewaterability, assessments of floc sizes using a particle size analyzer and of sludge dewaterability based on the capillary suction time (CST) test were carried out. Synthetic raw water had small floc sizes, and synthetic domestic wastewater had both larger median floc sizes and a better correlation between sludge dewaterability and median floc sizes. The floc size distribution results showed that synthetic raw water is associated with a narrow particle size distribution. In comparison, synthetic domestic wastewater produced a wider distribution. However, the CST values were similar for both waters. Compared to synthetic wastewater, natural wastewater had the largest distribution with generally larger particle sizes. [ABSTRACT FROM AUTHOR]

Highlights: [•] Traditional ‘community and environment’ variables do favour infiltration trenches, soakaways and belowground storage. [•] Generic ecosystem service categories and variables suitable for sustainable drainage systems were defined and quantified. [•] For the urban example case study, the overall ecosystem service scores were relatively low regardless of professional bias. [•] The novel ecosystem service variables promote permeable pavement systems regardless of the professional perspective. [•] Variable estimation errors are relatively low even for a virtually untrained example cohort of engineering students. [ABSTRACT FROM AUTHOR]

Highlights: [•] High removal was recorded for chemical oxygen demand and ammonia–nitrogen. [•] Small aggregates, long contact time and low loading rate are beneficial. [•] Small aggregates and short contact time lead to low solids accumulation. [•] Ammonia, ortho-phosphate and suspended solids outflows depend on oxygen demand. [•] Seasonal variations were noted for chemical oxygen demand, ammonia and nitrate. [Copyright &y& Elsevier]

Abstract: The retrofitting of sustainable drainage systems (SuDS) such as permeable pavements is currently undertaken ad hoc using expert experience supported by minimal guidance based predominantly on hard engineering variables. There is a lack of practical decision support tools useful for a rapid assessment of the potential of ecosystem services when retrofitting permeable pavements in urban areas that either feature existing trees or should be planted with trees in the near future. Thus the aim of this paper is to develop an innovative rapid decision support tool based on novel ecosystem service variables for retrofitting of permeable pavement systems close to trees. This unique tool proposes the retrofitting of permeable pavements that obtained the highest ecosystem service score for a specific urban site enhanced by the presence of trees. This approach is based on a novel ecosystem service philosophy adapted to permeable pavements rather than on traditional engineering judgement associated with variables based on quick community and environment assessments. For an example case study area such as Greater Manchester, which was dominated by Sycamore and Common Lime, a comparison with the traditional approach of determining community and environment variables indicates that permeable pavements are generally a preferred SuDS option. Permeable pavements combined with urban trees received relatively high scores, because of their great potential impact in terms of water and air quality improvement, and flood control, respectively. The outcomes of this paper are likely to lead to more combined permeable pavement and tree systems in the urban landscape, which are beneficial for humans and the environment. [Copyright &y& Elsevier]

A sustainable and low-cost point-of-use household drinking water solar disinfection (SODIS) technology was successfully applied to treat microbiologically contaminated water. Field experiments were conducted to determine the efficiency of SODIS and evaluate the potential benefits and limitations of SODIS under local climatic conditions in Karachi, Pakistan. In order to enhance the efficiency of SODIS, the application of physical interventions were also investigated. Twenty per cent of the total samples met drinking water guidelines under strong sunlight weather conditions, showing that SODIS is effective for complete disinfection under specific conditions. Physical interventions, including black-backed and reflecting rear surfaces in the batch reactors, enhanced SODIS performance. Microbial regrowth was also investigated and found to be more controlled in reactors with reflective and black-backed surfaces. The transfer of plasticizer di(2-ethylhexyl)phthalate (DEHP) released from the bottle material polyethylene terephthalate (PET) under SODIS conditions was also investigated. The maximum DEHP concentration in SODIS-treated water was 0.38 μg/L less than the value of 0.71 μg/L reported in a previous study and well below the WHO drinking-quality guideline value. Thus SODIS-treated water can successfully be used by the people living in squatter settlements of mega-cities, such as Karachi, with some limitations. [ABSTRACT FROM AUTHOR]

Multiple regression models, principal component analysis, redundancy analysis, and the self-organizing map (SOM) model were applied to assess the effects of physico-chemical parameters on the treatment performance of contaminated wetland sediments in replicate integrated constructed wetland (ICW) mesocosms treating either farmyard runoff or domestic wastewater. Dissolved oxygen concentration and conductivity were correlated with the reduction of ammonia-nitrogen () and/or molybdate reactive phosphorus (MRP), and the redox potential and conductivity were related to chemical oxygen demand (COD) removal. SOM was selected as the prediction model to provide numerical estimations for the performance of ICW mesocosms. The model was validated, indicating that , MRP, and COD removal can be predicted by input variables that are quick and cost-effective to measure. The SOM model is an appropriate method for monitoring the performance of mature ICWs as a source of contaminants such as nitrogen and phosphorus. Although no reduction in the overall performance was observed for ICW Sites 7 and 11, this laboratory-scale study provides valuable warning signs regarding the loss of contaminant removal for ICW systems that have been in operation for a relatively long time. [ABSTRACT FROM AUTHOR]

This review discusses high impact research in sustainable urban and land management. The focus is on large European projects that have a holistic and multi-disciplinary assessment approach towards the total environment. This paper clearly indicates that many projects propose decision-making tools partly supported by numerical models. Successful projects were identified as applying the following criteria: a communicative and holistic approach involving economic, environmental and social sciences throughout the project; sufficient geographic coverage; engagement of stakeholders from a wide variety of sectors; and plans for dissemination of project outcomes and active knowledge sharing. [ABSTRACT FROM PUBLISHER]

Abstract: This study aims to provide a rapid screening tool for assessment of sustainable flood retention basins (SFRBs) to predict corresponding dam failure risks. A rapid expert-based assessment method for dam failure of SFRB supported by an artificial neural network (ANN) model has been presented. Flood storage was assessed for 110 SFRB and the corresponding Dam Failure Risk was evaluated for all dams across the wider Greater Manchester study area. The results show that Dam Failure Risk can be estimated by using the variables Dam Height, Dam Length, Maximum Flood Water Volume, Flood Water Surface Area, Mean Annual Rainfall (based on Met Office data), Altitude, Catchment Size, Urban Catchment Proportion, Forest Catchment Proportion and Managed Maximum Flood Water Volume. A cross-validation R 2 value of 0.70 for the ANN model signifies that the tool is likely to predict variables well for new data sets. Traditionally, dams are considered safe because they have been built according to high technical standards. However, many dams that were constructed decades ago do not meet the current state-of-the-art dam design guidelines. Spatial distribution maps show that dam failure risks of SFRB located near cities are higher than those situated in rural locations. The proposed tool could be used as an early warning system in times of heavy rainfall. [Copyright &y& Elsevier]

The use of constructed wetlands for the treatment of wastewater is an approach that has received increasing attention over the last 30 years due to their innate ability to deal with a wide range of highly variable influent types. The treatment of swine wastewater is an on-going issue due to its generally higher nutrient concentrations and the limited land available to owners. The implementation of the European Union Nitrates Directive and Water Framework Directive is currently placing considerable pressure on agriculture in EU member states with its focus on the improvement and sustained quality of surface waters. The limit of 170 kg of organic nitrogen/ha/annum imposed by the Nitrates Directive can cause severe difficulties for wastewater management in the piggery industry in Ireland, where spreadlands are already receiving high application rates of organic N. A replicated mesocosm integrated constructed wetland (ICW) approach was examined for the effective treatment of anaerobically digested separated swine wastewater with emphasis on nutrient removal. These mesocosm systems are based on operations identified in the available literature as well as on the ICW Concept pioneered in Ireland. The removal efficiency yielded substantial results over an 18 month period and highlighted high mass removal of ammonia-nitrogen (98.1-99.9%) from the influent. The removal recorded in all operational replicates throughout the study period showed that wetlands based on the ICW concept may very well prove to be a viable and sustainable approach for the treatment of swine wastewaters in Ireland whilst successfully addressing both the Nitrates and Water Framework Directives. [ABSTRACT FROM AUTHOR]

Abstract: The concept of integrated constructed wetlands (ICW) uses in situ soils to construct and line their cells. The integrity of soil materials, however, may provide a potential pathway for contaminants to flow into the subsoil. In this study, the rates of infiltration and contaminants loading occurring beneath a full-scale ICW treating domestic wastewater were evaluated over an 18-month period. The ICW is located at Glaslough in Co. Monaghan, Ireland. It consists of two sludge cells and a sequence of five shallow vegetated wetland cells. The ICW cells were lined with 500mm thick local subsoil materials. Infiltration water was collected from zero-tension pan lysimeters, which were placed within the soil-liners of the first three ICW cells and analysed for water quality parameters such as chemical oxygen demand, ammonia-nitrogen, nitrate-nitrogen, and molybdate reactive phosphate. Infiltration rates were 4.3×10−9, 3.7×10−9 and 1.0×10−8 ms−1 from the first three ICW cells. The variation among locations was small. The apparent hydraulic conductivity of the soil liner, calculated with empirical water budgets, ranged between 3.5×10−9 and 9.8×10−9 ms−1across the cells. In the first two cells of the ICW, less than 0.5% of the influent contaminant loading to the cells was lost through infiltration to subsoil. Overall, the amount of infiltration and contaminant loading occurring beneath the ICW cells increased from the proximal cells to the distal one. Higher contaminant loading was recorded in the third cell, which received partially treated wastewater. This implies that each ICW cell has the potential to impact differently on the underlying groundwater and that the potential for groundwater contamination from ICW systems was minimal in the first ICW cells, when compared to the last one. [Copyright &y& Elsevier]

Artificial intelligence techniques, such as neural networks, are modeling tools that can be applied to analyze urban runoff quality issues. Artificial neural networks are frequently used to model various highly variable and nonlinear physical phenomena in the water and environmental engineering fields. The application of neural networks for analyzing the performance of combined permeable pavement and earth energy systems is timely and novel. This paper presents the application of back-propagation neural networks and the testing of the Levenberg-Marquardt, Quasi-Newton, and Bayesian Regularization algorithms. The neural networks were statistically assessed for their goodness of prediction with respect to the biochemical oxygen demand (BOD), ammonia-nitrogen, nitrate-nitrogen, and ortho-phosphate-phosphorus by numerical computation of the mean absolute error, root-mean-square error, mean absolute relative error, and the coefficient of correlation for the prediction compared with the corresponding measured data. The three neural network models were assessed for their efficiency in accurately simulating the effluent water quality parameters from various experimental pavement systems. The models predicted all key parameters with high correlation coefficients and low minimum statistical errors. The back-propagation and feed-forward neural network models performed optimally as pollutant removal predictors with regard to these two sustainable technologies. [ABSTRACT FROM AUTHOR]

The impact of temperature on the filterability of synthetic sludge,using the capillary suction time (CST) test, was investigated. TheCST was measured at five temperatures, six total suspended solid (TSS)concentrations, and two funnel geometries. The results were not consistentwith the hypothesis that the CST declines at higher temperatures throughthe lowering of the sludge viscosity. The impact of temperature onthe results of CST tests was moderated by other physicochemical propertiesof the sludge (desorptivity, particle size composition, and chemicalconstituents) associated with the efficiency of flocculation. [ABSTRACT FROM AUTHOR]

Meso-scale constructed wetlands have not been commonly used for the examination of interactions and operations within differently designed wetland systems. Sixteen meso-scale constructed wetland systems (4 operations with 4 replicates each) were therefore evaluated between November 2008 and June 2010. These systems were used to examine key operations identified in the literature including hydraulic loading rates, nutrient loading rates and nutrient recycling modes. The wetlands were managed in the following modes: normal, recycling, high nutrient loading and high flow rate. The designs were such that the influents could be varied at set loading rates and concentrations. The ammonia removal rates for the meso-scale integrated constructed wetland (ICW) systems were similar to other full-scale ICW systems that have been in operation in the south-east of Ireland for the past decade. These comparable results highlight the potential cost-effectiveness of these meso-scale experimental designs for the examination of novel operations for future ICW developments. [ABSTRACT FROM AUTHOR]

Abstract: Non-point source pollution such as land-spreading of nitrogen-rich piggery wastewater poses a significant threat to surface waters. The aim was to examine the treatment of anaerobically digested piggery wastewater using four different meso-scale integrated constructed wetland (ICW) systems planted with Glyceria maxima. Four replicates were used for each system to assess differences due to nutrient loading, hydraulic loading and effluent recycling. All systems were effective in removing total organic nitrogen, ammonia-nitrogen, nitrate-nitrogen and molybdate reactive phosphorus. However, ammonia-nitrogen removal was the greatest challenge for high flow rates (>100m3/ha/d). Nitrification was higher in summer than winter. Findings show for the first time that effluent recycling within ICW was beneficial to lower ammonia-nitrogen but was associated with higher operational costs. The cost–benefit ratio based on ammonia-nitrogen removal for standard, recycling, high nutrients and high flow rate treatments was 1.08:1.04:1.06:1.00. It follows that a high flow rate was only marginally more cost-effective. [Copyright &y& Elsevier]

Abstract: Non-point source pollution such as land-spreading of nitrogen-rich piggery wastewater poses a significant threat to surface waters. The aim was to examine the treatment of anaerobically digested piggery wastewater using four different meso-scale integrated constructed wetland (ICW) systems planted with Glyceria maxima. Four replicates were used for each system to assess differences due to nutrient loading, hydraulic loading and effluent recycling. All systems were effective in removing total organic nitrogen, ammonia-nitrogen, nitrate-nitrogen and molybdate reactive phosphorus. However, ammonia-nitrogen removal was the greatest challenge for high flow rates (>100m3/ha/d). Nitrification was higher in summer than winter. Findings show for the first time that effluent recycling within ICW was beneficial to lower ammonia-nitrogen but was associated with higher operational costs. The cost–benefit ratio based on ammonia-nitrogen removal for standard, recycling, high nutrients and high flow rate treatments was 1.08:1.04:1.06:1.00. It follows that a high flow rate was only marginally more cost-effective. [Copyright &y& Elsevier]

The capillary suction time (CST) and the specific resistance to filtration (SRF) tests are both commonly used to estimate sludge dewaterability. Both tests are known to be empirically related but the SRF is much more expensive and time consuming compared with the CST test. The aim of this study was therefore to develop a prediction methodology to obtain SRF test results from the data generated by CST tests under different experimental conditions. This study is based on empirical data sets linking CST with SRF. The prediction equations were developed by first estimating filterability from CST values and then relating it with SRF values using regression analyses. The relationships between the results of the CST and SRF tests were best described using an empirical model, which incorporated logarithmic and squared terms to account for the nonlinear relationship between filterability, total suspended solids, and temperature. The findings were statistically significant (p<0.05) and the model satisfied all the statistical assumptions. Therefore, the model can be used to predict SRF from CST values. [ABSTRACT FROM AUTHOR]

Treatment of log yard runoff is required to avoid contamination of receiving watercourses. The research aim was to assess if infiltration of log yard runoff through planted soil systems is successful and if different plant species affect the treatment performance at a field-scale experimental site in Sweden (2005 to 2007). Contaminated runoff from the log yard of a sawmill was infiltrated through soil planted with Alnus glutinosa (L.) Gartner (common alder), Salix schweriniiXviminalis (willow variety "Gudrun"), Lolium perenne (L.) (rye grass), and Phalaris arundinacea (L.) (reed canary grass). The study concluded that there were no treatment differences when comparing the four different plants with each other, and there also were no differences between the tree and the grass species. Furthermore, the infiltration treatment was effective in reducing total organic carbon (55%) and total phosphorus (45%) concentrations in the runoff, even when the loads on the infiltration system increased from year to year. [ABSTRACT FROM AUTHOR]

Abstract: The aim of the project was to assess the nutrient removal within integrated constructed wetlands (ICW). The study was based on twelve free-water surface ICW treating farmyard runoff in Ireland. The principal design criterion leading to adequate effluent water quality (i.e. molybdate reactive phosphate (MRP) less than 1mg/L) from ICW is that the total wetland area needs to be sized by a factor of at least 1.3 times the farmyard area. It is common practice to construct at least four wetland cells in series with individual aspect ratios of less than 1:2 (width to length). Most of the MRP concentrations after ICW treatment were in agreement with Irish urban wastewater standards for discharge to sensitive waters, which can be used as a benchmark to measure ICW performance and which are usually applied to ICW even if it may appear to be too stringent. Furthermore, the number of denitrifying bacteria detected in the benthos of ICW systems is higher than the number of ammonia-oxidising bacteria. Anoxic conditions at the wetland bottom create conditions which are favourable for denitrifying bacteria. It follows that sediment and litter components of the ICW system support denitrification. The outflow water quality was within recommended guidelines. The study suggests that phosphorus exported from an ICW system was similar to the typical background concentrations of phosphorus export rates from land to water. [Copyright &y& Elsevier]

Hurricanes pose a great risk to forestry, and lead to high financial losses due to destroyed wood. For example, the hurricane ‘Gudrun’ devastated a large part of the forests of southern Sweden in January 2005. Windthrown logs are commonly removed from forest, temporarily stored on log yards, and often sprinkled with water to avoid decay. However, the subsequent runoff may cause environmental pollution. The aim of this original article is to assess the treatment of log yard runoff, which was impacted by logs of different age, in an inexpensive free water surface constructed wetland. Considering that there is often insufficient space for treatment wetlands, a small wetland was retrofitted into an existing ditch next to the log yard. Among other parameters, total organic carbon, total phosphorus, and total nitrogen were measured. Results show insufficient treatment of log yard runoff. Storage of aged windthrown logs led to a higher content of total phosphorus in the runoff. It was likely that the hydraulic loading rate in this wetland case study was too high, and that the concentration of oxygen in the runoff was too low for the biochemical processes in the wetland to reduce the concentrations of total phosphorus, total organic carbon, and suspended solids. It follows that a similar wetland treatment system to be designed in the future should either be made larger or supplemented by alternative further treatment solutions such as increased oxygenation or the introduction of aggregates promoting the adsorption of phosphorus. [ABSTRACT FROM AUTHOR]

Abstract: The integrated constructed wetland (ICW) system studied in this research paper was constructed as part of a series of 15 wetland systems to improve the water quality of an entire catchment area (Annestown Stream watershed, Ireland) dominated by farming activities. The studied ICW comprised four cells and was used for the treatment of farmyard dirty water from a dairy farm near Dunhill (Ireland). The performance of this system was evaluated through physical, chemical and microbiological parameters collected for 7 years. The removal efficiencies were relatively good if compared to the international literature: biochemical oxygen demand (97.6%), chemical oxygen demand (94.9%), suspended solids (93.7%), ammonia-nitrogen (99%), nitrate-nitrogen (74%) and molybdate reactive phosphorus (91.8%). A molecular microbiological analysis of sediment samples collected from the site indicated that the number of denitrifying bacteria detected in the ICW system was higher than the number of ammonia-oxidizing bacteria. The monitored nutrient concentrations in groundwater and surface waters indicated that this ICW system did not pollute the receiving waters. The results showed that ICW are likely to be efficient in removing nutrients from farmyard runoff rich in nitrogen and phosphorus. [Copyright &y& Elsevier]

Abstract: A self-organizing map (SOM) model was applied as a prediction tool for the performance of an integrated constructed wetland (ICW) agroecosystem treating agricultural runoff to protect receiving watercourses. By utilizing the SOM model, the time-consuming to measure expensive biochemical oxygen demand outflow concentrations were predicted well by other inexpensive variables, which were quicker and easier to measure. Correct predictions for the outflow biochemical oxygen demand concentrations were between 89% and 100%. This novel approach allows for the real time control of the outflow water quality of the ICW and potentially also of other treatment system applications. Moreover, the missing values and outliers from the large but incomplete ICW data set were replaced accurately by most likely values determined by the SOM model. This was important because the proportions of unusable entries for chemical oxygen demand, suspended solids and biochemical oxygen demand were very high: 41%, 54%, and 61%, respectively. [Copyright &y& Elsevier]

Abstract: The aim of this paper is to recommend a rapid conceptual classification model for Sustainable Flood Retention Basins (SFRB) used to control runoff in a temperate climate. An SFRB is an aesthetically pleasing retention basin predominantly used for flood protection adhering to sustainable drainage and best management practices. The classification model was developed on the basis of a database of 141 SFRB using the River Rhine catchment in Baden (part of Baden-Württemberg, Germany) as a case study. It is based on an agglomerative cluster analysis and is intended to be used by engineers and scientists to adequately classify the following different types of SFRB: Hydraulic Flood Retention Basin, Traditional Flood Retention Basin, Sustainable Flood Retention Wetland, Aesthetic Flood Retention Wetland, Integrated Flood Retention Wetland and Natural Flood Retention Wetland. The selection of classification variables was supported by a principal component analysis. The identification of SFRB in the data set was based on a Ward cluster analysis of 34 weighted classification variables. Scoring tables were defined to enable the assignment of the six SFRB definitions to retention basins in the data set. The efficiency of these tables was based on a scoring system which gave the conceptual model for the example case study sites an overall efficiency of approximately 60% (as opposed to 17% by chance). This conceptual classification model should be utilized to improve communication by providing definitions for SFRB types. The classification definitions are likely to be applicable for other regions with both temperate oceanic and temperate continental climates. [Copyright &y& Elsevier]

This paper comprises the scientific justification for the Farm Constructed Wetland (FCW) Design Manual for Northern Ireland and Scotland. Moreover, this document addresses an international audience interested in applying wetland systems in the wider agricultural context. Farm constructed wetlands combine farm wastewater (predominantly farmyard runoff) treatment with landscape and biodiversity enhancements, and are a specific application and class of integrated constructed wetlands (ICW), which have wider applications in the treatment of other wastewater types such as domestic sewage. The aim of this review paper is to propose guidelines highlighting the rationale for FCW, including key water quality management and regulatory issues, important physical and biochemical wetland treatment processes, assessment techniques for characterizing potential FCW sites and discharge options to water bodies. The paper discusses universal design, construction, planting, maintenance and operation issues relevant specifically for FCW in a temperate climate, but highlights also catchment-specific requirements to protect the environment. [Copyright &y& Elsevier]

This review paper summarises the environmental effects of runoff from wood handling sites including log yards. The characteristics of site runoff and the corresponding effects on the receiving watercourses are presented for worldwide case studies, highlighting the urgent need to address the water pollution problem associated with the wood industry. The methods used to reduce the negative environmental impact of the runoff, such as constructed wetlands, soil infiltration and chemical oxidation, are evaluated. The principal environmental problem of runoff is usually the high concentration of organic substances originating from the wood and bark, some of which are toxic to aquatic life. Phosphorus is also a problem according to some studies. The toxicity of the runoff varies greatly, and depends on the species of tree stored, the amount of water the wood has been in contact with and the degree of runoff treatment. [Copyright &y& Elsevier]

Water purification is one of the most essential services provided by wetlands. A lot of concerns regarding wetlands subjected to climate change relate to their susceptibility to hydrological change and the increase in temperature as a result of global warming. A warmer condition may accelerate the rate of decomposition and release of nutrients, which can be exported downstream and cause serious ecological challenges; e.g., eutrophication and acidification. The aim of this study is to investigate the effect of climate change on water quality in peatland and constructed wetland ecosystems subject to water level management. For this purpose, the authors simulated the current climate scenario base on the database from Malmö station (Scania, Sweden) for 2016 and 2017 as well as the future climate scenarios for the last 30 years of the century based on the Representative Concentration Pathway (RCP) and different regional climate models (RCM) for a region wider than Scania County. For future climate change, the authors simulated low (RCP 2.6), moderate (RCP 4.5) and extreme (RCP 8.5) climate scenarios. All simulations were conducted within climate chambers for experimental peatland and constructed wetland mesocosms. Our results demonstrate that the effect of climate scenario is significantly different for peatlands and constructed wetlands (interactive effect) for the combined chemical variables. The warmest climate scenario RCP 8.5 is linked to a higher water purification function for constructed wetlands, but to a lower water purification function and a subsequent deterioration of peatland water qualities, even if subjected to water level management. The explanation for the different response of constructed wetlands and peatlands to climate change could be due to the fact that the substrate in the constructed wetland mesocosms and peatlands was different in terms of the organic matter quality and quantity. The utilization of nutrients by the plants and microbial community readily exceed the mineralization under a limited nutrient content (as we had in constructed wetland) when the temperature rises. However, concerning the extreme scenario RCP 8.5, the peatlands have shown a tendency to have reverse processes. [Display omitted] • The climate scenarios have a significant effect on NH 4 –N, DOC, DO & TSS. • The wetland type has a significant effect on all measured physiochemical variables. • Significant interactive effect of climate scenario & wetland type on TP, NH 4 –N & COD. • RCP 8.5: High temperature deteriorates the water quality of the peatland outflow. • RCP 8.5: High temperature improves the constructed wetland outflow water quality. [ABSTRACT FROM AUTHOR]

Abstract: The self-organizing map (SOM) model was applied to predict outflow nutrient concentrations for integrated constructed wetlands (ICWs) treating farmyard runoff. The SOM showed that the outflow ammonia-nitrogen concentrations were strongly correlated with water temperature and salt concentrations, indicating that ammonia-nitrogen removal is effective at low salt concentrations and comparatively high temperatures in ICWs. Soluble reactive phosphorus removal was predominantly affected by salt and dissolved oxygen concentrations. In addition, pH and temperature were weakly correlated with soluble reactive phosphorus removal, suggesting that soluble reactive phosphorus was easily removed within ICWs, if salt concentrations were low, and dissolved oxygen, temperature and pH values were high. The SOM model performed very well in predicting the nutrient concentrations with water quality variables such as temperature, conductivity and dissolved oxygen, which can be measured cost-effectively. The results indicate that the SOM model was an appropriate approach to monitor wastewater treatment processes in ICWs. [Copyright &y& Elsevier]

The aim of this paper is to recommend a rapid classification system for sustainable flood retention basins (SFRBs) to control runoff in a temperate climate. The system should improve communication among engineers and scientists, and was developed with a general database (approximately 660 basins) and a very detailed database (56 basins), using the River Rhine catchment in the South of Baden (Germany) as a case study. The classification system can be used by civil engineers, environmental scientists and planners to determine the following types of SFRBs: hydraulic flood retention basin, traditional sustainable flood retention basin, sustainable flood retention wetland, aesthetic flood retention wetland, integrated flood retention wetland and natural flood retention wetland. The most important system variables were rainfall, dam height, flood water volume, elevation, dam length, flotsam, floodplain elevation, forest and animal passage. However, 34 variables were applied to determine the different types of SFRBs, which were predominantly used for hydraulic purposes. [ABSTRACT FROM AUTHOR]

Abstract: The aim of this research was to assess the role of the macrophyte Phragmites australis (Cav.) Trin. ex Steud. in experimental temporarily flooded vertical-flow wetland filters treating urban runoff. For 2 years, hydrated nickel and copper nitrate were added to sieved road runoff to simulate contaminated primary treated urban runoff. During the first year, 5-day biochemical oxygen demand (BOD) removal efficiencies were lower in planted filters than in unplanted filters. However, the BOD removal performances of all filters were virtually similar irrespective of the planting regime during the second year. The nutrient removal performance of planted filters was more efficient and stable throughout the season particularly after the filters matured compared to that of unplanted filters. A substantial amount of nitrogen was also removed by harvesting P. australis, though metals were not, when compared to those retained in the filters. Furthermore, higher concentrations of nickel in the effluent were recorded in the planted filters, despite their ability to take up the heavy metals. P. australis provided undesirable conditions for precipitation of Ni by lowering the pH in the processes. Finally, after applying shock loadings of Cu, higher Cu outflow concentrations were recorded for planted in comparison to unplanted filters. [Copyright &y& Elsevier]

The Glasgow Sustainable Urban Drainage System (SUDS) Management Project satisfies the first phase of the Glasgow Surface Water Management Project. This is Glasgow City Council's contribution to the Transformation of Rural and Urban Spatial Structure (TRUST) project, one of the European Union's (EU) interregional (INTERREG IIIB) funded research projects. The remit of this EU project comprises also other representative regions in Europe. The project shows also how SUDS can contribute to the overall catchment dynamics of cities such as Glasgow, ultimately relieving stress on the current predominantly combined sewer system. Fifty-seven sites within 46 areas of Glasgow were identified for investigation. A detailed soil chemistry analysis, a preliminary SUDS feasibility assessment and a desk study relating to historical planning issues that may be relevant for subsequent future development and regeneration options were undertaken. Detailed design and management guidelines were then drafted for selected representative demonstration areas (Belvidere Hospital and Celtic FC Stadium Areas) of high public and property developers interest, and education value. A combination of infiltration trenches or swales with ponds or underground storage were the most likely SUDS options for the majority of the demonstration areas. Soil contamination issues were considered when selecting SUDS because heavy metals such as lead and zinc can cause environmental health problems. [ABSTRACT FROM AUTHOR]

Abstract: The self-organizing map (SOM) model was applied to elucidate heavy metal removal mechanisms and to predict heavy metal concentrations in experimental constructed wetlands treating urban runoff. A newly developed SOM map showed that nickel in constructed wetland filters is likely to leach under high conductivity in combination with low pH in winter. In contrast, influent pH and conductivity were not shown to have clear relationships with copper (Cu) concentrations in the effluent, suggesting that the mobility of Cu was not considerably affected by salt increase during winter. The accuracy of prediction with SOM was highly satisfactory, suggesting heavy metals can be efficiently estimated by applying the SOM model with input variables such as conductivity, pH, temperature and redox potential, which can be monitored in real time. Moreover, domain understanding was not required to implement the SOM model for prediction of heavy metal removal efficiencies. [Copyright &y& Elsevier]

The Glasgow Sustainable Urban Drainage System (SUDS) Management Project satisfies the first of three phases of the Glasgow Surface Water Management Project. This is Glasgow City Council's contribution to the Transformation of Rural and Urban Spatial Structure (TRUST) project, one of the European Union's (EU) inter-regional (INTERREG IIIB) funded research projects. The contribution of SUDS to the overall catchment dynamics of cities such as Glasgow was studied. Fifty-seven sites within 46 areas of Glasgow were identified for initial investigation, including a preliminary SUDS feasibility assessment and a desk study relating to historical planning issues that may be relevant for subsequent future development and regeneration options. The methodologies for a SUDS Option Decision Support Key and a corresponding SUDS Option Decision Support Matrix that are adaptable to different cities and countries have been outlined. The key should be used during a preliminary site investigation and can help to classify potential SUDS sites. Corresponding findings should be compared with the conditions listed in the matrix, which will inform the planner about potentially-suitable SUDS techniques for a particular site. Detailed design guidelines were then drafted for seven selected representative SUDS demonstration areas including the Pollok Centre area. This case study, for example, is representative for a class of 24 areas and sites. Combinations of infiltration trenches or swales with ponds or underground storage were the most likely SUDS options for the majority of the demonstration areas. [ABSTRACT FROM AUTHOR]

Yemen's agriculture and water resources sectors are in a crisis. The water availability is 150 m³/cap/a. This compares with an average of 1250 m³/cap/a for the Middle East and North Africa. All surface water and groundwater resources are exploited beyond the level of recharge. The agriculture industry uses 93% of the potable water, and does not actively encourage sustainable water saving techniques. Qat (Catha edulis; recreational drug) cultivation uses 40% of the potable water. The water crisis could be mitigated by reducing qat production, and promoting water reuse of treated wastewater for irrigation. However, this is currently socially unacceptable. [ABSTRACT FROM AUTHOR]

The aim of this research was to assess the treatment efficiencies for gully pot liquor of experimental vertical- flow constructed wetland filters containing Phragmites australis (Cav.) Trin. ex Steud. (common reed) and filter media of different adsorption capacities. Six out of 12 filters received inflow water spiked with metals. For 2 years, hydrated nickel and copper nitrate were added to sieved gully pot liquor to simulate contaminated primary treated storm runoff. For those six constructed wetland filters receiving heavy metals, an obvious breakthrough of dissolved nickel was recorded after road salting during the first winter. However, a breakthrough of nickel was not observed, since the inflow pH was raised to eight after the first year of operation. High pH facilitated the formation of particulate metal compounds such as nickel hydroxide. During the second year, reduction efficiencies of heavy metal, 5-days at 20°C N-Allylthiourea biochemical oxygen demand (BOD) and suspended solids (SS) improved considerably. Concentrations of BOD were frequently <20 mg/L. However, concentrations for SS were frequently >30 mg/L. These are the two international thresholds for secondary wastewater treatment. The BOD removal increased over time due to biomass maturation, and the increase of pH. An analysis of the findings with case-based reasoning can be found in the corresponding follow-up paper (Part B). [ABSTRACT FROM AUTHOR]

The aim of this research was to assess the treatment efficiencies for gully pot liquor of experimental vertical- flow constructed wetland filters containing Phragmites australis (Cav.) Trin. ex Steud. (common reed) and filter media of different adsorption capacities. Six out of 12 filters received inflow water spiked with metals. For 2 years, hydrated nickel and copper nitrate were added to sieved gully pot liquor to simulate contaminated primary treated storm runoff. The findings were analyzed and discussed in a previous paper (Part A). Case-based reasoning (CBR) methods were applied to predict 5 days at 20°C N-Allylthiourea biochemical oxygen demand (BOD) and suspended solids (SS), and to demonstrate an alternative method of analyzing water quality performance indicators. The CBR method was successful in predicting if outflow concentrations were either above or below the thresholds set for water-quality variables. Relatively small case bases of approximately 60 entries are sufficient to yield relatively high predictions of compliance of at least 90% for BOD. Biochemical oxygen demand and SS are expensive to estimate, and can be cost-effectively controlled by applying CBR with the input variables turbidity and conductivity. [ABSTRACT FROM AUTHOR]

The first aim of this invited literature review is critically to review and evaluate hydrological, physical and biochemical processes within natural and constructed wetlands. The second aim is to contribute the thoughts of the authors to the discussion with the help of a case study focusing on gully pot liquor treatment. The performances of constructed treatment wetlands with and without macrophytes, and aggregates of different adsorption capacities will be assessed, principle findings highlighted and conclusions, also relevant to the literature review, will be drawn. The relationships between aggregates, microbial and plant communities as well as the reduction of predominantly biochemical oxygen demand, suspended solids and heavy metals are investigated. After maturation of the biomass, which dominates the litter zone, organic and inorganic contaminants are usually reduced similarly for all wetland types. There appears to be no additional benefit in using macrophytes and expensive adsorption media in constructed wetlands. [ABSTRACT FROM AUTHOR]

The purpose of this case study was to optimise design, operation and maintenance guidelines, and to assess the water treatment potential of a storm water pond system after 15 months of operation. The system was based on a combined silt trap, attenuation pond and vegetated infiltration basin. This combination was used as the basis for construction of a roof water runoff system from a single domestic property. United Kingdom Building Research Establishment and Construction Industry Research and Information Association, and German Association for Water, Wastewater and Waste design guidelines were tested. These design guidelines failed because they did not consider local conditions. The infiltration function for the infiltration basin was logarithmic. Algal control techniques were successfully applied, and treatment of rainwater runoff from roofs was found to be largely unnecessary for recycling (e.g., watering plants). However, seasonal and diurnal variations of biochemical oxygen demand, dissolved oxygen and pH were recorded. [Copyright &y& Elsevier]

The Environmental Ministry of Schleswig–Holstein (Northern Germany) has implemented a novel peatland rehabilitation programme to utilise the high denitrification potential of degenerated, minerotrophic peatlands for the reduction of nitrate input into aquatic ecosystems, and to simultaneously improve the habitat conditions. Realisation of both goals requires changes to the water management adapted to the site-specific geohydrological conditions. The effect of raised groundwater levels and extensive land use on the water quality of heavily vegetated and groundwater-fed ditches was investigated in a riparian peatland located in the River Eider Valley (a nationally important wetland case study area). The water quality of the selected representative ditches was regularly assessed at different discharge levels during different flow obstruction cover periods. The hydraulic residence time was predominantly a function of the ditch geometry and the overall flow obstruction. A better understanding of the effect of ditch vegetation on the temporal flow patterns and the hydraulic residence times is of high environmental interest, especially for improving nutrient standards in lowland rivers such as the River Eider. Within-ditch vegetation and other hydraulic flow obstructions such as accumulated silt and organic debris increased the hydraulic residence time and led to an improvement of the water quality (e.g. reduction in nitrate content) along the ditch. While ortho-phosphate and ammonia concentrations were acceptable to German water quality standards, nitrate–nitrogen concentrations were frequently elevated due to high discharges despite high flow obstruction cover. Further findings show that the lower stretches of the ditches were flooded by the River Eider due to the absence of a macrophyte-mowing scheme that led to increased water levels during late summer. [Copyright &y& Elsevier]

The Environmental Ministry of Schleswig-Holstein has implemented a novel peatland management strategy in order to utilize the high nutrient retention potential of degenerated peatlands, and to improve the habitat at the same time. The effect of raised water levels and passive land use management on hydraulic properties of heavily vegetated and groundwater-fed open ditches was investigated at the ‘Eider River Valley’. The flow properties of selected representative open ditches were regularly assessed at different discharge levels during different vegetation cover periods. The hydraulic residence time is predominantly a function of the open ditch geometry and the overall obstruction cover including the presence of macrophytes. Typical mean discharges measured ranged between 0.2 and 2.5l/s. Within-ditch vegetation and other hydraulic obstructions, like accumulated silt and organic debris, slow down the hydraulic residence time. The experimental results were evaluated to acquire more realistic values for total bed-roughness under different hydraulic flow regimes. Further findings show that the lower parts of the open ditches were flooded by the Eider River due to the absence of a mowing scheme. Typical water level increases were 0.5m. This led to a reduction of the velocity and an increase of the dispersion within the ditch. [Copyright &y& Elsevier]