Eutrophication modelling of Amirkabir Reservoir (Iran) using an artificial neural network approach

The complicated non‐linear relationships between water quality and environmental parameters involved in predicting algal blooms necessitate a new approach, using data‐driven modelling. Accordingly, a multilayer perceptron (MLP) and time delay neural network (TDNN) were used to predict the eutrophication status of two monitoring stations in the Amirkabir Reservoir in Iran. Six scenarios for each monitoring station were performed to select a significant, independent input using 12 years of monthly data. The final inputs were temperature, turbidity, phosphate (PO₄), nitrate (NO₃), nitrite (NO₂), ammonium (NH₃), dissolved oxygen (DO) and electrical conductivity (EC). Applying an MLP neural network to the upstream monitoring station with 21–38 neurons in the first and second hidden layers, the minimum mean squared errors (MSE ) in training, validating and testing were 0.083, 0.81 and 1.95 cells/100 ml, respectively. Further, when the TDNN network was used with the same neuron numbers in the hidden layer for the similar monitoring station, the minimum MSE values for model training, validating and testing were 0.06, 0.72 and 1.76 cells/100 ml, respectively. For the Beylaghan monitoring station, using the MLP neural network with 29–23 neurons in the first and second hidden layer, the minimum MSE values gained in training, validating and testing were 0.181, 0.58 and 0.95 cells/100 ml, respectively. Using the TDNN network with the same neurons in the hidden layers of the MLP neural network for the station, the minimum MSE values for training, validating and testing were 0.152, 0.43 and 0.84 cells/100mL, respectively. Thus, TDNN exhibited a high accuracy and workability, compared to the MLP. Sensitivity analysis of the Amirkabir Reservoir dataset indicated increasing the value of nitrate is the first factor, followed by turbidity and NH₃, having the greatest impacts on eutrophication prediction.     

Water Quality Monitoring and Modeling in Lake Kastoria, Using GIS. Assessment and Management of Pollution Sources

Lake Kastoria, is a very fragile aquatic ecosystem, protected by several national and international conventions, situated in the Region of Western Macedonia, Greece. A monthly monitoring program has been operated by the Municipality of Kastoria, during the past 5 years (2002–2007). The water quality parameters monitored, are: Water Temperature (Tw), dissolved oxygen (DO), BOD, COD, pH, water conductivity (ECw), redox potential (RP), nitrate nitrogen (NO₃-N), nitrite nitrogen (NO₂-N), ammonium nitrogen (NH₄-N) and orthophosphates-dissolved inorganic phosphorus (PO₄-P-DIP). This study focuses on the water quality parameters of Tw, DO, NH₄-N, NO₃-N and PO₄-P. The sampling points are five, scattered in specific positions in the Lake (Sioutista, Xiropotamos, Mavriotissa, Northern Beach and Stavros—Southern Beach). A comparison took place between two spatial–geographic deterministic simulation algorithms “IDW” and “RBF”, using GIS. This resulted in the conclusion that the first algorithm is the most appropriate to formulate the equipotential curves of the selected water quality parameters. Data from two seasons (winter—frozen Lake and summer—high eutrophication level) and 2 years (2005 and 2006) are presented here so the compared periods are February 2005, July 2005, February 2006 and July 2006. The thematic maps obtained indicate the most probable sources of pollution in Lake Kastoria and present the geographic distribution of the water quality parameters using the “IDW” algorithm. The most significant drawback of monthly monitoring is the missing of the data influenced by extreme events. Therefore, the need for daily telemetric monitoring data is suggested, in order to prevent environmental hazards and confront pressures concerning on water quality status. Finally, management strategies of pollution reduction are proposed, in combination with systematic telemetric real time monitoring, in order to upgrade the natural environment of Lake Kastoria.     

Limnological characterization of interdune ponds of Curupu Island,Raposa – MA,Brazil

This study was conducted on four freshwater interdune ponds (Jacaré; Grande; Duna; Banho) located on Curupu Island within the municipality of Raposa (Maranhão State, Brazil). It focused on a diagnosis of the physical and chemical characteristics of the water and sediment in these water bodies, while at the same time obtaining basic data and information that could support the adoption of conservation strategies for the rational use of these ecosystems. Seasonal sampling of water from these ponds was conducted during the months of August, September and November 2008 and 2009 (dry period) and February, May, July 2009 and 2010 (rainy period), for the purpose of obtaining data on temperature, pH, electrical conductivity and dissolved oxygen, ammonium (NH₄), nitrite (NO₂), nitrate (NO₃) and phosphate ion (PO₄) concentrations in the pond water. Sediment sampling also was carried out to determine particle size, carbon, organic matter and phosphorus content. A large variation in most variables, especially the ammonia (NH₄), nitrate (NO₃) and phosphate (PO₄) concentrations, was observed during the study period. The pH values indicated the water in the ponds was mostly alkaline. Based on the average nitrate concentrations (137 μg L^?1 during the dry period; 123 μg L^?1 during the rainy period), the ponds exhibited primarily eutrophic conditions. The sediment samples exhibited a predominance of fine sand with low carbon and organic matter content, able to be classified by their mineral nature. Due to the fragile nature of the studied ecosystems, disciplinary control of grazing activities and tourism in the area is highly recommended, along with adoption of a basic sanitation infrastructure in the community for the purpose of rational and sustainable use of this ecosystem.     

Suitability of Water Quality Indices for Application in Lakes in the Mediterranean

Water quality indices (WQIs) are efficient and powerful tools for evaluating, organising and communicating information on the overall quality of surface water bodies. The use of these indices may be very helpful in evaluating the water quality of aquatic systems in relation to the EU Water Framework Directive (WFD). In this study, two well-known water quality indices have been selected for evaluation: the CCME (Canadian Council of Ministers of the Environment) and NSF (National Sanitation Foundation). These WQIs were applied in the Polyphytos reservoir-Aliakmon river in Greece where monthly water quality data were available for the period June 2004 to May 2005. The available dataset included values of the following parameters: water depth, water temperature, dissolved oxygen, electrical conductivity, pH, transparency (Secchi disk depth), BOD₅, COD, total phosphorus (TP), chlorophyll-a (Chl-a), ammonium (NH₄ ⁺), nitrite (NO₂ ^?) and nitrate (NO₃ ^?), and total Κjeldahl nitrogen (TKN). The application of the two WQIs was made using specialised, freely available software-tools. A comparison of their performance and a qualitative judgement on their suitability on expressing the quality of a surface water body is presented. The classification results were compared with those obtained by the WFD-ECOFRAME approach of the EU. Based on the applicability and drawbacks of the examined indices, useful conclusions were derived and discussed. Among others, it is concluded that the NSF-WQI is a more robust index and produces a classification nearer that of the WFD-ECOFRAME approach when compared to the CCME-WQI.     

Assessment of River Water Quality in Northwestern Greece

The effect of land use patterns on river water quality was studied in three different river basins located in Epirus, Northwestern Greece. Studies were conducted from October 2000 to {September} 2001. During this period, the parameters chemical oxygen demand (COD), biological oxygen demand (BOD), NO_2–, NO_3–, NH₄₊ and PO_43– were measured, employing standard methods of analysis. The results were subjected to principal component analysis (PCA) for the estimation of the underlying variable correlations and were further explored by means of cluster analysis. The values of the above parameters were also compared with those awkward in the Fresh Water Fisheries Directive (78/659/EEC). It was found that the phosphate content was much higher than the upper limiting criteria for eutrophication for salmonid waters, whereas nitrate levels were lower than the permissible criteria according to the Nitrates Directive 91/676/EEC for drinking water. The inorganic nutrient load was mostly attributed to sites that drain agricultural areas, especially during winter and spring. The organic matter was due to urban activities during autumn.     

The Influence of Green Roofs on Runoff Water Quality: A Case Study from Estonia

This paper describes the runoff water quality of Light Weight Aggregates (LWA)-based extensive green roofs and sod roofs in Estonia. Samples were taken from August 2004 to April 2009 from 10 different green roofs to determine what level of water quality may be found. The results presented here show that green roofs influenced water quality to a considerable degree. The runoff water of LWA-based green roofs generally had higher values of pH, BOD₇, TP and PO₄-P than that from sod roofs. However, COD, TN, SO₄ and Ca-Mg salt were higher in the sod roofs than in the green roofs. The results for NH₄-N and NO₃-N were similar for both roof types. According to the results, the character of the runoff and the contents in the substrate layer at the moment the samples were taken affected runoff quality more than the age and location of the green roof. The use of NPK-nutrients in the substrate or in the soil caused much higher values of COD and concentrations of TP, PO₄-P, TN, NH₄-N and NO₃-N in runoff water than on non-fertilized green roofs. The results of samples taken from the Tartu LWA-based green roof each spring in the period 2005–2009, at a time when the snow had almost melted, showed that concentrations of compounds in runoff water generally decreased gradually. The pH value and Ca-Mg salt concentration were, however, stable, and this was caused by the LWA material.     

Evaluation of alum-based water treatment residuals used to adsorb reactive phosphorus

Excess reactive phosphorus (PO₄) in waterways can lead to eutrophication. A low-cost approach to reducing PO₄ levels in surface water was evaluated using the alum-based water treatment residual (Al-WTR) or Al-WTR augmented with powdered activated carbon (PAC-WTR). Batch adsorption-desorption and continuous flow column experiments were performed to assess the specific adsorption capacities under various concentration and flow conditions. Both Al-WTR and PAC-WTR exhibited the ability to adsorb PO₄. The overall, cumulative sorbed amount after a 28-d desorption step for Al-WTR was 33.93 mg/kg, significantly greater than the PAC-WTR value of 24.95 mg/kg (p < 0.05). The continuous flow column experiments showed a theoretical PO₄ uptake of 9.00 mg/g for Al-WTR and 7.14 mg/g for PAC-WTR over 720 h. When surface water was used, the Al-WTR and PAC-WTR columns removed 67.4% and 62.1% of the PO₄, respectively. These results indicated that Al-WTR was more effective for in-field evaluation.     

Water Quality Assessment of the Mudurnu River,Turkey, Using Biotic Indices

In this study, the effect of domestic and industrial pollutants on the water quality of Mudurnu River was searched. Water and benthic macroinvertebrate samples were taken from five stations selected on Mudurnu River during 12 months (2006–2007). COD (Chemical Oxygen Demand), BOD (Biochemical Oxygen Demand), TKN (Total Kjeldahl Nitrogen), NO₃^-{\rm{NO}}_{3}^{-}–N (Nitrate–Nitrogen), PO₄^-3{\rm{PO}}_{4}^{-3}–P (Phosphate–Phosphorous), NH₄⁺{\rm{NH}}_{4}^{+}–N (Ammonium–Nitrogen), Phenol data and scores of BMWP (Biological Monitoring Working Party) score system, ASPT (Average Score per Taxon), TBI (Trent Biotic Index), BBI (Belgian Biotic Index), Margalef’s index (R), Shannon–Wiener diversity index (H), Simpson’s diversity index (D) were determined. The relationship between data of chemical parameters and scores of biotic indices were investigated by using statistical methods. With decision tree technique, artificial neural network (ANN) and logistic regression model, chemical water quality was predicted from scores of biotic indices. A success at 67% was provided in the prediction of chemical water quality class of Mudurnu River.     

Assessing the Impacts of Four Land Use Types on the Water Quality of Wetlands in Japan

This study examined how changes in the composition of land use can affect wetland water quality. Twenty-four wetlands located in Hiroshima prefecture in the western part of Japan were selected for this purpose. The water quality parameters that were explored include: pH, electrical conductivity, turbidity, dissolved oxygen, total dissolved solid, temperature and different forms of nitrogen. These important indicators of the water quality in the study area were measured from December 2005 to December 2006. The composition of land uses was determined for the catchments of the wetlands. They were then categorized into three classes, including non-disturbed, moderately-disturbed and highly-disturbed wetlands, based on the extent of urban area (as the most disruptive land use type within the catchment of the wetlands). The relationship between land use types and water quality parameters for the wetlands was statistically examined. The findings indicated that there were significant positive relationships between the proportion (%) of urban areas within catchments of the wetlands and EC (r?=?0.67, p?<?0.01), TDS (r?=?0.69, p?<?0.01), TN (r?=?0.92, p?<?0.01), DON (r?=?0.6, p?<?0.01), NH₄ ⁺(r?=?0.47, p?<?0.05), NO₂ ^? (r?=?0.50, p?<?0.05), while negative relationships were observed between the proportion (%) of forest area in these wetlands and EC (r?=??0.62, p?<?0.01), TDS (r?=??0.68, p?<?0.01), TN (r?=??0.68, p?<?0.01), DON (r?=?-0.43, p?<?0.05), and NH₄ ⁺ (r?=??0.55, p?<?0.01). Analysis of the variance also revealed significant differences within the wetland groups in terms of the annual mean of electrical conductivity, total dissolved solids, total nitrogen, nitrite, dissolved inorganic nitrogen and dissolved organic nitrogen in the study area. Moreover, the study also indicated that the forest area plays a significant role in withholding nutrient loads from the wetlands, and hence, it can act as a sink for surface/subsurface nutrient inputs flowing into such water bodies from the watersheds.     

Temperature,redox, and amendments alter wetland soil inorganic phosphorus retention dynamics in a Laurentian Great Lakes priority watershed

Surface water phosphorus loading must be reduced to improve water quality and decrease harmful algal blooms. Many wetlands have a natural capacity to retain inorganic reactive PO₄^3? via soil sorption. However, soil PO₄^3? retention capacity is finite and may be limited by soil legacy phosphorus effects in agricultural and urban areas. This study evaluated soil PO₄^3? retention in soils from a wetland constructed on former agricultural land in the Lake Erie, Maumee River watershed targeted for nutrient load reduction. Soil PO₄^3? sorption isotherms were evaluated under cool (10 °C), warm (22°), aerobic, and anaerobic treatments to determine changes in PO₄^3? retention due to environmental conditions and estimate seasonal changes in PO₄^3? sorption. The soils displayed a strong capacity for PO₄^3? retention by sorption. However, results indicate that cooler temperatures and anaerobic conditions decreased PO₄^3? sorption and lowered retention rates at PO₄^3? concentrations observed in the region. Soil amendment experiments investigated opportunities to increase PO₄^3? retention because many soils display elevated phosphorus concentrations due to historic land use, limiting their ability to adsorb additional PO₄^3?. Amendments increased PO₄^3? retention capacity compared to unamended soils in the presence of high PO₄^3? concentrations, suggesting soil PO₄^3? retention can be improved in areas where natural storage capacity has been exhausted. Results from this study can inform natural resources managers in the Laurentian Great Lakes and elsewhere when identifying potential nutrient reduction wetland locations and assist with developing operational guidelines to optimize PO₄^3? retention and water quality improvements using wetlands.