Water2015, 7(4), 1687-1711; doi:10.3390/w7041687 (registering DOI) - published 20 April 2015 Show/Hide Abstract
Abstract: Surface water quality has been identified as potentially vulnerable to climate change. This study assesses the impacts of climate change on the water quality of Hsinshan Reservoir, Taiwan, through CE-QUAL-W2 simulations. The model parameters were calibrated by field data collected during 2004–2008, and verified against observations made during 2009–2012. The projected temperature and precipitation data for the near- and long-term future were downscaled to regional and daily scales, and used to simulate the projected changes in water quality through the validated model. The simulation results were reported as probability-based cumulative distribution functions to access the impacts of climate change on water quality. The results indicated that the intensified thermal stratification caused by the rising temperature is the primary driver of water quality decline, which increases the probability of deep-layer oxygen depletion and the flux of limiting nutrients for algae growth, resulting in a higher risk of algal blooms and eutrophication. The adaptation strategies of multilevel-intake operations and increasing bottom-layer dissolved oxygen without destratification are recommended.
Water2015, 7(4), 1670-1686; doi:10.3390/w7041670 - published 17 April 2015 Show/Hide Abstract
Abstract: Multifractal detrended fluctuation analysis (MFDFA) can provide information about inner regularity, randomness and long-range correlation of time series, promoting the knowledge of their evolution regularity. The MFDFA are applied to detect long-range correlations and multifractal behavior of streamflow series at four hydrological stations (Toudaoguai, Longmen, Huangfu and Ganguyi) in the main channel and tributaries of the Yellow River. The results showed that there was one crossover point in the log−log curve of the fluctuation function Fq(s) versuss. The location for the crossover point is approximately one year, implying an unchanged annual periodicity within the streamflow variations. The annual periodical feature of streamflow was removed by using seasonal trend decomposition based on locally weighted regression (STL). All the decomposed streamflow series were characterized by long-term persistence in the study areas. Strong dependence of the generalized Hurst exponent h(q) on q exhibited multifractal behavior in streamflow time series at four stations in the Yellow River basin. The reduction of dependence of h(q) on q for shuffled time series showed that the multifractality of streamflow series was responsible for the correlation properties, as well as the probability density function of the streamflow series.
Water2015, 7(4), 1649-1669; doi:10.3390/w7041649 - published 17 April 2015 Show/Hide Abstract
Abstract: Choice experiments can be designed using information gathered in stakeholder consultation processes. Information from these two sources can be used to consider both consultation outcomes and population preferences in environmental decision making. This approach is demonstrated using a case study of New Zealand’s Hurunui River which has been hotly contested between those who seek to divert water and increase agricultural production and those who would like to see the river undeveloped and the natural resources in the river and catchment improved. Data from the choice experiment is used to describe and quantify the preferences of Canterbury Region residents for existing conditions (good quality in the main river and poor quality in the tributaries) and potential future land use scenarios for the catchment. Six scenarios ranging from forestry to intensive irrigation could result in deterioration or improvement. Quantitative information from the choice experiment was provided to policy makers as they considered the outcomes of the consultation process. Community stakeholders agreed on a development strategy for the Hurunui catchment that would improve water quality in the tributaries and maintain quality in the main river. Results from the choice experiment support this approach. Willingness to pay for improvements in the main river was limited but residents would require substantial compensation before they would accept a decline in water quality in the main river or in the tributaries.
Water2015, 7(4), 1628-1648; doi:10.3390/w7041628 - published 17 April 2015 Show/Hide Abstract
Abstract: The Puqu Fault is situated in Southern Tibet. It is influenced by the eastward extrusion of Northern Tibet and carries the clockwise rotation followed by the southward extrusion. Thus, the Puqu Fault is bounded by the principal dynamic zones and the tectonic evolution remains active alongside. This study intends to understand the tectonic activity in the Puqu Fault Region from the river profiles obtained from the remotely sensed satellite imagery. A medium resolution Digital Elevation Model (DEM, 20 m) was generated from an Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) stereo pair of images and the stream network in this region was extracted from this DEM. The indices of slope and drainage area were subsequently calculated from this ASTER DEM. Based on the stream power law, the area-slope plots of the streams were delineated to derive the indices of channel concavity and steepness, which are closely related to tectonic activity. The results show the active tectonics varying significantly along the Puqu Fault, although the potential influence of glaciations may exist. These results are expected to be useful for a better understanding of tectonic evolution in Southeastern Tibet.
Water2015, 7(4), 1610-1627; doi:10.3390/w7041610 - published 16 April 2015 Show/Hide Abstract
Abstract: With decreasing water availability as a result of climate change and human activities, analysis of the influential factors and variation trends of chlorophyll a has become important to prevent reservoir eutrophication and ensure water supply safety. In this paper, a structurally simplified hybrid model of the genetic algorithm (GA) and the support vector machine (SVM) was developed for the prediction of monthly concentration of chlorophyll ain the Miyun Reservoir of northern China over the period from 2000 to 2010. Based on the influence factor analysis, the four most relevant influence factors of chlorophyll a (i.e., total phosphorus, total nitrogen, permanganate index, and reservoir storage) were extracted using the method of feature selection with the GA, which simplified the model structure, making it more practical and efficient for environmental management. The results showed that the developed simplified GA-SVM model could solve nonlinear problems of complex system, and was suitable for the simulation and prediction of chlorophyll a with better performance in accuracy and efficiency in the Miyun Reservoir.
Water2015, 7(4), 1595-1609; doi:10.3390/w7041595 - published 15 April 2015 Show/Hide Abstract
Abstract: Applications of geotextiles within tertiary stormwater treatment systems and for stormwater infiltration can provide a substrate for biofilm formation, enabling biological treatment of contaminants. Geotextiles can serve as an efficient part of stormwater filtration within the urban water environment. The project assessed the applications of three experimental granular filters as a sustainable urban drainage system (SUDS) for the decomposition of organic pollutant loading present in stormwater. The three filter rigs were packed with alternating layers of filter media consisting of gravel, pea gravel, sand and either a single, double or no layer of geotextile membrane. A nonwoven geotextile was layered within the filter media. The hydraulic loading capacity for the three filters matched that commonly used with conventional sand filters systems. Water quality parameters were quantified by measuring suspended solids, chemical oxygen demand, dissolved oxygen, pH, nitrate-nitrogen, and phosphate concentrations. It was found that Filter Rig No. 3 (upper and lower geotextile membrane) and Filter Rig No. 2 (single geotextile membrane) had a significant statistical difference in treatment performance from Filter Rig No. 1 (no geotextile membrane).