Water2016, 8(8), 315; doi:10.3390/w8080315 - published 26 July 2016 Show/Hide Abstract
Abstract: This work develops a rule curve-based conjunctive use management model for optimizing the operating rules for a lake–groundwater system with off-stream storage lakes. The proposed procedure is a simulation-optimization approach that embeds an Artificial Neural Network (ANN) instead of a groundwater numerical model into a genetic algorithm (GA). The direct physical exchange between lake water with groundwater is simulated using the ANN model, which is a reduced version of a full numerical model, MODFLOW with an LAK3 module. By applying the ANN model, the proposed procedure can reduce the computational burden that is induced by the nonlinear exchange. An operating rule-based optimal conjunctive use management model for the Gaopin Artificial lakes system in Taiwan was thus developed using the proposed framework. A set of optimal solutions involves rule curves and a discount ratio. Simulation results demonstrate that the embedded ANN model can accurately simulate the nonlinear exchange of a lake with groundwater. The embedded ANN model is less computationally complex than the numerical model. This work demonstrates a methodology for reducing the computational burden of the optimal conjunctive use management model that is associated with an internal nonlinear system by using the ANN reduced model. Specifically, the concept of, and results obtained using the developed operating rule-based model incorporating five artificial lakes and considering the nonlinear exchange of those lakes with the groundwater system provides a valuable practical reference for solving related conjunctive use problems.
Water2016, 8(8), 316; doi:10.3390/w8080316 - published 26 July 2016 Show/Hide Abstract
Abstract: Small aquatic ecosystems of the boreal zone are known to be most sensitive indicators of on-going environmental change as well as local anthropogenic pressure, while being highly vulnerable to external impacts. Compared to rather detailed knowledge of the evolution of large and small lakes in Scandinavia and Canada, and large lakes in Eurasia, highly abundant small boreal lakes of northwest Russia have received very little attention, although they may become important centers of attraction of growing rural population in the near future. Here we present the results of a multidisciplinary, multi-annual study of a small boreal humic lake of NW Russia. A shallow (3 m) and a deep (16 m) site of this lake were regularly sampled for a range of chemical and biological parameters. Average multi-daily, summer-time values of the epilimnion (upper oxygenated) layer of the lake provided indications of possible trends in temperature, nutrients, and bacterio-plankton concentration that revealed the local pollution impact in the shallow zone and overall environmental trend in the deep sampling point of the lake. Organic phosphorus, nitrate, and lead were found to be most efficient tracers of local anthropogenic pollution, especially visible in the surface layer of the shallow site of the lake. Cycling of trace elements between the epilimnion and hypolimnion is tightly linked to dissolved organic matter speciation and size fractionation due to the dominance of organic and organo-ferric colloids. The capacity of lake self-purification depends on the ratio of primary productivity to mineralization of organic matter. This ratio remained >1 both during winter and summer periods, which suggests a high potential of lake recovery from the input of allochthonous dissolved organic matter and local anthropogenic pollution.
Water2016, 8(8), 317; doi:10.3390/w8080317 - published 26 July 2016 Show/Hide Abstract
Abstract: Sustainable water resource management requires dams operations that provide environmental flow to support the downstream riverine ecosystem. However, relatively little is known about the hydrologic impact of small and medium dams in the smaller basin in China. Flow duration curve, indicators of hydrologic alteration andrange of variability approach were coupled in this study to evaluate the pre- and post-impact hydrologic regimes associated with dam construction using 44 years (1967–2010) of hydrologic data in the Jiulong River Watershed (JRW), a medium-sized coastal watershed of Southeast China, which suffered from intensive cascade damming. Results showed that the daily streamflow decreased in higher flow while daily streamflow increased in lower flow in both two reaches of the JRW. The dams in the North River tended to store more water while the dams in the West River tended to release more water. The mean daily streamflow increased during July to January while decreased during February to May after dam construction in both two reaches of the JRW. After dam construction, the monthly streamflow changed more significantly and higher variability of monthly streamflow exhibited in the West River than in the North River. The homeogenizing variability of monthly streamflow was observed in both two reaches of the JRW. The earlier occurrence time of extreme low streamflow event and later occurrence time of extreme high streamflow event exhibited after dams construction. The extreme low and high streamfow both decreased in the North River while both increased in the West River of the JRW. All of the indicators especially for the low pulse count (101.8%) and the low pulse duration (−62.1%) changed significantly in the North River. The high pulse count decreased by 37.1% in the West River and the count of low pulse increased abnormally in the North River. The high pulse duration in the post-impact period increased in the two reaches of JRW. The rise rate decreased by 26.9% and 61.0%,and number of reversals increased by 40.7% and 46.4% in the North River and West River, respectively. Suitable ranges of streamflow regime in terms of magnitude, rate, and frequency were further identified for environmental flow management in the North River and West River. This research advances our understanding of hydrologic impact of small and medium dams in the medium-sized basin in China.
Water2016, 8(8), 313; doi:10.3390/w8080313 - published 25 July 2016 Show/Hide Abstract
Abstract: Regions of scarce fresh water resources, such as the Middle East and North Africa, are facing great challenges already today, and even more in the future, due to climatic and socioeconomic changes. The Middle Drâa valley in Morocco is one of many semi-arid to arid mountainous areas struggling with increasing water scarcity threatening self-sufficient husbandry. In order to maintain people’s livelihoods water management needs to be adapted. The Water Evaluation And Planning System (WEAP) software has been widely used to examine complex water systems in the water resource planning sector all around the world and proved to be a helpful asset to show the various interactions of water supply and demand. This paper presents the application of WEAP on the Middle Draâ valley’s water demand and supply, including several socioeconomic and land use scenarios under one basic climate change scenario. The climate scenario shows a significant decrease in available water resources up to 2029 while all socioeconomic scenarios show an increase in water demand. In years of droughts groundwater is used for irrigation, leading to increasingly depleted aquifers. The aquifers are recharged by percolation losses from irrigation and by river bed infiltration the latter of which is stronger in the northern oases than in the southern oases due to water withdrawal rules. A drastic reduction of irrigated agricultural area is the only solution to guarantee sustainable water use.
Water2016, 8(8), 314; doi:10.3390/w8080314 - published 25 July 2016 Show/Hide Abstract
Abstract: Understanding the changes in water consumption structure in order to take measures for demand control is very important for sustainable water resources management. In this study, using the Southern China area of Nanjing as an example, we employed the information entropy method to analyze the water consumption structure, as well as the grey incidence analysis to analyze synthetic incidence degree of the factors associated with agricultural, industrial, domestic, and ecological water consumption. The results show that the degree of balance among water consumption sectors has increased from 0.755 to 0.825 between 1993 and 2014. Gradual decrease of the relative proportion of a single water user structure in a water consumption system has made the utilization of water resources in Nanjing rational and diversified. The study identifies three stages of transformation of water structure in Nanjing, namely, a growth period from 1993 to 2002, an adjustment period from 2003 to 2010, and another growth period from 2011 to 2014. The synthetic incidence degree analysis indicates that adjustments of the agricultural and industrial water consumption as well as water saving measures are the main factors that affected water consumption structure in Nanjing. It is expected that the results obtained from this study will provide references to optimize the utilization of urban water resources.
Water2016, 8(8), 312; doi:10.3390/w8080312 - published 23 July 2016 Show/Hide Abstract
Abstract: Stormwater quality modeling has arisen as a promising tool to develop mitigation strategies. The aim of this paper is to assess the build-up and wash-off processes and investigate the capacity of several water quality models to accurately simulate and predict the temporal variability of suspended solids concentrations in runoff, based on a long-term data set. A Markov Chain Monte-Carlo (MCMC) technique is applied to calibrate the models and analyze the parameter’s uncertainty. The short-term predictive capacity of the models is assessed based on inter- and intra-event approaches. Results suggest that the performance of the wash-off model is related to the dynamic of pollutant transport where the best fit is recorded for first flush events. Assessment of SWMM (Storm Water Management Model) exponential build-up model reveals that better performance is obtained on short periods and that build-up models relying only on the antecedent dry weather period as an explanatory variable, cannot predict satisfactorily the accumulated mass on the surface. The predictive inter-event capacity of SWMM exponential model proves its inability to predict the pollutograph while the intra-event approach based on data assimilation proves its efficiency for first flush events only. This method is very interesting for management practices because of its simplicity and easy implementation.