Modeliranje razdiobe napetosti smicanja u prirodnim malim vodotocima metodama mekog računanja

In this study, artificial neural networks (ANNs) and adaptive neuro-fuzzy inference system (ANFIS) were used to estimate shear stress distribution in streams. The methods were applied to the 145 field data gauged from four different sites on the Sarimsakli and Sosun streams in Turkey. The accuracy of the applied models was compared with the multiple-linear regression (MLR). The results showed that the ANNs and ANFIS models performed better than the MLR model in modeling shear stress distribution. The root mean square errors (RMSE) and mean absolute errors (MAE) of the MLR model were reduced by 47% and 50% using ANFIS model in estimating shear stress distribution in the test period, respectively. It is found that the best ANFIS model with RMSE of 3.85, MAE of 2.85 and determination coefficient (R2) of 0.921 in test period is superior to the MLR model with RMSE of 7.30, MAE of 5.75 and R2 of 0.794 in estimation of shear stress distribution, respectively.U ovoj studiji su za procjenu razdiobe napetosti smicanja u vodotocima korištene umjetne neuronske mreže (ANNs) i prilagodljivi neizraziti sustav zaključivanja (ANFIS). Metode su primijenjene na 145 nizova podataka prikupljenih na četiri različite postaje na vodotocima Sarimsakli i Sosun u Turskoj. Točnost primijenjenih modela uspoređena je s točnošću modela višestruke linearne regresije (MLR). Rezultati su pokazali da su oba modela (ANNs i ANFIS) bili bolji u modeliranju raspodjele napetosti smicanja od MLR modela. Pri korištenju ANFIS modela za procjenu raspodjele napetosti smicanja u testnom razdoblju srednje kvadratne pogreške (RMSE) i srednje apsolutne pogreške (MAE) su u odnosu na MLR model bile smanjene za 47%, odnosno 50%. Utvrđeno je da se za testno razdoblje najbolji ANFIS model, s RMSE = 3.85, MAE = 2.85 i koeficijentom određenosti R2 = 0.921, pokazao superiornim u procjeni napetosti smicanja u odnosu na MLR model, s RMSE = 7.30, MAE = 5.75 i R2 = 0.794

Implementation of the EU ecological flow policy in Italy with a focus on Sardinia

River ecosystems are characterised by a naturally high level of hydrodynamic perturbations which create aquatic-terrestrial habitats indispensable for many species, as well as for the human beings’ welfare. Environmental degradation and habitat loss caused by increasing anthropogenic pressures and global change affect freshwater aquatic ecosystems worldwide and have caused changes in water flow regimes and channels morphologies. These, in turn, decreased the natural flow capacity and reduced habitat availability, thus causing severe degradation of rivers’ ecological integrity. The ecological flow (e-flow) is commonly intended as the quantity, timing, duration, frequency and quality of water flows required to sustain freshwater, estuarine and near shore ecosystems and the human livelihoods and well being. Maintaining the e-flow represents a potential tool for restoring and managing river ecosystems, to preserve the autochthonous living communities, along with environmental services and cultural/societal values. In the last decade, methods for the determination of the e-flow in European rivers moved from a simply hydrological approach towards establishing a linkage between the hydrological regime and the good ecological status (GES) of the water bodies, as identified by the European Water Framework Directive (WFD; 2000/60/EC). Each Member State is required to implement and integrate into the River Basin Management Plans (RBMP) a methodology for the determination of the e-flow, ensuring that rivers can achieve and maintain the GES. The competent river basin authorities have thus to ascertain whether national methodologies can be applied to different river typologies and basin environment characteristics. In this context, we narratively review the e-flow assessments in the heterogeneous Italian territory, in particular on a water scant region such as Sardinia, by analysing laws, guidelines and focusing on study cases conducted with micro and meso-scale hydraulic-habitat approaches. In the sight of a more ecological-based application of national e-flow policy, we suggest that meso-habitat methods provide a valuable tool to overcome several limitations of current e-flow implementation in the Italian territory. However, to face future challenges, such as climate change adaptation, we stress the need for further experimental studies to update water management plans with greater attention for nature conservation

Multi-criteria decision analysis in Bayesian networks-Diagnosing ecosystem service trade-offs in a hydropower regulated river

The paper demonstrates the use of Bayesian networks in multicriteria decision analysis (MCDA) of environmental design alternatives for environmental flows (eflows) and physical habitat remediation measures in the Mandalselva River in Norway. We demonstrate how MCDA using multi-attribute value functions can be implemented in a Bayesian network with decision and utility nodes. An object-oriented Bayesian network is used to integrate impacts computed in quantitative sub-models of hydropower revenues and Atlantic salmon smolt production and qualitative judgement models of mesohabitat fishability and riverscape aesthetics. We show how conditional probability tables are useful for modelling uncertainty in value scaling functions, and variance in criteria weights due to different stakeholder preferences. While the paper demonstrates the technical feasibility of MCDA in a BN, we also discuss the challenge

Experimental and numerical analysis of river lake system and non-traditional water usage in a new Eco-City

In recent years, Eco-City, which is designed with consideration for environmental impact and is inhabited by people dedicated to minimisation of required inputs of energy, air pollution and water pollution, has emerged as a way to address sustainability issues by adapting it to their local needs and context. The sustainability of urban water resources, water recycling and more efficient use of water resources will be the key features of the Eco-City. The current study takes Sino-Singapore Tianjin Eco-City as an example to investigate the sustainable use of water resources which focus on non-traditional water usage and ecological water requirements assessment. Firstly, the potential non-traditional water supply was evaluated based on the data acquired from the gauging station and the Eco-City planning data. It was found that rainwater has a great potential for domestic use in the Eco-City from June to September. Differing from other water consumption, ecological demand of the river lake system in the Eco-City was analysed by minimum ecological water requirements determination. An improved wetted perimeter method was used in order to determine the minimum ecological water requirements in the river system. It was found that the current monthly flow rates, with the exception of January to March, are fairly satisfactory. Secondly, an idealised river-lake system was assessed by hydraulics laboratory experimentation and 2D numerical modelling. The experimental and numerical investigations described in this study were undertaken to improve understanding of the hydrdynamic and flushing process within such a river lake system. A water diversion scheme was implemented in order to study lake recharge by river water during dry periods and under augmented flows. Fluorescent tracer experiments and related computer simulations were conducted to assess the performance of different parts of the system before and after implementing the diversion scheme. The results showed that such measures improved flushing, as seen from the perspective of reducing the mean detention time. However, due to poor cross-sectional velocity distribution, recharge alone had little impact on the overall mixing level in the lake waters. The effect of inserting flow deflectors near the lake inlet combined with flow augmentation was then assessed and was found to positively affect the distribution of solutes, by mitigating the occurrence of dead zones. Finally, an eco-hydraulic model was used to determine the levels of fish habitat suitability in the fluvial and lacustrine regions of a new Eco-City. This model has been developed by combining a depth integrated hydrodynamic and water quality model with a Habitat Suitability Index model. Carps were selected as the target species as they represent the major fish population in the study area. Hydrologic data recorded during 2001-2010 were analysed to determine the base flow, average flow and high flow rates, which were used to represent the discharges in the river for the three stages of the carp life cycle: overwintering, spawning and growth, respectively. Numerical model simulations were undertaken to determine the levels of habitat suitability for carps to live at these three life stages. The model results indicated that under the current flow regime the habitat suitability level in the lacustrine region is too low for carps at the growth and overwintering stages. DO depletion, overriding the role of velocity and depth, was attributed to the poorly suited habitat conditions in the lacustrine region. To improve the suitability conditions in the lacustrine region, a DO enhancement scheme was used. Model results showed that the scheme has significantly enhanced the water quality in the lacustrine region. Due to the high flow requirement for carps to spawn in the fluvial region, further numerical model simulations were undertaken to investigate the effect of flow augmentation on the carp spawning habitat suitability

Optimal operation of dams/reservoirs emphasizing potential environmental and climate change impacts

Mahdi studied the potential ecological and climate change impacts on management of dams. He developed several new optimization frameworks in which benefits of dams are maximized, while above impacts are mitigated. Governments and consulting engineers can use the proposed frameworks for managing dams considering environmental challenges in river basins