Advances in Environmental Hydraulics, 2nd Edition

The purpose of this study is to enhance the performance of the mesohabitat model MesoHABSIM by lowering the necessary hydraulic modelling effort. This proof-of-concept study tests an application of the MesoHydraulics model to simulate the hydraulic characteristics of hydromorphological units (HMUs) occurring in a regulated river at different low discharges. In this quantitative approach, hydraulic patterns are transferred from a source site, where depth and velocity distributions were derived from field measurements and a 2D hydrodynamic model, to a target site, where only a single field hydrometric survey was conducted. Instead of modelling changes in individual hydraulic measurement values to estimate hydraulic responses to discharge, the model relies on statistical distributions of these values within HMUs. We were testing whether changes in the distribution of HMU’s and their hydraulics can be transferred between morphologically comparable river sections to serve as a sufficient hydraulic input for mesoscale habitat modelling. The hydrodynamic component of the River2D software (V.0.95a), routinely used in MesoHABSIM, served as a baseline for testing the MesoHydraulic model’s performance and for producing source data for deriving distribution functions. The test was conducted using data from two one-kilometre sites on the upper Oder River (Poland). The model transfers the HMU area distributions, along with corresponding depth and velocity frequency distributions, for a number of flows from one site (the source) to another (the target). The hydraulics at both sites were surveyed under single-discharge conditions. For the source site, the hydrodynamic model was applied to classify the HMU mosaic at three additional discharge stages. At the target reach, the HMU mapping was conducted based on survey data, and statistical frequency functions were used to model distributions of hydraulic patterns at discharges modelled for the source. The hydraulic model’s performance was evaluated at the target reach by comparing simulated hydraulics and HMU patterns with those modelled using River2D. Finally, both models were used to calculate habitat availability for the fish communities, and dissimilarities were observed. The resulting hydraulic distributions were similar, with an average affinity index of 90%. Higher affinity indices were reached at flows close to the measured value, with increasing model disagreement toward flow extremes, most notably for Run and Backwater units. Regardless, habitat models for the fish community were also highly correlated with R² = 0.98 for amounts of suitable habitat and almost identical habitat distribution among the species. Yet, the MesoHydraulics-based model slightly, but consistently, overestimated habitat availability. While the model was tested in a large and regulated river system, its accuracy may vary depending on the natural river morphology. Further research should evaluate modelling uncertainties and their applicability in less-modified water bodies. Full article

As the global environment continues to deteriorate, water blooms and red tides occur more frequently, making it increasingly important to control eutrophication in water bodies. This study focuses on optimizing an adjustable vortex well alga extractor for deep-well alga removal to reduce the risks associated with algal blooms and red tides. Numerical simulation was employed to model the working process of the vortex well alga extractor and to determine its most efficient structural parameters. The optimal dimensions of the adjustable vortex well alga collector optimized by the PSO-GP model are as follows: during the experiment, the water depth at the suction inlet is 200 mm, the diameter of the suction inlet is 480 mm, the distance of the fence is 2000 mm, and the average flow velocity of the water area is 0.12 m/s. Under these conditions, the working flow rate of the pressurizer can reach up to 18,400 cubic meters per hour at a maximum. Under these conditions, the collection efficiency for blue-green algae can reach 92%. The proposed optimization method can assist project managers in improving the design and operation of deep-well alga removal systems, achieving higher accuracy and efficiency, conserving energy, and enhancing overall alga removal performance. Full article