ISSN / EISSN : 1741-7589 / 1751-7729
Published by: Thomas Telford Ltd. (10.1680)
Total articles ≅ 342
Latest articles in this journal
Water Management, Volume 172, pp 218-228; https://doi.org/10.1680/jwama.15.00099
One of the challenges facing water managers is how to supply various downstream claims with conflicting priorities, especially during drought conditions. This study calculates the total volumes of water released from the Shahid reservoir in the Fars province, Iran, during a five-year drought period using a standard operation policy (SOP) and genetic programming (GP). The calculated releases with these two methods show the vulnerability index (VulMax) equals 87 and 82 %, the time-based reliability index is 45 and 42 %, and the resiliency index reaches 23 and 13 % for the SOP and GP, respectively, whereas the volumetric reliability index equals 55 % for both methods, demonstrating superior results for the GP method. The releases calculated with SOP and GP are allocated to meet downstream water demands according to their supply priorities. The proportional (Pro) method is used for this purpose considering the available reservoir water is less than the sum of demands. Compliance with the priority of supplying demands is approached with Nonlinear Programming (NLP) in the Pro method. The vulnerability index VulMax of allocated releases obtained with GP for urban, environmental, industrial, and agricultural demands equals 5, 50, 60, and 100 %, respectively. Our results show that using the Pro method under water-scarcity conditions with optimized release factors is effective in allocating water resources to meet downstream demands that have conflicting water-supply priorities.
Water Management, Volume 172, pp 257-269; https://doi.org/10.1680/jwama.18.00020
Water Management, Volume 172, pp 229-240; https://doi.org/10.1680/jwama.17.00079
In this paper, the influence of rigid vegetation on longitudinal dispersion coefficient in a compound open channel is examined using image processing technique. To simulate floodplain vegetation, cylinders 5 mm in diameter were attached to the flood plain surface. Potassium permanganate solution (KMnO4) was used as a conservative tracer. Instantaneous velocity components were measured using Particle Image Velocimetry (PIV). The results showed that flood plain vegetation decreases the depth-averaged longitudinal velocity and maximum tracer concentration up to 83% and 12.5%, respectively, compared to non-vegetated conditions. It was also found that the magnitude of the longitudinal dispersion coefficient, K, increases with relative flow depth, Dr, the ratio of the flood plain to main channel flow depth. Furthermore, the value of K increases by up to 39.3% for vegetated tests compared to non-vegetated tests. Moreover, the results were compared with several previous empirical equations and the most appropriate equation for prediction of the longitudinal dispersion coefficient in compound channels with partly vegetated flood plain was found to be that due to Fischer (1975).
Water Management, Volume 172, pp 195-206; https://doi.org/10.1680/jwama.16.00097
In the past, the islands of Carriacou and Petite Martinique in the Grenandines have depended on domestic rainwater harvesting for their water supply. Although the availability of water from this has increased over time, there is a growing gap between water demand and availability, driven mainly by growth in tourism. Closing this gap is essential, particularly in the context of adaptation to climate change. In this regard, solar-driven desalination plants have been installed in the islands to augment rainwater harvesting supplies, creating a hybrid system. Although, the desalinated water is highly subsidised, there is a general reluctance to embrace its availability and to pay for it. In Carriacou, the borehole supply that was used to augment rainwater in the urban area was replaced by desalinated water, resulting in an increased use of the public supply. The potential of augmenting rainwater with desalinated water can be restricted by concerns about quality, a general unwillingness to pay for the water, the high preference of rainwater and the inability of the utility company to recover the cost. The initial lessons learnt from this hybrid system can be important for developing appropriate water policies for islands that have traditionally been dependent on rainwater harvesting.
Water Management, Volume 172, pp 180-194; https://doi.org/10.1680/jwama.17.00004
Flow characteristics downstream of free and submerged hydraulic jumps with and without blocks were experimentally studied for Froude numbers ranging from 3.48 to 6.85. The streamwise variation of the mean longitudinal velocity, turbulence intensity, and turbulent kinetic energy as well as bed shear stress and water surface fluctuations were studied and compared for different flow regimes. Empirical equations are presented for longitudinal variations of the bed shear stress and water surface fluctuation for free and submerged jumps with and without blocks. The length required for the bed shear stress and water surface fluctuation to attain asymptotic magnitudes was used to define new characteristic lengths for hydraulic jumps. The results of this study show the effects of blocks in determining the longitudinal extension of hydraulic jumps. It was found that the presence of the blocks damps the streamwise variation of the studied flow parameters in a significantly shorter distance. It was also found that the deflected surface jet regime that occurs in submerged jumps with blocks has streamwise characteristics similar to those of free jumps with blocks. The results of this study confirm that this flow regime of submerged jumps can effectively be used as an energy dissipator within a stilling basin with a length approximately equal to the one required for free jumps.
Water Management, Volume 172, pp 170-179; https://doi.org/10.1680/jwama.17.00076
Defluoridation of water through adsorption process using biosorbent is attracting greater significance in the current scenario. A thermo-chemically developed biosorbent derived from bark Ficus glomerata is utilized in the present study. The adsorption data is analyzed for Langmuir, Freundlich, Temkin, and Dubunin- Radushkevich isotherm models at varying initial adsorbate concentration (2-25mg/L). It is found that the adsorption of fluoride onto Ficus glomerata biosorbent follows Langmuir isotherm. Langmuir isotherm constant ‘a’ and 'b’ obtained are 2.27 mg/gm and 0.651 l/mg at an adsorbent dose of 5g/L and temperature 26±1°C. The mean free sorption energy, E obtained, is 8.770 KJ/mol indicating that the adsorption of fluoride onto Ficus glomerata bark adsorbent is by chemisorption mechanism. The kinetic study also supports chemisorption with adsorption data fitting well with Pseudo-second order kinetic model. The thermodynamic study indicated the spontaneous and endothermic nature(ΔH=15430.78 J/mol) of fluoride adsorption onto Ficus glomerata adsorbent. Field Scanning Electron Microscopy and Energy Dispersive Spectroscopy (FESEM-EDX), BET and FTIR methods were used to analyze the surface morphology of adsorbent before and after fluoride adsorption process. Practical application of Ficus glomerata Roxb. biosorbent to fluoride contaminated ground water sample showed encouraging results.
Water Management, Volume 172, pp 109-122; https://doi.org/10.1680/jwama.17.00048
The time of concentration (Tc) is one of the most contributing parameters for assessing the response of a catchment to rainfall events and estimating the peak flood in many hydrological models. The aim of this work was to evaluate 36 time of concentration equations based on Tc values obtained based on the salt dilution tracing approach. In addition, hierarchical cluster analysis (CA) was applied to identify the degree of similarity between all the Tc formulas and categorise them into several groups. The findings, based on seven sub-watersheds of the Meime river basin in Iran, demonstrate that the Picking, Pickering, DNOS, California and Kirpich-Ten equations provide reliable estimation of Tc; the average bias of these formulas was found to be in the range 2·6–15 min while, for all 36 equations, the bias was 2·6–132·8 min. Furthermore, based on CA, all Tc equations were categorised into four overall groups with the maximum similarity within the members of each group.
Water Management, Volume 172, pp 149-162; https://doi.org/10.1680/jwama.17.00063
Water Management, Volume 172, pp 86-101; https://doi.org/10.1680/jwama.17.00039
To better understand the influence of non-uniform flow in coarse-bed streams with submerged vegetation strip on flow characteristics, data have been collected from both experiments in a laboratory flume and field investigations in a cobble-bed river reach in central Iran. Results of experiments in laboratory and field observations in natural streams show that the velocity profiles for non-uniform flows in cobble-bed streams with vegetation strip can be divided into either two or three sub-zones. Velocity profiles for non-uniform flows in laboratory flume and cobble-bed streams deviates from the log-law in wake and mixing zones, but fits approximately in the log-layer zone. The distribution of Reynolds stress for non-uniform flows is influenced by vegetation strip, and showed a non-concave shape. Near channel bed, the sweep motion occurs more frequently than ejection process. Close to the top of vegetation strip, the correlation coefficient (ru'w’) is negative. This means the downward momentum transport due to sweep and ejection processes. However, this coefficient (ru'w’) is positive near water surface. This indicates an upward momentum by vegetation strip due to inward and outward interactions. The present study shows that the laboratory results cannot be easily applied to natural rivers without considerable assumptions.
Water Management, Volume 172, pp 68-85; https://doi.org/10.1680/jwama.16.00101
This paper introduces a ‘collocated discrete subdomain meshless method’ to solve shallow water equations for free-surface flows with conservation of sediment mass. The computational domain in the method is discretised by distributed nodal points. Shape functions are made using the moving least-squares method for efficiency and simplicity. A number of collocation points, independent of nodal points, are used to form the specified residual function. The sum of residuals at the collocation points for each subdomain is zero in the problem domain and boundaries. In addition, boundary conditions are readily enforced. The model was verified by comparing results of simulated and physically modelled dam-break flows. There was good agreement between the analytical solution and experimental measured data, and a high convergence rate and efficiency were achieved. The method appears to have significant potential for investigating a variety of problems concerning coupled flow with sediment transport.