Journal of Hydro-environment Research最新文献

Experimental data and numerical predictions of steady and unsteady flow in a 4 m high, 86 mm internal diameter tube fishway were compared quantitatively, and reflected expected uncertainties characteristic of the experiments and flow hydraulics. We then measured the response of a neutrally-buoyant fluid sensor and the behaviour of live fish transported vertically within the tube fishway. Ten repeat tests using the sensor and tests with seventy individual live fish demonstrated transport with 100% reliability. No ill effects were observed over a post-test monitoring period for two species of Australian native fish (Australian bass (Percalates novemaculeata) and Silver perch (Bidyanus bidyanus)) or as a function of size of the Silver perch that can be related to their passage through the fishway. There may have been temporary bruising of a few of the largest Silver perch tested. The largest Silver perch averaged 137 mm in length. The spatial distributions of the inert sensor and fish relative to the moving front during the transport process were quantified. Consequently, the volumes of water required during each operational cycle to ensure reliable delivery of fish over vertical distances less than 4 m were determined. The sensor measurements indicated negligible interactions with straight pipe walls but exposure to significant accelerations at sharp bends. Further experiments with live fish are required to quantify the possible adverse effects of alternative pipe transition designs on animals transported through them. Safe transport of fish up to a fish length/tube fishway delivery diameter ratio of 1.6 is demonstrated.

The key features of the equilibrium scour depth $d_{\mathrm{se}}$, width $W_{\mathrm{se}}$, length $L_{\mathrm{se}}$ and the volume $V_{\mathrm{se}}$ with large abutment aspect ratios (i.e., abutment width $L_c$ divided by its length $L$) in floodplain are different compared to narrow abutments. Seven models with $L_c/L$ ranging from 0.125 (narrow abutment) to 4 (very wide abutment) were tested. The results show that the combined effect in terms of the abutment aspect ratio $L_c/L$ is a key parameter with wide abutments. Furthermore, the average equilibrium scour width observed was much larger than previous studies and extends up to 3.5 times the floodplain water depth. This implies the current guideline by FHWA (Federal Highway Administration), (2009) to provide a riprap countermeasure apron width for 2 times the floodplain water depth may be insufficient. The much wider scour formation is caused by the migration of the maximum scour location around wide abutments. The results show generally the scour hole dimensions for setback abutments in compound channel are less than that abutments in rectangular channel under the same flow conditions. To this end, empirical equations, which agree well with the data from the present and previous studies are proposed to predict these characteristics at the equilibrium state.

Shallow flows are common in natural and human-made environments. Even for simple rectangular shallow reservoirs, recent laboratory experiments show that the developing flow fields are particularly complex, involving large-scale turbulent structures. For specific combinations of reservoir size and hydraulic conditions, a meandering jet can be observed. While some aspects of this pseudo-2D flow pattern can be reproduced using a 2D numerical model, new 3D simulations, based on the unsteady Reynolds-Averaged Navier-Stokes equations, show consistent advantages as presented herein. A Proper Orthogonal Decomposition was used to characterize the four most energetic modes of the meandering jet at the free surface level, allowing comparison against experimental data and 2D (depth-averaged) numerical results. Three different isotropic eddy viscosity models (RNG k-ε, k-ε, k-ω) were tested. The 3D models accurately predicted the frequency of the modes, whereas the amplitudes of the modes and associated energy were damped for the friction-dominant cases and augmented for non-frictional ones. The performance of the three turbulence models remained essentially similar, with slightly better predictions by RNG k-ε model in the case with the highest Reynolds number. Finally, the Q-criterion was used to identify vortices and study their dynamics, assisting on the identification of the differences between: i) the three-dimensional phenomenon (here reproduced), ii) its two-dimensional footprint in the free surface (experimental observations) and iii) the depth-averaged case (represented by 2D models).

Due to the simultaneous impacts of economic development and climate change, the Lijiang River Basin in China—the largest karst tourist attraction in the world—has experienced dramatic water shortages during the dry season. As actual evapotranspiration (${\mathrm{ET}}_a$) plays a critical role in the water cycle, accurate estimation of ${\mathrm{ET}}_a$ and water stress are important for sustainable water resources management. In this paper, we mapped the distribution of daily ${\mathrm{ET}}_a$ using a modified Operational Simplified Surface Energy Balance (SSEBop) model in combination with Landsat 8 images and assessed water stress using the Crop Water Stress Index (CWSI) during the dry season in the Lijiang River Basin. In general, the daily ${\mathrm{ET}}_a$ simulated by the SSEBop model with aerodynamic resistance value of 110 s m⁻¹ was higher than that of satellite-based actual evapotranspiration products (i.e., MOD16A2 and Penman-Monteith-Leuning (PML)_V2 actual evapotranspiration products in this study). Aerodynamic resistance plays a critical role in the estimation of energy fluxes in the SSEBop model and should be readjusted and calibrated with available datasets to improve the model’s performance in estimating actual evapotranspiration for particular regions. Readjusted values between 20 and 35 s m⁻¹ of aerodynamic resistance produced reasonable agreement with satellite-based actual evapotranspiration products in the Lijiang River Basin. In addition, insufficient ground-level measurements of actual evapotranspiration might have increased the uncertainty of the SSEBop model’s performance. The achievement of higher accuracy in the estimation of actual evapotranspiration and water availability will require establishing local flux towers, particularly in forested areas, to collect evapotranspiration, temperature and other in situ data. For different land-cover classes, forest areas exhibited the highest actual evapotranspiration, whereas farmland and built-up areas had the lowest actual evapotranspiration values compared to the other land-cover classes. All land-cover classes, especially farmland areas, experienced severe water stress. Inadequate precipitation as a result of climate change, combined with high actual evapotranspiration will result in less water being available for the Lijiang River Basin. Additional water is required to compensate for evapotranspiration and support plant growth in the Lijiang River Basin during the growing season.

From 1950s to 1980s, various observational studies around the globe found a significant decrease in surface solar radiation (SSR), which reversed in late 1980s for most of the countries including India. SSR observations at 12 stations located across India revealed that a much stronger dimming has reappeared during the last decade (2006–2015) after a brightening during 1996–2005. In the present study, effects of renewed solar dimming on actual evapotranspiration and runoff were analyzed using a semi-distributed hydrological model, Soil and Water Assessment Tool (SWAT) in 24 river basins (ranging from 1260 to 40000 km²) located in peninsular India. For these river basins, calibration (2003–2009) and validation (2010–2014) were performed using the observed daily discharge data, obtained from water resources information system (WRIS) of India, with a 3 year warm up period (2000–2002). The sequential uncertainty domain parameter fitting algorithm (SUFI-2) of SWAT-CUP (calibration and uncertainty program) was used with modified Nash–Sutcliffe efficiency (MNS) as the objective function to calibrate 13 model parameters, which can potentially affect streamflow. In nearly all the river basins, the p- and r-factor of 95 percentage prediction uncertainty (PPU) were more than 0.7 and less than 1, respectively. At daily timescale, MNS values were more than 0.5 in most of the river basins, reaching up to 0.66 and 0.71 during calibration and validation periods, respectively. Calibrated model was used to analyze the water balance of these river basins and different sets of experiments (with observed SSR trends) were performed to find SSR impacts on it. The model was simulated with and without the observed declines in SSR trends. The average change in SSR (in terms of evaporation equivalent) was −267.93 ± 100.92 mm/day/year (−5.62 ± 2.12%) with maximum reaching up to −417.12 mm/day/year (−8.99%). Due to this SSR change, actual evaporation was reduced resulting in 18.97 ± 9.78 mm/day/year (4.13 ± 2.50%) change in percolation. The percolation changes were higher for river basins having areas covered by forests and cropland/woodland, and having loam and sandy-clay soils. The increase in runoff generated was 6.90 ± 3.42 mm/day/year (2.14 ± 1.58%) with a maximum of 15.25 mm/day/year (7.56%) whereas corresponding increase in streamflow was found to be 9.93 ± 5.27 mm/day/year(4.21 ± 2.38%) with a maximum of 26.71 mm/day/year (11.86 %). The study reveals that the recent observed SSR changes are significant enough to have resulted in increased streamflow in the monsoon dominated tropical river basins of India.

In the present study, scattering of surface gravity waves by multiple slotted vertical barriers arranged in a zig-zag manner is analyzed by employing Computational Fluid Dynamics (CFD) and validated with physical model tests. The porosity of the vertical slotted barrier is varied from 10% to 40%, and the number of slotted barriers varied from 1 to 6. The results from CFD correlate well with the laboratory measurements on the scattering coefficients for a wide range of input conditions giving a high level of confidence. For relatively short waves ($h/\lambda$ > 0.3, $h$- water depth and $\lambda$- wave length), slotted barriers up to 3 numbers and porosity from 20% to 30% are required to achieve wave transmission coefficient in the range of 0.2 to 0.3. For relatively long waves ($h/\lambda$ < 0.3), slotted barriers of 5 to 6 numbers and porosity in the range of 10% to 20% are needed to obtain wave transmission of 0.2 to 0.3. The results presented in this study can be used for a wide range of wave damping applications in the field of coastal engineering.

This study presents three different models, namely power-law rating curve, one-dimensional lateral distribution method (1D–LDM), and gated recurrent network (GRU) model that can be applied to evaluate water discharge from water surface elevation time-series in a river cross-section for a long time period. A river section at Vinh Tuy location on the Lo river basin (Vietnam) is used to demonstrate the models. Appropriate values of modelling parameters are carefully determined using (i) the daily observed discharge values collected in the period from 2012 to 2018 and (ii) five error estimates for quantitatively assessing the agreement between estimated and observed water discharges. The results showed that all three models reproduced very well the observed discharge values, with root mean square error and mean absolute error, as well as mean error of discharge, are only about 5.5% of the maximum value of discharge monitoring in the studied cross-section, while Nash–Sutcliffe efficiency and Pearson’s correlation coefficient are greater than 0.89. The models are then applied to evaluate discharge values in the studied cross-section for the period from 1972 to 2011, revealing that statistical indicators, i.e. mean value, standard derivation, and covariance of estimated water discharge, are consistent with those obtained from the observations. Among three investigated models, the GRU model was finally proved to be the best one, providing even better results than the 1D-LDM and power-law rating curve.

In this study, multi-tracker optimization algorithm (MTOA), particle swarm optimization (PSO), and differential evolution (DE) algorithms were integrated with support vector regression (SVR) to predict energy dissipation downstream of labyrinth weirs (ΔE). In order to evaluate the performance of these methods, the results are compared with corresponding outcome obtained by applying two other methods, namely, multilayer perceptron neural network (MLPNN) and multiple linear regressions methods (MLR). The input parameters comprise the discharge, the upstream flow depth, the crest length of a single cycle of the labyrinth weir, the width of a single cycle of the labyrinth weir, the apex width, the number of labyrinth weir cycles, the sidewall angle, and the height of weir. The results indicate that the meta-heuristic algorithms substantially improve the performance of SVR. The results show that the integrative methods, SVR-MTOA, SVR-PSO, and SVR-DE, are more accurate than the MLPNN and the MLR. In average, the integrative methods provide 39.63% more accurate results than the MLPNN and 79.34% more accurate results than the MLR. The average RMSE and R² for the integrative methods are 0.0054 m and 0.977, respectively. Among all integrative methods, the SVR-MTOA yields the best results, with RMSE = 0.0044 m and R² = 0.986.

Climate change, besides global warming, is expected to intensify the hydrological cycle, which can impact watershed nutrient yields and affect water quality in the receiving water bodies. The Mahabad Dam Reservoir in northwest Iran is a eutrophic reservoir due to excessive watershed nutrient input, which could be exacerbated due to climate change. In this regard, a holistic approach was employed by linking a climate model (CanESM2), watershed-scale model (SWAT), and reservoir water quality model (CE-QUAL-W2). The triple model investigates the cumulative climate change effects on hydrological parameters, watershed yields, and the reservoir’s water quality. The SDSM model downscaled the output of the climate model under moderate (RCP4.5) and extreme (RCP8.5) scenarios for the periods of 2021–2040 and 2041–2060. The impact of future climate conditions was investigated on the watershed runoff and total phosphorus (TP) load, and consequently, water quality status in the dam’s reservoir. The results of comparing future conditions (2021–2060) with observed present values under moderate to extreme climate scenarios showed a 4–7% temperature increase and a 6–11% precipitation decrease. Moreover, the SWAT model showed a 9–16% decline in streamflow and a 12–18% decline in the watershed TP load for the same comparative period. Finally, CE-QUAL-W2 model results showed a 3–8% increase in the reservoir water temperature and a 10–16% increase in TP concentration. It indicates that climate change would intensify the thermal stratification and eutrophication level in the reservoir, especially during the year’s warm months. This finding specifies an alarming condition that demands serious preventive and corrective measures.

Piano Key Weir (PKW) is a special type of overflow weir which provides an improved discharge capacity with its increased crest length. Increased discharge capacity makes this weir an attractive alternative in the rehabilitation of existing spillways. After the introduction of this new weir type, many experimental and numerical studies are conducted to understand the effect of the numerous geometrical parameters on the discharge capacity. However, empirical discharge formulas suggested by different researchers are not conforming to a unique expression mostly due to dependence on the experimental conditions from which they are derived. A numerical approach is used in the present study to investigate the dependence of discharge capacity of a PKW unit on several geometric parameters. Numerical models are developed and three-dimensional velocity fields are computed using FLOW-3D® software. Discharge efficiency of a PKW over an equivalent linear sharp-crested weir is evaluated within the practical range of parameters from 145 numerical solutions for 29 different PKW models. Numerically obtained data is used to form dimensionless expressions for the weir height and length as function of discharge efficiency which are proposed to facilitate an iterative numerical solution to meet the design requirements of a given project. This approach allows cost optimization while dimensioning the PKW for the required hydraulic capacity. The design procedure based on iterative numerical solutions is described and exemplified.