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The scouring of cohesive and non-cohesive materials downstream of sluice gates is primarily based on high-velocity flow. The present study considered an experimental hydraulic model of submerged water flow issuing from a sluice gate installed on an apron that leads to the scour hole and dune in a downstream mixture of sand and clay bed. The purpose was to achieve a suitable efficiency of the weight ratio of clay in the sand–clay mixture (c) for the sediment bed. Scour parameters, including maximum scour depth (dse) and its longitudinal location (xse), and maximum dune height (hd) and its location (xd), were measured and compared for three variations, c = 0.1, 0.2, and 0.3, under five hydraulic conditions. Results revealed that all scour parameters were reduced by adding clay to the sand soil, and the maximum reduction was for dse with the maximum value of 27.66%. The observed data were analyzed by multiple nonlinear regression analyses for each scour parameter to present new prediction equations for practical uses. The computed statistical parameters of correlation coefficient (R2), root mean square error (RMSE), mean absolute percentage error (MAPE), Nash–Sutcliffe efficiency (NSE), and scatter index (SI) present good accuracy for the predicted equations in the ranges of experimental data.

Investigating aerosol composition and particle dynamics in densely populated and polluted urban centers is crucial for understanding and managing urban air quality. Ahvaz, in southwestern Iran, consistently ranks among the most polluted cities globally, primarily due to high PM 10 concentrations. This study analyzes trends in suspended particle concentrations in Ahvaz over a 12-year period (2008–2019) to identify the contributions of natural and anthropogenic sources to air pollution. Diurnal, monthly, and annual variations in PM 10 and PM 2.5 levels were examined, revealing key insights into the city’s pollution dynamics. Diurnal PM 10 peaks around noon (232 µg/m 3 ), mainly driven by natural dust sources, with minimal anthropogenic impact indicated by similar weekend and weekday concentrations (only 1.5% difference). Monthly analysis reveals significant dust activity in June and July (maximum PM 10 concentration of 388.18 µg/m 3 ), while higher PM 2.5 levels in winter (average 54.8 µg/m 3 ) are attributed to fossil fuel combustion. The PM 2.5 /PM 10 ratio (mean = 0.24) highlights the dominance of coarse particles from dust events, especially in summer. The Hoffmann classification identifies 3425 dusty days in the study period, with PM 10 levels notably higher due to dust sources in southern Iraq and southwestern Iran. Seasonal wind patterns, particularly Shamal winds, facilitate dust transport, corroborated by Windrose and PM 10 rose data. The study underscores the need for regional dust suppression strategies in southern Iraq and southwestern Iran to mitigate air pollution in Ahvaz, highlighting the importance of regional cooperation.

The role of weirs in flow regulation in water resources infrastructure and flood control is well known. In the meantime, the study of full-width plate weirs (FWPW), due to their wide application and lacking findings, is of great importance. In this study, experimental models were conducted at Babol Noshirvani University of Technology to investigate flow passing through FWPWs with five different heights (p = 0.07, 0.09, 0.11, and 0.15 m) under eight discharge conditions (Q = 1.4 to 6.3 L/s). The experiments were carried out in a flume measuring 4 m in length, 0.6 m in width, and 0.2 m in height. The discharges were measured with a calibrated flowmeter, and the water depths upstream of the weir (h) and the tailwater depths (h1) were measured with a point gauge with an accuracy of 0.1 mm. For each test, the discharge coefficient (Cd), relative residual energy (E1/E0), and relative energy dissipation ((E0 − E1)/E0) were computed. The proposed equation for calculating discharge achieved good accuracy with RMSE = 0.0002, MAE=0.0002, and R2 = 0.997. Results show a reducing trend of Cd by increasing h/P, which is compatible with previous results. It was observed that at a constant discharge, relative residual energy reduces by an average of 47% by increasing weir height, and at a constant P, increasing flow discharge increases it a little. A novel accurate equation for relative energy dissipation in FWPW was proposed based on h/P that provided specific constant coefficients for each p value.

This study presents an elastic one-dimensional numerical model to simulate the filling process of a large-scale, partially drained pipeline with an undulating profile, incorporating bypass systems. The model uses the Method of Characteristics to solve water hammer equations and integrates the Discrete Gas Cavity Model to capture column separation effects. Validation is performed using two experimental test rigs and comparisons with existing numerical models, showing RMSE values between 1.06 and 7.95. The results highlight three key findings: (1) oversized bypasses generate severe transient pressures; (2) effective air management enables higher filling flow rates, significantly reducing filling time; and (3) bypass lines help dampen pressure fluctuations, with a notable drop in ∆H from 528 m to 6.8 m occurring in stage b, following the release of trapped air. Additionally, this study challenges the practicality of the AWWA’s recommended pipeline filling velocity limit of 0.3 m/s, showing that strict adherence to this guideline is often unrealistic for large-scale systems. Overall, the findings emphasize the need for a balanced design approach that reduces transient risks while maintaining operational efficiency in large-scale pipelines.

Studying the influences of the debris settled by the flood upstream of the bridge pier on the scour is important. In the present study, experimental tests were performed as four models including the bridge pier, the bridge pier with buried debris, the bridge pier with the free debris, and the bridge pier with free debris and the bed sill with the downstream gap equal to 0, 1, 2, 3, and 4 times of pier diameter. The results showed that buried debris increased the maximum length of the scour hole (ls), and the maximum width of the scour hole (ws) by about 50, and 180% respectively in comparison with the alone pier. It resulted that buried debris has a more increased effect than free debris. Free debris at low submergence ratios reduces ls by up to 27%, and in high submergence ratios increases it by up to 37%. Also, free debris increases ws in all submergence ratios, which is by up to 127% for the critical case compared to the case without debris. At all distances, the bed sill reduces ls and ws, and the best performance for reducing ls and ws is when it is attached to the bridge pier.

Sharp-crested weirs are commonly used in hydraulic engineering for flow measurement and control. Despite extensive research on sharp-crested weirs, particularly regarding their discharge coefficients, more information is needed via research on their energy dissipation downstream. This study conducted experimental tests to assess the influence of contraction ratio (b/B) of rectangular sharp-crested weirs (RSCWs) on energy dissipation downstream under free flow conditions. Five RSCWs with different b/B equals 6/24, 7/24, 8/24, 9/24, and 10/24 were used. The results showed a consistent decrease in relative energy dissipation (ΔEr) with an increase in the head over the weir. Furthermore, as the discharge per unit width (q) increased, the relative energy dissipation (ΔEr) decreased, indicating more efficient discharge over the weir. A higher b/B further reduces ΔEr, suggesting that wider weirs are more effective in minimizing energy losses. The maximum relative residual energy (E1/E0) and relative energy dissipation (ΔEr) occurred at b/B = 10/24 and 6/24, with values of 0.825 and 0.613, respectively. Additionally, the maximum discharge coefficient (Cd) of RSCWs is found at b/B = 6/24, with an average value of 0.623. The results support the accuracy of the proposed equation with R2 = 0.988, RMSE = 0.0083, and MAPE = 1.43%.

Nonfundamentalness arises when current and past values of the observables do not contain enough information to recover structural vector autoregressive (SVAR) disturbances. Using Granger causality tests, the literature suggested that several small-scale SVAR models are nonfundamental and thus not necessarily useful for business cycle analysis. We show that causality tests are problematic when SVAR variables cross-sectionally aggregate the variables of the underlying economy or proxy for nonobservables. We provide an alternative testing procedure, illustrate its properties with Monte Carlo simulations, and re-examine a prototypical small-scale SVAR model.

Climate change has made flash floods increasingly common. It's crucial to have confidence in the structural integrity of dams during a flash flood. According to the International Commission on Large Dams (ICOLD), approximately one-third of dam failures are attributed to inadequate spillway capacity. The current study aims to compare the discharge of slit weirs with that of ogee spillways and sharp-crested weirs. Various experiments were conducted using rectangular slit weirs with different opening ratios ( b/B = 2/24, 3/24, 4/24, 5/24, 6/24, 7/24, 8/24, and 10/24). The results indicate that ogee spillways have an average discharge capacity of 13–68 times greater than that of the slit weirs, while sharp-crested weirs have a discharge capacity of 1.39–7.3 times that of the slit weirs. The ratio of ogee spillway discharge to the slit weir ( r ) and sharp-crested weir discharge to the slit weir ( r' ) increases with the rise of h/P . Moreover, the highest average values of r and r' are observed at b/B = 2/24, measuring 65.46 and 7.3, respectively. Conversely, the lowest values, 11.53 and 1.22, are associated with b/B = 10/24. Notably, the maximum values of r and r' , 71.2 and 7.61, respectively, also occur at b/B = 2/24.

An unusual dust event over the Atacama Desert occurred in July 2016. Here, a synoptic study of the event is carried out using the NCEP FNL analysis data and WRF‐chem simulations. The “zonalization” of a mid‐tropospheric trough leads to the formation of a horizontal convergence band over the Northern Atacama and thus downward wind below it. As the descending air masses warm adiabatically, strong temperature contrasts to the colder air over the western Andes occur and intensify the down‐valley winds, thus leading to extraordinary strong easterly winds in the Atacama. Simulations with WRF‐chem indicate that these surface winds are sufficient for large‐scale dust emission, and simulated dust plumes traveling far over the eastern South Pacific agree well with the observations. As the integrated dust load is comparable with the load observed in major dust sources of the world, our findings highlight the importance of such unusual events. (a) MODIS true‐color image of the dust plume over the coast of northern Chile on July 8, 2016 (source: https://www.earthobservatory.nasa.gov) (b) model domain and topographic height in m of the WRF simulation. The brownish contours show isolines of the erodability of 0.2, the red dot the location of station CAMA, and the stippled black lines the position of the cross sections represented in the synoptic analysis. (c) Mean observed day course for winter (June–August; black line) and observed time series for July 8, 2016 (gray stippled line) of 10‐min averaged 5 m wind speed in ms−1 at station CAMA, and WRF simulated time series of 10 m wind speed at the grid point nearest to location of CAMA (red line)

Groundwater resources play a crucial role in supplying water for domestic, industrial, and agricultural use. In this study ACCESS-CM2, HadGEM3-GC31-LL, and NESM3 were selected for validation from Coupled Model Intercomparison Project Phase 6 (CMIP6). In the following, the feedforward neural network was employed to predict monthly groundwater level (GWL) based on the emission scenarios of the sixth IPCC report (SSP2-4.5 and SSp5-8.5) for the next two decades (2021–2040) in the Sari-Neka coastal aquifer near the Caspian Sea, Iran. In this regard, the monthly maximum and minimum temperature, precipitation, and water table of previous month from four piezometers from 2000 to 2019 were used as input variables to forecast GWL. The evaluation of the three GCM models demonstrated that the ACCESS-CM2 provided the best values of the R2 and RMSE with observation parameters. The results of r, R2, RMSE, and MAE were evaluated for the model and indicated good performance of the model. The results also illustrated that under such mentioned scenarios, the mean monthly temperature would rise approximately from 0.1–1.2 °C. In addition, the mean monthly precipitation is likely to witness changes from -10% to 78% in the next two decades. As a result, this seems to lead to improvement and recharge of groundwater level for the near future. The results can help managers and policymakers to identify adaptation strategies more precisely for basins with similar climates.