فهرست مطالب محمد میرناصری

Ensuring the health and sustainability of the environment is one of the secondary goals of hydraulic structures. Water pollution and the reduction of its quality are serious threats to the health of the earth and will turn rivers into channels for polluted industrial wastewater. Increasing the residence time of flow in rivers by constructing hydraulic structures such as gabion spur dikes can increase the self-purification capacity. In this research, a laboratory investigation of pollution transport using NaCl tracer material in a laboratory channel with a sediment bed with a medium diameter (D50) of 11.85 mm, thickness of 12 cm, and length of 12 meters in a different number of fine-grained or coarse-grained gabion spur dikes from 1 to 4 were performed. Analytical solutions of Advection-Dispersion equation (ADE), OTIS model, and solution of Transient Storage Model (TSM) were used for numerical simulation. Laboratory results showed that gabion spur dikes with fine-grained materials reduce the peak concentration of pollution (Cmax) compared to coarse-grained materials. The results showed that the gabion spur dikes in the flow path increase the residence time of the pollutant by increasing hyporheic exchanges. The advection-dispersion equation (ADE) has low accuracy in the simulations due to the lack of attention to the role of the storage zone exchanges, with a determination coefficient (R2) of 0.71 to 0.83. On the other hand, the OTIS model, which is based on the transient storage model (TSM), considering the role of the porous zones of spur dikes in the transient storage of solute, has high accuracy with a determination coefficient (R2) of 0.91 to 0.98. The estimated coefficients of longitudinal dispersion (Dx) and storage zone exchange (α) by the temporal moment analysis were evaluated lower than the estimates of OTIS model in most of the simulations.

Environmental quality and health safety assessment often require prediction of solute transport in rivers. The process of moving suspended sediment in rivers acts like contamination. In this study, the transient storage model (TSM) was used to simulate the contamination transport in dense flow conditions (with suspended sediments). OTIS-P numerical model and Temporal Moment analysis (TM) were used to solve the transient storage model (TSM) and the breakthrough curves (BTCs) were simulated. Grain material with an average diameter (D50) of 11.85 mm and the porosity (n) of 0.28 were used to create a sedimentary bed. Experiments of tracer material (NaCl) were performed in a flume with a length of 12 m, a width of 0.5 m and a height of 0.7 m applying three different flow discharges (10, 12.5 and 15 l/s). In order to create dense flow conditions, suspended sediments with initial concentrations of 187500 ppm (SC1) and 375000 ppm (SC2) were injected. Experimental results showed that the existence of suspended sediment in the stream (dense flow conditions) increased the medium residence time (MRT) of contamination in the main stream. The results of numerical solution showed that storage zone exchange coefficient (α) in dense flow conditions was 1 to 3.2 times the storage zone exchange coefficient (α) compared to clear flow conditions. The results of numerical solution showed that the longitudinal dispersion coefficient (Dx) in dense flow conditions was 2 to 7 times the longitudinal dispersion coefficient (Dx) compared to clear flow conditions. The BTCs simulated by the OTIS-P numerical model and the temporal moment analysis (TM) were highly agreement with the laboratory BTCs with the Nash-Sutcliffe index between 0.89 to 0.97 and 0.89 to 0.95.In natural rivers with high concentrations of suspended sediment, hyporheic exchanges have an important role in the transport of contamination. Therefore, the use the transient storage model (TSM) is recommended instead of the analytical solution of the advection-dispersion equation (ADE).

In recent years, pollution of surface water resources, especially rivers, has posed an environmental challenge. Pollution from municipal or industrial wastewater and waste disposal into rivers are important problems for human societies to protect the environment. Knowing the level of river water pollution as one of the sources of human water needs is essential and therefore modeling the quality of river water is very important. Hydraulic structures in rivers are one of the ways to control pollution in open-channel flows. Check dams are one of the types of these structures that due to the porosity of their environment can play a controlling role in the transport of contamination by increasing hyporheic exchanges as well as transient storage of contamination in their porous media. Transient storage model (TSM) is one of the methods of pollution transport analysis, especially in rivers with high hyporheic exchanges. The efficiency of the (TSM) is in the correct estimation of the four parameters of the model (Dx, As, A and α). Previous studies have not investigated the effect of hyporheic exchanges due to gabion check dams on the four parameters of thel (TSM). In this study, the effect of gabion check dams on pollution transport and the four parameters of the (TSM) with OTIS numerical model were investigated.

Experiments of tracer material (NaCl) were performed in a flume with a length of 12 m, a width of 0.5 m and a height of 0.7 m in four flow discharges (2.5, 5 and 7.5 lit/s). An ultrasonic flow meter was used to measure the flow discharge in all experiments. Materials with medium diameter (D50) of 11.85 mm and porosity (n) of 0.28 were used to create a sedimentary bed with a length of 12 m and a thickness of 12 cm at the bottom of the flume. In this study, two types of gabion check dams with medium diameter (dg) of 11 mm (fine-grained) and 19 mm (coarse-grained) were used. In each experiment (except for the control experiment), 1 to 3 check dams were used at intervals of 2.5, 5 and 7.5 meters from the beginning of the flume, respectively. In this study, check dams with lengths of 0.75 and 0.35 m, widths of 0.5 and heights of 0.4 m were used. The length of the flume was divided into four equal reaches (L1, L2, L3 and L4). Two sensors were placed to measure the electrical conductivity (EC) of water at the end of each reach to measure the amount of contamination. Micro-propeller and ultrasonic depth-gauge were used to measure the velocity (V) and depth (h) of water flow in each reach. The laboratory results in L4 reach were simulated by the OTIS-P numerical model and the four parameters of the (TSM) were estimated.

The results showed that gabion check dams increased the transient storage of solute in the porous media of such dams, thus reducing the peak contamination concentration (Cmax) in the main flow area. On the other hand, check dams in the flow path will act as a sedimentary bed-form, which increases the hyporheic exchanges between the main flow area and the porous media of such dams. Increasing hyporheic exchanges into the porous media of the dams will also reduce the (Cmax) in the main flow area. Increasing hyporheic exchanges into the porous media of the dams also reduces the contamination concentration (Cmax) in the main flow area. Reducing the (Cmax) in the main flow area will also increase the longitudinal dispersion coefficient (Dx).Comparison between the storage zone exchange coefficients (α) estimated by the OTIS-P numerical model showed that these coefficients decreased with decreasing the length of check dams (a). Reducing the length of check dams (a) will reduce the space of the porous media in the flow path. Therefore, the solute will leave these storage zones with a shorter residence time, so the storage zone exchange coefficient (α) decreases with decreasing the length of check dams (a).Gabion check dams made of fine-grained materials reduce the exchange discharge between the check dams and the main flow area. The use of fine-grained materials reduces the rate of contamination transfer to the downstream reaches, so the (Cmax) in the downstream reaches will decrease, so the(Dx) will increase in the fourth interval (L4).

 Increasing the number of gabion dams (N) from one dam to three dams caused an approximately 1.43 to 1.71 times the value the (Dx). Increasing the length of gabion dams (a) from 35 cm to 75 cm caused approximately 1.43 to 2.49 times the value of the(Dx).Increasing the length of gabion dams (a) from 35 cm to 75 cm caused an approximately 1.10 to 4.43 times the value of the (α). The use of fine-grained materials in gabion dams increased the (α).

The industrialization of human societies is one of the factors in increasing the injection of pollution into surface waters. Contamination in the river is maintained both in the water stream and in the sediment bed of the river. The hyporheic zone is the saturation zone of the riverbed, which has a very important function in the transmission of pollution. River bed-form is one of the effective factors in creating hyporheic exchanges between surface flow and sediment bed. Transient Storage Model (TSM) is one of the suitable methods in the analysis of advection and dispersion of pollution in rivers with hyporheic zone. The efficiency of the Transient Storage Model (TSM) depends on accurate estimation of the four parameters of the model (Dx, As, A and α). Previous studies have investigated the effect of bed-form on hyporheic exchanges, but the effect of these exchanges on contamination transmission has not been investigated. On the other hand, previous studies have not investigated the effect of hyporheic exchanges caused by the formation of the bed-form on the four parameters of the transient storage model (TSM). In this study, the effect of dune bed-form on the transmission of pollution was investigated. Also, the effect of dune formation on the four parameters of the transient storage model (TSM) with a numerical model (OTIS and OTIS-P) and the temporal moment approach (TM) was discussed.

Experiments of tracer material (NaCl) were performed in a flume with a length of 12 m, a width of 0.5 m and a height of 0.7 m applying four different flow discharges (5, 7.5, 10 and 12.5 l/s). The experiments were performed in the range of average flow velocity (U) from 0.087 to 0.361 and in the range of Froude number (Fr) from 0.069 to 0.290. An ultrasonic flow-meter was used to measure the flow discharge in all experiments. Grain material with an average diameter (D50) of 11.85 mm and the porosity (n) of 0.28 were used to create a sedimentary bed. The first bed (WF1) with a thickness of 32 cm, a width of 0.5 m and a length of 10 m was created in the Flume. In order to investigate the effect of sediment bed thickness on contamination transmission, a second bed (WF2) with a thickness of 8 cm, a width of 0.5 m and a length of 10 m was also created. In this study, the effect of dune bed-form on the transmission of contamination was investigated by creating three dune bed-forms (D1, D2 and D3) with different wavelengths (λ) and different amplitudes (∆) in the second bed (WF2). The length of the flume was divided into three equal reaches. Two sensors were placed to measure the electrical conductivity (ec) of water in each reach aiming to monitor the concentration of contamination. A Pitot tube and an ultrasonic depth-gauge were used to measure the velocity (U) and depth (d) of water flow at each reach, respectively. The laboratory results were simulated by the OTIS-P numerical model and the four parameters of the Transient Storage Model (TSM) were estimated. OTIS-P numerical model estimates the four parameters of the Transient Storage Model (TSM) using the Nonlinear Least Squares (NLS) optimization algorithm and then simulates the breakthrough curves using the Crank-Nicolson implicit finite difference method. The parameters of the transient storage model (TSM) were estimated by optimizing the temporal moment approach (TM) relations using the Genetic Algorithm (GA) method and the breakthrough curves were reproduced using these parameters in OTIS software.

The results showed that increase the thickness of the sediment bed (from 8 cm (WF2) to 32 cm (WF1)) reduces the (Dx). Hyporheic exchanges decrease with increasing d_b/d, so the amount of hyporheic exchanges in WF2 bed is more than WF1 bed. Increasing hyporheic exchanges in the WF2 bed-form reduces the amount of contamination concentration in the main flow area, so the amount of (Dx) in this bed-form increases. The results showed that increasing Froude number (Fr) increases the (Dx) in both cases of bed thickness. The results showed that the storage zone exchange coefficient (α) in WF2 bed was higher than WF1 bed. Decreasing d_b/d increases the hyporheic exchanges at the time scale (t_f^*), so the residence time of contamination in the sediment bed increases. Since the storage zone exchange coefficient (α) indicates the amount of time exchanges of contamination in hyporheic zone, so reducing the bed thickness (db) increases this parameter. The results showed that the formation of the dune bed-form does not cause an absolute increase or an absolute decrease in the longitudinal dispersion coefficients (Dx). The main channel area (A) considering the D2 bed-form case was estimated more than that in the D1 bed-form case. Therefore, increasing the wavelength of the bed-form (λ) increases the share of the main flow region area (A) in the contamination transmission. On the other hand, in the case of less exchanges of contamination with the storage zone, the share of the storage zone area (As) decreases with increasing wavelength of the bed-form (λ). The results showed that the effect of dune bed-form on changes in TSM parameters was in the range of Fr

In the present study, the efficiency of the advection-dispersion equation in simulation of the pollution transport through the Gravel-Bed Rivers with Riffle-Pool bed-form was investigated. Experiments of tracer material (NaCl) were performed in a flume with a length of 11 m, width of 0.5 m and height of 0.7 m and with a longitudinal slope of 0.006 in three flow discharges (7.5, 10 and 12.5 lit/s). Four bed-forms of Riffle-Pool with different heights and wavelengths were considered to simulate hyporheic exchanges. The laboratory results were also simulated by the OTIS numerical model. The laboratory results showed that in bedless-form flow, increasing the flow rate increases the longitudinal dispersion coefficient. The opposite of this trend was observed at the presence of bed-form due to hyporheic exchanges. Increasing the height of the bed-form increases the Reynolds number in the hyporheic zone and consequently hyporheic exchanges increase and the longitudinal dispersion coefficient increases. Simultaneous increase of flow rate and the bed-form height causes excessive increase of hyporheic exchanges. Therefore, the residence time of the pollution in the sedimentary bed area is reduced and as a result, the pollution returns to the main flow area with less temporary storage in the storage zones. Therefore, increasing the longitudinal dispersion coefficient with increasing the bed-form height in the range of high flow rates is not significant. Increasing the wavelength of the bed-form also increases the residence time of contamination in the hyporheic zone, which increases the longitudinal dispersion coefficient. Increasing the flow rate reduces the role of hyporheic exchanges so that the main volume of pollution is transferred to the main flow area. Therefore, the effect of increasing the wavelength of the bed-form on the longitudinal dispersion coefficient decreases with increasing the flow rate. The comparison of laboratory results with numerical solution of OTIS model shows the high accuracy of this model in predicting the transmission of contamination.

In a stepped spillway, the steps can considerably reduce the flow energy. The purpose of this study was to investigate and comparing the amounts of energy dissipation in stepped spillways with different longitudinal profiles using physical models. For this purpose the experiments were done in a channel with 12 meters of length, 0.5 meter of width and 0.8 meter of height. For doing this research, the stepped spillways that had plexi glass gender with 4 ratios of hL = 0.5, 0.67, 1 and 2 was designed and constructed. The results showed that the amount of energy dissipation in hL=1 have maximum value, in the other words, when step length and step height be equal causes energy dissipation will be more. The results showed for hL≤1, increasing height of steps has been increase the energy dissipation. In a constant ych, the increase in the number of steps Increases relative energy dissipation and increasing dimensionless parameter ych, reduces energy dissipation almost 5 %. Finally, third degree equations for relative energy dissipation extracted, that the calculated statistical parameters indicate high accuracy of equivalents. The results showed relative energy dissipation in our study was in agreement with Chanson equations and Fratino-Piccinni equations.

Climate scientists have concluded that the air temperature of earth’s surface warmed to 0.6 during the 20th century, and that warming induced by increasing concentrations of greenhouse gases accompanied by changes in the precipitation and hydrologic cycle. Monthly, seasonal and annual precipitation trends of meteorological stations have been analyzed and interpolated in the northern part of Iran for three periods (30, 40, 50 years). The Mann-Kendall trend test was applied to examine the monthly precipitation data. Significant positive and negative trends at the 90, 95, and 99 percent confidence levels were detected for numerous stations. The detected trends were spatially interpolated by applying the inverse distance weighted (IDW) interpolation method. The amount of RMSE for different variables obtained using IDW less than 0.2, indicating the effectiveness of this method in the interpolation of rainfall. The results showed that the trend of variation, both in terms of time and spatial is different in the study area, as has experienced downward trend in cold season and upward trend in warm season which indicates the importance of climate change in the study area. The spatial variation trends results for mean annual precipitation of 30 and 40 years period showed that the east of region have downward trend and the west of region have the upward trend. For the 40-years period, downward trend of station nearly are situated in eastern part of region, as downward trend at 90% confidence level are evident for Talar basin. The western part of region experienced upward trend at 99% confidence level especially in Chaloos-roud basin. The results of this study indicated that the region has experienced the severe climatic change which the better understanding of the climate variation and its impacts on water recourses, natural environment and other related sector are necessary.

Due to importance of Harazriver in supplying drinking water, pollution of agricultural water around this river and also discharging several pollutants into it, water qualitative evaluation of this river seems necessary. The purpose of this research is zoning of water quality of Harazriver using NSFWQI index. In order to recognize the effect of agricultural and industrial wastewater and residential centers, investigated the qualitative parameters of river water in a 6 months period from February 2013 to July 2014 at interface discharge from Lar dam to entry of water into the Caspian sea in 6 stations. The results showed that the amount of coliform faecal, Do, temperature, nitrate and phosphate had significant variations in the entrance of river to the flood land, so that in Sorkhrood station in all months had significant different. The water of Haraz river in 5 stations (Poloor to Karesang), had medium class of quality with index of 50-70 in most months. Whereas in Sorkhrood station, had low water quality during all months. Also, the results of statistical analysis of T-TEST on discharge rates, temperature, TDS and DO parameters showed that two periods of low and high water had significant differences.

Weir and Gate are widely used in control, diversion and measurement of flow in irrigation projects due to their simpler and relatively exact relationship. There are sediment and suspended materials in the direction of channels. The accumulation of sediments and suspended materials in the back side of weir and gate caused change of canal shape and reduction of water measurement accuracy. The combined model of weir- gate have the capability of passing settling down from under the gate and suspended materials over weir simultaneously and prevents from accumulation of sediment and suspended materials in the back side of the weir and helps to the accuracy of water measurement and passing flow. The present research investigated ten combined model of labyrinth weir- gate on the effects of plan shape change and gate height on discharge coefficient in the laboratory. The results showed that the existence of gate and increasing of opening height, increased discharge coefficient in combined model of labyrinth weir- gate. On the other hand, existence of gate in combined model of rectangular labyrinth weir- gate in low total upstream water height to weir height have higher effect on the increasing of discharge coefficient. Whereas in combined model of trapezoidal labyrinth weir- gate, with the same of total upstream water height to weir height, had uniform effect on the increasing of discharge coefficient. The results showed that increasing of upstream water height caused interference of water jets of cycles of labyrinth weir and also interference of water flow passing under the gate and flowing water over the weir. Therefore discharge coefficient was lower in deeper depths. On the other hand, in the same depth, the trapezoidal labyrinth weir had less flow interference with respect to rectangular labyrinth weir, which caused higher increase in discharge coefficient in combined model of trapezoidal labyrinth weir-gate with respect to combined model of rectangular labyrinth weir- gate.