مجله محیط زیست و مهندسی آب
سال ششم شماره 4 (زمستان 1399)

In this research, it has been tried to investigate the limitations of using the plain’s groundwater through using the monthly values ​​of discharge of agricultural wells, groundwater level and quality values ​​of electrical conductivity in areas of South Khorasan Province in 2013-2014. In this regard, a combination of groundwater resource index, modified standard electrical conductivity index and standardized well discharge index was used. Finally, hydrogeological drought management index (HDMI) was used to manage the groundwater drought and to investigate hydrogeological drought. HDMI is one of the useful and practical indices in this field that has been less studied. The results of groundwater resource index showed that in the study area, groundwater drought is clearly seen in the southeastern regions of the study area. Hydrogeological drought management index in the studied area showed that operation of groundwater in most of the studied area has a problem and operation of groundwater in these areas should be limited. About 86% of the studied areas are in limited operation condition, 10% are in problem-free operation condition and 4% are in non-operation condition. In general, the results of hydrological drought management index at the study area indicated that this index has high ability to provide an aquifer management and has a great help to water managers in the country. Relying on the results, it is possible to restrict water use at the aquifer and manage the water delivery.

By analyzing the historical records of the drought phenomenon and relying on the available statistics and information, it is possible to estimate the period of drought returns for different regions. By creating drought preparedness plans, the problems caused by drought can be greatly reduced. Frequency along with severity, duration and range are the most important features studied in drought studies. The purpose of this study was to calculate the relative drought frequencies of the Persian Gulf basin with the help of the standardized precipitation evapotranspiration drought index (SPETI)  and to prepare a map of their frequencies. For this purpose, SPETI index was used as a selected index to study droughts in 10 stations located inside and outside the basin with a common statistical period of 30 years (1988-2017) in four scales of 12, 9, 6 and 3 months. After reviewing the output results, the relative frequencies of drought were extracted and mapped at each scale. Trend graphs of precipitation and temperature showed that the annual data of precipitation and temperature had a decreasing and increasing trend, respectively, with a temperature increase of 28%; hence, the results showed that SPETI index in presenting drought phenomena was faced with an increase in temperature and a decrease in precipitation. Therefore, these stations are introduced as stations with the potential for drought sensitivity.

Cement manufacturing can be an entrance source for heavy metals to the environment. Hence, the purpose of this study was to determine the amount of pollution of heavy metals, cadmium and nickel, in the lands around the Yasouj Cement Company. For this purpose, 61 soil samples from zero to 30 cm depth around the plant were randomly sampled. Some of soil properties and total concentration of Cd and Ni were measured. Kolmogorov-Smirnov test was used to examine the normality of the data. In the normal and abnormal data series, kriging and IDW methods were used to prepare zoning maps. The highest concentration of cadmium was observed in the northern part of the plant (11.12 mg/kg). The results of nickel concentration zoning showed that the amount of nickel was highest in the sampled areas. The levels of cadmium in 10% of the samples and nickel in 100% of the samples were higher than the standard values reported by the Department of Environmental of Iran, and this indicates the risk of accumulation of these metals in the soil and pollution of the cement plant. Generally, high concentrations of these metals in soils around the cement factory showed that the pollutants are as a result of the different activities such as material processing in the process of cement production and the movement of vehicles around the cement company. According to these results, it is recommended that environmental preventive measures be taken to reduce the emission of pollutants in the cement production line.

One of the most important steps to prevent and deal with the destructive effects of floods is to identify areas with the highest flood potential in the watershed and its sub-basins. In this research, an attempt was made to determine the regions with the highest capacity of runoff and flood production in Mazandaran Province basin using the hierarchical analysis process (AHP) model. On this basis, six factors including heights, slope, land use, geology, flow accumulation, and rainfall were used. After calculating the final weight of each input factor using the hierarchical process model in ArcGIS (V. 10.5) software, a combination of input layers was used to construct a flooding map of the study area in five different categories including very high, high , Medium, low, and very little. Results showed that 38.79% of the Mazandaran Province, equivalent to the area of 9244.82 km2, has a high and very high flooding hazard. Moreover, almost half of this province, equivalent to the area of 12028.51 km2 has a moderate flooding hazard. The results reveal that flooding hazard at each hydrometric stations was in good agreement with the historical observations of floods, that most of them have the return periods of 50- and 100-year. It implies the high accuracy of the method and the weights assigned to each of the effective factors. This clarifies the usability of this research results for future preventive implementation.

Groundwater vulnerability assessment is important in order to prioritize these resources from the perspective of exploitation, management and control of pollution in different areas. The purpose of this study was to evaluate the qualitative vulnerability of Birjand plain aquifer using DRASTIC-LU model. In this research, the DRASTIC base model with the land use parameter of the developed lands was used. In this method, the basic model parameters including groundwater depth, net nutrition, aquifer environment, soil type, topography, unsaturated area constituents, and hydraulic guidance were analyzed in GIS environment along with land use variable as a model development based on standard weights and the vulnerability zoning map was prepared. Vulnerability zoning map of DRASTIC-LU model showed that 62.27, 25.07, 17.17, and 2.38% of the area have low to medium, medium to high, low and high vulnerability, respectively. In addition, the sensitivity analysis of the model used to evaluate the assigned weights was performed. To validate the model, the correlation of the model with the nitrate concentration was performed; the obtained correlation of 86% indicated the appropriate correlation of this model with the nitrate concentration as an indicator of groundwater pollution.

Accurate estimation of reference evapotranspiration has great importance in irrigation scheduling. Moreover, the lack of availability of lysimetric data has led researchers to use indirect methods, including data-driven approaches. In the present study, the ability of Gaussian process regression (GPR), support vector regression (SVR) and random forest (RF) data-driven methods was investigated to estimate the evapotranspiration of the reference plant. For this purpose, meteorological data on average temperature, wind speed, relative humidity and sunny hours in the period 2013-18 were collected in nine northern stations of Iran including Astara, Bandar Anzali, Rasht, Ramsar, Nowshahr, Sari, Turkmen port, Gorgan, and Gonbad Kavous. Evapotranspiration calculated using FAO-Penman-Montith method was considered as the target output and four combined scenarios of meteorological parameters were considered to calibrate and validate the studied methods. The accuracy of the mentioned methods was compared using the statistical parameters of correlation coefficient, scatter index, and Wilmott’s coefficient. The results showed that GPR4 model with scatter index in the range of 0.132 to 0.179 in Astara, Bandar Anzali, Rasht, Ramsar, Nowshahr and Sari stations, SVR4 model with dispersion index of 0.116 to 0.120 in Turkmen and Gonbad Kavous stations and the Hargreaves-Samani method with a scatter index of 0.509 at Gorgan station had much more accurate estimates of the evapotranspiration of the reference plant.

Given the importance of soil and water resources in the development of sustainable agriculture, increasing world population and the growing need for crop production, predicting crop yields using plant simulation models and remote sensing technology is very crucial. The aim of this study was to estimate the yield of rice components including straw, paddy and biomass of Hashemi cultivar during different growth stages with SWAP model and to provide regression equations by extracting NDVI and SAVI plant indices from Sentinel-2 and Landsat-7 and 8 satellite images. It was done in the National Rice Research Institute. Comparison of statistical variables indicated that the mean values of coefficient of determination (R2) and model efficiency factor (EF) in estimating the yield of rice components in different stages of growth with SWAP model were more than 0.70 and 0.90, respectively, and with an error of 1.93 to 6.54% was equivalent to 134.21 to 470.43 kg/ha. The slight difference between the measured and simulated values showed that the SWAP model estimates the rice yield in the study area with appropriate accuracy. The results also showed that the extracted NDVI and SAVI indices with very good accuracy estimate the yield of rice components at different stages of growth. However, the highest amount of correlation was related to the reproductive development stage. Finally, R2 for NDVI at different growth stages as well as  the entire growth period for straw, paddy, and biomass were higher than the SAVI index, revealing more accuracy of NDVI than SAVI.

In this study, changes in flood characteristics due to the failure of Vahdat Dam (Gheshlagh) in areas where the cross section of the river has changed, because of human activities, were investigated. For this purpose, the HEC-RAS model was used to simulate the failure of the dam and the resulting flood flow. Data on the dam structures and flow of the Gheshlagh River in Kurdistan Province, on which the Vahdat Dam is located, were obtained from the Kurdistan Regional Water Company. Using the ArcMap software, after converting the digital elevation model (DEM) to a three-dimensional model (TIN), the required parameters and lines related to the cross sections on the river were drawn. This data was transferred to the HEC-RAS model. Through field studies, cross sections were corrected and Manning coefficient was measured in different zones. After preparing images of bridges and embankments along the flow path, the height of the bridge and the embankments in the flow path were measured using station GPS. The Grize Bridge and the location of the studied embankments in this study located 23 and 33 km downstream of the Vahdat Dam, respectively, were selected to investigate the changes in flood characteristics due to local narrowing. Changes in water height and width in the study areas were investigated. At the site of the Grize Bridge, the peak of flooding due to dam failure and water depth was 4773.79 m3/s and 10 m, respectively. These values ​​at the embankments were 4330.04 m3/s and 10.8 m, respectively. Comparing these numbers with the data calculated in the previous sections of these contracted sites indicates a significant reduction in the flow capacity.

Economic growth is the essence of all economic activities and actions of governments in a certain period, which if not desirable, has negative consequences, including environmental degradation. The environment is one of the main pillars of sustainable development; in recent decades, the importance of the environment has increased and the quality of the environment has become very important. With the growth of urbanization and the development of communities, more importance has been given to the quality of the environment. The aim of this study was to evaluate the effect of the selected economical indicators and urbanization on the emission of CO2 in Iran during the year's 1980 to 2018 using Bayesian causal map (BCM) analysis method in five scenarios. Testing the degree of impact of changes in economic variables on the growth rate of CO2 emissions using one-way sensitivity analysis showed that among these five indicators, first trade with 58.78 and secondly private sector credit with 32.48 and then tax with 4.85, followed by urban growth with 4.21 and finally private sector investment with a reduction of variance of 1.04, respectively, had the greatest impact on CO2 emissions. The results of the five scenarios show that after changing the probability of high status of variables, high probability of CO2 emission is also more likely.

In the present study, the electrochemical coagulation process (electrocoagulation) in the mining industry was investigated in order to remove one of the heavy metals, cadmium, from the leaching solution of the copper processing plant. The response surface methodology (RSM) was used to optimize the factors affecting the removal of this metal in the electrocoagulation process. For this purpose, Behnken Box Designv(BBD)  was used to optimize the experiments. The effects of three independent parameters such as pH (X1), electrolysis time (X2), current density (X3) were investigated in order to investigate the removal of cadmium from the leaching solution. The quadratic model was used to respond to the cadmium removal efficiency. The most important independent variables and the interaction between them were evaluated using ANOVA test. This study showed that the optimal operating conditions for cadmium removal are 96.96% at initial pH: 6.83, electrolysis time: 116 min and current density: 69.262 A/m2. The results showed that the ability of electrocoagulation process can be considered as a reliable method to remove cadmium from industrial effluents, especially in mineral processing plants.

The increase in greenhouse gases in recent decades and the resulting increase in temperature have upset the balance of the planet's climate system and caused widespread climate change in most parts of the world. In this study, first the SWAT model was calibrated for Jamishan watershed. The calibration and validation stages, NS and R2 coefficients were 0.6, 0.61, 0.52, and 0.54, respectively. According to the results of sensitivity analysis in the region, it was found that among the 20 parameters affecting runoff, the curve number was the most important parameter. Then, the values of temperature and precipitation for the next period based on the climate change scenario were subscaled with the outputs of the HadCM3 general atmosphere rotation model for the three scenarios A2, B1 and A1B using the LARS-WG model. Later, in order to simulate the watershed runoff, the data were introduced to the SWAT model and the results showed that the runoff in the statistical period of 2015 and 2026 increased by 6, 7 and 6% respectively compared to the observation period in each scenario A2, A1B and B1 and this shows the impact of climate change on runoff in the near future from 2016 to 2026. This study showed that changes in meteorological parameters will lead to significant changes in hydrological regime such as watershed runoff. Increasing rainfall and temperature are likely to cause floods in the region in the future.

Drought is one of the most important natural disasters that due to the frequency of occurrence needs to be assessed and monitored, especially in the field of agriculture. In the present study, the Reconnaissance Drought Index (RDI) was used to monitor drought and spatially assess its severity in central and southern regions of Fars province. The relationship between the severity and duration of drought during different years of the statistical period (1990-1991 to 2012-2013) was investigated. Kriging model was used in the geographic information system (GIS) environment for spatial evaluation. Based on the comparison between the different semivariogram of the kriging model, the most suitable model was selected. Based on the results of drought severity, its continuity and trend were determined during the statistical period. The results showed that severe droughts occurred in Darab and Neyriz stations during 2000-2002 and 2008-2010. In Fasa and Jahrom stations, in most of the years, climate fluctuations have led to drought with low to high intensities. At Larestan station, the results also showed several droughts have occurred, especially during the years 2000 to 2010. In spatial evaluation of drought using the Kriging model, the results showed that the best semivariogram is the spherical model. The evaluation of drought vulnerability in the studied areas also showed that the northern areas of Nayriz, Estahban, Fasa, Darab and Larestan have suffered more damage. Therefore, the use of drought indices, drought intensity monitoring and mapping methods are essential for better management and planning for advance planning and it is recommended for water resources management decisions.

Estimating the effect of sediment transport, especially suspended load, is important in river planning and management. The aim of this study was to investigate the effect of suspended sediment load on the roughness coefficient and the intensity of flow turbulence in Haraz, Rostamabad and Beheshtabad Rivers. In order to better understand these relationships, the geometric characteristics of the sections, the flow velocity and the suspended load were measured in different sections of these rivers. Then shear stress, Manning coefficient and Von karman coefficient were calculated using related equations in each section. The intensity of turbulence was also determined by measuring velocity fluctuations. The study of the effect of suspended load on roughness coefficient and Van Carmen coefficient showed that in most sections roughness coefficient and Van Carmen coefficient have decreased due to the presence of suspended load. In Haraz, Rostamabad and Beheshtabad Rivers, the ratio of roughness coefficient in the presence of suspended load to roughness coefficient without suspended load was 0.9, 0.94 and 0.6, respectively. The results of this study showed that the turbulence intensity distribution is independent from the flow rate and the distribution is always convergent and its maximum value occurred not in the bed but above the bed. Besides, the distribution of turbulence intensity in the presence of suspended load in gravel-boulder rivers is convergent and can be analyzed based on the boundary layer equation. Quadrant analysis was performed on the dominant events at three flow depths. In the areas close to the bed, the predominant phenomena were inward, outward and ejection, respectively, and the contribution of the sweeping event in this section was negligible.

Rivers, as the living artery of the watershed, have caused its life and have long determined the extent and establishment of civilizations, especially in the coastal plains. The Tajan River in the coastal plain of Sari has been directly polluted by water and sediment resources as a result of industrialization, agricultural development, and towns, and villages. The aim of this study was to determine the quality of surface sediments of Tajan River in the city to sea range based on the concentration of toxic elements As, Cr, Cd, Cu, Ni, Pb, Zn and to detect the level of pollution caused by them. The sampling strategy was designed to collect 25 surface sediment samples based on the distribution of point and non-point pollution sources and river morphology. Samples were conditioned and concentration of toxic elements and sulfur were measured using ICP-MS at dry weight with accuracy of mg/kg and percentage of total organic carbon. Using enrichment factor and sediment quality standards (ISQGs, PEL, SEL), the level of contamination caused by toxic elements was detected. The results well identified the polluted and clean ranges of the Tajan River. Accordingly, the southeast and downstream of the urban area of Sari were polluted by the toxic metal of As and upstream of the urban area, and adjacent to the effluent of industrial estates to the river were contaminated considerably by the toxic metal of chromium. Finally, superficial sediments of the Tajan River along the studied range were polluted significantly by the toxic metal of Ni at a risky level. Also, Pb enrichment was proven in the downstream sediments of the urban area due to fossil fuels. The research results emphasize the effect of urban-rural pollution (surface water drainage, construction waste and rubbish), industrial and agricultural effluents and sand mines on the pollution of water resources and sediment of Tajan River.

In this study, in order to investigate the trend of precipitation changes in Khuzestan Province, the data used were daily, monthly and annual data of precipitation of selected synoptic stations for a statistical period of 30 years (1987-2016). To study the trend of precipitation changes, precipitation-related indices defined by the ETCCDMI expert group were estimated using RClimDex software. Then, the ascending and descending trend of changes in precipitation limit values ​​was investigated using Mann-Kendall non-parametric test method. The age slope estimator method was also used to determine the rate of precipitation change. The results showed that all precipitation-related indicators (except for the number of days with more than 25 mm and very wet days) had significant changes at the level of 5%. In terms of stations, Dezful station with 26.41% had the highest rainfall and Shushtar station with 3.64% had the lowest rainfall. Behbahan station also had a 14.87% increase in rainfall.