مجله علوم و مهندسی آبخیزداری ایران
پیاپی 51 (زمستان 1399)

This study aimed to investigate the effect of soil physicochemical properties on gully erosion in the Qarranqou Chai watershed located in the south of East Azerbaijan province. Toward this, a rainfed area with 30 km × 30 km in dimensions and affected by gully erosion was selected in the area and gully erosion, morphological characteristics of gullies along with physicochemical soil properties were determined in each grid. Results indicated that gully erosion is ranged from 2.64 to 242.7 ton per square kilometer, with an average of 21.38 ton per square kilometer. It is significantly correlated with sand (r= 0.28), moisture saturation percentage (r= 0.27) and aggregate stability (r= -0.29). Aggregate stability in contrast with two other soil properties appeared negative role in gully formation. No significant correlation was found between gully erosion and silt and soil erodibility factor (K) estimated by the Universal Soil Loss Equation (USLE). This study revealed that aggregate stability is a major soil properties controlling gully erosion in rainfed lands. Maintaining crop residues is the first strategy to enhance soil organic matter content, improve aggregate stability and in consequence decrease the soil’s susceptibility to gully erosion in the area.

The soil erosion during the various stages of the process of separation to deposition, destructive affects on the physical and chemical properties of the soil. Today, various soil additives and modifiers are used to protect water and soil around the world. However, the role of organic materials and environmentally friendly materials has not been taken into consideration. Therefore, the aim of present study is to investigate of the effect of four modifiers including biochar, sheep manure, wheat straw and vermicompost in 1 × 2 m 2 plot, intensity 65 millimeter per hour with 3 repetitions and slop 8-12 percent using rainfall simulator. The results showed that long-term rainfall, heavy rainfall and extreme intensity had offset the positive effects of the treatments. However, the process of erosion has changed all the characteristics of the soil. So that the soil texture at the confidence level of 95 percent of the loam class is close to the loom-clay class and reduce 20.68 percent 41.17 and 19.12 percent organic matter, phosphor and potassium, respectively. During the erosion process, the soil lime was washed at 9.63 percent and the soil pH was reduced by 2.54 percent.

Physical development of cities and expansion of its dimensions is one of the important forms of land use change that has many environmental, economic and social consequences. Changes in the natural pattern of drainage systems in urban and suburban areas, unprincipled use, development Impermeable surfaces are a major cause of urban flooding. The purpose of this study is to estimate the changes in discharge and runoff volume leading to the city as a result of increasing impermeable levels and urban development. In this regard, land use changes related to Abshouran watershed in three time periods have been tracked using Landsat images. EPA SWMM model was used to investigate changes in runoff peak flow. After calibrating the SWMM model based on the observed rainfall-runoff events, the calibration and validation results confirmed the conformity of the model simulations. Fitting of land use changes and corresponding floods during the study period shows that the area of urban areas in 2018 and 2001 compared to 1991 has increased by 189.68 and 60.79 percent, respectively. With increasing the percentage of urban impermeable surfaces, peak discharge and runoff volume for rainfall with a 20 year return period in 2018 compared to 1991, 198.82 and 188.04, respectively, and compared to 2001, 72.34 and 94.85 percent, respectively. Increased.

Today SEA is one of the most important tools on which environmental considerations can be institutionalized in the planning system. In this regard, it is important to select the effect of scale jumps on the process of SEA. Therefore, in this study, with using the favor of spatial scale 1:250000 and satellite imagery ASTER and SRTM in the first order Persian Gulf and Omman sea watershed an attempt has been made to test whether SEA outputs are aligned with macro policies and to increase the scale in the spatial dimension. In this regard, first by inputting raw data of digital elevation model in Arc SWAT extension in Arc map software and processing their related calculations HRUs and then, introduce the 11 year climatic data to the SWAT model and implement (RUN) SWAT model at different spatial scales. The results showed that re-sizing the digital elevation model had a significant effect in the first order Persian Gulf and Omman sea watershed.

Experimental investigation on scoring and determination of depth of scoring are among the most important issues in T-shape spur dike designation with model T-shape spur dike was measured in a laboratory flume with 180 degree bend under clear water. In this study, we conducted evaluate the effect of relative distance between two T-shape spur dikes in the bend on the occurred scour. For this purpose, two spur dikes were installed at four different relative distances and four different relative lengths in the first half of an180 degree bend. All experiments were performed in four Froude number and a constant flow depth. The results show that with increasing the relative distance of T-shape spur dikes, the relative maximum scour depth increase at the opening of the spur dikes. Measuring depth of scouring based on experimental observation, an empirical relation is developed with high regression coefficient 0.98.

Recent droughts have caused a decline in the level of groundwater aquifers, which has affected water quality and usability. The aim of this study was to investigate the effect of drought on groundwater quality in Iranshahr plain aquifer. In this study, drought rates were studied using the statistics of Iranshahr synoptic station during the 30-year statistical period (1987-2017) based on SPI index in DIP software, for 6 to 24 months’ time series. Water quality was studied for 16 piezometer wells and 6 aqueducts during 2005-2017. Also, the top four models of semi-spherical, exponential, linear and Gaussin were evaluated using GS + 5.1 software. Then zoning maps of groundwater quality parameters were prepared using the models detected in ArcGIS 10.4.1. The results showed that during the period 1987-2016, normal drought has been dominated in the plain. Drinking water quality is divided into 4 classes in wet hydrological years (2005-2006) and 5 classes in drought (2016-2017). Good quality in terms of drinking decreased from 7.53 percent to 3.92 percent. Water quality has decreased from east to west of the region and the percentage of suitable and usable classes has decreased.

The increase in population and natural factors such as drought, have led to critical conditions of groundwater in most parts of Iran. Considering that Semnan province is in an arid region like other dry parts of the country, it is more vulnerable to a water scarcity crisis, So, Semnan plain was selected to study the quality of groundwater. In order to study water quality, 19 observation wells were investigated. After entering the data into GIS software, using point maps and Kriging method, the zonation maps of groundwater quality were prepared. The study of quality parameters maps showed that groundwater quality was declined in this area as the wells in the study area are affected by the increase of TDS, SAR, EC and also the decrease in pH.