مجله علوم و مهندسی آبخیزداری ایران
پیاپی 50 (پاییز 1399)

This study was conducted to investigate the capability of the Universal Soil Loss Equation (USLE) and its versions (RUSLE, USLE-M and AUSLE) models in predicting soil loss at the plot scale in a semi- arid region in Zanjan. Toward this, twenty two plots from 1m to 22.1m with the same widths (1.83m) were installed on a uniform slope 10 percent. The plots were maintained under the USLE standard plot conditions for a fourteen-month period (from March 2013 to Jun 2014). Based on the results, an increasing trend was observed in soil loss with increasing plot length from 1 m (0.01 ton/ha.year) to 6 m (0.07 ton/ha.year), which was associated with increasing runoff and its transport capacity. Mean estimated soil loss using the USLE, RUSLE, USLE-M and AUSLE for twenty two plots was 80.2, 65.4, 4 and 113.5 times bigger than the measured values, respectively. The USLE-M appeared the lowest error in soil loss estimation as compared to other two models. In this model, erosivity factor is determined using runoff along with rainfall characteristics. This study revealed that the calibration of the empirical soil erosion models using long period data is essential for predicting soil loss in the plot scale.

Simulation of self-purification and investigation the pollutant decay coefficient of rivers is one of the most important requirements of surface water resources pollution monitoring and treatment. In this paper, self-purification capacity and the pollutant decay coefficient values of Babolrood River, IRAN, was investigated based on field measurements of qualitative parameters including; DO, BOD, pH, EC, nitrate, phosphate and temperature in four seasons, 2018. To achieve this aim, QUAL2Kw software used. In this paper not only the modelling results and analyzes are presented but the measured data of the studied river are also presented, which can be used in the future researches. Based on the results, the average amount of dissolved oxygen of Babolrood River in all seasons except summer are varied between 6.55 and 7.65 mg/l, while the average of that is equal to 5.93 mg/l in summer. Also, the average value of BOD in summer, due to an increase in temperature, is recorded equal to 3.17 mg/l and in other seasons were recorded between 2.17 to 2.93 mg/l. The decay coefficient of the Babolrood River was estimated equal to 5.5(1/day) in summer and in other seasons it varied between 0.5 and 4(1/day), applying QUAL2Kkw simulations. According to the dissolved oxygen diagram and involving the Streeter-Phelps method, no reduction in dissolved oxygen during spring and fall, in this river, was recorded. However, in winter and summer, the dissolved oxygen was reduced to 6.5 and 5.7 mg/l, respectively.

In order to solve the flood damage and flooding problems, as well as adopting appropriate guidance methods to use of urban runoff and implementation of the correct water principles in urban watershed management, it is necessary to adopt appropriate methods to study the rain water cycle and the production runoff volume of precipitation events in urban areas. It should be noted that the rain water cycle in urban areas in this research was investigated using the water balance formula in district 9 of Mashhad city. Results showed that the delineation of watershed border is the first important issue in the hydrologic modeling of urban catchments which plays an important role to determine the total runoff volume generated from hydrologic homogeneous units. The results showed that runoff volume of buildings homogeneous units is more than streets and more than green spaces. The runoff volume values of hydrological water balance methods both were estimated to be almost identical. Finally, the correction runoff coefficient was estimated for hydrologic homogeneous areas. results showed that the correction runoff coefficient for the residential buildings homogeneous areas was estimated 80 percent. And for street homogeneous areas was estimated 78 percent and for homogeneous areas of the park and green space using the hydrological balance method obtained 0.048 percent.

The aim of this study was to evaluate the extent of development and recognition of the hydrochemical behavior of karst aquifers of Bistoon and Dalahoo limestone masses using graphical methods, clustering, factor analysis and saturation indices. The results of hydrochemical methods indicate that the dissolution process is active in the karst aquifers of the studied masses. These methods have acceptable efficiency in determining the origin of karst water, effective factors in quality characteristics, water retention in the aquifer and evaluation of the development of the internal network of karst systems of the studied masses., Shah Hossein, Sarableh, Varmanjeh and Mirahmad springs in Bistoon mass and Rijab and Marab springs in Dalahoo mass were identified as springs with internal karst development. The Bistoon Mass Formation due to its size and integrity, thickness and pure mineralogical composition, has much more karst formation capacity than the Dalahu Mass and plays a key role in the formation and development of the Biston Massif karst geomorphology.

Seasonal floodwater has been kept in the lands by using watershed projects so that it penetrates into underground beds, but this case causes different influences on graining, permeability, underground water and vegetation. Three sections were chosen as experiment sites to measure soil changes of watershed projects in Nodoushan watershed area of Yazd province. Seven permeability experiments with double cylinder inside every section and three experiments in the control group were performed. Along with each of these experiments, one sample was collected from 0.5 meter of the surface soil and graining experiment was performed on it. The significance of permeability was investigated by the use of non-parametric Mann-Whitney test and Kolmogorov–Smirnov test. The results show that permeability in Sadrabad, Nodoushan and Alaviyeh in control group were 4.92, 3.52 and 5.89 cm/ hr, respectively. After some periods of dewatering they were reduced 94 percent, 89 percent and 92 percent, respectively. And finally reached to 0.28, 0.37 and 0.47, respectively. Also, the average diameter of the particles decreased about 90 percent. The results of experiments showed that the decrease of permeability was significant in the level of 95 percent.

Jafarieh plain is part of Salt Lake watershed that is experiencing a crisis due to drought and excessive use of groundwater resources, so it is necessary to study groundwater, which is the main source of water in the whole plain. This study aimed to model the MODFLOW code of Jafarieh plain aquifer in GMS software as an efficient model in groundwater issues. The quantitative model of the Jafarieh aquifer was simulated over two ten-year statistical periods(1992-2002 and 2002-2012) using the water level statistics of the piezometric wells in the study area, and model calibration was performed in both steady and non-steady states. Finally, the model was validated with observational data. The results showed that the model is most sensitive to changes in groundwater recharge, and the average aquifer loss in the years 1992 to 2002 was from 0.05 to -1.5 m. So, the highest decline occurs in the eastern part of the study area. Also, the average aquifer loss in the period 2002-2012 has decreased from -0.26 to -7.2 m, indicating that the aquifer has declined more strongly during this period, with the highest decline in the northwest and southeast regions. Its consequence is the annual decline of 0.73 meters seen in these two-10-year periods in the region.

Storm sewer networks are important components of urban planning and civil engineering, and any negligence in their proper design can be a problem for human societies. Analyzing urban flooding by modeling and analyzing flood damage is an effective step to optimally manage urban transportation and reduce the damage caused by demolition of facilities. In this paper, using the SWMM model with 2, 5, 10, 20 and 50 year return periods with dynamic wave model and rational methods, the existing potential for evaluating the efficiency of surface drainage network for partial of District 2 of Tehran was investigated. After evaluating the existing storm sewer network of the mentioned area, the amount of runoff damage was estimated by statistical method. The results of the modeling show that there are flooding and surcharging in the link and node of drainage network for return periods of 5 years or more. This indicates the inefficiency of the existing network in collecting runoff from rainfall. The results also showed that the values of flood discharge obtained from the rational method are much higher than the dynamic wave routing method and this difference is due to the structure of the two methods. The results of the calibration process also show that the model has an acceptable capability to simulate the overall shape of the hydrograph and flood peak discharge. Also, with respect to the calibration results and the RMSE value, the dynamic wave routing method is closer to the observed results, so it is more accurate. Damage assessment also showed that damages to buildings in the study area for return periods of 5, 10, 20 and 50 were 7, 9, 11 and 14 million, respectively, using dynamic wave routing and 10, 12, 14 and 16 million by rational method.

In recent decades, along with the development of the residential area, the problems of runoff and flood in urban watersheds have increased dramatically. Check dams have a direct and rapid effect on the flood. One of the most important elements of the construction of these structures is the identification of the suitable location for construction of the structure. This stage should be done with the utmost accuracy and precision due to the stability of the structure and the financial issues. In this study, the general approach is based on the fact that after identifying the area and collecting the required information, the factors influencing the construction of the structures were determined and the layers required for suitable location were prepared. After fuzzing the layers using Arc GIS 10.5 software, each layer is weighted according to the amount of its effect on site selection. Then, the layers combined using the fuzzy gamma operator and finally, after the field surveys, 22 optimal points and 3 completely optimal points for constructing the structures in the Ilam catchment area were identified. By construction of a check dams in the selected areas, it is possible to significantly reduce the damage to the facilities and waterlogging of the passageways.