مجله علوم و مهندسی آبخیزداری ایران
پیاپی 48 (بهار 1399)

The permanence of rainfall shortage compared with the long-term average of meteorological droughts, reduces river flow, groundwater level and hydrological droughts. To quantify the drought, several indexes has been defined. In this study, two drought indexes, including standardized precipitation index (SPI) and standardized streamflow index (SSI), were used for meteorological and hydrological drought monitoring. The aim of this study was the monitoring the drought in 5 stations in Tehran province during the period of (1985-2016), determining the most appropriate cumulative distribution function for calculating the SSI drought index and also a comparative study of meteorological and hydrological drought indicators in this province. The results show that the most suitable cumulative distribution function at the  Darake station is Gen-Loglogestic, at the Firuzkuh and Abali station is Gamma, at the Namrud station is Fatigue life and at the Sharifabad station is Beta. Among the stations with proper functions, Derek with the highest P-value (0.996) and the lowest RMSE (0.916) had the best fit with the Gen-Loglogestic distribution  function. Also, the similarity in the process of drought resulting from two different indicators, indicates that the meteorological and hydrological indicators are completely same, in other words, surface water resources in Tehran province are completely influenced by rainfall.

This study was carried out to investigate the role of soil structure in splash erosion in semi-arid soils. Splash erosion was measured in four soil textures (silty clay loam, sandy clay loam, silt loam and sandy loam) with two soil structure conditions (with natural structure and under aggregate breakdown) using a simulated rainfall with 50 mmh-1 in intensity for 30 min in splash caps with 10-cm height and 8-cm diameter. Soil physical properties consisted of mean aggregate size, aggregate stability, bulk density and saturated hydraulic conductivity (Ks) were determine in the two soil structure conditions. Results indicated that sandy loam is the most susceptible soil structure to splash erosion, so it appeared about 52 percentages more splash erosion in the breakdown structure condition. Bulk density, aggregate stability and Ks were significantly deteriorated by aggregate breakdown in the soils. A significant relationship was found between the splash erosion variation and variation of Ks in the two soil structure conditions (R2=0.90, P<0.05). Splash erosion was largely increased in the soils with decreasing the Ks by aggregate breakdown. This study revealed that in the soils affected by aggregate breakdown, splash erosion is strongly increases due to decline in the soil’s saturated hydraulic conductivity.

Study of karstic rocks properties, understanding teh chemical and physical properties TEMPhas a special place in resent researches. By understanding of teh properties mentioned such as Bulk density, Porosity, coefficient of solubility, solubility rate … can be evaluated for karst development in teh soluble rocks. Teh purpose of dis study is teh assessment of seasonal variations of teh solute and solubility of karstic formations in Khorram Abad, Alashtar and Biran Shahr. To do so, circulation technique, as a commonly used method was applied to determine teh amount of solubility. Also, teh solute load was determined. Teh result showed dat teh maximum and minimum solubility (k) of Asmari-Shabazan and Omas formations can be 1.27*10-6 and 1.02*10-6 m s-1 respectively. Also result shown dat Khorramabad and Biranshahr watersheds TEMPhas a maximum and minimum solute load, respectively. In dis regard, annual solute load were estimated to be around 75.61 *103, 47.56 *103 and 44.49 *103 tons/year in Khorram Abad, Alashtar and Biran Shahr watersheds respectively.

This paper presents, a set of experiments was conducted in a Plexiglas flume setup to investigate the simultaneous use of pipe and blade in the scour control around a submerged pipe. A vertical cylindrical pipe with and without a blade placed below it was selected for the experiments. The experiments were carried out in two different sates: with blade and without blade the pipe. Moreover, they were performed for four different pipe diameters, flow intensities, and blades where clear water was also used. The results showed for all states that simultaneous installation of pipe and blade below it caused a substantial decrease in the scour length. In other words, applying the blade produced a decrease in the scour length below the pipe by %21. Furthermore, in all states, simultaneous use of pipe and blade engendered a more increased scour depth than the absence of the blade, by %22. Besides, maximum scour depth for simultaneous use of pipe and blade was obtained equal to %55 when the blade width, pipe diameter, and Froude number were set to 1.24, 4.8 cm, and 0.42, respectively.

The study area is located north of Urmia lake and Tasuj plain. The average height of 1700m and average rainfall in the area about 363mm. The average annual temperature 10/65°C. Investigations on the surface penetration of flood deposits are important for the implementation of artificial recharge aquifers. In this study, soil permeability changes from Plain to lake were measured using double cylinders. One of the objectives project is permeability monitoring in the plain geomorphology units. Quaternary deposits Were classified of three classes (Q1, Q2, Q3) with using wells log and geophysical sections showed, Q3 is the youngest deposition. The results showed that the amount of surface cumulative penetration and the rate of penetration of the base was decreasing from the plain to the lake. Plain deposits are mixed clay, sand and gravel. The texture analysis contains 13 percent clay, 18 percent silt and 69 percent sand. The highest rate of penetration of the base with 8.5cm/h corresponds to the north of the plain. The rate of base infiltration from the beginning of the plain to the lake has decreased from 1.3cm/h to about 0.22. The analysis in this unit contains 73 percent of sand in the upper plain and 46 percent on the margin of the lake.

Surface gravel cover is an important factor for contoroling of soil erosion in dry area specially in area that plant can not grow because of excessive dryness and salinity. The objective of this study was investigation effect of different surface gravel cover on runoff and sediment yeild. For this porpose, 36 field plots with 20 meter length and 0.5 meter width at 3 percent slope were constructed in research field of agriculturev faculty, Shahrekord university. Treatments were including four level gravel cover (0, 10, 20 and 30 percent) and three surface flow rate (2.5, 5 and 7.5 L min-1) at three replications that expriment was done in a factorial with randomized complete block design. The results showed that as increasing surface gravel cover decresed the runoff rate and sediment yield significanty (p<0.001) in comparision with control treatment as linear and exponential, respectively. Aso, statisticaly comparision of the effect different gravel cover on runoff and sediment indicated that the effective gravel cover on runoff and sediment was different with increasing surface flow rate, as suitable gravel cover for surface flow 2.5 and 5 L min-1 was 20 percent and for surface flow 7.5 L min-1 was 30 percent gravel cover.

Interrill erosion can change during rainfall due to change of soil conditions. This research was carried out to investigate the temporal variation of interrill erosion in different soils under different rainfall intensities. For this purpose, laboratory experiments were carried out in three soil textures consists under three simulated rainfalls under slope of 10 percent in three replications. In total, twenty seven experiments were stetted up according to completely randomized design in in soil erosion lab. The interrill erosion was measured using measurement of soil loss mass at 1 min intervals from beginning of surface runoff production. The results showed that there are significant differences between the rainfall intensities in the time threshold of surface runoff and interrill erosion and their rate (P< 0.001). Significant relationship was found between interrill erosion and rainfall intensity (R2= 0.93, P<0.01). Interrill erosion increased during rainfall with the same trend with surface runoff production from beginning runoff, but after reaching to the maximum value (at 45th minute. As a consequence this study revealed that temporal trend of interrill erosion in most times of rainfall from beginning runoff can controlled by surface runoff rate and in final times it value is limited by the existence of erodible particles.

Transferring mechanic of cohesive sediments are different from non-cohesive sediments. For determining the erosion rate of non-cohesive sediments, physical parameters such as average diameter and density are used, such as average diameter and density. Due to the nature of the cohesive sediments, their erosion rates are determined interrelated with the shear stress of the bed with fixed coefficients related to the characteristics of each sediment. In this study, experimental results on the cohesive sediments of the Loire estuary of France has been used. After validating the results in Mike software, experimental data were developed to study the erosion of sediment with more data and different hydraulic conditions. In the following, due to the number of various parameters affecting the sediment erosion phenomenon, a neural network was used to analyze the data. The parameters used in the model include flow components, sediment and fluid characteristics. Due to the better performance of the neural network, these data were used for dimensionless data. The correlation coefficient and mean absolute error of data in the neural network were 0.98 and 0.0036, respectively, which indicated the proper performance of the network. Finally, after performing the sensitivity analysis, the and  parameters were introduced as the most effective parameters for increasing and decreasing erosion rates, respectively.

Soil is very important for the production of crops and foodstuffs. One of the most important environmental crisesin the relationship with soil is the phenomenon of soil loss and therefore the soil conservation is very important. In conditions that, there is not the possibility of establishing vegetation, the use of soil conditioners can be useful in controlling soil loss. The present study was conducted with study objevtive of changing soil loss and sediment concentration using soluble montmorillonite nanocaly with rates of 3, 6 and 9 g m-2, and biochar with rate of 160 g m-2 on soil of lomay-sandy. The expriments evaluated under laboratory canditions using rainfall simulation with rainfall intensity of 40 mm h-1 in Tarbiat Modares University. The results showed that the soluble nanocaly with rate of 9 g m-2 and biochar had the more effects on the variations of soil loss. The soluble nanocaly reduced the surface soil loss, surface sediment concentration, subsurface soil loss and subsurface sediment concentration variables with rates of 89.17, 87.41, 13.64 and 87.31 percent, respectively. Also, biochar could decrese the surface soil loss, surface sediment concentration, subsurface soil loss and subsurface sediment concentration with rates of 85.27, 63.64, 45.20 and 92.88 percent, respectively.

In order to manage watersheds, especially in mountainous areas that are not adequately station  hydrological phenomena simulation is important. In this study, the SWAT model used to simulate hydrologic basin Eskandari. Calibration and validation of models for the periods 2006-1992 and 2009-2015, respectively, using the algorithm SUFI2 in software SWAT CUP was done. To evaluate the simulation results of the index R2, bR2, NS was used. In the calibration coefficients, R2, bR2 and NS, respectively, 0.76, 0.53 and 0.76 in the validation, 0.56, 0.29 and 0.52 was obtained. Sensitivity analysis showed that 23 parameters affecting runoff curve number was identified as the most important parameters and parameters constant groundwater discharge, Groundwater delay time and soil available water to more sensitive respectively. Indicators and charts obtained simulate monthly runoff rate, indicating that the calibration of the model has been more successful. The model has been able to determine the time of peak flow well, but peak flow estimates are higher than the actual values, which can be attributed to the distribution of rain gauge stations and the interpolation of rainfall.

In this study, the possibility of using a combination of gravel filters with plastic cover to increase water infiltration and soil moisture storage in rainwater catchment systems was investigated. For this purpose, five treatments (with three replications) including control treatment, vegetation removal with filter, vegetation removal without filter, semi-insulated system with filter, and semi-insulated system without filter were considered, and Apricot was planted in all treatments. Then, soil moisture storage was recorded by the soil moisture data recorder at two depths of 20 and 60 cm in each treatment. The data were analyzed using a completely randomized block design. The results showed that there was a significant difference between treatments. During the growing season, the highest soil moisture storage was related to the dry months of the year (June, July, August and September) and semi-insulated treatment with gravel filter. In other words, the moisture content of semi-insulated system with gravel filter was significantly higher than other treatments. The results of this study indicated that rainwater harvesting through semi-insulated surfaces and infiltrating it by gravel filter is a good way to increase soil moisture storage.

Increasing population and consequently demand for water needs, food supplies are among the limitations that the current world faces. The existence of such a process with limited natural resources needs to improve the optimal and continuous exploitation of available resources. Watershed management is one of the suitable ways to meet nutritional needs and prevent economic consequences. It is important to be aware of the effectiveness of any type of project, including water management, for project executives. The economic evaluation of these activities is essential in order to know the ratio of profit to project costs. To this end, we have investigated and evaluated the economics of multifunctional plots and flood control in Khuzestan province.