فصلنامه حفاظت منابع آب و خاک
سال هفتم شماره 2 (پیاپی 26، زمستان 1396)

Gully erosion in one of the different types of soil erosion by water that initiation and advancement of it can tend to the great changes on landscape and degrades the lands. The objective of the current study is to analyze the effects of soil-related factors on the occurrence of Gully erosion in the Age Imam watershed. This watershed, with an area of 5442.45 hectares, is located in the east of Golestan province, and experiences many substantial difficulties due to Gully erosion. In this study, ditches in the region were identified through field study. Then five ditches were selected and 10 soil samples from the within the ditch and 10 from outside the ditch were taken (a region in the adjacent area above the ditches), from two depths (0-30 cm, and 30-60 cm) and were subjected to laboratory analysis. The comparison of the averages of the two statistical populations was used to analyze the physical and chemical characteristics of soil taken from two depths, Results showed that significant differences existed (on a 5% level) among some soil characteristics between surface soil and the soil below that, as: Percentage of Silt (at both depths, taken from the ditch), percentage of saturation humidity (at both depths, taken from the ditch), electric conductivity (at the lower depth, taken from the ditch), neutralizing substances (at both depths, taken from outside the ditches), cation exchange percentage (lower depth, taken from outside the ditch), sodium absorption ratio (lower depth, taken from the ditches), and the percentage of exchange sodium (at the lower depth, taken from the ditches), had an effective role in Gully erosion, due to the higher amounts and statistical significances.

The main objective of this study was determination of the effects of water quality, installation depth and space of subsurface drip irrigation (SDI) laterals on soil nitrate under turfgrass culture at the experimental farm of the Shahrekord University, Shahrekord, Iran. Split Split Plot was employed as the experimental design with experimental arrangement of completely randomized block design including 16 treatments and three replications. Treatments included two types of water quality: fresh water (W) and treated wastewater (WW), two installation spacing of SDI laterals (45 and 60 cm) and four depths of placement of SDI dripper (15, 20, 25 and 30 cm). Soil samples were collected from two layers (0-30 and 30-60 cm) and analyzed for No3- at the end of the experiment. The ANOVA results show that interaction of irrigation water quality × lateral spacing × installation depth of SDI laterals was significant on No3- concentration in the layers. The results indicated that irrigation with the wastewater as compared to fresh water causes higher No3- concentration. The No3- concentration in the first and second layers increased by increasing lateral spacing. Also in the first layer, by increasing of lateral depth No3- concentration decreased at first, then increased, whereas in the second layer with increasing lateral depth, decreased.

One of the potential impacts of climate change is the change on extreme rainfalls frequency and magnitude. For active adaptation strategy, it is required to assess the impacts of climate change on heavy rainfalls. Many downscaling methods have been developed, however most of them are not adequate for assessing climate change impact on extreme rainfalls. Among them, the NSRP rainfall model, which is generally ignored in previous studies, have considerable capabilities for climate change impact assessment on extreme rainfalls. In this paper, capability of the NSRP for daily rainfall series generation and climate change impact assessment on extreme rainfalls in Kermanshah is evaluated. The results indicated that NSRP can realistically simulate daily rainfall series containing extreme rainfalls; and can be used for climate change impact assessment on extreme rainfalls. Using the model, 100 series of daily rainfall of length 30 years were generated under each of the future A2, B1 and A1B scenarios from the CGCM3 model. Based on the results, magnitude of annual maximum rainfall of durations of one to five days will increase in future. Seasonal cycles of monthly means and accordance of extreme rainfalls will change. Long-term average of rainfall will decrease while extreme rainfall magnitude will increase. So it can be concluded that change in rainfall averages in monthly or yearly timescales cannot provide credit information about change in rainfall extremes. Respect to the results, for the future plans which are impressible of heavy rainfalls, the climate change impacts on heavy rainfalls should be considered.

Clogging of emitters is one of the main problems in subsurface drip irrigation. The objective of this study was investigation of effect of Geocomposite on wetting pattern in subsurface irrigation system. This research was conducted in lysimeters located at Shahrekord University research field. The study was conducted as a factorial experiment based on a completely randomized design with 10 treatments and three replications of three factors. The first factor of experiment was geocomposite shape with the same area on two levels (shape square with dimensions (4 × 4) square centimeters and rectangular with dimensions (2 × 8) square centimeters), the second factor was combination of geocomposite material on two levels (two layers of geotextile on both sides of Geonet and The second level, a layer of geomembrane and a layer of geotextile on both sides of geonet), the third factor of placement in the soil at on two position (horizontal and vertical) and emitter with envelopment (in two position horizontal and vertical) were used as control. The ground wet and wet the maximum of soil depth profiles were measured. The results was showed that geocomposite of shape square with dimensions (4 × 4) square centimeters for a layer of geomembrane and a layer of geotextile on both sides and how to align horizontally in the soil wet ground level by lowering the 21.55 percent and increased 17.1 percent wet the soil deep profile compared to control (emitter with envelopment horizontally in the soil) is the most effective and best conditions on wetting profiles.

Knowledge of the change of soil properties in each event during sequence rainfalls is very important for recognition the critical period of that the soil would be susceptible to erosion processes is vital. This study was conducted to investigate the effect of sequence rainfalls on the changes of soil properties, runoff and soil loss in eighteen different soils with the same aggregate size (from 4 to 6 mm) using the simulated rainfalls. The experiments were performed at small erosion plots with 80 cm long and 60 cm wide under 9% slope steepness during seven sequence rainstorms with 80 mm h-1 in intensity for 30 min and 5-day interval. The results indicated that significant differences were among the soils in bulk density, water retention, runoff and soil loss (p

Assessment of the economic, social and environmental effects of water projects is required to achieve sustainable development. Therefore, the development of a model that can simulate the different dimensions of water resource development projects and interactions between different methods of operation, can be helpful to managers and decision makers in the water sector. The main objective of present study was development of water integrated model (IWMsim) to evaluate different management policies and contribute to improve decision-making in large scale systems, using system dynamics modeling approach. The developed model is capable of simulating the impact of various effective factors in the water utilization on economic and environmental sustainability. In this investigation, to study interactions between environmental and economic effects of water resources development projects, two macro indicators of national costs and national revenue were developed. The developed model was calibrated and validated using long-term climatological, hydrological, agricultural and environmental data of Varamin case study. The developed system dynamics model evaluation showed that the model was able to simulate key variables such as relative crop yield (RMSE=14.2%, ME=20% and R2=0.92), groundwater levels (RMSE=0.37m, R2=0.92 and ME=0.45m) and groundwater salinity (RMSE=57 μS/cm, R2=0.79 and ME=148μS/cm) with reasonable accuracy.

Soil erosion is one of the environmental problems which can be considered as a threat for natural resources, agriculture and the environment. Thus, determining the temporal and spatial extent of soil erosion is an effective way to management of soil erosion and sediment control through watershed management. Todays, the misuse of lands and converting forests and grasslands into agricultural land, overgrazing, tillage on steep slopes leads to increase soil erosion and sediment yield. Therefore, defining the contribution of different land uses has a significant role in preventing erosion and prioritization of land management activities The objective of this study is to estimate and compare the rate of soil erosion in in different land uses on the current status and prediction of erosion in Two main scenarios and each mail scenario has three sub-scenarios (25, 50 and 75 percent of area) at KalaybarChay watershed with an area of 452 km2 in the province of East Azerbaijan using USLE model. To predict the foregoing, land use map was prepared Using Universal Soil Loss Equation (USLE), Geographic Information Systems (GIS) and TM Sensor of satellite image Landsat5 on the ENVI 4.3 software. After the preparation of USLE model factors includes R, K, LS, C and P model was performed and mean value of each factor was calculated and soil erosion map was prepared by multiplying the average values. Results showed that the average amount of soil erosion rate is 12.3 (ton/ha/yr). Also the highest and least rate of erosion is assigned on conversion of rangeland to dry farming scenario; and the rangeland to tree dryland scenario equal to 15.43 and 9.03 (ton/ha/yr), respectively.

The amount of earth's surface net radiation directly depend on surface temperature, land use, soil and topography. In the present study, Landsat8 satellite imagery is used to estimate net radiation flux. Then, with using systematic sampling at 500 m intervals, the value of each surface layer for example The LST, NDVI, altitude, slope, aspect, soil type and land use at the sample points for analysis were extracted. Mono-Window algorithm has been used to extract LST. The results showed that there is a direct correlation between the increase in altitude and NDVI with net radiation flux. The linear correlation coefficients were also 0.68 and 0.19 respectively. There is also an inverse relationship with the linear correlation coefficient of 0.74 between net radiation flux and LST. And from survey the rate of net radiation flux in different geographical directions in the case study it was found that in the northwest with 637(w/m2) the highest net radiation flux and eastern orientation with 582.7 (w/m2) had the lowest rate of net radiation flux. The net radiation flux in these directions with the slope rate had a direct correlation with correlation coefficient 0.54. In addition, the rate of net radiation flux at water levels such as lake and reservoir dam with 817 (w/m2) has the highest rate of net radiation flux and saline lands with 509 (w/m2) of minimum net radiation flux. There is the highest and lowest rate of net radiation flux in inceptisols and badland areas, respectively.

Reducing irrigation losses due to surface evaporation by using water repellent soil surface can help in maintaining water in the current situation that our country is suffering from water deficit. In this research, the effect of creating a water-repellent layer on the soil surface in the form of anti-evaporation mulch layer was evaluated on three soil textures (sandy loam, loam and clay loam). For this purpose, soils artificially hydrophobized by Stearic acid at four different concentrations and water drop penetration time method to obtain four different degrees of water repellency. And its effect on the rate of surface evaporation from the small lysimeters (with height and diameter 30 cm) located at the ground was investigated in the form of water-repellent layer with three-centimeter thickness. All experiments were conducted at a field in Marand area (latitude: 38° 25' 16.87'' N and longitude: 45° 47' 30.30'' E) in summer 2016. The experiments were performed in a completely randomized design with five treatments degree of water repellency and three replications. After analysis by SPSS and Duncan test (5% level), the average comparison carried out between evaporation in the different water repellency degrees for three soils. The results showed that the surface the water-repellent layer significantly decreased the amount of evaporation in the mentioned three soils. Also, the surface evaporation reduction rate was increased with increasing the water repellency degree. The maximum reduction of evaporation with increasing in the water repellency degree compared to the control treatment (zero degrees of water repellency) was 78.3 %, 42.2 % and 30.1 % in the sandy loam, loam and clay loam soil, respectively.