مجله مهندسی و مدیریت آبخیز
سال پنجم شماره 4 (زمستان 1392)

Carbon storage is one of the assessment criteria of ecosystem sustainability, so land improvement and reclamation can be followed by investigating the effective managerial factors. This study was conducted to investigate the management scenarios and their effects on carbon storage in Sar Firoozabad watershed, Kermanshah province, Iran. Mapping units were prepared with combination of slope and aspect layers. The common management systems in the form of scenarios of residue management, crop rotation, and tillage were investigated and relevant indices were quantified. In the next step, the watershed area was separated into homogeneous zones and soil sampling in the units, was performed using a randomized systematic method. After transporting the samples to laboratory, soil organic carbon storage was calculated by determining their bulk density, texture, and organic carbon. Results of multivariate analysis showed that seven variables of tillage index, cereal sequence, straw burning, manure application, rotation systems, winter fallow and plow direction predict 52 percent of the soil carbon storage variability with 0.724 correlation coefficient and 0.46 modeling efficiency, using the cluster analysis,. In general, it can be concluded that cluster analysis is recommended for investigating carbon storage in soils and rotation and tillage systems are significant examples of soil management components that are certainly very important in terms of carbon storage.

In recent years, activities on trout fish farming is developed significantly in Ortakand River. Fish production may have huge impact on the river ecosystem if an environmental rule is neglected. This research was carried out in Ortakand River in Kalat city in Khorasan Razavi with the aim of investigation of fish production projects effluent effect on the river water quality. Two fish farms and seven stations were selected and during one year in each season, water samples were collected. The samples were analyzed in the laboratory for determining some physic-chemical and biological parameters of water samples. The results showed that the average of these parameters were within a range between 13.3-15 °C of temperature, 7.9-8.1 of pH, 354-732 mmhos/cm of EC, 8.4-9.6 mg/L of DO, 1-3.7 and 2.5-13.9 mg/L of BOD5 and COD, respectively. The results showed that BOD5 and COD concentration had a significant increasing toward upstream (p<0.01), spatially. Meanwhile, amount of DO showed a significant decrease (p<0.01), temporaly. This research revealed that changes in concentration of BOD5, COD and DO were dominantly due to fluctuations of environmental conditions and activity rates of the farms. Although, the amount of COD and BOD5 in fish farms effluent in current situation are less than the standard environmental amount, but environmental impacts could be increased by activities of new fish farms,.

In hydrologic models, a sensitivity analysis could be performed to identify important parameters and reduce their numbers in an easier and faster calibration process. This study describes an application of a useful method for sensitivity analysis of Soil and Water Assessment Tool (SWAT) model. This method determines parameters with the greatest impact on model results and gives a sensitivity ratio and an input-output relationship graph for each parameter. In this study, the SWAT model is used for a monthly rainfall-runoff simulation in Ghareh Su watershed with an area of 4062 km2. Calibration of the model were performed manually, using the recorded weather data from 2003 to 2008 and the validation was performed, using the recorded data from 2009 and 2010. The sensitivity analysis has been performed using One Factor At a Time (OAT) method to evaluate and demonstrate the influences of the model parameters on four major components of water balance, including surface runoff, lateral flow, groundwater and evapotranspiration. The results showed that the parameters of initial SCS runoff curve number for moisture condition Π (CN2), soil available water capacity (SOL_AWC), soil bulk density (SOL_BD), saturated hydraulic conductivity (SOL_K), maximum canopy storage (CANMX), soil evaporation compensation factor (ESCO) and minimum melt rate for snow during the year (SMFMN) have the greatest influence on remarked parts of water balance.

Eroded soil particles within watershed areas are transported in three shape of dissolved, suspended and bed loads by river water discharge. Knowing the amount of suspended and bed loads are necessary in estimating sediment yield of watersheds. Usually, suspended load is measured daily in hydrometric stations, while this does not happen for bed load. Although, there are many differences between geology formations, rainfall intensities and water discharges of watersheds, the amount of bed loads are considered as a constant unique coefficient of suspended load. So, there would be highly errors in watersheds’ sediment load estimates. In this research, after collecting bed and suspended load data of three hydrometric stations of Badlan on Alandchay, Pol Yazdakan on Ghotourchay and Mazraeh on Baroonchay Rivers in Western Azerbaijan, the data were analyzed and best relations were fitted between bed load and suspended loads. According to statistical analysis all data had high coefficient of correlation at the level of 99 percent and the best equations were chosen accordingly. The ratio of bed to suspended load in Yazdakan, Badlan and Mazraeh stations were 79, 49 and 13 percent, respectively. This ratio was 47 percent for all three stations.

The fire is one of the factors that have effect on the natural cycle of ecosystem. This project was established to deal with the effect of the fire on quality features of habitat in the research site of rangelands plants of Zagheh Gorge.It was occur at Khoramabad northeast 35 Km with 33° 29" N, and 48° 42" E, being at 1960 meters above the sea level. This study was formed by travel method, We Used Transects 200 m and plots 1 m that chose vegetation type and plants morphology Both Control area and treatment in Comparison Conclusion show that there are difference significant between canopy cover in the control area, and the fire (p<0.01). Also, after two years, there are not difference significant between organic matter, litter, pebble and rock (p<0.01). But there are significant difference between Soil Conservation level inside and outside of the fire area (p<0.01).This Statistics show that there are difference between the plant production of Class I and III in the control area and the fire with 30.32 and 5.54 in control area and 24.84 and 2.72 gr/m2 in the fire area (p<0.01). The Control area with 69.32 Percent of Canopy Cover is better than the fire area with 51.6(p<0.01) so, high percent of Canopy cover in the Control treatment caused heap of crucibles and numerous branches in this area. Forbs plants, decreased from 46.8 % in the control Canopy Cover area to 35.6 % in the fire area; whereas, grasses increased from 53.2 percent in the control area to 64.4 percent in the fire area. So, the fire is effective on increase of grasses and decrease of forbs.

Investigating local scour phenomena due to jet flow on downstream of hydraulic structure is an important and necessary issue. In this article, the results of a laboratory study about the impact of tail water depth on local scour below of jet flow are provided. Circular, square and rhombus sections with a water jet from a hole, and, with a discharge of 2.46 to 4.8 liters per second, on a medium material bed of d50 of three mm made of sand, with tail water depth ranged from 10 to 24.8 cm, for 60 minutes, was simulated. The dimensions of scour holes were measured and analyzed. Results demonstrated that the maximum scour depth, with increased tail water depth to a certain extent, increased, and then, tail water will be reduced with more depth. It also became clear that the dimensions of scour holes with the following parameters of, and their relation with power. Finally, the dimensional relationships for the estimation of scour depth of discharge and the tail water variety have been proposed.

The wind erosion is one of the most striking examples and the most devastating flow identifiers of desertification among the difficult obstacle of development in many countries. The rate of affected area by wind erosion in Iran is more than six times the global average. So, the purpose of this study is climatic zonation in west and south-west of Iran with emphasis on wind. In this study, 77 annually and monthly climate variables were selected within and adjacent areas of studied location from weather stations of the Weather Organization of Iran. To reduce the number of variables and determining effective factors, factor analysis with varimax relation was used, and then the spatial distribution of the factor score area plotted in Surfer Ver. 10. The result of the factor analysis identified six factors of heating temperature-precipitation, wind mean speed, prevailing wind speed, relative humidity, the fastest wind speed and solar radiation. These factors included 24.01, 19.78, 14.65, 12.66, 9.85 and 3.09 percent and in total 84 percent of the data variance. In this region seven climate zones were determined with Ward method that include moderate Mediterranean region with relatively fast winds, hot and semi-arid region with fast winds, hot and relatively arid region with calm air, extreme hot, arid and windy with fast winds, extremely hot, arid and windy, relatively hot and semi-arid with calm air, extremely hot and arid with relatively fast winds that extend on 17, 10.5, 15.1, 22.1, 7.9, 9.9 and 17.4 percent of the study area, respectively.

Study of soil erosion without simplification of experimental conditions is difficult and sometimes impossible. Soil clay content has significant relationships with soil aggregates stability and infiltration, that these relationships in various clay contents may be positive or negative. Many properties of soil in successive rainfalls can be changed and also affect on runoff and sediment production. Hence, this study attempted to investigate the effect of soil clay content on runoff and sediment production during successive rainfalls under rainfall simulator using erosion plots and eliminates the effects of the overlapping factors. To achieve these aims, 1.5 m2 erosion plots containing soil without clay, combined with 0, 10, 20, 30, 40 and 50 percent of clay soil in three replications, respectively (totally 18 plots) and then were subjected to two successive runs under 70 mmh-1 rainfall intensity for 30 minutes and 24-hours intervals. Sampling and measuring the volume of runoff during rainfall was done each 2.5 minutes. Based on observed data, the amounts of observed sediment in the second runs were 1.5 to 2 times higher than those found in first runs (with a total average of 9/2 and 15/0 grams per liter, respectively for first and second runs), but amounts of runoff in 0 and 10 percent of clay soil mixtures were higher in first runs (2613 and 2045 volumes in milliliters, respectively), whereas for the other mixtures, runoff volume in second runs were higher (2694, 2677, 2315 and 2752 volumes in milliliters for 20, 30, 40 and 50 percent of clay mixtures, respectively). Finally, the statistical analysis showed that in both successive runs in all mentioned soils containing various clay soil mixtures, runoff and sediment values were different significantly (p<0.01). The results showed that there are significant temporal variations within soil properties and also soil clay content has great effects on the quality and quantity of soil erosion process.