Soil organic carbon (SOC) is a principal component in soil quality assessment. Knowledge of SOC AND total nitrogen (TN) stocks are important keys to understAND the role of SOC in the global carbon cycle AND, as a result, in the mitigation of global greenhouse effects. SOC AND TN stocks are functions of the SOC concentration AND the bulk density of the soil that are prone to changes, influenced by lAND use changes, AND soil erosion processes. This study has evaluated SOC AND TN stock under different lAND use types AND soil erosion types at catchment scale. SOC AND TN stocks were measured in 112 different sampling sites of four main groups of lAND use/soil erosion: rangelAND/surface erosion, orchard/surface erosion, dry-farming lAND/surface erosion, AND rangelAND/strea mbank erosion at HIV AND ZIDASHT CATCHMENTS, Iran. The results showed that SOC AND TN stock under all lAND use AND erosion groups was significantly different. SOC AND TN stock was greatest in the orchard lAND use AND the total SOC stock for the 20 cm soil layer under different lAND uses AND erosion types varied for HIV in order of orchard/surface erosion (46), rangelAND/surface erosion (31), AND rangelAND/stream bank erosion Mg/ha (p<0.005). For ZIDASHT, the variance was, in order: orchard/surface erosion (43), dry-farming lAND/surface erosion (23), rangelAND/surface erosion (23), AND rangelAND/streambank erosion 22 Ton/Hector (p<0.005). The TN stock has the same trend in all studied lAND use AND erosional groups. Therefore it was concluded that rangelANDs were affected by erosion, with a subsequent decreasein productivity level. These results can be useful as a scientific basis for selecting the proper soil erosion control methods as a simple, low-cost approach to mitigate SOC AND TN loss.

This study was done in order to estimate the erosion rate in the ZIDASHT – FashANDak watershed (of Talaghan rood sub – watershed) with area over 26/737 km s, AND there is no gravimetric station: also, The two models are used, named, EPM AND STEHLIK. For doing this work, first, the homogeneous units were provided, AND by overlaying the maps of the litho logy, slope, geomorphology facies AND combining them, 18 units were made which are the base for estimating AND evaluating the erosion rate.The required data are provided by study the watershed management of the watershed which has been done before, AND by take the areal photography's AND the field studies. For make digit AND combining AND providing the maps, Arc Gis soft ware is used. By using two models EPM AND STEHLIK, was estimated the rate of the erosion at the watershed level, AND the results compared. These results of the two models aren’t consistent. It seems that the obtained results of the model STEHLIK aren’t reliable in the target area.

In order to manage AND implement conservational activities in watershed successfully, it is necessary to determine the sediment sources. In recent years, sediment fingerpering techniques have been used for estimating sediment sources contribution. With respect to small source samples, having many answer as a result of over fitting, there are some uncertainties in estimated sources contribution. In this study, the uncertainty associated with the multivariate mixing model was estimated using Monte Carlo simulation AND GLUE approach in ZIDASHT-FashANDak sub- watershed. The sediment AND source samples were taken in the study area AND then, 54 geochemistry AND three organic characteristics were measured.17 elements were also selected as optimum tracer composition using Kruskal–Wallis H-test AND multivariate discriminate analysis. Meanwhile, sources contribution were estimated using multivariate mixing models. Results showed higher contribution of sub-surface sources than the surface resources. Also, the distance between lower AND upper limits for all sources AND resolutely uncertainty bANDs were high.

Prediction equations for runoff depth from rainfall in small mountainous CATCHMENTS located in the north AND south face of the Alborz chain have been derived in this research. For this purpose two CATCHMENTS were selected so as having full AND reliable rainfall runoff data AND suitable regionally representative distribution over the studying area. The prediction equations have been obtained based on the rainfall depth, antecedent precipitation index AND base flow. Statistical methods were used to obtain the multiple linear regression equations, correlation coefficients AND the stANDard error for each of the techniques used for the watersheds. All peak events greater than 0.7 cms for Amameh representative catchment AND also all peak events greater than 1.0 cms for Kasilian representative catchment were considered for analysis AND deriving final equations. The stANDard error of the optimum prediction equations for runoff was 0.248 AND 0.205 mm for Amameh AND Kasilian representative CATCHMENTS, respectively. Also, the multiple correlation coefficient (R) was 0.842 AND 0.857, respectively. Finally, the results of the developed regression equations were extended to the neighboring CATCHMENTS of similar hydrological characteristics.

To day, the progressive of technology AND access able various software AND also to recognize in significant parameters of soil erosion AND sediment yield is provided in possibility of using different mathematical models. The models, demonstrate to create of hydrologicalevents through mathematical relationships between catchment's parameters. Whereas, the results of using some of models has been satisfied for this purpose. Therefore, using of these models is increased in the most watersheds through more than 40 models. Other side, as the mountainous CATCHMENTS is very complicated, so simulation models are suitable for estimation of erosion AND sediment yield. One of the reliable models for above purpose, is known SWAT model. Where is applied in Amameh CATCHMENTS. SWAT model has been modified. At present study, the SWAT model has calibrated by monthly AND annually observed data, which is recorded in Amameh stations with monthly AND daily estimated data, which are obtained by model. In this study catchment's parameters are used as physical parameters for SWAT model. After calibration process, the model has been evaluated by some of sensitivity testing models such as, Nash - Sutcliff model AND P-bias model. This process is shown which some of physical parameters are sensitive among the another parameters of the SWAT model such as, K (Soil erodibility parameters) AND n (Roughness coefficient parameters). In final, the determine coefficient of observed value AND estimated value is obtained, R2=0.74. This result can be obtained for unpaged CATCHMENTS at same hydrological condition.

Prediction of runoff is very important in ungauged CATCHMENTS to design hydraulic structures. Estimation of the parameters of the rainfall-runoff in many cases is not simple. Therefore, hydrologists usually attempt to develop AND apply simple AND even accurate enough methods to model runoff in such catchment. In this study, the Nash storage coefficient (k) was defined as a function of time of concentration by combining the Nash AND Clark models AND assuming the number of reservoir be 5. A non-dimensional equation to obtain synthetic unit hydrograph of CATCHMENTS was presented based on the Nash instantaneous unit hydrograph. In the new equation flow discharge is a function of time AND time of concentration. The model was used to simulate runoff in Kasilain catchment, North of Iran, AND Ajay, India. The results showed that the efficiency coefficient for three of four events is higher than 0. 82 for Kasilian AND for four events varied from 0. 78 to 0. 89 for Ajay catchment. The error value for peak flow prediction was from 5. 3 to 9. 7 for the Kasilian catchment. The mean of error value for four events was 7. 8 for Ajay. Generally, the accuracy of the prediction of the new model was shown to be satisfactory in the two CATCHMENTS.

Large hydraulic structures AND the consequent dangers originated from the break of such structures make the designers apply extreme conditions in their designs. Probable maximum flood (PMF) is one of the design criterions that are widely used in this regard. To calculate PMF, huge data AND information such as probable maximum precipitation (PMP), storm duration, rainfall temporal pattern AND antecedent soil moisture condition are required. This study aims at calculating PMF, considering the conditions governing ungauged CATCHMENTS. For this purpose a combination of effective factors affecting PMF, especifically rainfall temporal pattern accompanied with different rainfall systems direction AND antecedent soil conditions have been evaluated for the rivers located in the east of Hormozgan Province. The results show that combining the observed average of temporal patterns AND rANDom block procedure is a relevant approach for the study area.Also the results show sensitivity of PMF to antecedent soil moisture AND not significant response of PMF to the rainfall systems direction.

The main aim of the current paper is to discuss the important effective variables, particularly synoptic patterns, in creating flood in Masoule basin using flood discharge data in Komadoul station during 20 year period (1984-2003). To achieve the aim, daily average AND instantaneous maximum of discharge in mentioned station were used. Data accuracy was done using the data for Chomesghal station AND technical report from the unexpected events section in the area. In the study period, among the 181 identified flash flood events, 61 events were chosen between years 1996-2003. Then, based on the most effective creator parameters, they were classified into two main groups; events which were due to atmospheric instability AND synoptic patterns AND those occurred as a result of combination rainfall AND short length of main channel. About 51% AND 49% of destructive floods in the study area belong to the first AND second groups, respectively. Using the synoptic maps of surface level, 700 AND 500 HP, AND based on the position of cyclone AND anticyclone on basin AND their movement over the moisture resources, three specified patterns was distinguished. The cyclonic systems come from Mediterranean Sea AND Black Sea, while the anti-cyclonic models mainly come from Caspian Sea AND rarely from Black Sea. The result of the research also showed that mentioned systems, based on their characteristics or establishment period on the basin, have been made flood with different magnitude. Among the sampled events, 34, 13, AND 14 events were adjusted with one, two AND three consecutive day rainfall, respectively. From the temporal point of view, distribution of flood shown that most of them were occurred between Sept. AND Oct., late winter AND early spring.

This papare is resaults of analysing the data which reported from a harvesting project. The site for collecting data is buildings' roofs of Azad Islamic University of Mashhad. A rain gauge AND a small reservoir (capacity is 4 cubic meters) were set at this site. Then the amount of precipitation AND its runoff were measured during two years (from 1386, Dey, 23 to 1388, Tir, 3).The sample size is 35 observations. The relationship between runoff AND rainfall was estimated by regression methods. The best model was chosen by analyzing residuals AND testing the Models. Then the runoff were estimated through this model. The 55-year annual rainfalls of Mashhad synoptic station (1951-2005) were selected AND frequency analysis was done on them. Then the roofs' runoff was estimated by this frequency analysis for both wet AND dry years. The total area of roofs AND their mean annual runoff in ordered are 18680 square meters AND 8428 cubic meters.

Soil is one of the most vital natural resources in any country. Nowadays, lANDs are rarely found worldwide without having severe erosion problem. LANDslide is one of the soil erosion processes in which a huge volume of soil is washed away. SHETRAN Model was used in this study to assess the lANDslides being occurred in ZIDASHT catchment, Taleghan. At the first stage, sediment-water mixed samples were gathered at the outlet of the Catchment for calibration purpose in 2011. To run the model, regions undergoing lANDslide were identified using GISLIP sub-model. Secondly, after hydrological AND sediment production simulations in a sub-model of SHETRAN for the region, calibration was made for spring season. After the calibration process, the model was run again, this time for the regions having lANDslide (for 418 spots), AND in regions where lANDslide sediments do not pour into water courses, these regions were omitted, the final amount of sediment was calculated using SHETRAN sub-model AND the results were compared with the previous studies. The results show that 19. 75% of the total sediment belongs to lANDslides. With regard to the current sediment quantity of about 111248 kg, total sediment in lANDslides was estimated to be around 120668kg.