نشریه پژوهش های آبخیزداری
پیاپی 92 (پاییز 1390)

Sediment control at 90º diversion using compound submerged vanes is experimentally studied. The compound submerged vanes are considered from joint of bottom and surface vanes as a new idea in this study. A total of 52 experiments are carried out in a flume with 17m length، 100 cm width and 90 0 diversion angle with 2. 53m length، 40 cm width in the hydraulic laboratory using a non-tilting flume. Sediment control at intake entrance is examined with different flow discharges and intake ratios using bottom submerged vanes in parallel arrangement and compound submerged vanes with three surface vane heights. Compound submerged vanes with CH=0. 5 (surface vane height parameter) among different cases of compound submerged vanes، has shown the best performance in sediment control at lateral intake. The case with CH=0. 5 in 8 percent intake ratio، eliminates sediment entrance into intake and also in 16 percent intake ratio shows the best performance among other cases. Compound submerged vanes can decrease sediment entrance to intake as parallel submerged vanes therefore it shows the feasibility of some promises for the further developments.

Water infiltration rate is one of the most important parameters of soils and it is a function of the physical and chemical soil characteristics. Also، the infiltration rate is a basic input data in irrigation and drainage projects. Wrong estimation of the infiltration values can lead to wasting the national investments. Although، the infiltration phenomenon has been focused by many researchers، recently، but it is necessary to investigate the importance of the best fitting equations between the infiltration rate and the physical or chemical soil characteristics. The current research، which is based on a case study، aims to determine the relationship between final infiltration rate and the physical or chemical soil characteristics and the emphasis has been to work out the accuracy criteria of the calculation by comparing different correlation coefficients. The main recorded physical parameters were; soil texture، porosity، color and the specific gravity of the soils. Also، some chemical factors such as; pH، EC، Na، Ca+Mg and the amount of organic materials were measured and recorded. Kostiakov- Lewis method was used to measure the infiltration rates in three repetitions. General basic statistical methods were used to analyze data and find the relationships between the final infiltration rate data and either physical or chemical characteristics of the soils. The regression functions، correlation coefficients and the best fitting equations were calculated. According to the results، the biggest rate of the correlation coefficient (r) belongs to the power regression، which shows the relationship between the final infiltration rate and the EC of the soils. However، there was not recorded very strong correlation coefficient in the results. The importance of the best fitting equations has been demonstrated.

The study of anion transport toward groundwater is very important since these ions are not adsorbed to the soil particles and leach easily from the soil profile. Bromide is one of the anions which has been considered as a tracer for water and solute transport through the soil. This study was conducted to simulate bromide transport in disturbed soil columns (10 cm in diameter and 25 cm in height) using HYDRUS-1D software. Treatments included soil texture (sandy loam and loamy sand) and rate of bromide application (10، 20 and 30 mg kg-1) with six replications. Bromide was applied in the form of potassium bromide. Leaching of Bromide was conducted for 4 pore volume and its concentration was measured in drained water. Bromide transport was slower in sandy loam soil compared to loamy sand. Sensitivity analysis showed that Dw (ion diffusion coefficient in water) and θs (saturated water content) had the least and the greatest impact on model predictions، respectively. Bromide concentrations in discharge were well predicted using HYDRUS-1D model (R2>90%). Non-equilibrium convection–dispersion equation (NECDE) in HYDRUS-1D produced much reasonable calibration and test results than CDE equation.

Vegetation cover establishment in mountains is the large part of arid lands vegetation. Rock slope and outcrops mostly landscapes there are in these areas. In this study on granitic and andesitic lithologies we surveyed relationship between vegetation cover and lithology. We measured weathering degree، number of crevice in regard to different dimensions in different scales and amount of vegetation in different slope degrees and aspects، also measured amount of EC، pH، organic materials، CaSo4، CaCo3، soil texture، N، P، K، Ca، Mg in soil. the results shows no significant different between vegetation of granitic and andesitic lithology، but there are significant relationship in 1 level percent between vegetation on different lithology and number of large crevice wide، medium crevice wide، large crevice depth and large crevice length. It was concluded that the crevice dimensions could be role in vegetation cover establishment on outcrops in arid lands.

Different methods can be used for estimation of floods in regions facing lack of data out of which the methods leading hydrographs are able to present accurate details on floods. Information and data on rainfall and runoff are required to develop watershed unit hydrograph. Providing the unit hydrograph (UH) for all storms of a watershed is not simple and it demands plenty of time، expenses and facilities. Because of various limitations like insufficient hydrometery stations and difficulties in collecting hydrometrical data، application of the simple hydrological models based on easily accessible data seems logical and useful in order to estimate the flood hydrograph. This study was therefore aimed to provide synthetic 2h-UH using rainfall data in Kasilian watershed. Towards this attempt، 15، 19 and 12 hyetograph، UH and time relating characteristics were respectively considered for 23 storms. The relationship was investigated by using bivariate and multivariate regressions. Results showed 2h-UH could be reproduced based on hyetograph components. The results also verified the effective roles of time of occurrence of I30 and rainfall duration in simulating 2h-UH of the study watershed.

The proper prediction of temporal and spatial variation of sediment yield from the watershed is a need for sediment control، river engineering and soil and water conservation studies. The present study was therefore planned to simulate the sedimentgraphs for Chehelgazi watershed in Gheshlagh dam upstream in Kurdistan Province، Iran، using Time-Area Model. Towards this attempt، the study area was divided to 7 time-area segments based on the time of concentration. The soil erosion in each segment was estimated using USLE model and then routed to the main outlet using sediment delivery ratio as a result of division the slope of downstream isochrones by adjacent upstream one. The temporal variation of sediment was ultimately predicted with the help of lag time of sediment arrival to the outlet and the concept of superposition for 11 storm events occurred during winter 2006 and spring 2007. The comparison between estimated sedimentgraphs with corresponding observed ones verified the weak performance of the model in simulation of sedimentgraphs under consideration. The results also verified the calibration necessity of the model to achieve appropriate estimation for important components of the sedimentgraphs. The results of the calibration finally proved the considerable capability of the model in predicting of total volume of sediment yield with respective estimation and verification errors of 29. 05 and 38. 40%.

Artemisia sieberi a permanent wooden plant expands in arid margins. It is a resistance plant to aridity in dry land and desert margins، which plays an important role in preservation and keeping soil. The aim of this research was assessing effect of drought stress on germination behavior of Artemisia sieberi. To pass the dormant period، seeds were pre-chilled for 9 days at zero to 50 C. Germination in a petri dish with two experiments under the effects of A: drought stress treatment carried out at drought levels of zero (Control)، -2، -4 and -6 Bars using PEG solution and B: a 12-hour alternate light and dark and 24 hours dark treatments were tested in a complete randomized factorial design، was used to analyze results SAS statistical software. Results indicated that an increase of drought level leads to a decrease in the percentage and rate of germination، plumule length، and allometry factor priority 45 and 25 %، 0. 6 Cm and 0. 13 toward cotrol. But radicle length than the other traits measured by less sensitive to drought stress had a significant level is 5 percent، So that with increasing stress up to -6 bars radicle length increases and then decreases.

The main problem of travelling gun sprinkler is creating seal and destruction of soil surface. Therefore، effect of irrigation by travelling gun sprinkler on physical characters، infiltration and erosion was investigated under bare soil conditions in Karkaj Research Station، Tabriz Univ.، Iran. Factorial experiment based on randomized complete design (RCD) with two units of travelling gun sprinklers (model DT -280-85، Bauer Co.، Austria and model TSD -300-85، Azarbaidjan Devl. Ind. Co.، Iran) and three various combinations of operational pressures and travelling speeds (7-26، 8-28 and 9-28 bars and meters per hours) with 3 of replication was done. Experimental data were analyzed. Results were showed that irrigation with gun sprinkler increased soil bulk density، but the effect of different treatments on bulk density were not significant at 5% level. Effects of irrigation treatment on means of crust thickness were significant at 1% level. The highest thickness was occurred at 7 bar pressure and 26 m/hr speed by Iranian sprinkler and the least occurred at 9 bar pressure and 28 m/hr speed by Austrian sprinkler. Means of final infiltration rates were significant at 1% level with different factors such as kinds of sprinklers، levels of pressure and speed irrigation. Maximum and minimum average of final infiltration rates، resulted by Austrian sprinkler with 9 bar pressure and 28 m/hr speed and Iranian sprinkler with 7 bar pressure and 26 m/hr speed، respectively.

The temporal and spatial inventory of snow cover area and snow equivalent is one of the important challenges in watershed management. The present research was carried out for comparison of snow cover area in NOAA satellite and MODIS images in the watershed area of Taleghan. For this reason، 14 NOAA satellite and MODIS contemporary images have obtained from Iranian space agency for 2003، 2004، 2005 and 2006 years. Snow cover area (SCA) was extracted from all images. Also، the NOAA and MODIS images were comprised together. The comparison of NOAA and MODIS images revealed that the accuracy average of SCA estimation error was 57. 97 percent ranging from 3. 87% to 267. 42%. Overlap of two images is good regarding to SCA، so that can be acknowledged that the overlap of two images is 100%.

Distinguishing the susceptible areas to landslide using appropriate experimental models of landslide susceptibility mapping is one of the primitive and basic works to reduce probable damages and reduce risk in country watersheds. In this research، at first، nine factors including slope، aspect، elevation، precipitation، and distance from road، distance from fault، and distance from drainage، land use and lithology are identified as effective parameters in landslides occurrence in the studied area. After preparing these layers in geography information system (GIS)، the landslide distribution map of the watershed was prepared using aerial photos interpretations and field studies. Then، landslide susceptibility mapping was performed with two methods including information value (WINF) and proposed Gopta-Joshi method (LNRF). Finally، in order to evaluate the efficiency and verification of the landslide susceptibility mapping and determine the suitable model for landslide hazard mapping in the study watershed، the Landslide index was used. Based on this index، the information value and proposed Gopta-Joshi methods respectively classified the 79. 8 and 58. 5 percent of occurred landslides in high and very high danger classes; therefore، the information value method is more efficient in landslide susceptibility mapping in the Talkhab watershed than the proposed Gopta-Joshi method. Among the nine effective parameters، the geology factor has the highest effect in landslide occurrence; because about 50 percent of landslides occurred in Quaternary sediments which are susceptible to landslide.