Watershed Management Research
Year:2013 | Volume:25 | Issue:4 (97)|Papers Count:12

This study was performed, in 2007at Lahijan basin, to investigate the effect of land use change from forest to agricultural land. Four land use types were selected, including forest, blackberry-tea orchard, 40 year -and 50 year- tea orchards.For each treatment six samples were harvested using auger from the depths of 0-30 cm and 30-60cm and used for measuring organic carbon content, total N, pH, Lime, phosphorous and absorbable potassium. The results revealed that by changing land use from forest to other use types the amounts of lime, organic carbon content, total N and pH have decreased in the first layer, more obviously in 50-year old tea-orchard. In this layer, absorbable potassium has increased while absorbable phosphorous remained intact. In the second layer (30-60 cm), organic matters, pH, lime and total N have diminished, respectively in blackberry-tea orchard, 40 year tea-orchards and 50 year- tea orchards, whereas no significant differences have been for other factors estimated.

In this research, morphological characteristics, soil properties, geological and climatical parameters of southern Guilan province gullies were studied. Since, marl lands in south of Guilan province, is favorable bed for gully formation and the source of large amount of sediments in Sefidroud watershed and chief factor for sediment accumulation behind Sefidroud dam, so, study of their properties is indispensable. In this investigation, after geological map observation and land studies, three dominant representative gullies with linear, dendretic and head-dendretic view plan and two repeat of each kind of them was selected and sampled.36 Samples were carried to laboratory for physical, chemical and mineralogical analysis.The results of these experiments demonstrated that formation of all kinds of gullies is the function of clay content, kind of clay minerals and amount of soluble and exchangeable sodium. So that, with increasing in amount of fine clay and 2: 1 smectite clay minerals and Na ions, piping erosion and formation of gullies enhances, as well. This fact, result to branches increasing. This causes that gullies change from linear plan to dendretic one. Also, increasing of clay content and sodium ions from surface to depth, leads to increase in water infiltration to subsurface clayey layer and piping erosion occurs.These processes aggravate gully formation and increase the gully branches.

In a typical bend flow lines shift to the outer bend by centrifugal force. Thus, thalweg shifts to the outer bend, too.This condition can lead to outer bank erosion. Recently, submerged weirs have become a popular method to control or reduce bank erosion along meandering rivers. Any experimental tests weren’t perform on these structures in 90 degree sharp bends, so the purpose of this study is to conduct experimental tests to study the effect of submerged weir space on thalweg condition at a 90 degree sharp bend. To reach the purpose of this study, a 90o bend flume was constructed in the hydraulic laboratory of Shahid Chamran University. The ratio of bend radius to the flume width is equal 2. weirs are designed according the design procedure outlined in the literature. Weirs were installed at three different spaces equal to 24, 32 and 40 cm (3L, 4L and 5L). During the tests flow discharges kept constant equal to 18 Lit/s (Fr=0.25). At the end of each test, bed topography was measured using a digital bed profiler. Using these data, 180 cross sections were plotted and the longitude profile of thalweg for each test was plotted. Comparison of these plots have shown that the location of thalweg at the bend has been shifted to the nose of weirs and it was found as the weirs space become larger, the maximum scour is getting close to the end of flume and the thalweg is deeper.

The utilization of flood and its spreading on flat plains is a reclamation approach for natural resources in most countries such as Iran. But existance of information about moisture condition in the different parts of spreading area and its impact on tree species is necessary. Therfore, this project was performed in Qarecharian spreading station (Zanjan province) during five years (2005-2009). Four seedlings from each tree species of Elaeagnus angustifolia, Amygdalus communisand Robinia pseudoacacia were planted at four locations considering moisture condition at the three spreading canals first, third and fifth in three replications for each. The vitality of each seedlings were noted after flooding and drought periods. The height and diameteric growth were also noted. The results showed, the third canal with the vitality of 63, third location with 72, and E.angustifolia with 91 seedlings were the best.

Desertification refers to land degradation phenomenon in arid, semi-arid and dry sub-humid areas, resulting from various factors including: climatic and anthropogenic activities. There are vast natural areas in Iran, which have susceptible and fragile ecosystem and desert condition. In order to challenging with desertification, it is necessary to do some scientific research and assessment in different parts of the world. In this respect, a comprehensive model entitled" Iranian Model of Desertification Potential Assessment" has been prepared in Iran. In this research, among different existing methods IMDPA was selected and desertification intensity was evaluated on the basis of 4 criteria including: Climate, vegetation cover, soil and wind erosion and 16 indices. Each criterion was assessed based on the selected indices which result in qualitative mapping of each criterion cased on geometric average of the indices. Finally, sensitive map of region was extracted using geometric average of all criteria. Analysis of desertification criteria in Konarak region showed that among study criteria, soil criteria is a major problem in the study area with a geometric average of 1.7 which shows very high class while wind erosion criteria with a weighted average of 1.63 stands in second order of desertification class. Among the whole study area, 27.71% was found to be in medium and about 53.33% in very high class of desertification.

In this research, the effect of important environmental variable on Artemisia sieberi species quantitative and qualitative were determined in Nodoushan region, Yazd province. In this purpose, forty-six various sites were studied. Forage yield, Canopy Cover and density over three line transects were measured in random plots 2 m2. Environmental data recorded were including the site location (longitude, latitude), altitude, aspect and slope. For each sampled site, four soil samples were collected from profiles of 0–40 cm depth. These four samples then were pooled together to form one composite sample, air-dried and thoroughly mixed. Measured soil properties were included: gravel, texture, calcium carbonate, gypsum, pH, EC, soluble ions (Na+, Mg+2 and Ca+2) and SAR. The matrix of environmental and species characteristics were prepared. The relationships between species characteristics and environmental variables were determined using of Redundancy Detrended Analysis (RDA) method. The results showed that the forage yield, canopy cover and density are related to both soil and topographical variables. Among the soil variables, saturation percentage (SP), Na+, Ca+2Mg+2 and soil texture have the most effect onA. sieberi forage yield, canopy cover and density. The A. sieberi species growing characteristics were also significantly correlated with the topographic variables, elevation and slope.

Problems of water appropriate delivery correct Planning for the proper distribution needs indifferent parts of drinking water, agriculture and more are one of the reasons for poor performance of optimization operation of water resources projects. These problems lead to high operational losses and miss-match of water delivery with water requirements.The use of analytical and optimization methods could resolve some of these difficulties. Water delivery planning for optimization operation is a complex, multi-variable, and multi-constraint problem, which requires powerful optimization methods to be solved. Classical optimization methods are facing some limitations such as: being trapped in local optimum points, and difficulties in handling different variables. To overcome some of these limitations, new techniques which can solve complex problems could be used. In the paper two of these methods, particle Swarm optimization and genetic algorithms are introduced and their efficiency in optimization reservoir operation problems is compared. objective function downstream water issue needs to establish relationships based on continuity were selected. Comparison of two models in four different populations 100, 200, 300 and 400 showed that the PSO algorithm with average best objective function value of 190.44, 188.34, 187.07 and 187.04 the number of objective function evaluation less than genetic algorithm with objective function value of 193.96, 191.03, 188.23 and 187.94 with a number of further evaluation of the objective function to achieve higher capacity is the optimum answer.

The present study addressed the effect of physiographic attributes on Biodiversity indices of vegetation (diversity, richness and evenness) in Rangelands of Pishkooh-Yazd. The study area was located in latitude 31o 45’ -32o 3’ N; longitude 53o 28’ -53o 47’ E. Sampling sites were selected based on Land stratification method that allowed the study area to be subdivided into Land Unit Tracts (LUT), according to specified criteria including landform attributes (slope, aspect and altitude) and substrate type. Vegetation samplings were performed using randomized-systematic method.The size of sampling plots was selected based on minimal area method. Totally 45 plant species were recognized in this area. The results showed that elevation A.S.L. had significant effect on Biodiversity indices and mean elevation of 2300-2600 meters A.S.L. had higher diversity, richness and evenness than other elevation classes. Slope also affected diversity and richness significantly and high slopes (30-60%) had the highest diversity and richness. The aspect had no significant effect on biodiversity indices.

High level of erosion, water deficiency and low soil moisture, are considered as limiting factors in recovery and reform of semi-arid rangeland areas. Considering the problem of erosion, water deficiency and low soil moisture in lands discussed, small dams' projects can be one of suitable strategies to compensate for increasing the groundwater resources in such areas. On the other hand, considering several criteria that must be considered in this selection, it is difficult to choose the appropriate locations to execute projects such as Small Dams. These factors include Technical and Social-Economical criterias. In this study, in order to locate suitable areas for building small dams, Analytical Hierarchy Process has been used in three stages. Meykhoran region in Kermanshah Province was considered to do this research. The first stage involves determining hierarchical levels consisting of object, criterias, Subcriterias, and factors. During the second stage, standardization of criterias on the basis of Fuzzy Logic, weighting criterias and Subcriterias based on Analytical Hierarchy Process, and paired comparisons of criterias and subcriterias with preference values of one to nine with incompatibility rate of less than one tenth were done in ARC-GIS software environment by using AHP subprogram. In the final step, after integration of these layers, the final maps of optimal sites for building small dams were prepared. Using this template to locate other natural resources projects will help to optimize using data, saves time, and decrease costs.

Water deficiency and low soil moisture, are considered as limiting factors in recovery and reform of semi-arid rangeland areas.Considering the problem of water deficiency and low soil moisture in pastures discussed, atmospheric descending storage projects can be one of suitable strategies to compensate for water shortages in such areas. On the other hand, considering several criteria that must be considered in this selection, it is difficult to choose the appropriate locations to execute projects such as Water Spreading. These factors include technical and Social-Economical criteria. In this study, in order to locate suitable areas for Water Spreading projects, Spatial Decision Support System has been used in three stages. Meykhoran region in Kermanshah Province was considered to do this research. The first stage involves determining hierarchical levels consisting of object, Criteria, Sub criteria, and Factors. During the second stage, standardization of Criteria on the basis of Fuzzy Logic, weighting Criteria and Sub criteria based on Analytical Hierarchy Process, and paired comparisons of Criteria and Sub criteria with preference values of one to nine with incompatibility rate of less than one tenth were done in ARC-GIS software environment by using AHP subprogram. In the final step, after integration of these layers, the final maps of optimal sites for Water Spreading were prepared. Using this template to locate other natural resources projects will help to optimize using data, saves time, and decrease costs.

In this study, the germination characteristics of Prosopis spicigera and P.juliflora were studied. The purpose of this study was to investigate the effect of salinity on germination of these species at two different temperatures. So seeds of these two species were collected from Kangan region in Boushehr peovince. Seeds were treated with 0, 200, 300, 400 and 600 mM of NaCl at 25oC and 35oC. Daily and final germination percentages were recorded and germination velocity was calculated. The results showed that high salinity caused decrease in final germination percentage and germination velocity of both species. Salinity of 200 mM and temperature of 35oC is the optimum condition for germination of P.juliflora. The highest difference of germination percentage of these two species occurred between 300 - 400 mM, and it was concluded that according to low soil salinity in study area, P. spicigera planting as a native species has more priority. P.juliflora is more tolerant to salinity and can be used in harsh environmental condition of southern parts of Iran, like costal line, which no native species can be established.

The aim of this research was to investigate the effects of soil characteristics and topographic factors on distribution of (Agropyron cristatum). Study area which is about 4600 ha is located at Polur Summer Rangelands. After identification of the species sites in this region, data of vegetation, soil and topography were collected. Sampling was conducted in the key area of each site based on randomized-systematic pattern. Within each site was done along three 100 meter transect 10 plots (1m2) established along each transect in 10 meter distances. Three soil samples in each area collected in 0-30 cm and parameters such as N, P, organic material, pH, EC and texture were determined. After collecting data, Plant parameters of Ag.cristatum were analyzed using SPSS software. A matrix of plant stands and environmental factors was prepared and data were analyzed by the Principal Component Analysis (PCA) using PC-ORD software. Results showed that Ag.cristatum species have scattered more along second axis that plant stand were in western aspect and had more density and cover percentage. the most important effective environmental factors in vegetation distribution pattern were elevation, aspect, organic matter, soil texture, N, P and litter.