مجله ترویج و توسعه آبخیزداری
پیاپی 8 (بهار 1394)

The main factors that control the variability of water erosion could be classified into physical and management parameters. The physical factorsincludeslope geometry (length, steepness and shape of slope and distance from drainage), surface properties (soil properties, roughness and cover of surface and etc.), and environmental factors (climate condition, water table depth, and soil moisture and precipitation regime) andmain management factors include vegetation and land use parameters. Somesubstantivedifferencesthatcontrolerosion processes in plot surface comparing hillslope surface,arising from limited dimension of plot and kind of its exploitation. These encountergeneralizeability ofthe plotsize data to hillslope scale withuncertainty. However, erosion measurement in plot scale,because of the easeandpossibility ofmonitoringthe long-termerosion, possibility of dynamic tracing of erosion and erosion models development, is very important. In addition,a wide range ofsimulationerosion models, bothempiricalandprocess based models, were developed based on plot size data. Therefore,in this article, methodology and challengeshillslope erosionestimates using erosion plot data explored.Studyofthe worldsbackgroundresearches indicatethat these efforts can be classified in threecategories including multivariate parametric analysis, scaling generalization or up scaling and multi-scale modeling techniques. Multi-scale modeling techniques are relatively youngandin existed in developing stage.Therefore, have less diversity comparing statistical and up scaling methods. The use ofpattern recognitiontechniques, based on data mining techniques including nonlinear non parametric analysis and intelligent methods, for finding optimum model for generalized point based erosion data to hillslope and wider scales are the options that fewerhave beenevaluated.

Hydrochemistry studies play an important role in the management and efficient and correct using of water resources. Mainobjectives ofthese studiesare identifythe limitations ofusingwater resources,situations of crisis and Suitable andunsuitablelocations with different consumptions,such asAgriculture. In this regardchanges in Qezel-Ozanwater quality an indicator in terms of agricultural were monitoredinthis study. 64 sites along the main Qezel-Ozan River and 22 sites of the major sub-branches were chosen that leading to this river.Samplingwas conducted on the days without rain in the springandsummer season, in May and September. The results showed that thegreatestchanges have been in theKhodabande, Ijrod, Mahneshan, andZanjan. Talwar and Bezinerod have most corrupting influence on the quality of the QezelOzan River.These rivers are poured of Khodabande and Ijrod lands. But other rivers in downstream have a positive impact on Qezel-OzanRiver’s quality because of their good quality. So when move to the end of the river route, water quality improve thata major factor in this part is perfect quality of sub branches in downstream. The results in comparison of Qezel-Ozan river’s quality in spring (May) andsummer (August) showed significant differences between measured chemical properties. Concentration of the most parameters increased in the summer and thus water quality in thespring is lower than summer.

In arid and semi-arid regions due to a lack of rainfall and high scattering of rainfall stations, the rainfall distribution estimation among the stations is necessary for the water, soil and flood in this research to study the spatial variations of maximum and pervasive rainfall in Kohgiloyeh va Boyerahmad Province the observational storms (in 35 stations) were collected and studied. In this study 45 storms were selected. To investigate the spatial distribution of rainfall amounts in the methods studied, the observational storms spatial pattern with 4 methods such as kriging, cokriging, inverse distance and precipitation gradient equation were analyzed. The results were evaluated using the comparison of the estimated error of each method. The maximum rainfall were determined using models derived from depth area duration relationships in durations 2,3,6,9, 12, 18, 24, 36 and 48 hours in Kohgiloyeh va Boyerahmad Province. According to the results, correlation coefficients are provided the appropriate values for durations 6, 18, 36, 48 hours. The DAD relationships derived from this method show lover values of percipitation to geostatistical method. This study indicated that the most of storms in cokriging method have lower errors.

Nowadays one of the main concerns is quantification and evaluation the effects of surface cover and land use changes on the watershed hydrological conditions. Lack of appropriate land use planning, leading to soil erosion, increasing sediment yield, environmental problems and that is serious threat to sustainable economic and social development. There are several methods to evaluate the effects of land use and land cover changes that physical models helps to better understand the effect of these variations on watershed hydrological processes. Integration of semi-distributed model (SWAT) with Geographic Information System is powerful tool for assessment of current watershed conditions, predict and also simulate the effect of management decisions on ecosystems. This paper discusses application of SWAT model to evaluating the effects of land use and land cover change and the best management practices in many watersheds over the world. Application of this model and other simulation models increase accuracy and reduce costs on evaluating the land use changes effects and provides the possibility to simulate a wide range of conservation activities in the watershed scale

Check dams are small structures which use in order to reducing the channel slope, reducing flow velocity and channel erosion control. These structures construct using wood, stone, cement and metal grid. One of the factors effectiveness on stability of check dams is stabilization of stream bed, slope modification and sediment control. In this paper taken in the Goush Sub-Watershed at the upstream of Kardeh dam which heck dams already constructed c in different types. The investigation showed that the leaching downstream check dam because lack of inadequacy bottom section long of gabion dams and inadequate joint between wing wall and stream bank are the main factors of failure of Gabion dams. While, for check dams, main factors of destruction of lose check dams were improper choice of location and check dam type, unsuitable material, rocks relocation by livestock and tractor.

Soil erosion is a serious problem in the most regions of the world, especially a developing countries such as Iran that induce offsite and insite problems. Accordingly, the holistic understanding of the provenance, sediment source and sink areas, transport and fate of produced sediments is a very essential tool to achieve comprehensive management of watersheds. Sediment connectivity isone of concepts which is important to achieve aforesaid goals. Sediment connectivity is defined as the integrated transfer of sediment across all possible sources to all potential sinks in a system over the continuum of detachment, transport and deposition, which is controlled by how the sediment moves between all geomorphic zones. Assessing characteristics of spacial patternes of connectivity in a watershed allows to determine and identify degradation areas as source and effective catchment areas in sediment yield, sediment aggregation areasand sediment transfer pathways. So, mentioned approach and identifying sectors with similar sediment connectivity patterns support applying similar and integrated sediment control mitigation strategies. On the other hand, location and spatial configuration of landscape with different managerial scenarios are one of the most important factors which significantlyaffects sediment connectivity of watershed components and finally leads to decrease or increase sediment yield. Totally,a watershed hasdifferent erosions, sediment transfer and sediment yield responses to a unique and similar human disturbance but only with different locations and spatial configurations of landscape. Accordingly, to present comprehensive watershed management programs, investigation of structural and functional sediment connectivityunder sediment management programs, practicable scenarios and with respect to sediment degradation, transfer and aggradation patterns is indispensable.

Watershed operations are carried out in order to apply a set of provisions and changes in land-use, vegetation cover and other structural and non-structural actions in a watershed with the goal of managing it. Watershed operations, as well as other projects have four effects (outcomes): environmental, social, economic, and distributional. These impacts or outcomes are used to assess (evaluate) the progress of project and its achievements to the desired goals and also the fails and successes of the project. Evaluation is carried out on both the project or program reports and their implementation reports. Since criticisms can come to the most of the assessment reports of study and implementation projects that have been done in variouscatchments of Iran, So in current study it is tried to criticize the evaluation reports of watershed study projects, which are done in various regions of Iran; also by the means of introducing some of standard evaluation approaches, suggestions are presented to improve these evaluations.