Journal of Range and Watershed Managment
Year:2009 | Volume:62 | Issue:3|Papers Count:12

Climatic data was used to create a Site Index through which long term forage production of rangelands could be predicted. The research was conducted on a site called Nemati in a 10 year period using water balance model. The production of four rangeland species, i.e. Artemisia sieberi, Salsola rigida, Noaea mucronata and Stipa barbata on Nemati were predicted using soil characteristics, rainfall, soil moisture and also plant characteristics based on ERHYM- II model in early growing season. Inputs were long term climatic data, soil characteristics, plant characteristics, moisture in early growing season and long term forage production. Outputs were evapotranspiration of major plants, their potential and actual evapotranspiration, rainfall, surface runoff, soil moisture, available moisture and climatic index. The analyses were done by Penman Montieth FAO (P.M.F) using Cropwat 8.0 software. The surface runoff in daily rainfall was analyzed by SCS (Soil Conservation Service) based on soil curve number. The results show that CN was 86 and runoff in growing season was 7 mm. The capacity of soil moisture was 58.90 mm/meter. This amount provides the situation for plant to use moisture in early growing season to 25.40 mm/meter. The amount of actual evapotranspiration in growing season was 1.36 times of average rainfall in growing season. According to drought conditions in 2000 this amount is twice more than rainfall in growing season. Mean of production index for forage estimation in Namati rangeland was estimated T/Tp=17%. In this regard, long term forage production and production in ten year period (weather yield site index) was 242 kg/ha, and equation used for prediction was Y=80.42+1.941(ETact).

The proper and suitable utilization of rangelands will cause their sustainable utilization and decrease range degradation. It also promotes range condition and plant composition. So the objective of present research was identification of criteria to help range managers to choose proper utilization level. To do this, Taleghan catchment was selected. Criteria of soil sensitivity to erosion, range condition and trend were considered. Vegetation types were considered as management unit and in each vegetation types, sensitivity of soil to erosion, range condition and trend were evaluated. Based on the mentioned factors the proper utilization factor was determined. According to the results, proper utilization factor in Taleghan rangelands varies between 20-50% depending on the criteria condition in each vegetation type. Consequently, map of allowable use in the study region was prepared. Generally, in Taleghan rangelands allowable use depends on criteria and differs among vegetation types.

Check dam spacing is of great importance technically and economically in mechanical watershed management. Empirical models are usually used to determine check dam spacing developed in certain conditions in other countries but they are not calibrated in Iranian watershed conditions. This research has been carried out in the watershed of Doroudzan dam due to oldness and frequency of check dams. After field surveying and visiting of 2000 dams with ages ranging from 10 to 30 years, 73 check dams were selected to measure required parameters in the models such as Heede and Mufich(1973). Parameters such as effective height, stream bed gradient, sediment balancing gradient and length of deposition were measured. Empirical coefficient of Heede and Mufich model was estimated using the obtained data for 80 percent (60 dams) of check dams. The precision of empirical models such as primary Heede and Mufich, revised Heede and Mufich and Tulu were tested using data obtained from 13 remained dams. The results of this research reveal that primary Heede and Mufich and Tulu models have maximum and minimum errors, respectively, between current empirical models. Statistical comparison show that between primary Heede and Mufich and other models exist there is a significant difference in 95% level but no significant difference was obtained between modified Heede and Mufich and Tulu models. Due to non-significant difference between modified Heede and Mufich and Tulu models, simplicity and the need for fewer parameters to measure, using modified Heede and Mufich model is recommended in the watershed of Doroudzan dam and those of similar conditions. Linear and semi- logarithmic curves for a proper suggested model are drawn and introduced to use in similar conditions that require to measure effective height and stream bed gradient.

The Overlay Index method is used to evaluate the groundwater vulnerability as well as aquifer vulnerability mapping. This method uses the groundwater depth, hydraulic conductivity, net recharge, soil type, topography, unsaturated zone effect, and aquifer perimeter. However, selection of the rate and weight of each parameter is important. The paper deals with the application of sensitivity analysis for DRASTIC Overlay Index method in Ghazvin plain. The presented analysis in this research has evaluated the influence of the parameters rating and weighting based on the map removal and single-parameter sensitivity analysis. The results of map removal sensitivity analysis show that seven DRASTIC parameters should be considered together. The hydraulic conductivity has the highest sensitivity. On the other hands, the results indicate that groundwater depth strongly affects vulnerability in the region but the most unexpected results is the perimeter of aquifer which mostly influences the vulnerability index, with an average weight of 25.4% against the theoretical weight of 13%.This practical method provides a methodology for the evaluation of vulnerability mapping and for more reliable interpretation of vulnerability DRASTIC index in this region.

The storm movement clearly affects runoff processes. This work shows the results of an assessment that were undertaken to study the effects of moving storms on the rainfall - runoff processes. Using gravity center theory, analytical solutions are derived for flow due to storms moving over the drainage area. To simulate moving rainstorms, the rainfall distribution was simulated over the study area (Latian basin). Simulations were also undertaken by varying the storm pattern (e.g. spatial and temporal rainfall). By comparing the flow caused by a moving storm and stationary storm of the same duration, the influence of storm movement on the flow hydrograph is investigated. A simple mathematical model, based on the NRCS-CN, was used for comparing the results for hypothetical storms moving and stationary storms. The results show that the rainstorm movements have a pronounced effect on the discharge hydrograph. The results of 6 event simulation showed that considering storm movement leading to better simulation. According to results 5 events showed better hydrograph and in one hydrograph there was no difference between them.  

The spatial and temporal distributions of ecosystem characteristics are required for sustainable management and optimum exploitation of the resources. Soil quality preservation is one of the most important factors in sustainable ecosystem management. Therefore, knowing the spatial distribution of soil characteristics is very important. In the present study, Kriging and IDW methods were used for prediction of spatial distribution of salinity, Pb, Cu, Zn, Mn, CEC; and percentage of OM and clay in soils of Akhtarabad region. After data normalization, the variogram was developed. For selecting the best model for competing on experimental variogram, the lower RMSE value was used. The best model for interpretative was selected by means of cross validation and error evaluation methods, such as RMSE method. The results showed that Kriging method is better than IDW method for prediction of soil properties spatial distribution due to strong spatial structure. Finally, the soil characteristics maps were prepared using the best interpolation method in GIS environment.

The main purpose of this study was to analyze perception of pastoralists towards effectiveness of extension methods for improving range management plans in Tafresh and to analyze the factors influencing pastoralist’s perception. This study was a correlational research design. The statistical population of the study consisted at 95 pastoralists in the area of study. A sample of 55 pastoralists was selected using “systematic random sampling” method and questionnaires were used to collect data. For determining the validity of questionnaire, the content validity was used in which the viewpoints and expert judgment were considered to validate the questionnaire. Cronbach's alpha coefficient was used to measure reliability of scales of questionnaire and its value was obtained 0.7 through highest for different scales. The data were analyzed using descriptive and inferential statistics such as mean, standard deviation, coefficient of variation, correlation analysis and regression analysis. The findings revealed that extent of awareness about plan, participation in range rehabilitation, participation in range conservation, motivation for participation in plans, extent of using mass media, participation in extension programs and educational level significantly and positively correlated with pastoralists' perception towards effectiveness of extension methods for improving range management plans. The results of multiple regression analysis also showed that variables of extent of participation in range rehabilitation, extent of using mass media, educational level and motivation of participation in plans explained 56% of the variation in extent of pastoralists' perception towards effectiveness of extension methods for improving range management plans.

Wind erosion is one of the most important desertification processes in windy regions of Iran such as Sistan region that "120 days" wind dominated it which must be controlled using biological and mechanical approaches. A fundamental parameter in windbreak design is wind erosion threshold velocity trend. The most effective method for threshold velocity measurement is direct measurements in field. Due to heterogeneity in nature, understanding its spatial and temporal distribution is essential. Therefore this study carried out to survey spatial distribution of threshold wind velocity as a main effective factor in wind erosion, to compare different methods on threshold wind velocity interpolation and to provide spatial distribution map of threshold wind velocity. For determination of sampling points a regular grid of sampling on topographic map was drawn and the selected dots in contact of grids for sampling points were considered. Then theirs coordinate systems transferred into GPS system. The wind erosion threshold velocity was measured by erosion meter system directly and carefully. Then kriging, co-kriging and Inverse Distance Weighting methods using Gs+ and GIS software were used to determine wind erosion threshold velocity. For comparing these methods, cross validation were used by statistical parameters such as MAE and MBE. The results indicate that best semivariogram model in threshold wind velocity estimation at the study region is spherical model with RSS of 1.6 and correlation coefficient of 0.98 but there was not significant difference between kriging and co-kriging methods and both methods were introduced as suitable methods for interpolating in this region.

The eastern part of Esfahan especially Varton and Segzi plains are considered as the arid lands of the country. In this area due to the existence of sensitive soils, desertification is increasing. IMDPA model was selected to study the most effective criterion and indicator in desertification process in the Segzi region. In this case study three criteria including: water, vegetation cover and land were studied and some indicators for each criterion were considered based on the local condition. Then the final map of desertification intensity of the region was prepared by composing the layers and using of their geometrical average. According to the three selected criteria, the map of desertification shows the high and very high levels of desertification in the Segzi region. The water criterion with average value of 3.97 was settled in very high class while the land criterion with value of 3.26 and vegetation criterion with value of 3.12 were considered as in high class of desertification.