Iranian Journal of Watershed Management Science and Engineering
Year:2009 | Volume:2 | Issue:5|Papers Count:11

This study was carried out to investigate the relationships between soil, topography and geology factors and range plant types on Ghazvin-Kohin region. On the basis of fieldwork, four vegetation types were identified and their relationships with topography, soil characteristics and geology factors were investigated. Samples were taken based on random systematic procedure. The number of samples were calculated using statistical technique while the area of plot varied between 1.5 to 2 times of the biggest available plant species in terms of canopy cover. For each plant type, five soil profiles were duged. The soil samples were taken form different layers of soil and the soil parameters were determined including: texture, EC, pH, N, K, P, OM, SAR and Lime. To do this, the USDA standard method was used. Topography factors such as elevation, aspect, slope as well as geology were considered. A multivariate analysis was carried out to determine the rate of relationship between vegetation types and studied factors. A matrix of vegetation types and factors were then prepared. The ordination of vegetation and studied factors was done by the Principal Component Analysis (PCA) using PC-ORD software. The results showed that the environmental factors affect both the vegetation establishment and flora distribution. Among others the most important factors are geology, lime, texture, OM and K.

In sustainable watershed management, research and study about environmental factors are important issues. It is because such studies often produce some valuable data used to select the proper locations for spatial arrangement of rural settlements. Every human activity in natural system must be based on knowledge, otherwise it would cause some disruptions in phenomena balance and widely changes the function of the natural phenomena. The aim of this study is to identify the role of environmental factors in spatial arrangement of rural settlements of Mahabad watershed to reduce the various natural accidents and prevent the vulnerability of rural people. Research method in addition to literature review is based on locally and field research and questionnaire techniques.In this research, some environmental factors such as slope classes, elevation, distance from fault and landslide were considered as independent variables and rural settlement distribution was defined as depended variable. ILWIS and GIS software and SPSS as statistical software were used to analyze data. The results showed that landslide and creeping not only cause some damages on man- made environments but also lead to some degradation, erosion and environmental poverties in rural regions. In this relationship, mountain location of Mahabad watershed affects deeply on this problem. Two factors such as altitude and slope act as limiting factors in spatial arrangement. The results showed that various faults locally folding generated from tectonics, cause the great amount of quakes that made study region to be hazardous.

Simulation of river flow in order to understand the river yield in the future is one of the important and practical issues in water resource management. In this study, monthly discharge of Taleghan river in Glinak stations at one step proceeding were forecasted using Artificial Intelligent (Artificial Neural Network MLP, ANFIS with Grid Partition and Subtractive Clustering) and time series methods. Two inputs including raw discharge data and de-seasonalised discharge data were used for different models. For time series models, ARIMA (3,0,0) (0,1,1) were selected as suitable model. The optimum structure in Artificial Intelligence method after pre-processing was determined using input and output data based on trial and error, and then, using the optimum structure, the streamflow discharge was forecasted. After the output of each single model was obtained, the structure of hybrid models were determined. The results showed hybrid methods 3 and 2 have the best application and time series model has better results than Artificial Intelligent methods.

The CN-SCS method is one of the most common methods in runoff and peak discharge estimation. Sensitivity analysis and relative importance assessment of five parameters, CN, time of concentration, rainfall in different return periods, watershed area and α were studied in this research. The CN-SCS approach has not completely processed by sensitivity analysis. For finding the nature of curve number SCS method in estimating peak discharge and its reaction to change in input parameters, the effects of 5 parameters including CN, time of concentration (TC), watershed area (A), rainfall amount in different return periods (P) and finally, α coefficient (the coefficient for obtaining the time of effective rainfall and it is usually equal to 0.133) were surveyed on peak discharge. Results indicate the effective role of CN on peak discharge as the most important output of model. The sensitivity of the model in estimation of peak discharge highly increases in large return periods. The sensitivity analysis of curve number SCS method was performed in MATLAB programming environment.

Measurement of soil erosion and its controlling factors can be conducted under field or laboratory conditions using permanent or ephemeral experimental plots. Considering a study area in Resket village arable lands, in Northern Iran, event based runoff and sediment plot data were compared under different land management scenarios. Towards this attempt, 10 plots having 5 different treatments and 2 replicates were considered. These treatments were strip cropping, contour tillage, terracing and top down plowing tillage systems and notillage control plot. The results of 9 rainfall events led to runoff generation and sediment yield showed that the maximum of sediment yield derived from top down plowing tillage of 156 g/m2. So, terrace tillage scenario had minimum rate sediment yield of 6.2 g/m2. The maximum and minimum runoff coefficient was also observed in no-tillage plot (%21.24) and terracing scenario (%7.08), respectively. It was also found that plowing, crop establishment and crop harvesting stages are the most sensitive phases in sediment yield.

Evaluating and modeling of volume of loaded sediment is one of the most important subjects in water resources management. Investigation of experimental relations and mathematical equations shows that yet analytical or suitable experimental method has not presented for the estimation of suspended load carried by a river. For the mentioned reason, in the current study we use contemporary data of water discharge and sediment discharge of Glinak Station located on Taleghan River for modeling of daily suspended load by using Fuzzy method and regression model. We assess results of these two models by using statistical parameters like RMSE, MAE, and R2. Results show that Fuzzy method (RMSE=51.3, MAE=31.16, R2=0.9604) has more accuracy than regression model (RMSE=93.3, MAE=52.85. R2=0.81) to assess daily suspended load.

Groundwater is one of the major sources of exploitation in arid and semi-arid regions. Thus for protecting groundwater quality, spatial and temporal distribution of data are important. The objective of this research was to evaluate interpolation methods for predicting spatial distribution of some groundwater quality such as TDS, Na+, EC, SAR, Cl- and SO4-2. Data related to 65 wells in Rafsanjan plain were used and IDW, kriging and cokriging were studied. After normalization of data, variograme was drawn. For selecting suitable model for fitness on experimental variograme, less RSS value was used. By using crossvalidation and RMSE, the best method for interpolation was then selected. Results showed that for interpolation of groundwater quality, kriging and cokriging methods are superior to IDW method. At last, the maps of groundwater quality were prepared, using the best interpolation method in GIS environment.

The rivers account as vital arteries of most plains in Iran. This type of water resources depends on dominant climate types of different regions, represents different reaction versus environmental stresses, especially hydrological drought. The hydrological and climatological droughts have priority and coming next together. Therefore, investigated relationship between hydrological droughts of Babolrood river in Babol plain were compared with climatological drought synoptic station affecting the discharge of Babolrood river. In this research, stochastic and probability models (Markov chain), Run theory, moving average and SPI index were used, so that hydrological and climatological drought and wet year were simulated at 10 years later. Results represent that Ghaemshahr synoptic station will have the most droughts frequency occurred in study period. Using Markov chain showed that the most static probable in normal state belongs to Babolrood river with value of 0.633. The occurrence of drought and wet years in Babolrood river are more under effect of Ghaemshahr station. This relation was established by using paired sample T test with significance level of (p<0.05) and correlation equal to 0.576.