JOURNAL OF WATERSHED MANAGEMENT RESEARCH
Year:2013 | Volume:4 | Issue:7|Papers Count:9

The amount of sediment load significantly changes along a river due to environmental effects. This variability should be considered to estimate the amount of sediment load. In this research, spatial and seasonal variation of sediment load along of Gorganroud river were evaluated based on the information of 7 hydrometry stations sited in main branch of the river namely, Tamar, Hajighoshn, Gonbad, Voshmgir, Aghghala and Basirabad. Since the amount of sediment load is directly correlated with water discharge, for assuming the effect of water discharge, linear form of sediment rating curve is used where the linear form is produced by the logarithm transformation. Based on this linear relationship with possibly different slopes, the generalized analysis of covariance with logarithm of discharge as its covariate was used to compare the logarithm of sediment load as its response. In order to precisely estimate the amount of sediment load and adequately modify the sediment rating curve, the spatial comparison was drawn separately at low, middle and high rate of water discharge. Spatial evaluation demonstrated an increase in sediment load from Tamer station to Basirabad but there are some distinctive areas between mentioned stations with noticeably decreasing (80% in average) in their sediment load mainly due to reservoir building. For seasonal evaluation of sediment load, the percentage of sediment yield at different seasons was compared. This evaluation revealed that spring with at least 50% and at most 70% of total suspended sediment discharge has the highest amount of suspended sediment yield in this river.

Sedimentation problem in the reservoirs is one of the important effects after dam’s construction. This phenomenon encounters optimum utilization of the volume stored in the dam’s reservoir with some problems. Moreover sedimentation affects on the energy production, navigation, turbine’s operation, production and supplying the water and dam’s safety. In this research, for predicting of the sedimentation trend of Shahid Rajaee Reservoir, the GSTARS3.0 model was used due to half 2D and semi stable properties, ability for simulation of the sediment transport in imbalance status and using wide range of sediment transport equations. After calibration model with 10 years hydrography data of the Shahid Rajaee Reservoir, the amount and manner of sedimentation along the longitudinal and cross sections of the reservoir was investigated. The calibration results showed that the selecting Yang (1979) model as sediment transport formula, 3 number of flow pipe and roughness coefficient of 0.04, the model has the best agreement with real satiation. Also simulation results of the model shown that after 50 years from dam operation, the volume of the deposited sediments in the reservoir will reach to 21MCM that will occupy about %22 of the useful volume of the reservoir.

Non-normative construction and occupation of the land along the river bed of Manshad basin in Yazd Province has significant effects on distress and exacerbation of flood risk. In many cases, the width of main channel is less than the allowable width of the bed and the floods with return period less than 25 years were limited. Under existing regulations, the bed widths based 25-years floods as river limits is necessary. As results, average bed width range in main channel is 8.07 meters. The bed of Manshad River is 1.2 meters is higher than the natural or initial condition. For passing a 25-yr flood, the width of Manshad River should be broader to 12.8 meters. It’s suggested for offloading flood quickly from Manshad basin, cross structure and retaining walls should be destroyed. Also, to reducing the risk of damage and natural disasters, with acceptance of only 5% risk, should not allow any construction at a distance of 25 meters from the river Tallweg.

Knowing of vegetation spatial models related to nutrition elements variations and their sources can help us in suitable management of Basin. So, this research was investigated the relationship between macro and micro elements with indicator species in Lar basin. First, the land units were obtained in study area and sampling was done by randomly-systematic method in each land unit after field surveying. Size and number of plots was obtained based on minimal area and statistical method respectively. Kind of species for sampling was determined by TWINSPAN analysis. Then vegetation percentage and frequency was recorded in each plot. Soil and plant sampling was done in each plot and soil physico-chemical characteristics and nutrition elements was calculated by ICP in lab. Data analysis was done by analysis of variance, regression and correlation coefficient in SAS 9.1 Software. The relation between soil elements and species was determined by DCA and CCA analysis in Canoco for Win4.0 Software. The results showed that the plants nutrition elements were more than the soil. The relationship between the nutrition of different species and soil absorbable elements wasn’t constant and depended on site condition such as moisture, pH, chalk, organic matter and texture. Also, the other elements in soil were affected on plant-soil relations.

A country’s water resources, especially groundwater, is a national treasure. For optimal use of available water resources comprehensive planning is necessary to make informed and accurate understanding of this important component of water resources will not be possible. The purpose of this study was to evaluate the accuracy of interpolation techniques for spatial zonation of quantity parameters (water table and depth) and changes in these parameters for a ten years period base on the data collected from peizometric wells of Alashtar plain in Lorestan province, several geostatistical approaches such as simple Kriging, ordinary Kriging, simple CoKriging and ordinary CoKriging as well as other deterministic interpolation methods includes Inverse Distance Weighing (IDW) with different powers were investigated. After quality control and normalization of the data, the variogram was drawn. According to the Residual Mean Square Error (RMSE), below, the most appropriate variogram was chosen. Then validation approach and Mean Absolute Error (MAE) criteria were considered to determine the most appropriate interpolation technique. The results showed that among the all methods, Kriging method is most suitable for zonation of groundwater depth, simple CoKriging is most suitable for zonation of groundwater table (using H variable).

Prediction of river hydraulic behavior for probable flood is most important in flood mitigation in the urban area and for installation has been make, farmland and other land use in river environs. In the other hand, flow estimation at a point in a river is vital for a number of hydrologic applications include flood forecasting. The human impacts on river channel limitation occur in various forms, which its intensity and weakness are different in various rivers. Therefore, simulating the hydraulic behavior of the rivers, in order to predict the damage caused by floods in various conditions, river engineering projects, feasibility study, economic and social programs and flood control and other studies related to the river system is necessary. The purpose of this study is to combination the hydraulic model HEC-RAS software and Arc View GIS software using HEC-GeoRAS extension for simulating the hydraulic parameters of river Basher located in the Kohgiloyeh d Boyerahmad province. The results of this study indicate that the HEC-RAS model can provide the appropriate numerical values for investigating the hydraulic characteristics of flow in rivers and for flood hazard mapping with more accuracy and low cost used.

By development numerical models for prediction of climate variables, analyzing the effects of climate changing phenomena on water resources has been provided more. General circulation models of atmosphere are known as the best numerical models for predicting future climate. These models, considering production and emission of greenhouse gases scenarios, predict temperature and rainfall variables. In this study, regarding low stream regression, using temperature and rainfall parameters in monthly and seasonal scales, are produced in a seven-day manner in different return periods. As a result, relative error for 5, 10 and 20-years-lasting return periods, are 1.6, 2.2 and 0.13 percent, which have less error than other training models. Using outputs of GCM (HadCM3) models, temperature and rainfall variables for three periods of (2011-2040), (2041-2070) and (2071-2099) are predicted. Q7,T model is performed for each 30-year period and minimum streams are estimated for these periods.

Study area is located at southwestern of Qom, which its area is 16079 ha and minimum and maximum of height in this basin is 1005 and 2500m, respectively. In this study, in addition to design the respective maps and use of M-PSIAC to identifying the sediment, primary and secondary environmental factors that affecting the erosion was measured. Estimation of watershed sediment using M-PSIAC was 19/85 ton/ha/year. Reviewing the weighted average value of 9 factors, indicates that in study area, MV–int (8.9%), S1- 2- int (9.8%), S1- int(11.4%), S2- 1 –int(9.1%), S2- int(11.8%) and in S- int (10.3%) and S1- 1 1 (12.4%), S1- 1 – int (7.4%), S1- 2-1 (12.5%), S1-2 2 (10.5%) and S2 -1 -1 (10.1%), S2- 1 -2 (9.6%) and then S2 – 2 (8.4%) sub- basins, presence of river erosion, geology, topography, vegetation and current state of erosion are contributed, respectively.

Accurate prediction of daily discharge in ungauged watersheds is an important issue in hydrology. Several models have been developed for predicting discharge. The IHACRES is a friendly use model with limited input data which is being used for simulation of watershed outputs. The present study was conducted to assess the applicability of the IHACRES model to simulate daily mean discharge in seven sub-watersheds of Gorganrood in Golestan Province, Iran. Daily time series data of rainfall, stream flow and temperature were applied for the duration of 1986 to 2007. The model was calibrated and consequently validated for each study watershed. The results of the evaluation showed that the model performance in prediction of high flows was fairly good while its performance for flows with frequency of more than 60% was weak. The results also indicated that the simulated peak flows were lower than observed values in almost all stations and in both the calibration and validation periods. The efficiency of IHACRES model in predicting daily discharge was found to be fairly good with maximum and respective coefficients of determination and efficiency of 0.67 and 0.70 (P<0.05).