مجله علوم و مهندسی آبخیزداری ایران
پیاپی 30 (پاییز 1394)

The aim of this study is assessment and detection of climate change in Iran during recent decade. Daily precipitation، minimum and maximum data from 1437 synoptic، climatology and rain gauge stations during 1/1/1962 to 31/12/2004 has been used. Daily data interpolated by Kriging geo-statistical method over 15×15 kilometer pixels. A matrix with 15706×7187 dimension has been created that on the rows located days and on the columns، pixels. In order to detect climate change، 27 climate change indices used that was recommended by Expert Team on climate Change and Indices (ETCCDI). The results of this study show that warm extreme indices، including Summer Days (SU25)، Warm Days (TX90p)، Warm nights (TN90p) and Tropical nights (TR20) are increasing during the study period. While extreme cold indices for example Frost days (FD)، Ice days (ID)، Cold nights (TN10p) and Cold Days (TX10p) are decreasing. Warm Spell Duration Index (WSDI) is being longer while Cold Spell Duration Index (CSDI) is being shorter. The increase of maximum daily temperature and minimum temperature result in a decrease in Diurnal Temperature Range (DTR). The results also show positive trends for the frequency of occurrence of extreme precipitation.

Water management and best use are among the topical issues today and for this human should reverse and mitigate the negative trends they have caused to water quality. We have tested various water quality improvement scenarios in this research. We selected nine water quality factors and generated an initial set of 41 independent variables relating to landform، physical and biological plus landscape metrics of the surrounding environment of the rivers. Regression and correlation analyses helped narrow down the independent variables and define equations between dependent and independent variables. Five management items were devised based on the regression relationships and expert opinions including: decreasing fractal dimension of remnant tree patches، pasture extension onto bare land، decreasing area under agriculture based on a special multi-criteria analysis (MCE)، decreasing road density based on a pattern suggested through least cost algorithm and increasing area under pasture management and the number of tree patches. To balance the results of the scenarios and select the optimum one، LP approach was adopted during which the analytical hierarchy process was applied and the 32 scenarios were analyzed through technique LP. The best scenario was found to be the one including incress NP onto bare land and decrease of fractal dimension of the remnant tree patches. These were the best in terms of the selected criteria for water quality improvement.

Downstream trends in sediment size variation provide valuable information for related catchment sciences. Downstream sediment fining is one of basic beliefs in the river systems and numerous studies have also been conducted in this regard during recent decades. The main goal of this study was to determine and analyze downstream trend of sediment size in the streams of Vartavan catchment (4811 ha) in Qazvin province. For this purpose، 25 sediment samples from streams with rank 1 to 6 and 30 soil samples of various lithology units were collected. Various morphometric indices were determined after grain size analyses. The results showed according to hydraulic sorting rules and based on decreasing slope and increasing main channel length and drainage area، the particle size of channel-bed material must be fine downstream. But particle size of channel-bed material increases downstream، and downstream trend was affected by floods of semi-arid climate and heterogeneous lithology of catchment. Therefore downstream trends of sediment particle size is predominantly controlled by catchment climate and lithology، and hydraulic variations impose secondary role to the overall trend. Results of this study are expected to improve our understanding of downstream trends in the composition of alluvial deposits of semi-arid and geologically heterogeneous catchments.

Prediction of wind components (like wind speed) is considered one of the important factor، especially in relation to evaporation in a watershed. In this paper، in order to increase the efficiency of artificial intelligence models، for predicting wind speed، two neural network and neuro-fuzzy models combined with wavelet and two new hybrid models were presented. This research was carried out by some climatic parameters in Yazd synoptic station including wind speed، mean temperature، maximum temperature، relative humidity and evaporation. Then، efficiency of wavelet neural network and wavelet neural –fuzzy models were compared with the neural network and neuro-fuzzy to predict the wind speed for next 12 months. Finally، in order to confirm the efficiency of the best model، wind speed in 2005 was predicted using effective climatic parameters in 2004. The obtained results showed higher efficiency of the wavelet neural network and wavelet neural – fuzzy than the neural network and neuro-fuzzy. Verification of hybrid models confirmed the efficiency of wavelet neural – fuzzy in comparing to the other models.

Dam underground structures that block the natural flow of ground water and underground water resources are causing. The purpose of this study was to determine the suitable location for the construction of an underground dam method of fuzzy and boolean logic and the AHP. The parameters which are used to locate underground dam slope، geology، permeability، curve numbers، land use، EC، distance from roads، distance from the village، residential water demand and the thickness of the alluvium. Layers corresponding to each parameter is weighted by the theory of fuzzy logic and analyse hierarchy process and the operator product algebra multiplication factors were combined. Also because of the underground dam constructed on the bed of the stream and the slope is less than 5%، These two layers are considered as a filter، The underground dam was set to 17 fertile region of the 11 points in the underground dam was right And 6 points in the area of underground dams were relatively favorable

In this study، discharge coefficient in a rectangular sharp-crested side weir in movable and fixed bed channels was investigated experimentally. The first part of the experiments was carried out in a mobile bed channel with sediment median size of. In the second part، the channel bottom was fixed and experiments were performed. The multiple nonlinear and linear regression models are used to develop empirical equations based on the dimensionless parameters for calculating discharge coefficient of the rectangular side weirs. The bed morphology changes in mobile bed channel axis alongside the weir influenced on the flow over the weir and discharge coefficient. The accuracy of the proposed models was evaluated using Root Mean Square Errors (RMSE) and Mean Absolute Errors (MAE). The diverted discharges from the main channel were calculated using proposed models and compared with the observed data. In the conclusion، the results obtained from the models are in good agreement with the observed values and the developed models are capable of predicting discharge coefficient of rectangular sharp-crested weirs in a reasonable way in movable and fixed bed straight channels. The mean relative errors values for discharge coefficient calculated by proposed models are obtained 4. 63%، 4. 72%، 1. 16% and 1. 33% for both movable and fixed bed channels.

GIS users usually use the contour line maps for construction of Digital Elevation Models (DEMs) but the accuracy of these data is not completely obvious in terrain and hydrologic analysis. The aim of this paper is determination of quality and accuracy of drainage network analysis resulted from a DEM which is derived from contour lines map with 1:50000 scale. Study area with 443 squares Km is located in the northeastern of Iran and combined of mountain، hills، pediment، alluvial fans and floodplain. ArcGIS package have been used for manual digitizing of contours and extraction of stream network respectively. We have compared the Extracted networks from TOPODEM (DEM layer) with the one derived from high resolution satellite Images (IRSpan) for assessment the DEM accuracy. For determination of TOPODEM accuracy we took the extracted networks from satellite images as a real stream channels. This is partly because more detailed scale of the satellite images guarantees a good reference map with which to compare the network obtained from the DEM. The comparison process has been done in both raster and vector formats. These comparisons are included morph metric characteristics as river frequency، stream length، stream density and drainage ratio as well as the spatial pattern of the drainage lines، which was evaluated by visual analysis and calculating the differences rate between two networks. Visual study and numerical results showed only a network map which is derived in 50 threshold value is near to the network extracted from satellite images. River order and cell frequencies is been decreasing in higher threshold values. The comparison of the cell and line frequencies presented good agreement for all stream orders but there are large differences for 4، 5 and sixth- order streams. The differences were measured more than 80 percents for 4، 5 and sixth-order Rivers in the study area. it means the distribution of first- order rivers have a big difference with natural drainage patterns caused we were done the extra analyzing in the separate geomorphologic units. the results showed better agreement in the mountainous and hilly parts only for first and second-order streams. The differences for above areas are ranged between 20 to 40 percentages at the first and two river orders. The highest differences were found in the alluvial fan and plain area which is ranged between 60 to more than 80 percents in different orders. The results for river lengths shows satisfied agreement degree for pediment and mountain units especially for second-order Rivers. We found the lower agreement degrees for alluvial fans and plain sectors. The Drainage density calculated for whole basin area shows good agreement between rivers، which extracted by different methods. Obviously، differences appear in separate Geomorphologic units as we can see completely incorrect results for alluvial fan and plain sectors for rivers delineated from DEM. The best agreement of drainage density is been recognized for the pediment where the surface slop is moderate. In the mountain area drainage density for the layer extracted from satellite image is higher than the layer extracted from TOPODEM while the results are inversely for alluvial fans and plain areas. Then it should be better to use the results only for mountain and pediment units. results for alluvial fan and plain sectors for rivers delineated from The best agreement of drainage density is been recognized for pediment where the surface slop is moderate

This study tries to assess the capabilities of a numerical model in monitoring and predicting the governing processes of the river channel flow and sediment transport. With regard to the significant role of the flow velocity and shear stress forces on river bank erosion، two-dimensional numerical modeling was performed using CCHE2D to simulate flow and sediment transport patterns of a meandering river reach located in the downstream of the Minab dam (Hormozgan province، Iran). Various algorithms and parameters were employed for simulation of two-dimensional (2D) flow and sediment transport to gain an insight into the modeling capabilities of CCHE2D. First، the geometry model and after that a numerical mesh system were calculated by taking advantage of topographic surveys. Second، the required parameters for running CCHE2D were collected through field works. Finally، the model outputs including flow depth and velocity، shear stress، Froude number، specific discharge and changes in suspended load and bed load sediment were obtained for the considered river reach. Furthermore، two statistical criteria (RMSE and MAPE) were used to evaluate the performance of the model. The values of RMSE for the flow depth، flow velocity and the energy slope were 0. 075، 0. 116 and 0. 0008، respectively. The results indicated that the simulated values are in good agreement with the field measurements.