Watershed Management Research
Year:2010 | Volume:23 | Issue:3 (88)|Papers Count:10

One of the common methods of river improvement and bank protection is using spur dikes. Building spur dikes makes the flow path to be modified. Concentrating the flow in the middle part of the river causes the river side not to be washed out. The new flow path makes the river bed next to the end of the spur dikes to be washed out. Usually the spur dikes are built in group because of extending the protected zone. The stability of these spur dikes against the river flow depends on stability of the first spur dike. The purpose of this laboratory research is to investigate different ways for reduction of erosion in the first spur dike. It is suggested to use a shorter (minor) spur dike at the upstream part perpendicular to the flow direction. Aim in this research , it is intended to find the optimum distance between shorter spur dike and first spur dike in order to have minimum erosion in the first spur dike. From the hydraulics point of view, L’/L (the length of shorter spur dike to the length of first spur dike ), X/L (the distance between first spur dike and shorter spur dike to the length of first spur dike) and Froude number has been studied and results has been presented in the form of equations.

Tree ring are one of the most important data sources for reconstructing past climate variability. In order to understand climate variability, it is necessary to get a spatial and temporal coverage of climate information. In dendroclimatology, ring width has been a variable of choice when assessing the tree ring and climate relationships of trees species. We were assessing a ring-width from a dendroclimatic perspective using beech (Fagus orientalis). The aim of this paper is to use tree ring information of Fagus orientalis to assess its capability as a model for reconstruction of Mazandaran province past climate. Therefore, for this purpose tree ring samplings were performed on three selected growing heights of 400, 500, and 700 meters above sea level at northern aspect of Darabcola forest in Mazandaran province. Increment cores were taken from the diameter of breast height (d.b.h.). The rings’ widths were measured using a binocular microscope. Standardization and comparison of tree ring series for each growing elevation were performed for all sites. Radial growth of all Beech tree species in three sites was positively correlated with climatic variables in this regional. Tree Ring chronology show significantly positive correlation with October and December minimum temperature in previous growing season. Maximum temperature in April has inverse relationship with regional chronology. Monthly total precipitation in March and September in current year had positive effect on Radial growth in three sites. Therefore Beech one of the usable species in dendroclimatology studies, this show may can be chronology of Beech extended more than a century in this regional. Also, may can be possible the reconstruction of meteorological data such as mean, minimum and maximum temperature and monthly total precipitation for this region.

Rainfall-runoff relationship is one of the most important and complex hydrological processes whose perception is very important in hydrology and water resources. A plenty of physical and statistical models have been developed for this that apply some parameters due to this relationship. The application of artificial neural network as a black box model is one of the methods to evaluate rainfall-runoff relationship. In this study, rainfall-runoff relationship of Plasjan Basin, upstream Zayandehrud River, is evaluated using multilayer perceptron network. Due to high variation of observed series, 3 daily rainfall series of regional stations and daily discharge of Plasjan station were first normalized and according to autocorrelation and cross correlation of rainfall-runoff data, 6 variables were selected for input of the network and a 4-hidden-layer network was found to be more valid comparing with other networks. The selected network was validated using comparison of the mean, standard deviation and probability density function of observed and simulated discharge.

The purpose of this study was to determine the related factors to sustainable on-farm water resources management in modaress watershed of Khuzestan province. The research design was a descriptive and correlation surveying method and factor analysis technique. Wheat farmers in north of Modaress watershed were the target population for this study. A random sample of wheat farmers selected (N=1370, n= 141). The main result of the study revealed that there exist correlation between the level of education, participation in extension course, rate of using communication channel, rate of farm demonstration visit, social participation, mechanization level, rate of extension agent visit with sustainable on-farm water resources management were significantly positive. By using Bartlett’s test and KMO test determine whether research variables are appropriate for factor analysis (Sig=0/000, Bartlett test=7254.342 , KMO=0.72).The number of factors was determined using Scree plot, Eigenvalue and percent of variance. An examination of the items and their factor loadings was used to understand the nature of the five factors. To reduce subjectivity, items with factor loading equal to or greater than 0.5 were considered most important when factors were labeled. The nine factors were labeled (1) Extension and education activities, (2) Economical characteristics, (3) Governmental support, (4), (5) Social characteristics. The results obtained from the factors analysis reveal that the six factors explain 71% of the variation of the sustainable on-farm water resources management.

Instantaneous unit sediment graph (IUSG) is one of the methods for predicting sediment graph of the flood events and its application needs to estimation of storage coefficient (Ks), dimensionless shape factor (ns), time to peak (tp) and instantaneous sediment supply. Investigation of relationships among the mentioned parameters and rainfall and water discharge characteristics could facilitates use of IUSG in ungaged drainage basins. In this research concurrent flow and sediment discharge of five flood events in Poledouab hydrometric station monitored hourly .IUSG parameters calculated using observed sediment graphs and rainfall hyetographs and their relationship investigated with excess rainfall and peak water discharge of flood events. The results show that correlation coefficient (r2) of power regression equation between Ks and rainfall excess is greater than peak flow (0.79 and 0.42).dimensionless shape factor of ns shows statistically weak relationship with rainfall excess and peak flow but its ratio to time to peak of sediment graph (ns/tp) resulted in statistically meaningful relationship with the rainfall excess and peak flow (respectively 0.85 and 0.67 of r2).application of the obtained equations in this research for predicting sediment graph of some flood hydrographs and comparing the results with the sediment rating curve methods show that rising limb of the sediment graph could be predicted more accurately than falling limb of sediment graph.

The correct prediction of effective factors in water resource projects is one of the most important problems of water recourse engineers. Suspended sediment volume carried by rivers is one of these important factors due to its negative issues in water quality, reservoirs capacity and river morphology. In fact deriving a proper method for sediment volume estimation can be one of the most important problems in erosion and sedimentation process. Although During recent decades, some black box models based on artificial neural networks (ANN), have been developed to overcome this problem and those accuracy privilege to empirical relations such as sediment rating curves have been shown, But these type of models are implicit that can not be simply used by other investigators. Therefore it is still necessary to develop an explicit model for the discharge–sediment relationship. It is aimed in this study, to develop an explicit model based on genetic programming (GP). Explicit models obtained using the GP are compared with artificial neural network technique in suspended sediment load estimation. The daily stream flow and suspended sediment data from one station on Lighvan River in Orumieh lake basin are used as a case study. The results indicate that the proposed GP method performs quite well compared to artificial neural network models and is quite practical for use.

The purpose of current study is to investigate the cause of plant types distribution in association with some of environmental factors to find the most important governing factors in the relation to vegetation cover and environmental factors (soil characteristics, slope, aspect, elevation, lithology, geomorphology faces and precipitation). In order to study plant cover 17 plant types were determined in study area and random-systematic sampling in each plant type was conducted in 10 plots. Regarding the species type and distribution, the area of each plot was determined based on the minimal area method. Floristic list and canopy cover of species were determined in each plot, and vegetation type of the area was listed with respect to two dominant species. Furthermore, 5 profiles were sampled within the plots to study soil characteristics in 0-50 cm depth as the effective depth of rooting. Subsequently, the texture, percent of lime, organic matter, pH and EC were measured. Statistical analysis of soil and vegetation cover was done using the Principal Components Analysis (PCA) through PC-ORD4 software program. The results showed that among environmental factors, slope, aspect, organic matter, surface stone, loam and sand percentage as the first set of factors determine the change in the vegetation cover by 54.06% while the second set of factors, including EC and elevation plays contributes to the change by 21.17%. These two sets of factors altogether explain 75.23% of vegetation cover variation in Semirom region.

Close relationship is found between vegetation and environmental factors in rangeland ecosystems. Determination of these relationships using canonical discriminate analysis is aim of this research. This study was carried out in Rineh rangelands with equal random classification sampling method and was considered to presence and absence of dominant species in the study area. Study area was classified using elevation, slop and aspect and was partitioned 37 homogeneous units.1m2 plots 750 and 25 m2 plots 75 were established in total of study area. Soil samples 150 form 0-30 cm depth were gathered. Some of environmental factors including 16 soil characteristics, 3 topographic factors and 16 climatic factors were selected. IRS satellite imageries included Red, NIR and PAN bands with compound bands produced from RVI, NDVI, PCA and fusion were used in process of modeling as supporting data. Canonical discriminate analysis was used for determination of effective environmental factors on each species and among of investigative factors, some were discriminated important factors of effective on species. Results of this study can use in management purposes of constant development in rangeland ecosystems, reclamation, protection, supervision and assessment.

It is necessary to understand habitat conditions and quantitative variables of medicinal plants for better management and use of medical productions. These characteristics are the indicators of habitat growth which are under some limitations of arid environments. In the present research, the effect of flood irrigation on quantitative variables of medicinal species Dendrostellera lessertii (Van Tiegh) at Gareh Bygone plain of the Fars was studied. The crown coverage and density of the species were measured using plot and amount of aboveground and underground biomass were measured by double sampling method and Profiles were dug beside the species at two sites of without and with water spread conditions. The results showed that there were no significant difference (p<5%) of water spread on quantitative parameters of the plants. These results show that these plant species were tolerant to water stress under harsh environment and they may be established in arid areas. On the basis of these results, the study of autecology, the methods of cultivation, establishment and also, effect of limitation factors on establishment of these plant species were recommended for the vast areas of arid areas of Iran.

Determining of utilization factor is one of the most important factors which used to evaluation of equality between livestock and rangeland. Water points are one of the effective factors that effect on the grazing distribution in rangelands. While some factors such as slope, height and soil factors have no limitation, distance from watering points is limited the use of forages. In this research, the percentage of use factor of Artemisia sieberi Besser was calculated around watering points using ocular estimate method. The aptest regression equations were determined for each of watering points. Before grazing of livestock, 10 pair plots of 4m2 were established with pegs. The dry weights of forage at 10 plots were calculated randomly. After grazing, the factor of use in the other 10 plots was estimated and the real utilization of them was calculated by clipping and weighting method. The estimated and real data were used to calculate of regression equation. And the estimated data modified with it. In this stage, after grazing, two transects of 1.7 km were established around each of watering points randomly. In each of 100 m of one transect, the utilization rate of A. si. was estimated by establishing of a plot of 4 m2. All of the estimated data were modified by regression equation that calculated in previous stage. The regression coefficients of two equations were compared each other using group regression method. And final regression equation was calculated. The results show that the utilization factor of A. si, and distance from watering point have a high correlation each other (R-sq = 85%). As well as, with increasing of distance from watering point, the utilization factor decreases.