نشریه پژوهش های آبخیزداری
پیاپی 85 (زمستان 1388)

Flood is a natural phenomenon that caused financial and human damages in the many places of the world every year and that has been caused major problems in the way of economical developing of countries. Therefore، many cautions have been done for research in effective factors on the flood and estimated methods in decades ago. In this research at 24 watersheds in Fars Province، with geographic information system (GIS)، 21 variables include physiographic and climatic characteristic was obtained. Factor analysis was employed and four factor (Area، annual average rain، drainage density، compactness coefficient is recognized as the effective factors on flood. For determination of homogenous region، Cluster analysis was used and using of area and watershed average slope، two homogeneous regions is obtained. discriminant function analysis was employed and confirmed Homogenous region. On the other hand، with regard to four factor، One Function coefficient was defined and canonical correlation، chi-square، wilks’ lambda values reveal that two homogenous region was completely desperate.

In the method of regional flood frequency analysis one of the main actions is grouping of homogeneous watersheds. The main target of this paper is to survey the circumstances of determining hydrologic homogeneous watersheds based on analysis of factors of physiography، climate and distribution parameters of annual peak flows include coefficient of variation، skewness and kurtosis. For investigate the consequences of homogeneity of basins and selection of effective variables to explanation of it، totally 16 sub basins with 30 years data series or longer have been selected in the Sefidrood Dam’s basin. After the physiography specifications of them measured and so by use of dominant probability distribution of region، the quantile flood of related hydrometry stations with different return periods estimated. Then by Ward’s clustering method، the conventional and L-moments of peak flows data in hydrometry stations and so based on physiography specifications of sub basins some clusters recognized and completely separated by canonical discriminate function. In continuing by use of physiography specifications and method of factorial analysis، the effective factors to peak flow defined and by fitting of multyvariations linear regressions the R2 of every of them have been computed. The results show that to many hydrological homogeneous basins that grouped based on distribution parameters the R2 in %1 level is significant but based on physiography specifications there is not significant. The conclusion is that recognizing the homogeneity of basins have to be done based on the moments of is not hydrometry stations.

Range management to develop the shrub species in arid and semi arid rangelands is one of the inexpensive and multi-purpose methods to decrease CO2. Rangelands exclusion is one of the most simple and inexpensive methods of range management. In this study، in order to investigate the effect of exclusion in rangelands on carbon sequestration potential of shrub species، two key areas were selected within and outside in the excluded area in Gomishan rangelands. After determining the key area، dominant species of halophyte shrubs Halocnemum strobilaceum and Halostachys caspica in both excluded and control area were selected. In both areas، the amount of aboveground and underground biomass of the species were estimated by determining the weight of stand biomass. Ash method was used to determine carbon sequestration coefficient of the studied species. Comparing amount of carbon sequestration in biomass of studied species in excluded area with their same biomass in control area showed no significant difference between carbon sequestration of same biomass (p<0. 05). Moreover the comparison of carbon sequestration of studied species in the unit of the measuring surface in both excluded and control areas showed the difference of this ability between two areas (p<0. 01). The result of this research shows that in spite of the different responses of carbon sequestration of the studied species to the exclusion، in general، there is no significant difference between carbon sequestration in the unit of the measuring surface by standing biomass of studied species in excluded rangeland with the average of 49. 142 kg/ha and control area with the average of 49. 194 kg/ha.

Nowadays land degradation makes serious problems، especially for developing country. It resulted in arid، semi arid and dry – sub humid area because of various factors such as: man activity، Climate variation. For providing lands from degradation، the most suitable way is modeling. We can estimate the grade of desertification with models. Many researches are accomplished in and out of the country in order to evaluate and provide the land degradation map، which present several regional models، but each of them that can show all aspect of Iran is the best. In this research، that was done in Hable rood Catchment’s، MEDALUS model is applied. This research is accomplished with water Standards that consist of these indexes: EC، SAR، Water subsidence، irrigation systems، dry index، Drought Continuance. We analyze MEDALUS model by the use of SPSS software and it showed that there isn’t any significant differences between indexes and 72. 3 percentage of whole region was in low class of land degradation. Also the problem of irrigation systems is increased because farmers use the old systems. More paying attention must be done in this field with an education advanced system to farmers. instead of old ones، also with this goal they can decrease the second salinity

Gully erosion is one of the most important erosion types in southern Iran that destroys lands and threats the life of the residents. This study was conducted in Darehshahr city located in Ilam province، Iran، owing to the importance of gully erosion in the study area to assess allometric relationships and to find out affective accessible variables for designation of other gully morphometric characteristics as well. To achieve the study purposes، the area induced by gully erosion was designated and 18 axial، digitated and frontal gullies were recognized and then categorized into five classes through applying cluster analysis. The different gully morphometric characteristics viz. length، head distance، depth، head height، top and bottom width، cross section area and perimeter، length، hydraulic radius، mean depth، maximum depth، longitudal slope، side slope and form factor were surveyed. The relationship between morphometric factors were then assessed with the help of regression analysis. The results of the allometric studies oft-approved linear and significant relationship among different gully morphometric characteristic. It was also verified that the easily accessible variables of gully length، head distance، height difference، head height and bank slope with the significant determination coefficient of 0. 6 to 0. 97 and different and mainly acceptable estimation and validation errors

Nowadays، the rangelands were devastated as result of population and domestic growth and hence unsparing use of food. Thus correct management as restoration، plantation of seedling، fair and rain harvesting techniques is a method that human can use for rangelands improvement. In this research were selected two treatments as have done management plan range and an audition range then were selected three same parts as repetition for every treatment. Then in every replication had been amount of forage production by cutting-weight method and vegetation cover by plot (1×1) m2 and range condition by four factory and range condition trend by balance method. After data collection were analyzed by using T-test. results showed there is significant between forage production and range condition in management plan and audition ranges (P<0. 01). Also range condition trend is not significant between both of them (P>0. 05) and there is significant vegetation cover between both of them (P<0. 05).

Flood spreading is one of the most important approaches to control floods، to increase soil infiltration rate and to remediate soil conditions، similarly it can prevent damages on down stream area. objectives of this research was to evaluate the effect of 3 planting on the base infiltration rate at planted and non-planted and control area. In this way 3 flood spreading stripes were selected in site no. 2 of Miankooh flood spreading area and measurements of main factors (vegetation cover، strip، year) were made at 2 plots with dimension of 60×60 square meter in each strip. One of this plots was planted (T) and the other one had the natural vegetation (p)، the control area was located at upper part of the selected stripes، these 3 plot types were the treatments of this research، in which infiltration rates were measured results show that there was not significant difference (P>0. 05). between planted and non-planted plots، while the difference between non-planted area with control and planted area with control was significant at 1 percent level (p<0. 01). so It is recommended to enhance native vegetation through flood spreading and to prevent 3 planting in flood spreading area.

Presently، flood-spreading schemes are used as aquifer management projects in the country. In these projects، spreading a large volume of floods containing salts and suspension load on the spreading network، it may lead to some differences in soil salinity and alkalinity. So it is necessary to study the amount and the trend of these differences in time in order to produce the suitable method to increase the utility of such designs. This research was conducted by the aim of study and determining the effect of flood spreading on the trend of salinity and alkalinity differences on the Poldasht station located in West Azarbaijan evaluated by comparison with control during 5 years، measuring soil physical and chemical properties such as EC and SAR among spreading channels of three lines of flooded، 6 sample from each line and 3 depth of soil 0-20، 20-40 and 40-60 cm gathered with sediment soil and control points. The data obtained were analyzed by t-student method if their statistical distributions are normal otherwise a non-parametric method was used. Results showed soil salinity and alkalinity were not differed significantly during 5 years. Among the lines and soil profile depth these factors were differed significantly. Soil EC and SAR showed significantly differences between lines during time.

Purpose of this study is investigation about mineral elements variances of Eurotia ceratoides in different elevations of Nodooshan rangelands in Yazd. Sampling was done in a random-systematic way in these elevations: 2200، 2300، 2450. In each elevation، in 5 points، Eurotia ceratoides bushes were selected، that they hadn’t been changed through the examination. Sampling was executed in three stages of growth، flowering and seeding of the bushes. In laboratory، calcium، phosphorus، nitrogen and potassium were evaluated. For examination، analysis of variance and Duncan were used. Results show that there’s no significant difference between the examined elements during the growth stage in three elevations. In the flowering time، there is a significant difference between nitrogen and plant protein in three elevations that in 2200 meters of height it is maximum (1. 251). In the seeding time، there is a significant difference between all of the examined elements except potassium in 2200 meters. There is maximum amount of nitrogen، phosphorus، calcium and protein with the average percentage of 0. 658، 0. 015، 3. 20، 4. 11 respectively.

The aim of this research was to study the relationships between presence of Rheum ribes and environmental factors in Chah-torosh rangelands of Yazd province. Topography، climate، geology، soil and grazing intensity were determined. Sampling method was randomized–systematic. Within each sampling unit 3-5 parallel transects with 300-500 length، each containing 30-50 quadrates (according to vegetation variations) were established. Quadrate size was determined for each vegetation type using the minimal area. Soil samples were taken from 0-30 and 30-80 cm in starting and ending points of each transect. Measured soil properties included gravel، texture، available moisture، saturation moisture، organic matter، lime، gypsum، pH، electrical conductivity and soluble ions (Na+، K+، Mg2+، Ca2+، Cl-،Co3-2، Hco3-، and Sou-2). Logistic regression and geostatistical technique was used to analyze the collected data. The results showed that the presence of Rheum ribes is mainly related to soil characteristics such as clay and organic matter. The presence of Rheum ribes has inverse relation with clay and positive relation with organic matter.