Journal of Water and Soil Conservation
Year:2012 | Volume:19 | Issue:1|Papers Count:17

The aim of this study was to investigate the physico-chemical, biological properties and micromorphology of the soils covered by lichen (biologic crust) in Alagol area of Golestan Province. In-three points, pairwise samples were collected from 0-10 cm depth with eight replications and also undisturbed samples for micromorphological studies in Alagol pastures. These were selected randomly and were the common borders of the uncovered and lichen covered soils. Soils samples were analyzed and some properties such as texture, organic matter, CEC, bulk density and mean weight diameter were determined. In addition the micromorphological study of some pairs of soil samples were determined by polarized microscope. Results of analysis indicated that soil organic carbon content increased markedly in the covered soils compared to the uncovered one. Aggregate stability also increased about three folds in soils covered with lichen. Micromorphological studies showed that uncovered soil had a weak and massive microstructure but soils covered by biocrusts showed strongly developed blocky microstructure. The soils covered with lichen showed two types of b-fabric, crystallitic and speckled. While the uncovered soils was dominant with crystallitic b-fabric. The soils covered with lichen showed various layers of the accumulation of carbonate the form of micritic Polysaccharide excretions of lichen bind soil particles together and increased aggregate stability.

In this study the role of ENSO atmospheric-ocean phenomena in variability of the number of country rainy days was studied. For assessment of ENSO role indexes of SOI, MEI, NINO1+2, NINO3.4, NINO3, NINO4, NOI, SST and PNA were used. Zoning map of the country and the number of rainy days showed, rainy days of country wide level is between 15 to 56 days in year, which indicated that more than half of the country is dry annually, between 309 to 350 days without rainfall. The results of applying the Pierson correlation analysis, expressed the relationship between ENSO climatic indexes and the number of rainfall days annual stations isometropia of country. Among the climatic indexes, the correlation between NINO3 indexes with rainy days was the maximum number of stations and SST index were in the next rank. However PNA climatic index with rainy days showed only four stations had correlation and that PNA index is a weak one. Comparing the number of rainy days in the warm phases (El-Nino) and cold (La-Nina) showed the number of rainy days in El-Nino was more than La Nina phase that confirmed, the occurrence of El-Nino phase increase the number of rainy days of country. Among the stations studied, the highest correlation with the number of rainy days was in Nino3 index Sabzevar (0.49) and the lowest correlation in Shiraz and Bushehr stations (0.28). Calculated correlation coefficient between the number of rainy days with Nino3 and other indexes, expressed the important role of other factors such as geographical factors. So that in the area of South and South-East to Northeast, the correlation or the effect of the ENSO phenomenon increases.

The influence of organic materials on soil aggregate stability in the presence of earthworms is of great importance for the maintenance of soil fertility and quality, which might be relatively different in saline than non-saline environments. The main objective of this study was to realize the interactive effects between soil salinity and organic materials on aggregate stability in a soil inoculated with an anecic earthworm (Lumbricus terrestris L.) The experiment was a 4×4 factorial consisting of three levels of salinity (2, 4, and 8 dSm-1) obtained using NaCl and a control soil, and three organic materials (alfalfa and corn residues, cow manure) with an unamended soil as the control arranged in a completely randomized design replicated three times under controlled greenhouse conditions. The experiment lasted 19 weeks. At the end of 19 weeks, wet aggregate stability was measured. The aggregate stability decreased consistently with increasing salinity levels from 0.1 to 24%. The results showed that organic materials added to saline and non-saline soils improved aggregate stability (1-53%). The influence of various organic materials on soil aggregate stability and subsequent soil structure is largely dependent on the level of soil salinization imposed. Briefly, salinity would reduce aggregate stability, and that the utilization of plant residues and animal manures in saline soils may reduce the negative effects of salinity on soil fauna resulting in enhanced microbial activities, probably through the stimulation of the microbial community and feeding earthworms.

Generally, Climatic extreme events, like the heavy rain falls and sudden changes cause the greatest range of damages to water resources, agriculture and even human daily life. Therefore, correct and regular monitoring reduces their negative effects. This study evaluates the effects of large-scale climate factors such as ENSO, on how occurrence and severity of seasonal precipitation changes in Southern and Razavi Khorasan provinces. The data of 44-year period in four stations is used. Statistical analysis showed that extreme precipitations frequency and intensity has no long-term trend. The results of the correlation between Southern oscillation index and extreme precipitations pointed out high value with one month lag for spring and fall precipitation indices and with one year lag for winter precipitations. Also, a five-six months lag for unexpected rainfall events in winter season such as the number of rainfall more than 50 mm yielded the highest correlation.

The knowledge of the effect of ecological factors on establishment of vegetation distribution is crucial in the management of rangeland ecosystem. The purpose of this study is to understand the relationship of some environmental factors such as soil and topography features to the distribution of important medicinal plant species in Kachik Watershed. The percentage of vegetation cover and density were measured by random-systematic sampling method in indicator points from each land unit which is developed from overlaying of rangeland use map on the geographical aspect map. The soil samples were collected from the depth of 0-30 cm of soil surface on the basis of the zigzag method along 70 until 100 cm. The percentage of clay, silt, sand and the amount of Ca, pH and EC were analyzed for each sample. The environmental factors and plant features were analyzed by using regression, DCA and CCA analysis from PC-ORD 5, MINITAB 15 and Canoco 4.0 softwares. The results showed that plant species distribution of this area could be affected by %29.4 of soil, %25.3 of topographical parameters and %45.25 by these two environmental factors together. Among the topographic features aspect and slope with the regression value of 0.86 and 0.57 and among the soil features pH and texture parameters with 0.56 and 0.43 were the most influential features on the plant species distribution for this area.

Landslides are natural disasters that cause a lot of financial and life losses in the country, annually. Identifying high risk areas can reduce the damages and be effective on land development policies. In this research, spatial multi criteria evaluation method was used for landslide hazard zonation. Maps of various factors were made using image satellite, thematic maps and field observation. Criteria tree was designed for factors and constraints in ILWIS software. Geology, slope, aspect, land use and proximity to roads, rivers and faults maps as factors and the slope map and the river as constraint were introduced to the model. After weighting the factors and sub factors the landslide susceptibility map was obtained as a value from 0 to 1 respectively. The final map was classified from very low to very high susceptibility category and was crossed with landslide distribution map to check its accuracy. The results showed that over 85 percent of landslides locate in high and very high susceptibility classes so map accuracy was confirmed.

River discharge forecasting and analyzing its influencing factors is one of the most important issues in water resources management. In this research, a fuzzy based model (Fuzzy Inference System (FIS) and Adaptive Neuro-Fuzzy Inference System (ANFIS)) is used for performance of river flow forecasting process. Three parameters of precipitation, temperature, and daily discharge of the Lighvanghai basin is used for daily river flow forecasting in Lighvan River. On initial preprocessing of data, the randomness of data studied by return points test. Then, for determination of optimum lags of input parameters correlogram of data was studied. Finally, prediction was performed in two parts of synthetics and discharge of previous days. Assessment of prediction results by using various values as Nash-Sutcliff value showed that ANFIS model could predict discharge of these river with high exact (CNS=0.998) and low dispersion rather than FIS model (CNS=0.993). Also, in prediction of daily discharge through assessment of two designed parts, temperature had no significant effects, but precipitation of current day is more effective than discharge of two days ago.

Golestan Province considered as a major agricultural region, contains a vast area of salt affected soils in the northern parts originated mainly from the near surface water table and/or high evaporation. The present study was performed to investigate the physico-chemical and mineralogical properties of saline-sodic soils and to determine the concentrations of salts, identification of the type of salts and their sources. For this purposes, four profiles were selected and sampled at the north of Gorganrood and south of Atrak river basins based on the available maps and studies at the North and South of Gorganrood. These profiles were located in the different distances (km) from the Caspian Sea. Profiles number 1 and 2 are closer to the sea and the distance increases towards the profiles number 3 and 4. All the routine physico-chemical analyses were carried out on the sampled soil horizons. Profiles 1 and 3 were classified as Aquisalids and profiles 4 and 2 classified as Haplosalids and Cambids based on the Soil Taxonomy. In WRB system all of the profiles except profile number 2 that is classified as Cambisols, are classified as Solonchaks. To identify the types of salts, at first XRD analysis was carried out on the powder sample and then SEM/EDS analyses was done. Gibbs chart was used to determine the source of these salts. The salts identified by XRD analyses included gypsum, halite, hexahydrite, epsomite and mirabilite. Gypsum in the profiles was found at the surface and subsurface horizons in the form of lenticular crystals. Halite was also present in the profiles at the both surface and subsurface horizons. Epsomite in profile 1 was observed at the surface and in profile 3 at the subsurface horizons. Mirabilite was observed only in profile number 1 at the surface horizon. The source of these salts in these zones based on the results of the cation and anion analyses of the available ground and surface water and using the Gibbs modeling was recognized as evaporate minerals.

The most important component of the hydrologic cycle, which plays a key role in water resource management, crop yield simulation, and irrigation scheduling is evapotranspiration. Therefore, developing a low cost and precise model is very essential for hourly ETo calculations. Although, there are numerous empirical formulas, due to the complicated nature of the hourly evapotranspiration event, the data availability, high cost, and data gathering error, their performances are not all satisfactory. Thereafter, this paper develops an hourly ETo estimation model based on fuzzy inference system (FIS) technique. After analyzing the different models and different combinations of hourly meteorological data, hourly reference evapotranspiration calculated with four fuzzy models. Penman-Montieth-FAO56 Model considered as the comparison basis for hourly estimating reference evapotranspiration models. Comparing models was done with mean root squared error, mean deviation error, coefficient of determination, Jacovides (t) and Sabagh, et al (R2/t) criteria. The Required data gathered from the private weather station in Fariman city. With removing missing data, 9128 hourly data extracted from two-year statistical period, 2008-2009. Meanwhile, 70 percent of the data was used for model training, and 30 percent for model testing. The results showed that, fuzzy model output is acceptable in relation to Penman-Montieth-FAO56 and ASCE models output. The fuzzy model with four inputs has the highest correlation (0.99) to reference model. The fuzzy model with two inputs: solar radiation and relative humidity, presented proper values for evaluation criteria (RMSE=0.048, MBE=-0.018, R2=0.97, t=32, and R2/t=0.0295) in training phase. Under the testing phase, results were very similar to training phase. The comparison of Fuzzy model outputs with ASCE models also indicated that fuzzy model with three inputs of radiation, relative humidity, and temperature has the highest matching value (RMSE=0.05, MBE=-0.014, R2=0.95, t=13.9 and R2/t=0.068), in the training phase, which was justified with testing results. According to this study, fuzzy model can be a proper method for estimating hourly reference evapotranspiration. While, fuzzy model is simple, accurate, and does not have complex calculations like hybrid models.

Accurate estimation of mean velocity and discharge of open channels is one of important goals in hydraulic knowledge. Application of Manning equation is one of the methods with abundant use for mean velocity calculation. Application of this equation in several cross sections such as circular section is associated with error.In this study, effective hydraulic radius is defined based on cross section shape in Cartesian coordinates. In this definition, the effect of water surface roughness is applied in calculations with respect to a weight factor greater than one. By application of effective hydraulic radius in Manning equation for circular cross section a good accordance was observed between calculated and existed experimental results. Root square means error of relative computational velocity and discharge from the conventional and effective hydraulic radius toward experimental data are 0.14904, 0.08125 and 0.01113, 0.00042, respectively. Results showed that application of effective hydraulic radius has a significant effect on increasing the accuracy of Manning equation compared with conventional hydraulic radius.

Identification of areas susceptible to landslide occurrence is one of the basic measures taken to reduce the possible risk, and hazard management. In this paper, compared applicability weighted (AHP) bivariate statistical model and weighted linear combination (WLC), two semi-quantitative hazard analysis methods, and stepwise and logistic multivariate regression, two quantitative hazard analysis methods, were compared in order to determine suitable model for landslide hazard management in the watershed. First, landslide was mapped through field observation, using local data and watershed management agency information and GPS devices. The nine factors including elevation, slope, aspect, lithology, distance from fault, stream and road, land use, and precipitation amount were chosen as effective factors on landsliding through studying conditions of Chehel-chay watershed, and relative hazard map was prepared via 4 above models. Quality sum (Qs) index was used for evaluation of models accuracy. Results show that weighted (AHP) bivariate statistical model is suitable for chehel_chay watershed with Qs equal to 3.625. and weighted linear combination (WLC) with Qs equal to 2.2019, logistic multivariate regression with Qs equal to 1.703 and stepwise multivariate regression with Qs equal to 1.627, were the next in order of priority.

In this study, the sensitivity of daily potential evapotranspiration (ET0) (as calculated by Penma-Monteith FAO 56 and REF-ET software) in Sanandaj, Urmia and Tabriz to the certain changes in wind speed was assessed. Using a 41 years (1965-2005) dataset, 12 different weather parameters were employed in monthly scale as the input of PM-FAO 56 method. The aforementioned parameters include: Mean of maximum temperature; mean of minimum temperature; monthly mean temperature; mean of dew point temperature; minimum relative humidity; maximum relative humidity; monthly mean relative humidity; wind speed; precipitation; vapour pressure and sunshine duration. The sensitivity of the PM-FAO-56 to 10-20 percent changes in above weather parameters was investigated. The model results indicated that the daily ET0 in the study sites is more sensitive to the changes in wind speed than other weather parameters. As expected, the maximum changes were observed for 20% senario, but the absolute changes were higher for the reduction case (-20%). The highest and lowest ET0 sensitivities were occurred in Tabriz and Urmia, repectively. For Tabriz and Sanandaj sites the sensitivity of the ET0 to the changes in wind speed behaved linear, but in Urmia was nearly non-linear.

The transient flow patterns in the Gheshm canal is due to tidal fluctuations in two open boundaries of the canal. Due to Variations of water level in the Hormoz strait and the Persian Gulf, there are considerable differences in tidal behavior of two ends of the canal. In this investigation, applications of Nasir software for solving tidal flow patterns with moving boundaries in Gheshm canal is introduced. This software computes water level variation and velocity components in horizontal plane by solving depth averaged from of continuity and momentum equations using cell vertex finite volume method for unstructured triangular mesh. For damping out of numerical oscillations of explicit solution procedure, an artificial viscosity formulation suitable for the triangular unstructured meshes was applied. A wetting and drying model is applied in present work using edge-base algorithm. The results of computer modeling have been compared with data measurements in the domain and demonstrated high performance of the model to simulate tidal currents in Gheshm canal.