Desert
Volume:17 Issue: 2, Summer - Autumn 2013

Playas are low-lands which is considered to be the locations of accumulation of superficial and ground waters from higher elevations and these waters have different types of salts and various salinity level. Therefore, because of lack of rainfall and fresh-water both for human and animal useage or even for plants, it is needed to apply proper methods to harvest fresh water from these saline-waters to develop agricultural and animal husbandry industry in this areas. Therefore, the research will try to investigate fresh water harvesting from playa’s saline waters with the aid of saloar enegy and without implementation of import and complicated technology. The method is called Evaporating Water Harvesting (EWH). In this method, to install plastic covers on playa’s wetlands, productive fresh water obtained by condensation of evaporated water from soil surface (disturbed and undisturbed suface) was measured. Factors such as soil genesis, soil’s salts, water table, rate of saolar radiations and atmosphere temperature changes, had influence on the rate and term of water harvesting. The result showed that Daily average of gathered water from 1m2 soil surface in disturbed statement was 0.3 liter. The Minimum and maximum rates were 0.1 and 0.35 liter in May and July, respectively and Daily average of gathered water from 1m2 soil surface in undisturbed statement was 0.03 liter. The Minimum and maximum rates were 0.0 and 0.05 liter in May and July respectively. Then SPSS 11 software for being any relationship between sites’s water harvesting and environmental factors (such as water table, temperature, relative humidity, sun shine hours) was used. Results showed that the mean correlation of 99 percent had been between rate of sites’s water harvesting and temperature and water table factors and 95 percent to sun shine hours. At last, water table map was drawn. This method has some advantages such as producing fresh waters in playas, simplicity and being conomical and so on (see result section), and some disadvantages including limitation by using plastic covers, calcic and gypsic horizons in soil, not being usable in higher water tables (>3m).

The problems of land degradation and soil loss are among the major problems of watersheds in Iran. For erosion and sediment estimation one can use statistical and empirical methods. For doing this, land unit map and the map of effective factors should be prepared. For erosion and sediment estimation one can use statistical and empirical methods. However, these empirical methods are usually time consuming and do not give accurate estimation of erosion. In this study, we applied GIS techniques to estimate erosion and sediment of Menderjan Watershed at upstream of Zayandehrud River in central part of Iran. Erosion features of each land unit were defined on the basis of land use, geology and land unit maps using GIS. The UTM coordinates of each erosion type with higher erosion intensities such as rills and gullies were inserted in GIS using GPS data. The frequency of erosion indicators of each land unit, land use and sediment yield of these indices were calculated. Also by using sediment yield changes in watershed outlet (hydrometric station), the effective parameters in sediment production were identified. The results of this study can be used for more rapid and more accurate estimation of erosion than traditional methods. These results can also be used for regional erosion assessment and can be applied by using remotely- sensed data.

Relationships between soil factors and vegetation types in playa of Damghan was investigated. Six vegetation types including Artemisia.sieberi, Arundo. sp, Artemisia.sieberi-Peganum.harmala, Alhagi.cammelerom, Artemisia.sieberi-petropyron.sp, Tamarix.passerinoides-Halocnemum strobilaceum. One bare land was recognized in the study area and the research was conducted within mentioned types. Canopy percentage of plant in different types was estimated based on randomized-systematic sampling method, within 1 m2 quadrats. Along four transects 300 m each, 15 m2 quadrats established for estimating cover percentage in each type. Soil sampling was performed from 0- 15 and 15-50 Depths at the starting and end points of transect. Measured soil factors included EC, pH, texture, Ca2+, Na+, Mg2+, Co32-, HCO3 -, Cl-, CaSO4, CaCO3. In order to find the relationship between soil factors and vegetation properties, multivariate analysis was used. The results showed that separation of understudy types was mainly related to soil characteristic including texture, Ec, Na+, Mg2+, Cl-.

Land cover is one of basic data layers in geographic information system for physical planning and environmental monitoring. Digital image classification is generally performed to produce land cover maps from remote sensing data, particularly for large areas. In the present study the multispectral image from IRS LISS-III image along with ancillary data such as vegetation indices, principal component analysis and digital elevation layers, have been used to perform image classification using maximum likelihood classifier and decision tree method. The selected study area that is located in north-east Iran represents a wide range of physiographical and environmental phenomena. In this study, based on Land Cover Classification System (LCCS), seven land cover classes were defined. Comparison of the results using statistical techniques showed that while supervised classification (i.e. MLC) produces an overall accuracy of about 72%; the decision tree method, which improves the classification accuracy, can increase the results by about percent to 79%. The results illustrated that ancillary data, especially vegetation indices and DEM, are able to improve significantly classification accuracy in arid and semi arid regions, and also the mountainous or hilly areas.

Due to increasing importance of desertification challenges and its consequences the necessity of sustainable development achievement in arid and semi-arid regions is essential in order to avoid limited sources asting, increase the efficiency of controlling, reclamation and restoration projects of natural areas. Based on the iterature review, it has been recognized that combating desertification projects in Iran were yet inconsequential and incomprehensive. It is essential to achieve sustainable and comprehensive development in combating desertification issue. In relation to the mentioned case, investigation and ranking of current status of development indices of combating desertification process in different areas, is crucial which will determine the level of, budgeting and manpower polices. Therefore, numerical taxonomy model was recognized as a suitable tool for determination of ranking and classification of combating desertification indices. The study model is used for investigating and ranking of existing situation of combating desertification in the urban areas of Yazd province during the period of 2002-2007. The model evaluates development and extension of combating desertification indices in the urban areas using analytical structure and the final results are shown as the assessment Maps. The results show that Yazd, Taft, Mehriz and Khatam urban areas with expansion score of 0.89 from total combating desertification indices have unsuitable situation while Bafgh, Sadough and Tabas with expansion score of 0.44, 0.45 and 0.49, respectively had better situation. Moreover, it is recognized that budgeting and future development planning of the urban areas from combating desertification on the basis of the obtained results and raking of this research.

Arid and desert lands in terms of specific environmental characteristics such as low annual precipitation, sequential droughts, huge drop in ground water levels or the like, have always faced strict limitations in water resources. In the shadow of these characteristics and many other factors, Water Price Index (WPI) is significantly affected. This study set out with the aim of identifying and determining the priority of factors influencing Agricultural Water Price Index (AWPI) in arid and desert lands from farmers'' point of view. The Charkhab village in Yazd province was selected for this study. Detailed field surveys using structured questionnaires were considered with the statistical society comprising the whole of the farmers of the village. The identification of the influential factors is done by means of reviewing the literatures and eliciting experts'' opinions. We implicated the factor reduction and analyzing frequency distribution and CV correlation methods. Data interpretation was carried out by using SPSS software. The results of the factor analysis method have revealed 9 important factors being accounted for 92.06% of the variance. From 26 detected variables, “constructing and expanding greenhouses” are the most influential factors according to the farmers’ responses. Moreover, from other cases investigated lower ranks are assigned to the role of well costs, water supply costs and agricultural input costs.

Since direct experimental evidence is not available, this must be verified through a modeling approach, provided adequate data be available. Many statistical methods are used to study the relation between independent and dependent variables.This research was carried out at the western part of Jazmurian basin tlocated in the southeast of Iran. In this paperused ten physical characteristics such as area (A), perimeter (Pr), average elevation of basin (av.e), average slope (av.s), gravelious coefficient (G), length of main stream (L), pure slope of main stream (P), length of output to one point equivalent center of basin (Lc), Time of concentration (Tc) and lag time(Tl) as independent variables and nine hydrograph component such as Qp, Q25, Q50, Q75, Tp, T25, T50, T75 and Tb as dependent variables.We investigate flood hydrograph through the physical attributes using two and multiple variables regression factor and cluster analysis.With the data of twelve hydrometric stations. Normality test was done using Kolmograph- Smironov. After using four mentioned methods and with the use of modeling, the relations between dependent and independent variables weres defined. The evaluation of hydrologic model behavior and performance is commonly made and reported through comparisons of simulated and observed variables. Frequently, comparisons are made between simulated and measured stream flow at the catchments outlet. Significant models have correlation coefficient bigger than 0.325 at 0.01 significant level and higher than 0.250 at 0.05 significant levels. Three criteria such as root mean square error (RMSE), relative error (RE) and coefficient of efficiency (CE) were used for selecting the ultimate models. The results revealed that with the use of physical characteristics of the basin we can determine the synthetic hydrograph. The results also showed that the two- variable models have higher efficiency in estimating the discharge variables of the simulated hydrographs. After the cluster analysis for group in which are more station s, it results in more significance of the model than one whose group included less stations.

In order to study of the effect of priming and salinity on physiological and chemical characteristics of wheat (Triticum aestivum L.), an experiment was carried out at the Experimental Farm of Shiraz University. Results showed that primed plants significantly reduced its gas exchanges by accelerating senescence under a series of salt stress, which became more serious along with the increasing of salt concentrations, especially at 21 d after anthesis. Under each level of salt stress, dry matter accumulation of primed plants was always higher than the non primed plants. Primed plants had higher potassium selectivity against sodium than non-primed plants with the former could maintain relatively stable balance of ions, potassium/sodium was found not to be the limited factor for salt tolerant plants, but it was in salt-sensitive plants. Net photosynthesis (Pn) significantly positively correlated with leaf potassium/sodium (K+/Na+), relative water content (RWC), and leaf area duration (P < 0.01). So those four parameters might be ideal criterions of salt tolerance in wheat. In conclusion, salt stresses caused significant declines in growth period of wheat by accelerating leaf senescence at reproductive stage. Primed plants of wheat successfully preserved normal growth by maintaining Pn, K+/Na+, leaf area duration (LAD) and dry matter accumulation (DMA), while non-primed plants decreased considerably in those parameters. The improvement of photosynthesis and related traits in reproductive stage was a key to the growth of wheat under saline conditions.

The aim of this study is to determine the area affected by dust storms in different wind speeds using satellite images. In the first step, windy conditions of the Sistan plain were analyzed using wind statistics data. Next, five stormy days of Zabol city, indicating different wind speeds and horizontal visibilities during those storms, were selected. Then, high temporal resolution MODIS data was used as appropriate satellite data in this study. After that, a storm index was defined by means of analyses of storm radiance profile in bands with maximum and minimum storm reflection. The index is the square of difference between visible and thermal infrared bands, which is able to segment stormy confines with the range of reflection changes between 0 and 16. The reflection values were segmented in center of a 1 km2 network using usual interpolation methods such as Local Polynomial, Radial Basis Function, Inverse Distance Weighted, Ordinary Kriging and Universal Kriging. In order to assess the above mentioned interpolation methods, validation techniques were applied using ArcGIS 9.2 software. The result of these assessments such as standard deviation method indicates that the Ordinary Kriging had lower standard deviation. By analyzing the variograms and spatial analysis of the data using GS+ software, the best mathematic model able to fit the points was selected and classification was done by using this model. Finally, the stormy corridors with different dust densities were determined and by calculating the area and determining the villages located in these corridors, the critical regions were recognized. In this study the data from visible bands (4 and 9) and thermal band 21) of the MODIS sensor shows better results compared with the other bands, to segment and classify relative density of dust storms. Moreover, variographic analysis of the satellite data indicates that in most of the dust storms, power models with spherical threshold is the best for interpolation.

Understanding of the runoff generation processes is important in understanding the magnitude and dynamics of groundwater discharge. However, these processes continue to be difficult to quantify and conceptualize. In this study, two digital filter based separation modules, the Recursive filtering method (RDF) and a generalization of the recursive digital filter (GRDF) were1991–2002 in the Hableh Roud River at the stream gauge of Bonkuh, Semnan province. A technique for assessing the recession constants of the sub flows based on calibration the average value of the inverse of the value of the inverse of the slope of the linear path in the recession periods of an Ln (q)-time graph is presented. The result show that, the GRDF method gave higher (Baseflow index) BFI values than the RDF method with less variability and the mean baseflow calculated on an annual basis, ranged from 3.27 m3/s to 4.04 m3/s over period of study by RDF and GRDF, respectively. Since the true values of the baseflow index are unknown, it cannot be said, which one of the methods gives the best estimates.