Physical Geography Research
Year:2013 | Volume:45 | Issue:3|Papers Count:9

Introduction: Drought is one of the devastating hazards of human history. It can occur in all times and any places. Drought is a regional event that its occurrence in many world zones cannot be avoided.It is more important than other natural misfortunes due to loss of life and property and social factors. This event is more display in arid zones such as Iran for the sake of regional characteristics like small precipitation, intensity in oscillations of rainfall in different years, inappropriate distribution of the rainfall in a period of years and the great fluctuations in place and time of the rainfall. For this reason this research has studied the severity and spatial organization of these droughts over the country.

Introduction Snow, as one of the basic factors of water supply, plays an important role in water resources management, especially in areas with cold winters and warm summers. The data obtained from snow gauges as well as temperature and precipitation time series data are generally being used to develop experimental models in order to estimate the spatial and temporal distribution of snow in watersheds. However, when reliable snow or other necessary climatic data records do not exist, using proper substitutes becomes essential. Hence, the snow cover area (SCA) derived from satellite images can be used as a representative of the amount of snow in a basin.Moreover, Remote Sensing (RS) is a useful tool in identifying snow and calculating SCA in mountainous regions with low accessibility and deficiency of snow gauges. Accordingly, the SCA time series data can then be used as input dataset in flow forecasting by hydrologic models.

Introduction: Among factors affecting crop production, especially rainfed crops, the rainfall and its distribution during crop season have a significant role. In addition, all the precipitation that falls during the growing season does not have the same effect on crop yield, and is not used in agriculture. So, quantification of Effective Rainfall (ER), as a portion of the precipitation which is stored in plant root zone and meets the needs of evapotranspiration requirements in different climatic zones is an essential component of water resources in rainfed wheat areas. Effective rainfall used in this study is “That portion of the total precipitation on the cropped area, during a specific time period, which is available to meet the potential evapotranspiration requirements in the cropped area. A precise estimation of effective rainfall is still needed not only for planning and management of rainfed wheat production, but also for risk management strategies in farms.Since a precise estimation of effective rainfall is necessary for increasing agricultural production, major challenge is to design a soil-water balance model that provides more accurate calculation of effective rainfall. The main goal of this study was to compare different effective rainfall estimation methods for rainfed wheat.

Introduction: Despite academic advances in spatial analysis within archaeology, primary uses of computer based GIS in archaeology were initiated by Cultural Resource Management (CRM) needs in the world. In conjunction with the development of environmental GIS data within several organizations, other federal agencies saw its potential for the management and spatial representation of archaeological data. Therefore, in other ways, developing methods of analysis and visual representation of data, previously impossible, were started. New methods of exploratory data analysis became possible and the efficiency within GIS environments for manipulation and analysis of spatial data contributed to exploratory and experimental use of data.

Introduction: Soil is the main source for human basic needs and land utilization. It makes a linkage between climatic and biogeochemical systems and meets a variety of human requirements (Young et al., 2004). An unsuitable land- use change may lead to a decrease in areas of pastures and forests, soil and water pollution, soil quality reduction and lossing land productivity (Islamet al., 1999).Forest destruction and its conversion into agricultural lands and reforestation by broad-leaved and coniferous species are the common forms of forest land-uses in the mountainous Hyrcanian forests in north of Iran. Soil quality as the combination of physical, chemical and biological properties of soil may be altered by changing in soil conditions affected by land use type (Brejda et al., 2000). Impact of different land – uses on soil quality was evaluated by measuring several soil properties. The present study aimed to investigate the effect of land use change on soil physical, chemical and biological properties and soil quality index in managed Beech stand, destructed forest stand, Pine plantation, Ash plantation, and agriculture land in Alandan forests.

Introduction: Study about quality and characteristics of wind erosion forms and also relationship between these forms with other environmental landforms is an important criterion in the assessment of natural resources. When wind blows on sandy beds, sand grains hop and roll into downwind shaping sand ripples. Morphometry is quantitative analysis of geomorphic characteristics of a region of landforms (Bayati Khatibi, 2010, 2). Study of surface sand grain size shows that larger ripples wavelength are created in the sands and coarse wavelength ripples in finer grain sands (Chorley et al 1985: 434). Ripples are common forms of roughness in desert areas.

Introduction: One of the natural disasters that affected Khozestan province's is the phenomenon undesirable of dust due to its geographical location and its neighborhood with a large expanse of desert regions. When dust sits on leaf crops, it can reduce the amount of light absorption and photosynthesis and the growth and production will suffer loss consequently (Abdali Dehdezi 1390: 19).

Introduction: Groundwater is one of the essential resources for supplying requirements of drinking water, agriculture and industry. This resulted in establishment of civilization in plains and lands where are far from rivers of freshwater.Regarding low amount annual rainfall in Iran and loss of water as a result of evaporation, volume of water production is about 128 billion cubic meters. From this volume about 83 billion cubic meters form surface water resources and 45 billion cubic meters join the groundwater by penetration. In recent decades, the growth of population and the need for water resources have led to an increase in exploitation to these essential sources hidden in the heart of the earth.