فهرست مطالب ریحانه مسعودی

Desertification is a major problem in many countries. International efforts have been considered to combat and prevent this phenomenon. The most important cases of these measures are the United Nations Convention to Combat Desertification. In this study, IMDPA model and GIS were used to assess desertification phenomena in Kashan Plain. Some indices of Climate and water criteria were selected to consider for each condition of the region. Final desertification intensity was calculated based on geometric average of the selected criteria and their indices. The numerical value was classified in 5 classes including non-significant, low, medium, severe and very severe and desertification intensity map was drawn using GIS in the studied period. According to the results, among the studied indices, the groundwater level depletion, EC and Transu aridity index with 3/82, 3/04 and 3/01 numerical values are the most effective factors. The threshold of ground water level, EC and Transu aridity index were determined respectively: more than50 cm/year, 2250-5000((μmohs)⁄(cm)) and 0/05-0/2. Also, the case study has classified in medium class of desertification with DS=2/4. Regarding the determined thresholds were specified the sensitive areas, and the required equipment are proposed to install on these areas for observing the thresholds.

In this study, the groundwater level depletion and electrical conductivity (EC) were chosen to assess the water quality and quantity changes in Kashan plain, Iran. The relevant hydrographs were drawn using Thiessen polygons based on the piezometric data. Moreover, the groundwater depletion, the elevation contour line and iso- electrical conductivity maps were provided using GIS. Also, the relation between EC and Anions and Cations (such as Ca2+, Mg2+, K+, Cl-, Na+, SO42-, HCO3-) were determined. The calculated Standard Index of Annual Precipitation (SIAP) in five meteorological stations showed that normal precipitation has the most percentage of frequency. Also, the results of drawn maps showed that the groundwater flows from south of the plain towards the Kavir in the north part of the plain. The most depletion of groundwater level and the withdrawal have also occurred in the south and south-eastern parts of the plain mainly due to the concentration of agricultural lands. Electrical conductivity has direct relation with concentration of ions in all cases, except bicarbonate. According to the hydrographs; the average level of groundwater has decreased 10.02 meters over 19 years and the groundwater level depletion has consequently decreased poor water quality.

In many parts of arid and semi-arid regions of Iran, agricultural activities such as mismanagement of land as well as inappropriate irrigation systems have seriously led to land degradation and desertification. Therefore, it is necessary to do some researches in order to determine which region is suitable for agriculture or not and if the region is suitable, what type of agriculture management should be applied prevalently. To achieve this goal, a region in Arak Mighan playa (Savarabad watershed) was chosen. At first, different maps of region including soil map, elevation and land use maps were prepared by ArcGIS 10.1. Five land uses were recognized as treatments including garden lands, dry farming systems, irrigation lands, dry lands and rangelands. Soil samples were taken and soil factors including N, Ca, Mg, and Humus as well as degradation factors such as EC, SAR, pH, Na and Hco3 were measured at two depths of 0-30 cm and 30-60 cm. The analysis of factors was done by SPSS software and results showed that there were significant differences among treatments based on Duncan test. In addition, rangeland was identified as a favorable treatment in terms of EC, pH, SAR in the surface layer. According to the results, it was found that rangelands had ideal conditions and dry farming and dry lands were identified as the most unfavorable treatments.

In this study, IMDPA model was used to assess desertification phenomena regarding the importance of agriculture in Mehran plain. Climatic and hydrologic criteria were selected to consider over two periods 2002-2007 and 2008-2012. Two climatic indices (Precipitation index and SPI) and three hydrologic indices (Groundwater level depletion, EC and TDS) were chosen to quantify climatic and hydrologic criteria, with which desertification intensity was calculated and classified for mapping by Arc GIS 9.03. Desertification intensity was classified in four classes including negligible and low, medium, high and very high. According to the results, among studied indices, SPI with the values of 2.45 and 2.78 and the groundwater level depletion with the values of 3.68 and 3.97 were the most effective factors. The results of analysis indicated that drought, decreased precipitation and groundwater level depletion cause an increase in desertification in Mehran Plain.

Water resources management especially for groundwater resources is a very important task in arid and semi-arid regions. Over last decades, because of various natural and anthropogenic factors, critical condition and declined groundwater level have been reported in most regions of the country. With regard to importance of this issue variation pattern of groundwater level in Garmsar plain was assessed using the best geostatistics estimator method over 2002-2011 period.‌‌ Among the various interpolation methods including Kriging and inverse distance weighting (IDW) with power 1-3, Kriging method was determined as the best interpolation method based on RMSE criterion. Results showed that spatial zoning maps of groundwater level in this period indicates intense depletion of groundwater level in the northwest of the region. Results also show that the average level of groundwater in the whole plain has decreased 3.5 m because of decreased rainfall and over-pumping of groundwater for agricultural uses in the period.

Assessment of natural resources projects is one of the most basic problems that are done to program the upcoming applied plans and management of these fields in different countries. In this study, the assessment of watershed operation in Tochal watershed basin was carried out through some primary studies and then integrating them together. In addition to watershed operation, was studied biological operation in study region. According to pizometric statistics wells in studied area, was appraised to improvement of water resources in before and after of Implementation of operation. At first, the efficiency percentage was determined for each of the applied structures by evaluating the condition of structures through field study. The aim of the execution of biological operation has been increase of the rate of permeability in construction operation, in addition of consolidation of sediment in area. The result of reviews show, the efficiency percentage of gabion, stone – cement, and the other structures were 75, 66, and 14. 8 respectively. In biological operation, some activities are offered, for example, nothing Spades, working Plant, seeding, drilling and protection. that among of this the proposed operation is executed: 10 hectare for working plant,1000 hectare for drilling, 700 hectare for seeding and 500 hectare for protection. The biological operation has just done for erosion controlling and soil conservation the volume of the precipitation behind the structures was calculated as 49775. 3 m3 and most of the structure capacity to control precipitation was for sediment control. Also with considering climatic parameters, SPI index statistical period was drawn. With drawing underground water hydrograph, the performance of biological and structural operation was considered in increasing of underground water level. The average of discharge has increased 30.36 liter/second.