Rainfall characteristics, which include Spatial Variability, exert a major influence on runoff properties. Many techniques have been proposed for determining the Spatial distribution of daily rainfall. One of these techniques is Spatial modeling, based on rainfall data measured by rain-gauge networks. In this study, application of different interpolation methods in the GIS environment, for estimating the Spatial distribution of daily rainfall in the southwest of Iran with low rain-gauge density, have been compared on a regional scale. The cross validation technique was selected as an accuracy index and statistical parameters, such as MAE (Mean Absolute Error) and MBE (Mean Bias Error), were used for comparing the results of cross validation. The ranking of MAE and MBE values was used for determining the best interpolation method. The interpolation methods that were studied for mappingthe Spatial distribution of daily rainfall include nearest point, moving average, moving surface, trend surface and kriging. Since the Spatial pattern of daily rainfall is random, the moving average method, with inverse distance weight function, was determined as the best method for interpolating daily rainfall data in the region of study.

An agricultural system will be sustainable while the lost nutrients are substituted in some ways. Chemical fertilizers is one of the main resources to nutrients supply for plant that optimum use of them, have an important role in field of ecologically sustainability and the agricultural products safety. One of the suitable tools that make it possible to manage the soil fertility is the use of soil nutrients elements maps. On the other hand zoning maps of nutrients can be guideline for proper application of chemical fertilizer. In this research, it was assessed the Spatial variations and zoning of macronutrients included nitrogen, phosphorus and potassium. Based on these, 96 soil samples collected from surface (0-25 cm) and sub surface (25-50 cm depths) in campus of University of Zanjan, Iran. The sampling method was based on regular network and the distance between two adjacent samples was selected 250 m. Statistical analysis presented that nitrogen has the lowest variation coefficient among the studied elements. Results of geostatistical analysis revealed that exponential model describes Spatial variations of the three elements properly. In the studied depths, minimum effective range of potassium were estimated between 328.1 and 553.7 m.Zoning maps of the macronutrients showed that distribution of them is not random and is following a Spatial pattern.

Today, water erosion is considered one of the most important forms of nature destruction, and the problems caused by it are inseparable problems of the country's watersheds. Among the numerous environmental factors affecting soil erodibility, lithology, topography and climate factors are the most important factors affecting soil erodibility. The purpose of this research is to investigate soil properties including number of drops impact (NDI), mean weight diameter of soil aggregates (MWD), soil penetration resistance (PR), soil cohesion (COH), saturated conductivity (Ks) and soil erodibility index (K). Therefore, six rock types (granite, limestone, ophiolite, shale, marl and sandstone) were selected in Razavi Khorasan province and sampling was done in three slope classes 0-10, 10-25 and more than 25% in 2021. In order to compare soil erodibility in similar rocks in different climates, limestone was selected in Tabas city (dry climate). The results showed that the average soil erodibility index and other indices have a significant difference (P<0.001). The results of measuring soil erodibility index in different slopes showed no significant erodibility index in three slope classes (sig=0.893, p<0.05). The comparison of the average soil erodibility in different climates in rocks similar to Paleogene limestone with a value of 0.83 in Tabas limestone and 0.96 (ton ha h / ha MJ mm) sarakhs limestone showed that the average soil erodibility in different climate has a significant difference (sig=0.023, p<0.05). The results of measuring CSEI index showed that the highest amount of reduction in erodibility reflected by this index is in granite with a value of 64% and the lowest value in shale with a value of 25%.

Introduction:The Urban Heat Island (UHI) effect refers to the temperature rise of any man-made area. It is a phenomenon in which cities become warmer than the surrounding suburbs. In other words, there is a temperature difference between the cities and the area surrounding them. Generally, the UHI effect could be a result of excessive and unplanned growth of urbanization. The behavior of artificial urban texture in terms of absorption of short-wave and long-wave radiation, transpiration, releasing of anthropogenic heat, and blocking prevalent wind is significantly different from that of the rudimentary nature. Surface geometry on the other hand, decreases wind speed in urban regions which plays a great role in formation of UHI. As the energy balance inside a city alters, UHI intensity varies. This means that UHI intensity is not Spatially and temporally similar in different cities.

The intensify process of lowering Urmia lake level has led to reduce water quality, making it brackish and unusable in wells of Lake Marginal Lands. The present study investigated changes in groundwater salinity in Urmia plain using geostatistical models, and compares the results of the mapping in three time periods. To assess salinity of the groundwater, data from 57 wells in the period of 1380, 1384 and 1387 were analyzed, using Kriging in GIS, GS+ and ARCVIEW8 soft wares. The results indicated that application of Kriging, experimental semi-variogram with spherical model provided better predictions with correlation coefficient of 0.99. According to the obtained groundwater salinity maps, land area with more than 2 dS/m groundwater salinity in 1380 was equal to 1924 hectares that has increased to 8331 hectares in 1387. During these years, in the study area the groundwater salinity with less than 1 dS/m was decreased about 14675 hectares. The observed maximum salinity value in 1380 has increased from 1.91 to 5.8 dS/m in 1387.

Rainfall erosivity is the ability of rainfall to detach the soil particles. This study was conducted to evaluate Spatial Variability of rainfall erosivity indices in Khouzestan Province. The point data of indices (EI30, AIm, KE>1 and Onchev indices) in 74 stations were used to generate Spatial erosivity maps through deterministic and geostatistical interpolation methods (Radial Basis Functions, Inverse Distance Weighted, Kriging and Cokriging). Results indicate that cokriging have least error and most correlation with determining coefficient of 0.89, 0.89, 0.48 and 0.49 for EI30, AIm, KE>1 and Onchev indices. Based on the correlation relationships between the basins specific sediment yield (in basins dominating the sedimentation stations) and mean indices of EI30, AIm, KE>1 and Onchev, EI30 index with correlation coefficient of 0.98 (P<0.01) is selected as the appropriate rainfall erosivity index. Based on the prepared map on the basis of Cokriging method with secondary variable of maximum mean monthly rainfall, the east and northeastern regions presented the highest values of EI30 index, while the southern and western regions showed the lowest values of EI30 index. The annual rainfall erosivity (EI30) ranged from 404 to 3064 Mj.mm.ha-1.h-1.y-1.

Rainfall erosivity factor is the most important factor influencing soil erosion. Various indicators has been developed to quantify it. Selection the appropriate index due to ecological conditions is necessary. Therefore mapping rainfall erosivity and awareness its changes, plays an important role in soil conservation, erosion control and land management. The purpose of this study is the selection of the best geostatistic method for mapping the rainfall erosivity factor in Fars province. In first step Fournier factor was calculated for 42 stations in Fars province and its surrounding and was determined the best geostatistic method using IDW, GPI, LPI, RBF, Ordinary and Simple and was prepared zoning map for Fournier factor. The results showed that among the various geostatistic techniques, RBF method (Thine plate Spline) is the best method for mapping rainfall erosivity factor in Fars province. Also, Noorabad city in northwest of province with an average of 31. 6 mm Fournier and Izadkhast city with 8. 67 were determined as the highest and lowest of the erosivity index. Also, Fournier index has increased from the East to the West as 46% of the province has a low erosion and 3% of the province has been high erosion that have had the highest and lowest levels.

To model the Spatial Variability of groundwater chemical characteristics, our research was performed using Geostatistic and deterministic methods. In our study, Na+, CI-, HCO3-2, total Cations, TH, SAR, EC and TDS from ground water characteristics were selected. At first, normality of data tested using Kolmogorov-Smirnov test, then we transformed EC, total Cations and TDS using logarithmic transformation. Variography and interaction variogram of data calculated. The result of estimated and expected amount using MAE and MBE were presented. Result showed significance of Geostatistical methods in comparison to deterministic methods and Cokriging increased result's precision. Cokriging is the best method for modeling of Cl-, total Cations and TH. Disjunctive Kriging is the suitable methods for modeling of HCO3-2 and Na+. Universal Kriging resulted best model for TDS. On the other hand ordinary Kriging is the best method for SAR modeling.

Introduction: Drought can occur in all climatic regions, that's why its characteristics are different in different regions. The concept of drought is a temporary disturbance and is different from with dry, because dry spells is limited to areas with little precepitation and is a permanent state of the climate of a region. Drought also occurs in dry and wet areas and is a natural state of climate. So far, not presentation exact and universal definition of the phenomenon of drought that is accepted by everyone. This phenomenon can occur in all climate and diffrent regions, that's why its characteristics are different in different regions. Researchers consider drought to be the result of a lack of rainfall over an extended period of time. In most definitions, a drought refers to a continuous and sustained period when the amount of water available in an area decreases significantly.Materials and Methods: To conduct this research, several methods were used in several stages. in First step, daily precipitation data for the synoptic station (411-precipitation), rain gauge (3303-precipitation) and climatology (546-precipitation) have been extracted during a long-term period of 51 years, from 1970 to 2020. for interpolation we used Kriging method in time period of data. Also, 4260×18628 grid or matrix was selected for each daily precipitation map. In this way, 18,628 daily maps were formed with 30,459 cells. After forming a database, SPEI has been used to calculate the drought index. Finally, by calculating the SPEI index, a matrix with dimensions of 51*30459 was formed. After extracting this index, Mann-Kendall's method was used to investigate the trend of drought severity, and spectrum analysis was used to investigate fluctuations of drought. for analysis trend period we use Mann-Kendall model.Results: According to the findings of this research during the first period, the drought areas of Iran are scattered in different parts of the country. During this period (1970-1990), there has been moderate and severe drought in the country. In the often of area in country has faced drought. During this period, 39% of the country experienced moderate and severe drought. In this period (1991-2010), moderate and severe drought and moderate and severe drought have prevailed in different regions of the country. The level of areas with drought in this period has increased by about 7% compared to the first period. In this period a large part of the country experienced drought and drought areas are seen scattered in the northwest, northeast, central and western regions. In the fourth period (2000-2010), against the third period, the drought has advanced to large parts of the country. The central parts of the country such as Isfahan, Yazd and Semnan occur wet condition. In Third period (2001-2020), a large part of the country is suffering from drought. against the previous period, in this period severe drought is also seen in many parts of the country.Discussion: Drought and its degree of occurrence are not related to a specific area of the country and every part of the country will be exposed to this random phenomenon. Therefore, droughts have been increasing all over the country. The lowest increasing trend can be seen in part of center and desert areas, part of the southern coast, west, northwest and also small areas in the northeast. The highest increasing trend of droughts is also seen in the southwest of the country in Khuzestan province.