نشریه پژوهش های خشکسالی و تغییر اقلیم
پیاپی 3 (پاییز 1402)

The purpose of this research is to evaluate the accuracy of GPM satellite precipitation products in Mazandaran province. In this regard, the accuracy of satellite precipitation products was compared with weighted interpolation methods of image distance and kriging. For this purpose, the data of 21 meteorological stations and 24 monthly images and 2 annual images of GPM satellite in 2016 and 2018 were used. The evaluation of the methods was done using the mean square error, skew error, and absolute mean error percentage indicators. Also, annual rainfall maps of the province for 2016 and 2018 were drawn and analyzed. The results showed that GPM satellite precipitation products have a high bias error, so that the amount of overestimation/underestimation of this satellite reaches more than 140 mm per year. Of course, the interpolation methods of kriging and weighted image of the distance also have a significant error and do not accurately distinguish between the low and high rainfall rings of the province. Investigating and evaluating the possibility of combining the precipitation products of the desired satellites with latitude and longitude variables and altitude in most of the 4-dimensional gradient equations also showed that the combined Grad-GPM method has significantly increased the accuracy of the spatial estimation of precipitation and the error of interpolation methods. And the satellite reduced the GPM by about 25 to 40 percent. In addition, the examination of precipitation maps also shows the increase in accuracy of combined methods compared to other methods.

The continuation of droughts and the reduction of water resources have made the water input as the most important input affecting the composition and amount of cultivated area of agricultural products in the cultivation pattern of Razavi Khorasan province. In fact, the economic efficiency of the water consumption of each crop has a central and decisive role in the composition of the cultivation pattern. Therefore, in this study, the economic efficiency of water consumption during the past years was investigated. The information needed to estimate this index for the main agricultural products, from the cost system of the production of agricultural products during the years 2006 to 2020, and the basic residual method was used to estimate the economic productivity index of water. Statistics and information of 4 agricultural years 2013-2016 were used, to calculate the physical and economic efficiency of water consumption of all agricultural and garden products. The results of the study showed that the product price, as a variable outside the control of farmers, plays an important role in changing the economic productivity index, and establishing stability in the relative price of agricultural products depends on the formation of value chains in parallel with the implementation and modification of the crop pattern that has been notified by the ministry of Jihad Agriculture.

Concept of vulnerability used in order to determine the pollution risk of Qazvin plains aquifer. Vulnerability map of the aquifer was developed by qualitative rating, and then pollution risk map was provided. Results shows, some part of the plain and south eastern part has high pollution risk, because of the high electric conductivity (EC) and the high groundwater level respectively. Some parts were in the low risk region and due to the high ground water level the confirmation based on the chemical analysis is unexpected. By using Nitrate data the vulnerability maps reveal dramatic changes. In the corrective drastic method, areas which were in low risk region in conventional drastic moves to the moderate risk region. Also, results from the fuzzy drastic was close to the corrective drastic. Major parts of the plane were in the moderate risk region. From the experts point of the view the results from the corrective drastic was realistic. Results from sensitivity analysis shows that weight of the aquifer depth layers and feeding decreased, unsaturated slop layer's weight and hydraulic conductivity increased. Also, the weight of the ambience of the aquifer layers and soil was remained constant.

Since groundwater is very important in meeting the water consumption needs of different sectors, as a result, managing and planning the consequences of drought on underground resources is considered one of the important and vital issues in the planning and administration of countries. For this purpose, in this research, using the combination of quantitative indicators of drought GRI (Groundwater Resources Index), SDWI (Standardized Well Discharge Index) and qualitative index MSECI (Modified Standad Electrical Conductivity Index) to the Hydrological drought management index HDMI in Urmia Plain during the years 2003 to 2018. The monitoring results of this drought management index in Urmia Plain show that the longest drought duration observed according to this management index is 7 years, which started from 2012 and continued until 2018, and the most severe drought observed in 2018 was -2/2. In order to observe the drought trend on the drought indicators, Mann-Kendall test was used. The results show that with the continuation of the current trend in the region, the value of the GRI index will reach less than -2 by 2026 and the HDMI drought management index will reach less than -6 by 2031. It is a sign of the state of non-exploitation and the exposure of underground resources to severe drought. If the current situation continues, it will be impossible to sustainably use the underground resources of the Urmia Plain.

Flood is one of the most important threats to human society, which has increased in recent decades with the increase in population and climate change. Therefore, studying the features of the basins that are related to the level of flooding can help to properly manage this risk. Nowadays, several methods such as morphological characteristics, This research was carried out using SWAT hydrological model in 21 sub-basins of Sarbaz watershed located in Sistan and Baluchistan province. After preparing the parameters and input data, while considering two years for warming, the model was recalibrated for a 17-year period from 1999 to 2016 and then validated during a five-year period from 2017 to 2021. The results obtained in the calibration stage were NS=0.76 and R2=0.86 and in the validation stage NS=0.56 and R2=0.58. The initial curve number parameter for medium humidity conditions and the alpha parameter in the return flow had the greatest effect in the sensitivity analysis. The results showed that sub-basin 20 with an average runoff height of 2.46 was ranked first and sub-basin 10 with a runoff height of 0.06 was ranked last. Based on the explanation and Nash-Sutcliffe, it can be concluded that the model has performed well in the simulation of Sarbaz watershed and can be used for modeling in the basin. Flood control by prioritizing flooding in sub-basins and by implementing management measures to improve pasture coverage and build watershed structures in the Sarbaz river basin has reduced the amount of flood discharge and prevented sudden damages.

To investigate the main and interactive effects of various meteorological parameters on the rate of evaporation from the water surface, variance analysis was used. Based on the analysis, all the mentioned parameters had a significant effect on the rate of evaporation. Eta squared for the main effects was 0.69, indicating that the main effects could estimate 69% of the output variance. Based on this parameter, the amount of solar radiation had the most significant effect on the rate of evaporation, followed by surface pressure and relative humidity. The results of variance analysis considering the interactive effects showed that all the interactive effects had a significant effect on the rate of evaporation, and only the interactive effect of wind speed and radiation was not significantly different. The interactive effect of surface pressure on temperature and radiation had the most significant effect on the rate of evaporation, followed by the interactive effect of temperature and relative humidity. Investigation the effect of various meteorological parameters on the rate of evaporation from the water surface and their interactive effects can be used to investigate the efficiency of various methods to reduce evaporation.

Soil macro- and micro-nutrients can importantly affect wheat and rice tolerance in salt stressed conditions. The objective was to investigate salt distribution and pollution of nitrate and boron, resulted by chemical fertilization, in the non-alkaline and arid area of Khuzestan province, affecting wheat (Chamran genotype) and rice (Anbarbou genotype) yield. The research was conducted in the regions of Arab Asad (region 1) and Veis (region 2) and soil samples were collected from five different stations, in four different seasons and from the depths of 0-30, 30-60, 60-9-, and 90-120, and their salinity, and concentrations of nitrate and boron were determined. According to the results, for region 1, soil salinity at different depths was in the range of 1.96-5.16 dS/m, and for region 2 it was in the range of 1.90-4.92 dS/m. The highest nitrate concentrations for different depths were equal to 13.5, 18, 8.5, and 9 ppm (region 1) and 12.5, 16, 10, and 7 ppm (region 2). The corresponding values for boron were equal to 37, 49, 27 and 23.5 (region 1), and 37.5, 48, 28, and 24 (region 2). Increased levels of salinity decreased the yield of the two crops as wheat yield decreased by 17.8% (region 1) and 15.9% (region 2), and rice yield by 12.9% (region 1), and 14.4% (region 2). Investigating the distribution of salt, nitrate and boron in wheat and rice fields can be beneficial for the farmers to favorably use the present resources for optimum yield production.