نشریه پژوهش های خشکسالی و تغییر اقلیم
پیاپی 1 (بهار 1402)

Drought monitoring is an essential component of drought risk management. This paper presents characteristics of droughts simulated by 13 global climate models (GCMs) under two greenhouse gases emission (RCP4.5 and RCP8.5) at three levels of risk (0.25, 0.50, and 0.75) in the Semnan region. For this purpose, the Reconnaissance Drought Index (RDI) and standardized precipitation index (SPI) were calculated for three future periods 2010-2039, 2040-2069, and 2070-2099 at different time scales. The calculated RDI and SPI for different climate change scenarios were compared with those of the past period (1965-2009). The results revealed that as compared to the RCP4.5 scenario, in the RCP8.5 scenario, there will be more dry and wet periods. Drought duration predicted by RDI index compared to SPI index (at 1-year and 3-mon time scales), under both emission scenarios in the future period (2010-2099) has decreased compared to the past period (1965-2009), but the number of droughts has increased. Additionally, increases and decreases in the drought magnitude and severity were found at time scales 3-month and annually, respectively. These results provide observational evidence for the increasing risk of droughts as anthropogenic global warming progresses.

Since in the previous evaluations, the statistical trend of Iran's rainfall has fluctuated for 40 to 50 years, the purpose of this article is to make a long-term time series of Shiraz and then evaluate the rainfall trend of Shiraz in a long-term period of 98 years. The statistics of three stations The old meteorology of Shiraz was collected from the old sources and the water and synoptic organization of Shiraz as new sources. The time period of these two periods is 1302-1345 and 1346-1400, respectively. The randomness and homogeneity of the data were checked using the Run test. To measure the continuity of the averages of two statistical periods, two parametric and non-parametric t-Student and Mann-Whitney methods were used, respectively. Investigations showed that the data of the regional water company can be seen as a sequence of rainfall observations made at the stations of the British Consulate and Moshir Kohane Street and Third Army Street, and the 98-year time series is the longest. Made the statistical course. Using the non-parametric Mann-Kendall test and the slope of the age line, the trend in the time series was investigated. The findings indicated that the annual rainfall data and rainfall anomaly do not have a significant trend. Rainfall in spring and summer has an upward trend, but no trend was seen in winter and autumn.

In this study, the effect of time series decomposition of precipitation in the simulation of electrical conductivity values of the surface water in Eskandari sub-basin in the northwest of the of Zayandeh Rood Dam Basin in the period of 1990-2020 was investigated by two algorithms based on random tree and random forest. Decomposition of observation precipitation series was done using wavelet theory, Daubechies 4 and level 2. At first, the simulation of electrical conductivity values in the studied sub-basin was done using two random tree and random forest algorithms in two phases of training and testing according to the rainfall values corresponding to the electrical conductivity values on a daily scale. The results showed that the efficiency of the model was 0.67 and 0.73 in the training phase, respectively, for random forest and random tree algorithms, and the efficiency was 0.59 and 0.55 in the testing phase for the mentioned algorithms by the Nash-Sutcliffe statistic. By decomposing the rainfall series into an approximate series and two detail series and increasing the simulation dimension to 4 dimensions, the results showed that the combination of wavelet theory with random forest and random tree algorithms was able to reduce the simulation error (RMSE) of the conductivity values in the training phase compared to the random forest and random tree algorithms by about 77.5 and 54%, respectively. These numbers in the testing phase are about 10 and 22 percent, respectively.

Global warming and consequently, the phenomenon of climate change is considered one of the most important environmental challenges of the last century, and as a result, the need for a global consensus to reduce its impacts is felt more than ever. In such a context, regulation in the field of climate change is very crucial. In this research, laws related to adaptation to climate change in developed countries have been analyzed from the perspective of thematic axes. Therefore, developed countries are first classified based on the Human Development Index (HDI). Then, climate change adaptation laws are categorized based on socio-ecological systems in the form of three systems of resources, actors, and governance, In the next step, the time and spatial trends of laws based on these systems and subsystems are analyzed. The results indicate that regulation in the field of adaptation to climate change in developed countries began in 1957 and continued until 2018, and the largest share belongs to the European continent. Also, the actor system has received more attention than the other two systems. The analysis of the subsystems shows that water, energy, and economy-wide subsystems are more important than other subsystems in each system. In addition, laws were passed in water, agriculture, and health subsystems earlier than others. Finally, it is shown that over time, the laws have included more comprehensive and broader goals and, on average, they have reduced greenhouse gas emissions.

The climate change, the intensity and continuity of drought periods, will affect the frequency of its occurrence in the coming decades. Iran is one of the countries that suffered the most damage from drought. Soil infiltration, which is very important in the design and management of furrow irrigation, changes over time. This issue will have a great impact on the irrigation efficiency. The purpose of this research is to investigate the temporal changes of the parameters of the Kostiakov-Lewis infiltration equation in furrow irrigation of sugarcane plant. The values of inflow, outflow and advance time were measured during 4 irrigation in 6 repetitions.The infiltration parameters were estimated using the advance time data and the hydrograph of the inflow and outflow using volume balance method. The results showed that there are significant temporal changes between the average values and the values of the coefficients of the Kostiakov-Lewis infiltration equation in each irrigation and the maximum change was related to the first irrigation, so that the range of parameter a changes in the range of 0.59 - 0.09 and the maximum value was related to the first irrigation, the range of changes in parameter k were observed in the range of 0.90 - 0.25, the highest of which was observed in the second irrigation. The average of f0 were equal to 7.333* 10-5 m^3/m.min with a CV of 16%. The results showed that the trend of time changes of infiltration parameters is not constant and more research is needed in this field.

Drought is a phenomenon that in addition to the lack of water resources, causes decrease in the quality of surface water. The purpose of this research is to investigate the effect of drought on the water quality of Kashfroud river. In order to, precipitation, temperature and quality data of six meteorological and hydrometry stations were used during the 30-year statistical period (1989-2019). Calculated SPI and SPEI index, drought and wet were selected among all stations. The changes of water quality parameters were investigated in the statistical period and the drought and wet period. The results showed that the average quality parameters of water have changed significantly during drought. In all stations, the concentration of TDS, EC, Ca, Mg, Na, SO4-, HCo3-, and Cl- have increased in the drought period compared to the long-term average. Its maximum for Cl-parameter is 7.66 mg/l at Olang Asadi station. On the other hand, during the period when drought indicators increased and drought occurred, the value of this parameter decreased by 32.73%.Due to the increase in temperature in drought period and the increase in EC value, the highest percentage of changes is in Olang Asadi station with 70.73% and the lowest in Golmakan station is 1.75%. Based on the results, the average concentration of cations and anions in Olang Asadi station shows an increase of about 5 times compared to Golmkan station.Finally, it can conclude that the decrease in rainfall, increase in temperature and drought, the water quality has decreased, especially in the downstream stations.

Considering the state of water resources in Iran, using unconventional water for irrigation is inevitable. Investigating the regional plants response to salinity is essential. an experiment was conducted on the research farm of the Agriculture Faculty, Lorestan University. Mini lysimeters (pots) with a diameter of 25 and a height of 30 cm were used. In this research, irrigation schedule was based on weighing method. The research was carried out using five quality treatments of irrigation water including S0: Water of the region (control treatment), S1: EC= 2 dS/m, S2: EC=4 dS/m, S3: EC=6 dS/m and S4: EC=8 dS/m. NaCl was used to make saline water. The growth period of Satureja hortensis was 100 days. The amount of accumulated potential and reference evapotranspiration were obtained 758.68 and 884.26 mm. The results showed that the effect of salinity stress on morphological characteristics such as plant height, stem diameter, as well as dry leaf weight and flowering branch, root and stem in Satureja hortensis was significant at the probability level of one percent. The morphological characteristics decreased as salinity stress increased. The yield of Satureja hortensis in S0, S1, S2, S3 and S4 treatments was 1732, 1598, 1412, 1328 and 1230 kg / ha, respectively. The essential oil content increased significantly as salinity stress increased. These values during different experimental treatments were obtained 1.08%, 1.2%, 1.5%, 1.58% and 1.8%, respectively.