mohammad javad zareian

Using the most accurate methods and models to simulate the impact of climate change on meteorological variables in different regions of the world is of utmost importance. In this study, the accuracy of 10 AOGCM models related to the sixth assessment report of the IPCC (CMIP6) was investigated for simulating temperature and precipitation in the Sefidrood Basin. For this purpose, observational data of temperature and precipitation from 16 weather stations located in the basin during the time period from 1980 to 2014 were compared with the output of AOGCMs. The Kling-Gupta Efficiency (KGE) index was utilized for this comparison. The comparison was conducted on both annual and monthly time scales, and the more accurate models were identified for each time period. The results indicated that the accuracy of AOGCM models in estimating temperature in the study area was higher than their accuracy in estimating precipitation. Additionally, different models exhibited varying capabilities in simulating these variables across different months. Based on the results obtained, the MIROC6 and MRI-EMS2-0 models performed better than other models in estimating the temperature of different months. Furthermore, the HadGEM3-GC31-LL model showed a better performance than other models in estimating historical precipitation for most months of the year. Based on the results obtained, it is necessary to select and use the best AOGCM models for each month before conducting climate change simulation studies in the study area.

As a result of global warming, the climate will change in terms of average temperature and rainfall, with groundwater being one of the factors impacted. Consequently, the influence of climatic elements such as temperature and precipitation on groundwater drought values in the Talesh plain was investigated.

Initially, the LARS-WG model was used to calculate climate change values. Subsequently, using the Mann-Kendall test and the Pearson correlation of these two indices, the values of meteorological and groundwater drought indices were produced, as well as a study of the trend of these indices.

The findings of the annual changes in rainfall and temperature throughout the following period (2020–2040) reveal that precipitation of 9, 1.75, and 0.75% and the temperature of those have grown by 1.05, 1.32, and 1.81 °C under the scenarios of RCP2.6, RCP4.5, and RCP8.5, respectively. Also, in the basic period, the declined average level of the aquifer in this 15-year period was 0.86 m. On the other hand, the impacts of climate change on decreasing groundwater level over the future period compared to the base period under the above scenarios indicated that the aquifer by 2.07, 2.21, and 2.34 m, respectively. Although it indicates that the rainfall has risen in the area, unrestricted drain from the aquifer has resulted in a decline in groundwater. The study also reveals that meteorological drought occurred in the basic era at a rate of 49.66, 50.35, and 41.73% at the scales of 12, 24, and 48 months, respectively. Therefore, in order to mitigate the severity of the drought and avoid excessive groundwater aquifer fall in this plain, required actions are essential to decrease water consumption by water resources managers and executive bodies under the present circumstances.

Climate change is one of the most important factors affecting the world's climate. Due to the importance of estimating these effects, it is necessary to use appropriate tools and models to estimate the effects of climate change on climatic variables (especially temperature and precipitation). For this purpose, the use of Atmosphere-Ocean General Circulation Models (AOGCMs) as the most common of these tools, has found a lot of use in studies related to climate change. In this regard, the aim of this study was to evaluate the accuracy of the latest AOGCMs related to the sixth IPCC assessment report of IPCC in in different regions of Iran. For this purpose, the historical outputs of 10 AOGCMs in the period 1980 to 2014 were extracted from the IPCC database and compared with the ERA5 reanalysis data of the ECMWF center. This comparison was based on RMSE, Pearson correlation coefficient and Kling-Gupta combined index (KGE). The results showed that different models do not have the same accuracy in estimating the temperature and precipitation of Iran in different months of the year. The variability of the model errors in precipitation estimation were more than the variability of these errors in temperature estimation. On the annual scale, the results showed that the IPSL-CM6A-LR model had the best performance in estimating temperature and the HadGEM3-GC31-LL model had the best performance in estimating annual precipitation. Also, the results showed that the error rate of these models was lower in central and eastern regions of Iran than the other regions.

Due to the increase in greenhouse gases and numerous water and climate crises, accurate prediction of  the changes groundwater levels is very important and vital in the  water resources management. Therefore, in this paper,the  climate changes of Talesh plain is studied under RCP scenarios using Lars-WG and its water sources from SVR and ANN models. Also,aquifer pumping parameters, evapotranspiration potential, minimum and maximum temperature and  precipitation are used from (2021-2030). The results of the mean minimum and maximum temperature changes under RCP scenarios indicate the temperature increase by 0.9 and 0.69 °C. Also,studying  the accuracy of SVR and ANN models shows that the AUC in the training and testing phase in the ANN model, the maximum AUC values ​​were calculated as 0.876 and 0.769, while the SVR model, the maximum values ​​were equal to 0.867 and 0.819.Thus SVR has better predictive accuracy.In addition to that  during the time period (2005-2019) the groundwater level has decreased by 10 cm and in the SVR and ANN models by an average nine and six cm respectively more ever during in the time period(2021-2030) ground water levels have decreased in by 18, 20 and 21 cm, 20, 21 and 23 cm under the scenarios RCP2.6, RCP4.5 and RCP8 5 in SVR and ANN models,respectively.Therefor it is suggested that in Talesh plain considering the cultivation pattern appropriate to water resources in different parts of the plain should be the  priority for agricultural planners.

Climate change affects the hydrological cycle, available water resources and water demand by changing temperature and precipitation. In this regard, predicting temperature and precipitation changes by the models of the Sixth Climate Change Assessment Report due to more accuracy in their outputs can be helpful to plan and manage water resources in the future. In addition, identifying appropriate models among these climate models will pave the way for future research into the effects of climate change. In order to achieve these objectives, the present study was conducted.

At first Step, 138 and 113 meteorological stations were selected to study precipitation and temperature based on the appropriate location distribution in Iran, respectively. Then, monthly precipitation and temperature data of the historical period (1995-2014) were zoned in 30 basins of the country by Thiessen polygon method. In the next step, the results of simulation of precipitation and temperature of 10 CMIP6 models were extracted from website. Then, in order to equalize the time period of the base period of climate models with the observation period, the simulation results of models were used on a monthly basis.For each model, the position of network cells covering 30 basins of the country was determined and according to the percentage of the area of each cell in that basin, the average temperature and precipitation of GCM models were calculated at the level of each basin.Moreover, to increase the accuracy of the results of climatic models, the output of 10 climatic models in the historical period (2020-2039) were compared to observational data and were ranked based on KGE criteria. Then, the models were weighted based on the obtained rankings. In the next step, the forecasting results of climate models under three scenarios SSP126, SSP245 and SSP585 in the next period were obtained, after combining the output of the models based on their weight. Finally, the average changes in temperature and precipitation for the period of 2020-2039 compared to the historical period, were presented for all the basins.

The results of climate models ranking based on their ability in climate forecasting showed that the high score models are different depending on the variety climate in regions and their diversity in precipitation simulation is greater than temperature. So that, among 10 CMIP6 models, 6 high score models for simulation of precipitation and 4 high score models for temperature simulation in different parts of the country were determined. Furthermore, the results of climate forecasts indicate a change in precipitation from about +19 to -12% and an increase in temperature on average in the range of 0.1 to 0.6 degrees Celsius in different basins of the country over the next 20 years. Based on the average temperature changes of 20 next year, it can be seen that the northern regions of the country will experience more temperature increases than the southern regions of the country in the coming period. Increasing the temperature in the next period, while increasing evapotranspiration, will also increase water demand and consumption in different sectors. Therefore, it is necessary to develop policies to adapt to climate change in the agricultural, drinking and industrial sectors. Moreover, the western basins of the country will experience the greatest decrease in rainfall during this period. Due to the strategic location of some of these basins, both in terms of proximity to neighboring countries and in terms of dependence on agricultural activities to create food security and the lack of water resources, reduced rainfall can lead to several problems. Therefore, it is necessary to take measures to reduce water consumption, including changing consumption patterns and planning to compensate for economic losses and establish a balance between water supply and demand.

Iran is located in the Earth’s arid zone, and a drought crisis imperils the country as a result of declining water resources. Khuzestan Province, located in the south of Iran, is in critical condition due to water shortages; many of its groves have been destroyed. It also has many respiratory and pulmonary patients due to the constant presence of dust. The pandemic and this dust have caused acute problems for those diagnosed with COVID-19. Due to the importance of water deficit in this province, the present research calculated the Standardized Precipitation Index (SPI) and Standard Precipitation Evaporation Index (SPEI) in a thirty-year statistical period from 1984 to 2014; 12 stations were selected during the months when rainfall was more likely. This study utilized a geostatistical method to prepare zoning maps of SPI and SPEI. Then, various spatial statistics techniques in ArcGIS software were used to identify and locate the exact areas that were the sources of drought with the help of drought hot spots and strong drought clusters. Anselin Local Moran's maps indicated that the high-high precipitation clusters were located in the northeastern regions of Khuzestan. The hot and cold drought spots, which were identified by Getis-Ord G* spatial statistics based on both SPI and SPEI, showed that the hot spots were formed in the southern and southwestern regions; the cold spots were formed in the northwestern regions. Furthermore, the drought hot spots were identified with a 99% confidence level in places where the total ten-year precipitation was less than 270 millimeters.

This study was conducted to investigate the main factors affecting groundwater level fluctuations in the Najafabad plain. For this analysis, the 10-year period from 2004 to 2014 was considered and changes in temperature, precipitation, in river discharge between the beginning and end of the study area, groundwater withdrawal and in water flow in irrigation and drainage networks, were analyzed. In order to establish the relationship between each of the mentioned components with the changes in groundwater level in the study area, two general classifications were considered to determine the groundwater unit hydrograph. In the first classification, a groundwater unit hydrograph was prepared for all observation wells in the study area. In the second category, this hydrograph was prepared for observation wells around the river. Then, using multivariate regression analysis in SAS software, the best relationship between these components with changes in groundwater level was determined. Results showed that if the changes of groundwater unit hydrograph level are considered in the first group, changes in groundwater withdrawal with a share of 36.19%, had the maximum impact on changes in groundwater level. After that, the changes in the river flow with a share of 28.60%, had the greatest share in groundwater fluctuations. On the other hand, when the groundwater unit hydrograph is considered for the second group, changes in flow in the river with a share of 34.64% will have the maximum effect on changes in groundwater level and the share of groundwater withdrawal will reach to 28.53.

The aim of this study was to investigate the main options for adaptation to climate change in the Zayandeh-Roud Basin based on the passive defense approach. Therefore, in the first stage, the temperature and precipitation changes in the basin during future 20-years (2021-2040) were estimated using the weighted combination of the GCM models of the fifth IPCC assessment report. In the next stage, using the comments of various experts and researchers on water resources management and passive defense, the main criteria and options were identified for adaptation to climate change in the Zayandeh-Roud Basin. Based on the scores provided by the experts, pairwise comparisons were performed based on Analytical Hierarchy Process (AHP). The results showed that on average, the temperature of basin will increase by about 0.9 °C during the next 20-years and the precipitation of the basin will decrease by about 13.3%. Among the criteria selected for adaptation to climate change based on the passive defense approach, the criterion of "no damage to farmers' livelihood" had the highest score. Also, among the options for adapting to climate change, "water demand management", "increase water supply" and "reduce water supply" received the highest scores for adapt the basin to climate change, respectively. In general, the results showed that supply-side water policies as well as water rationing policies can not be good policies for reduce risks and conflicts in water management, and if water demand management policies are implemented properly, future threats to water resources management (with a passive defense approach), can be reduced.

Proper utilization of available water resources and implementation of development plans requires an accurate database and updating of statistical and meteorological information. The process of measuring meteorological data until it is recorded in a database is an accurate, sensitive and time-consuming process. This study examines the country's meteorological network, which is managed under the supervision of the Ministry of Energy, and the pathology of the current state of meteorological measurements. Accordingly, network evaluation was performed in three major sections: network status evaluation in terms of statistics and field visits and evaluation of the measurement trustee. The survey of measurement system administrators varies around the world, and the focus of measurement varies from ministry to ministry, depending on the macro goals of water and water productivity in each country. A study of the statistics of the country's measurement network showed that one of the most important problems is the lack of stations in the highlands and the lack of a long-term statistical period. Although the construction of the stations is more than half a century old, proper management over time has not been able to observe a proper network. Field evaluation of meteorological stations in the country also showed that the lack of attention to the necessary equipment and infrastructure, the cost of the measurement process, lack of culture regarding the need for measurement, managers' inattention to the measurement process and etc. have been caused that the quality and quantity of measurements are affected. Establishing a proper monitoring network, although it has high initial costs, but the return on investment is necessary and important due to the necessity of statistics and information to implement any development plan.

Acoustic Tomography (AT) Technology transmits reciprocal acoustic waves to measure the flow characteristics such as flow velocity, water temperature, suspended sediment concentration, salinity and the flow direction in rivers, dam storages, lakes, seas and the oceans. Although, this technique is widely applied in developed countries, it was not used in Iran yet. This research shows the first acoustic tomography experiment in Iran for measuring the flow velocity in a shallow lake located in the western of Shiraz City. Reciprocal sound transmissions were performed between the two acoustic stations located on both sides of the lake. The length of sound transmission line was 262m and the central frequency was set to 30 kHz. The experiment period was 20 minutes and the acoustical data was collected at time intervals of 40s. The surface temperature was measured by a Temperature Sensor (accuracy= 0.1 oC) at four positions along the acoustical ray path. The results showed the arrival time of acoustic waves were approximately constant and it was 177 ms. Finally, the depth- and range-averaged sound speed and the water temperature along the ray path were estimated from the mean travel time. The temperature varied between 19.7 to 19.9 oC that was confirmed by Temperature Sensor data. The temperature resolution of AT technique was estimated around 0.04 oC that shows the more accuracy than the Temperature Sensor. The result of this study showed the ability of acoustic tomography technique to monitor the water temperature in natural aquatic environments.

Understanding the concept of water balance is one of the most important prerequisites for sustainable management of water resources in the watersheds. Therefore, the components of water resources in a catchment system should be compared at different time periods, and also the effect of each of them should be identified on varied hydraulic components of the hydrological systems. The SWAT model is an example of a physically based hydrologic model which can be used for large-scale simulating and monitoring of water cycle processes based on the characteristics of the catchment area and its climatic conditions. The main object of this study is the hydrologic simulation and water balance estimation for the period 2000-2009 in the Zayandeh-Rud River Basin. The Zayandeh-Rud River Basin is located in the arid and semi-arid central region of Iran. This area is very variable in terms of rainfall. As well as the state of water resources and water consumption is very complicated in this catchment. In the present study, the soil and water assessment tool (SWAT) used to simulate water balance in the Zayandeh-Rud River Basin. The input required data included digital elevation model, land use map, soil texture map and meteorological information including daily rainfall data and minimum and maximum temperature data were introduced to the model and the model was implemented with these data. The sensitivity of the flow-effective parameters was determined using the p-value and t-state criteria by the SUFI2 algorithm in the SWAT-CUP program. The model was calibrated monthly and validated with the selected parameters in the sensitivity analysis using the Nash-Sutcliff criteria and the coefficient of determination by the application of the data of six stations including. Calibration of the model was conducted for 2000-2006 and validation of the model for the years 2007-2009. The results of sensitivity analysis showed that considering the characteristics of the study area, the SWAT model is more sensitive to the 17 effective parameters on runoff. The selected parameters also confirm the results of previous research carried out in the region. The sensitive parameters selected in the sensitivity analysis step were used to calibrate the model. In the next step, the parameters of SWAT-CUP software were entered. After that, these parameters were repeated 1000 times with the SUFI2 algorithm, and the optimal value for each parameter was determined. The Nash-Sutcliff coefficient and the coefficient of determination in the six hydrometric stations are greater than 0.56 and 0.69 in calibration and verification periods respectively, which indicates that the model has a satisfactory ability to run in runoff simulation. The contribution of the components of the water balance including evapotranspiration, surface runoff, lateral flow, groundwater flow, and deep aquifer recharge was calculated from annual basin precipitation. The amount of extracted water from the hydrological components indicated that the largest share of the water balance was related to actual evapotranspiration, the range of variations in the type of precipitation in the study area ranged from 60.1% (2000) to 92.7 % (2007). After evapotranspiration, surface runoff with a change of 22.2% (2005) to 8.6% (2009) and groundwater flow with a change of 14.2% (2000) to 20.5% (the year 2007) had relatively high fluctuations and a large share in the basin balance. These results indicate that the lateral flow with a range of 3.1 to 1.9% had no significant change in these years. Also, the deep aquifer recharge with the range of 1.2 to1.5% was the lowest in 2003 and 2009, respectively. The results showed that the calibrated model for the Zayandeh-Rud River Basin had a desirable performance for both calibration and validation periods. Therefore, the SWAT model has acceptable performance for simulating the water balance of the area. In addition, the results of this study showed that 65.98% of the total annual precipitation in the basin is in form of evapotranspiration, which compares to the other water balance components has the highest part. As well as surface runoff with 15%, groundwater flow with 13.7%, lateral flow with 1.5%, and deep aquifer recharge with 0.8% have other parts of the water balance components in Zayandeh-Rud River Basin. The results also indicate that the highest water losses in the soil and groundwater resources of the basin are due to evapotranspiration. Therefore, serious measures to prevent the loss of water through evapotranspiration in the region to be necessary. The results of this research can be used to predict the effects of climate change and the applicable management practices in the region, which are presented in scenarios to the model.

This study was conducted to investigate the effects of applying deficit irrigation on aboveground biomass، leaf area and root biomass for maize Hybrid 704 single-cross. Experimental treatments included 4 different irrigation levels، 5 growth stages with three replicates in a completely randomized factorial statistical design. Aboveground biomass، leaf area and root biomass in 4 longitudinal sections of root length were measured at different growth stages. Results indicated that different irrigation levels had significant effect on aboveground biomass، leaf area، root biomass of sectional root lengths and total root biomass (P<0. 05). The maximum aboveground biomass، leaf area and total root biomass were observed at milk stage in both years. These values were 318. 9 and 465. 1gr for aboveground biomass، 6497 and 6533cm2 for leaf area and 32. 3 and 36. 6gr for total root biomass in 2009 and 2010، respectively. The optimum level of water stress with maximum root biomass for maize can provide useful information for scholars and engineers to increase irrigation water use efficiency under deficit irrigation management.