مجله تحقیقات آب و خاک ایران
سال پنجاه و چهارم شماره 3 (پیاپی 87، خرداد 1402)

One of the main goals of this research is to evaluate the changes in intensity-duration-frequency (IDF) curves under the effect of climate change in the future to show the necessity of adopting new methods in urban flood management. In this research, the dynamic method and the PRECIS regional climate model were used for spatial downscaling, due to the need for high accuracy in urban areas. The data generated by general and regional circulation models are too large in terms of temporal resolution to be used in the development of IDF for short-term precipitation. In this research, a special and two-step method was used to convert daily rainfall into short-term rainfall up to a resolution of 10 minutes. In this research in the city of Rasht, as representative of the Semi-Mediterranean climate, the IDF curves for the distant future (2070-2100) were produced and were compared with the curves in the near historical period to ensure using the data belonging to the first and second decades of the 21st century, i.e. after occurring the climate jump in the region. The results showed that for storms with a short duration of 10 to 60 minutes for all return periods, the intensity of precipitation increases significantly. Therefore, it is necessary to review the intensity-duration-frequency (IDF) curves to adopt new methods in urban flood management in Rasht City.

Soil erosion by water is a global threat to the environment which negatively affects soil and water quality. Soil erosion modeling is an efficient method to simulate soil erosion, to identify sediment source areas, and to evaluate soil conservation measures. In this study the Soil and Water Assessment Tool (SWAT) was used to model runoff and sediment in Gawshan dam watershed in west of Iran. For this purpose, climatic data obtained from a period of 11 years, from January 1, 2005 to the end of December 2015, from the stations of Bavale, Ravansar, Sanghor, Ghorve, Sanandaj, Kermanshah, Kangavar and Kamiyaran were used. We used two different approaches for estimating of model parameters. In the forward deterministic approach model parameters were independently derived from digital elevation model (DEM), soil and land use maps and climate data, whereas in the inverse stochastic approach model calibration were performed by sensitive model parameters using Sequential Uncertainty Fitting (SUFI-2), which is one of the programs interfaced with SWAT, in the package SWAT-CUP (SWAT Calibration Uncertainty Programs). Model performance was evaluated using the coefficient of determination (R2) and Nash-Sutcliff efficiency (NS) for forward approach and P factor and R factor for inverse approach. Results showed that in the forward approach, based on monthly data (2008-2013), the model performance was satisfactory for runoff (R2=0.66; NS=0.63) and fair for sediment (R2=0.42; NS=0.3). However, model prediction improved for both runoff (R2=0.94; NS=0.83) and sediment (R2=0.61; NS=0.53) when they were averaged on monthly basis. Calibration of the model parameters improved its performance for runoff (P factor>0.6; R factor<1) and sediment (P factor>0.4; R factor <1). These results demonstrated that the SWAT has the potential to be used as a decision making tool for Gawshan dam watershed management.

Recently, the increase in water demand and the pollution of water resources have threatened groundwater resources. The purpose of this research is to investigate the impact of the conservative scenarios of groundwater resources and its effect on the restriction of the aquifer volume reduction process using the system dynamics approach in Marvdasht-Kharameh plain.The current conditions of the aquifer during the statistical period of 2005-2018 were simulated and recalibrated according to the observed values of the aquifer volume. The scenarios have been applied in three ways to investigate the effect of climate change, changing the amount of water allocated to farmers from Doroudzan dam and changing the cultivation pattern under the scenarios SSP1-2.6 and SSP5-8.5 on the volume of the aquifer. In order to investigate the effect of climate change on Marvdasht-Kharameh aquifer in the period from 2021 to 2046, the rainfall data of GFDL-ESM4 model under two scenarios SSP1-2.6 and SSP5-8.5 were considered. The study of the impact of climate change and the release of the Darudzen dam showed that the volume and recharge of groundwater will decrease in the scenario SSP1-2.6 (50 and 49 million cubic meters respectively), and in the scenario SSP5-8.5 (54 and 67 million cubic meters respectively),. Also, by removing the rice crop from the cultivation pattern of Marvdasht-Kharameh plain in the future climate conditions under two scenarios SSP1-2.6 and SSP5-8.5, which will add 495 and 207 million cubic meters to the aquifer volume respectively, the greatest effect on increasing the aquifer volume will be achieved. It will have 30 and 50 percent reduction in the area under rice cultivation. Therefore, in order to manage and preserve groundwater resources, it is necessary to change the cultivation pattern and replace high consumption crops with low consumption crops.

The large share of the agricultural sector in the consumed water resources shows the importance of agriculture water productivity improvement for coping with the water shortage crisis. Cropping pattern modification has been proposed as a key solution in this improvement. The efforts to implement cropping pattern modification policies have been largely unsuccessful. One of the most important reasons for failure to implement the cropping pattern is the uneconomical nature of the proposed model and the lack of required attention to stakeholders. In the Qazvin plain irrigation network, the concern is that the cropping pattern is not implemented by the stakeholders for the optimum use of the available water resources. In this research, based on previous studies review, the questionnaire survey was designed based on the Likert scale. Then, the stakeholders were sampled by purposive sampling using the Q methodology and the top 25 statements were selected as Q sets. The collected data were analyzed using KADE desktop software. The results showed that there are four dominant perspectives among the stakeholders those explain cumulative variations by 45 percentages. The identified perspectives were classified as follows: «Economy oriented and technical perspective», «perspective of socio-technical dissatisfaction and in favor with policy making», «perspective of agreement with technical, social and environmental issues and low attention to policy making» and «perspective of focus on policy making and paying little attention to social and technical issues». All perspectives had a reliability higher than 0.95, which shows perspectives have good reliability and validity.

Today, the increase in food demand has led to an increase in energy use, which has some environmental consequences such as air pollution and global warming. Irrigation is one of the energy-intensive operations in agriculture, which consumes great part of energy inputs and has harmful environmental effects. Applications of modern methods of irrigation in agriculture can be considered from different aspects. So, the aim of this study was to evaluate the energy and environmental indicators of walnut orchards under surface and pressured irrigation methods. The required data, including information about inputs and energy consumed in walnut orchards, were collected using questionnaires and face-to-face interviews in Shahr-e Kord and Saman region of Chaharmahal and Bakhtiari province. The collected data belonged to the production period of 2021–2022. The averages of total energy consumed for walnuts production in pressured and surface irrigation systems were 29573.53 and 25058.46 MJ ha−1, respectively. This shows that despite less water consumption in the pressured irrigation system, the total energy input in this irrigation system is more than the surface irrigation system. No significant difference was observed regarding the performance of walnut in the two mentioned irrigation systems. The inputs energy consumption in the walnut production with the pressurized irrigation system were highest for plastic and farmyard manure (about 32% and 15%, respectively); while in surface irrigation system, the share of nitrogen fertilizer and farmyard manure were highest (about 30% and 25%, respectively). Energy ratio of walnut production in surface irrigation systems was computed as 3.58, while the corresponding value in pressured system was 2.77. In other words, surface irrigation had better conditions in terms of energy indicators. The LCA results of walnut production showed that in the two irrigation systems, the greatest effects in human health and the ecosystems are from on-farm emissions. In general, the investigation of the environmental indicators of walnut production in the two irrigation systems showed that the use of the pressured irrigation system reduces the environmental damage.

Dust storm (DS) is a harmful climatic phenomenon that causes damage to the environment and agriculture. The aim of this study was to investigate the trend analysis of seasonal and annual changes of DS during climatic period of 1977-2021 in arid climates of Iran in 42 synoptic stations. First, the long term changes of DS, before and after 2005 were compared togeather and investigated. Then, time series trend analysis was performed using regression method and spatial analysis by Menn-Kendall and Sen`s Slope methods. The results showed an increase of DS after 2005. The trend of time series also showed an increasing trend in most climates and stations, with the most intense increasing slope during the periods of 2005-2010 and after 2011. The results showed that the frequency of stations with a significant increasing trend in the semi-arid climates on a seasonal and annual basis were up to 93 and 64; and in arid climates up to 83 and 83 percent of the stations, respectively. On the other hand, the incremental changes of 45-year DS in the extra arid climate in winter, spring, summer, autumn and whole year were up to 68, 69, 68, 55 and 261 days; in arid climate up to 54, 31, 37, 45 and 187 days; and in semi-arid climate has reached 23, 21, 9, 12 and 58 days, respectively. Therefore, the temporal change of DS is towards the winter and spring seasons, which indicates the spread of this phenomenon to the wet seasons.

Magnetic susceptibility (χ) is a fast, non-destructive and simple method for determining soil properties and describing soil formation processes, which has been studied at different geomorphic levels, in order to investigate the effects of soil formation factors (elevation, elevation, and parent materials). This research aims to evaluate the changes of different forms of iron, drainage, land use and human activities (agriculture) on changes in soil magnetic receptivity and investigate CIW, CIA and CPA aeration indices in different geomorphic units in the year 2021 in Chaldaran study area in the northwest Iran and West Azarbaijan province. For this purpose, 9 test soils were excavated and evaluated in five dominant geomorphic units in the region, such as slope plain, covered pediment, alluvial cone, plain and flood plain. After dissection and sampling from the genetic horizons of the excavated rocks and transporting them to the laboratory, the physicochemical properties of the samples were measured along with their magnetic properties and aeration indices of CIW, CIA and CPA. The results showed that the range of magnetic receptivity of the soils of the region varied from 42.90 x 10-8 to 1053.20 m3 kg-1. Also, the average value of χlf of the studied soils in different geoforms was observed as flood plain > alluvial cone > covered pediment > plain > slope plain. Although the values of magnetic receptivity depending on the frequency of the examined soil samples were variable between 0.07% and 3.50%; But in most horizons, the value of χfd was less than 2%. This result indicates the presence of multi-domain coarse particles in the region that were added through parent material. Also, the results of CIA, CIW and CPA aeration indices indicate the stage of weak to moderate aeration in the region. Further, it was observed that the leaching of diamagnetic materials to the lower soil layers, ferrimagnetic minerals transferred by water and agricultural activities, has led to changes in the χlf trend with depth. Also, according to the A-CN-K curve and the chemical composition of the oxides of the studied elements, a moderate aeration process was observed in the region. On the other hand, the studied region is affected by water sediments and agricultural activities; It seems that carrying out the processes of sedimentation, soil formation, aeration and cultivation in this area has changed the chemical composition of the soils. Finally, it can be concluded that the equitic conditions caused a decrease in the acceptability and amount of Fed due to poor drainage in the studied soils.