Climatology
Elham Alizadeh; hossein mousavi; Jamshid Yarahmadi; Abdollah Faraji
Abstract
Introduction Climate change is one of the most important phenomena of the present century, which has created many problems and challenges both globally and regionally and nationally. In the second half of the twentieth century, global warming relative to The first half of this century has increased ...
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Introduction Climate change is one of the most important phenomena of the present century, which has created many problems and challenges both globally and regionally and nationally. In the second half of the twentieth century, global warming relative to The first half of this century has increased and it is predicted that this increase in temperature will continue in future periods, resulting in changes in the level of climatic conditions in different parts of the world. Due to the lack of atmospheric precipitation, due to the increase in temperature, the rate of evaporation has increased significantly and can greatly affect the aggravation of water shortage conditions in surface currents, especially evaporation from the surface of lakes behind dams. Percentage by evaporation leads the country to higher values (Farajzadeh and Ghasemifar, 1398). Regarding the changes in Iran's water resources in the horizon of 2100, few studies have been done and most have been case studies (Fahmi, 1393). Although the results of these studies, based on the climatic models and different scenarios used, sometimes show contradictions, so it is necessary to do more studies in this field. Methodology The present research has been done in three specific sections and the output of each section has been used as the input of the next section. In the first part, climate change in the form of precipitation variables in the study area is detected and subsequently, rainwater runoff in the Daryan catchment is simulated. Then, while identifying the characteristics of hydrological drought periods in the basin, the probability of occurrence, intensity and duration of hydrological drought periods are calculated based on the fit of different statistical distributions for different return periods in the third section. Results and discussion Climate change is one of the most important environmental problems of this century. Thus, evaluating the phenomenon of climate change and reducing its effects on both global and regional scales has attracted the attention of many researchers, planners and legislators (Yohe et al., 2007). Proper assessment of these effects requires the existence of climatic information with appropriate spatial distribution and long-term time series, as well as a thorough understanding of its future trends at the regional and local scale. Despite the fact that today the output of public circulation models (GCM) are the main sources of future climate data production. One of the most important consequences of climate change includes changes in the hydrological cycle and river flow regime of watersheds. Therefore, the present study aimed to investigate the possible effects of climate change on rainfall and runoff in the Daryan catchment area north of Lake Urmia. In this study, statistical method (SDSM) and data of CanESM2 Canadian climate model in the form of three scenarios RCP2.6, RCP4.5 and RCP8.5 in order to micro-scale the precipitation data of five synoptic stations adjacent to the sea basin and changes Its future is used. Here, the basic period (1961-2005) and future periods (2049-2020), (2079-2050) and (2080-2100) were selected. In this research, the threshold level method has been used to identify hydrological drought periods and extract its characteristics. The results of the analysis of the last 35 years of hydrological droughts in the Daryan Basin showed that 44 drought events occurred in this basin, which in total, led to a reduction in surface flow volume of about 140 million cubic meters in this basin. Conclusion The simulation results of SWAT model showed that the annual average runoff of the sea basin in the first period (2020-49) in all three scenarios increases by 3.7 and 6%, respectively, compared to the base period. While in the rest of the periods of all scenarios, runoff reduction is predicted compared to the base period. Accordingly, a decrease in surface runoff compared to the base period is predicted for five months of the year (April to August) and an increase in the remaining months. Future changes in precipitation at Tabriz station, which is the basis for modeling runoff in the Daryan basin, are not very noticeable compared to the base period, and only in the period (2049-2020) all three scenarios are predicted to increase by 5, 2 and 8%, respectively, compared to the base period. In the other periods, in all three scenarios, a decrease in rainfall is predicted compared to the base period. Results of evaluating the effects of climate change on rainfall and surface runoff in the Daryan Basin with the results of other researchers in the catchment area of Lake Urmia, including: Goodarzi and Fatehifar (2010) in the Azarshahrchai Basin, Qaderpour et al. (2016), Dariane et al. (2019) ), Sobhani et al. (2015), Goodarzi et al. (2015) and Salehpour and Malekian (2019) are consistent.
Geomorphology
Jamsheid Yarahmadi; Nasrein Hajihassani; Asgar farajnia; Ali Tajabadei pour
Abstract
Recent permanent trend of drought in East Azerbaijan province has caused of the reduction in available water resources, a sharp drop in the groundwater levels as well as drying of the Uremia Lake and finally increasing saline lands surrounding the Uremia Lake. Also, the orchards and farm lands which ...
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Recent permanent trend of drought in East Azerbaijan province has caused of the reduction in available water resources, a sharp drop in the groundwater levels as well as drying of the Uremia Lake and finally increasing saline lands surrounding the Uremia Lake. Also, the orchards and farm lands which strangely depended on groundwater have been indiscriminately and disproportionately developed related to the current climate condition. Therefore, modification of agricultural patterns is one of the best solutions for efficient water usage in agricultural section and is considered as the only practical solution in relation to the sustainable development of agriculture. This study was conducted in order to determine the suitability for growing pistachio orchards and replacing it with second and third degree gardens. Suitable areas were determined by modeling in ArcGIS software environment based on various affective climate parameters in various stages of plant growth. Results show that about 25 percent of the area is completely suitable, 27 percent is relatively suitable and 48.4 percent is completely unsuitable for pistachio plantation. Also, marginal areas of the Uremia Lake are quite suitable which indicates that the replacement of the orchards of pistachio with high water consuming orchards in the area is fully practical and feasible. The results could provide more reliable basis for agricultural decision-making and planning to provide a new model to replace the pistachio orchards with high water consuming orchards.
Jamshid Yarahmadi; Mohammadreza Nikjoo
Volume 16, Issue 39 , May 2012, , Pages 151-169
Abstract
The present work aims to assess the effects that landuse change has induced on the flood frequency regime. Study area covers upstream of Alavian Dam (250 km2) in the Sofi Chai basin. The torrential periods (in terms of flood event frequency and duration) has been carried out by comparing each daily discharge ...
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The present work aims to assess the effects that landuse change has induced on the flood frequency regime. Study area covers upstream of Alavian Dam (250 km2) in the Sofi Chai basin. The torrential periods (in terms of flood event frequency and duration) has been carried out by comparing each daily discharge with the base flood. Here, the base flood (flood with 2 years return period) was calculated from maximum annual discharge based on fitting various distribution models, and then the best fit model was chosen by considering RSS criteria. The results indicate that flood events and their duration tended to be abated on the last decade.
In this research, landuse/cover changes have been detected by interpretation of remotely sensed data based on object oriented method. The results indicated that the positive changes of crop patterns (overdeveloping of orchards as well as dry farming increasing) were occurred in the study basin.
HEC-HMS model was applied for simulation of rainfall-runoff process and assessment of the effects of landuse changes on the flood frequency. HEC-HMS simulated results based on corresponding CN derived from 2000 to 2005 satellite images show 36% abated of flood event respectively.
It should be noticed that the construction of a part of mechanical watershed management operations can reduce the flood events by reserving the surplus runoff.
