Hamed Harriri; seyed abbas hosseini; Amir Khosrojerdi
Abstract
Introduction
Predicting changes due to climate change and its possible consequences on hydrological processes of the watershed helps to solve the challenges facing managers and water resources planners in the coming period. The effects of this phenomenon and gabion check dams simultaneously on the sedimentation ...
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Introduction
Predicting changes due to climate change and its possible consequences on hydrological processes of the watershed helps to solve the challenges facing managers and water resources planners in the coming period. The effects of this phenomenon and gabion check dams simultaneously on the sedimentation of Dehbar Basin have not been studied so far, so the aim of this study is to investigate this with the perspective of the next 30 years, using SWAT and LARS-WG models and the ability of these two models to simulate climate change and remove gabion check dams.
Materials and methods
In this research, the performance of gabion dams as a reservoir in the Dehbar Basin, 10 km west of Mashhad and south of the city of Torghabeh, which has a cold semi-arid climate, is compared to the amount of sediment output from the basin for the next 30 years with the LARS-WG statistical model and SWAT hydrological simulation model has been evaluated. There are five gabion dams in this area. To predict the meteorological variables of the upcoming period at the level of Dehbar Watershed, after recalibrating the LARS-WG model, the HadGEM2 model and three scenarios of RCP8.5, RCP4.5 and RCP2.6 were used for the microscaling of meteorological data in the period of 2050- 2020. Kolmogorov Smirnov (K-S), t and F statistical tests were used to check the performance of the simulation results in this model. To prepare and implement the SWAT model, the map and digital model information of elevation, soil, land use, hydrological and meteorological data were used. The tank was used to introduce gabion dams to the model. In order to analyze the sensitivity, calibration and validation of the SWAT model, SUFI-2 semi-automatic algorithm was used.
Results and discussion
The average values of the simulated precipitation are in good conformity with the observed values and the biggest difference is related to the months of February and April. Regarding the standard deviation values of monthly rainfall, the biggest difference belongs to the months of February and March. The average simulated minimum temperature is also in very good agreement with the observed values. Also, for the maximum temperature, a trend similar to the minimum temperature is seen. Also, the p-value obtained from the t-test for the aforementioned variables, there is no significant difference between the average temperature and precipitation data produced and the observed data, and the LARS-WG model has been able to calculate the average temperature and precipitation very well. To simulate monthly precipitation in all scenarios (RCP8.5, RCP4.5 and RCP2.6) in the horizon of 2050 in the first seven months of the year is lower than the monthly precipitation in the base period, but an increase in precipitation is observed for the second five months of the year. Also, in the horizon of 2050, the temperature will increase on average compared to the base period. To draw the curve of the sediment gauge, the method of batch average with modified FAO coefficient was used. The amount of observed sediment was calculated as 2.14 tha-1yr-1. For the calibration and validation of the SWAT model, at first, using CUP_SWAT software, the parameters that had a greater effect on the discharge and sediment output from the basin were identified. In order to analyze the sensitivity, calibration and validation of SWAT model, SUFI-2 semi-automated algorithm was used. After that, the effects of climate change on the amount of runoff and sediment in the basin were investigated using the validated SWAT model. The results show a decrease in rainfall, an increase in temperature and a decrease in runoff in the horizon of 2050. The precipitation changes for RCP4.5 and RCP2.6 scenarios are +9.3% and +3.1%, respectively, and -4.6% for RCP8.5 scenario. On average, gabion dams reduce 57.09% of sediment exit from the basin.
Conclusion
In this research, the effects of climate change on the sediment output from Dehbar Basin in the period from 2020 to 2050 and the effect of gabion dams in the existing conditions (presence of dams) and in the conditions of removal of these dams were investigated. In all scenarios, the minimum and maximum temperature increased in the 2020-2050 period compared to the base period. One of the negative effects of temperature increase is change in the amount and time-spatial pattern of precipitation. The results indicate that the SWAT model is capable of simulating hydrological processes and sedimentation in relatively small to medium watersheds with complex conditions such as Dehbar Basin, even with limited observational data, with acceptable accuracy. The increase in the amount of sediment at the outlet point of the watershed, despite the decrease in rainfall and runoff, indicates short-term rainfall with high intensity, which increases the occurrence of flooding conditions. From the changes in the amount of erosion and sedimentation in the horizon of 2050 and with different scenarios, it can be concluded that the climate change will affect the erosion of the basin in the future and the simulation model can be effective in predicting the erodibility. Therefore, the results obtained from the SWAT model provide the possibility of recommending its use in the region.
Navid Ziaee; Majid Ownegh; Hamid Reza Asgari; Ali Reza Massah Bavani; Abdolrasoul Salman Mahini; Mohsen Hoseinalizadeh
Abstract
The effects of a change in the temperature and particularly precipitation around the world are not well known due to their complexity and spatial variations. In this research, the impacts of climate change on some climatic variables (temperature and precipitation) has been studied in Hableh Roud ...
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The effects of a change in the temperature and particularly precipitation around the world are not well known due to their complexity and spatial variations. In this research, the impacts of climate change on some climatic variables (temperature and precipitation) has been studied in Hableh Roud Basin due to ecological sensitivity and special situation of this area and HadCM3 model data were analyzed using LARS-WG model according to A2, B2 and A1B scenarios. The seasonal variations of precipitation, minimum and maximum temperature of the synoptic stations of Firouzkooh and Garmsar were investigated in two periods of 2030-2011 and 2046-2065. Results showed that precipitation between 0.23 to 0.48 mm will increase in the near future and will decrease between 0.08 to 0.15 mm in the middle future. The minimum temperature will increase between 0.5 to 0.67° C in near future and between 1.54 to 1.97° C for the middle future. Maximum temperature will increase in near future between 0.43 to 0.6° C and between 1.47 to 1.89° C in middle future. Finally, the climatic conditions of the Hableh Roud Basin will have a significant difference compared to current conditions in upcoming periods. Therefore, regarding to this issue, as well as awareness of the direct and indirect negative effects of climate change in the various parts of the basin (agriculture, water resources, environment, natural resources, health, industry and economics), long-term planning and strategic management of new situations is essential.
Abbasali Mohammadian; Ali Talebi; - -; - -
Abstract
Weather generator models are used to predict climate parameters variations caused by climate change phenomenon. It can be used as a downscaling method for hydrological modeling, risk assessments in agriculture etc. Herein this research, HadCm3 model were used. Three different scenarios were considered. ...
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Weather generator models are used to predict climate parameters variations caused by climate change phenomenon. It can be used as a downscaling method for hydrological modeling, risk assessments in agriculture etc. Herein this research, HadCm3 model were used. Three different scenarios were considered. Downscaling were done using LARS-WG model. LARS-WG is a statistical downscaling model. Different climatic parameters such as minimum and maximum monthly temperature, minimum and maximum precipitation were predicted based on A1B, B1 and A2 scenarios. This research was done for Balqur Watershed in Kardeh Dam in Mashhad. Base line period is 1961-2010. Prediction was done for 2046-2065. Results showed that changes in minimum temperature would be higher than maximum in 2046-2065. Generally precipitation would be decreased except for a light increase in A2 scenario. But even if it is considered, it would not be as important as an increase in temperature would increase evaporation too. So, with regard to this fact and be aware of directly and indirectly negative effects of climate change on the environment and other sectors, strategic long-term plans to manage the new situation seems inevitable and necessary.
Boroumand Salahi; Massoud Goudarzi; Seyed Asaad Hosseini
Abstract
Predicting the temperature and precipitation changes is necessary for assessing the change in the future and to mitigate the harmful impacts of climate change on water resources and agriculture, environmental, economic and social issues. Accordingly atmospheric general circulation models (GCMs) have ...
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Predicting the temperature and precipitation changes is necessary for assessing the change in the future and to mitigate the harmful impacts of climate change on water resources and agriculture, environmental, economic and social issues. Accordingly atmospheric general circulation models (GCMs) have been developed for simulation of climatic parameters. In this research, output data of HadCM3 general circulation model (with three climate change scenarios A1B, A2 and B1) were downscaled using LARS-WG Statistical Model in selected stations of the Urmia Lake Basin and Results has been evaluated and analyzed from three selected synoptic stations, including Saghez, Tabriz and Urmia stations in the base period (1961-1990) and the 2050 (2046-2065) for three variables minimum temperature, maximum temperature and precipitation. In LARS-WG model analysis, evaluation of the amount of MSE, RMSE, MAE indexes were done and correlation coefficients were determined. The conclusion can be presented herein that: the model was fit for the region. The overall results for 20 years of 2050s, indicate a decrease of 12.1 percent in precipitation and also 1.3 Celsius degrees would be increased in temperature compared to the base period. In the study area, the highest maximum temperature increase would be in Tabriz synoptic stations and the highest minimum temperature and highest decries precipitation would occur in Urmia station. The results of this study would help enormous the policymakers and planners for water resources in the future.
