Geomorphology
Ali Bigham; S.Asedolah Hejazi; Mohammad Hossein Rezaei Moghaddam; Jamshid Yarahmadi; Fariba Karami
Abstract
Changes in erosion and sedimentation of the basin are one of the most important factors that affect different parts of human life and natural life. it is very necessary to receive these changes quantitatively, which mainly take place under temperature fluctuations and climate changes in different regions, ...
Read More
Changes in erosion and sedimentation of the basin are one of the most important factors that affect different parts of human life and natural life. it is very necessary to receive these changes quantitatively, which mainly take place under temperature fluctuations and climate changes in different regions, in order to be more prepared to deal with its negative consequences. In this research, erosion and sedimentation changes in Hajiler watershed were investigated and predicted using GeoWEPP and SWAT models. Based on this, first, by using the data of the current situation of the Ahar synoptic station and using the SDSM model, the changes of the statistical period2020-2040 in three scenarios RCP2.6-RCP4.5-RCP8.5 were investigated, then simulation and prediction of erosion changes was carried out. and sedimentation was done under the influence of climate change by using popular models. The output of the SDSM model indicates an increase in temperature and a decrease in rainfall for the basin until 2040.And the analysis of the simulation results of the sedimentation rate of the models showed that in the studied basin, the GeoWEPP with the selection of the domain method has a suitable level in estimating the sedimentation rate compared to observational statistics. The final model was chosen to predict the amount of sediment in the mentioned period of the basin. Using the downscaled results of the atmospheric general circulation model, the sediment changes in the statistical period of 2020-2040 under the above mentioned three scenarios were estimated as -1.97, 4.45, and 2.98, respectively.
Ziba Kounani; Alireza Ildoromi; hossien zenivand; Hamid Nouri
Abstract
1-Introduction Due to the importance of climate change and the effects it can have on runoff, developing a suitable model for simulating the present and future conditions of the catchment areas is of great importance (Rajabi et al, 2012). Nowadays, the LARS-WG and SDSM models are used to downscale environmental ...
Read More
1-Introduction Due to the importance of climate change and the effects it can have on runoff, developing a suitable model for simulating the present and future conditions of the catchment areas is of great importance (Rajabi et al, 2012). Nowadays, the LARS-WG and SDSM models are used to downscale environmental parameters in climate change studies nowadays. Studies show that the SDSM model has less uncertainty and a more complex simulation process, and the LARS-WG model with simpler process and faster performance is more efficient (Aghashahi et al., 2012). Considering that many of Iran's watersheds lack hydrometric stations, it is of great importance to use those methods that can estimate the amount of runoff obtained from the rainfall. Therefore, the present study aimed to investigate the role of climate change in estimating runoff from the Silakhor-Rahimabad basin of Lorestan using a rainfall-runoff model (SIMHYD). 2-Methodology Silakhor-Rahimabad basin is in the catchment area of Dez Dam in Borujerd, Lorestan Province, which is located between N 33º 45¢ and 34º 7¢ and E 48º 29¢ and 48º 57¢. First, the baseline data including observation data of minimum temperature, maximum temperature, precipitation and sunshine during the period 1990-2014, and rainfall-runoff data including evaporation, rainfall and flow data, which were available, were received from the General Department of Aerology and Regional Water Authority of Lorestan Province, respectively. In this study, the daily data from Borujerd metrological synoptic station were used as the basis because they were complete and the elevation of the station was equal to the average of other stations’ elevations. For the evapotranspiration variable, the mean daily data from Rahimabad, Borujerd, and Silakhor stations were used, the mean daily data from the six rain-sensing stations for the rainfall variable. Moreover, Rahimabad hydrometric station at the outlet was used as the base station to observe the runoff variation in the basin. 3-Results and Discussion The results of the evaluation of criteria show that the LARS-WG model has a good ability to simulate rainfall parameters, minimum temperature, and maximum station. The simulated precipitation is in good agreement with the observed values (Table 1 and 2). After assuring the ability of the LARS-WG model to produce the rainfall data, minimum and maximum temperatures of Silakhor-Rahimabad Basin, the output of the HADCM3 model was downscaled under the scenarios A2 and B1, the parameters were predicted and compared with their values in the period 1990-2014 (Figures 2, 3 and 4). The results of the LARS-WG model indicate a decreasing trend of precipitation and temperature rise under both scenarios A2 and B1 for the period 2046-2065. The average amounts of annual rainfall predicted under the scenarios A2 and B1 are 451.445 and 4.420 mm, respectively. If the annual rainfall is 453.8 mm in the base period, the study area will observe a decrease in precipitation from 51.0 to 20.7 percent. The results obtained in the SDSM model under the two climate scenarios A2 and B2 for the future period indicate that the average air temperature is increasing and in the period 2050, the monthly average temperature, compared to the 1990-2014 period, increases in most months of the year. Also, rainfall has a decreasing trend in this period (Figure 5). Investigations show that the model efficiency has a direct correlation with the recharge coefficient, infiltration coefficient and soil moisture storage capacity. The effects of climate change on runoff are presented in Figures 9-16. In the period 2046-2065, the amount of runoff in the studied basin will decrease compared to the 1990-2014 period. This decrease in runoff rate can be attributed to the increase in temperature, followed by an increase in evaporation and a decrease in rainfall. Regarding the study of temperature and rainfall for the future period and monthly runoff, it is observed that the amount of runoff will decrease in the future period. 4-Conclusion In recent decades, the increase in greenhouse gases and thereby, the rise in temperature, have made Earth’s climate system imbalanced and caused massive climate change in most parts of the planet. Therefore, it seems necessary to apply climate predictions in national macro plans, especially in relation to natural disasters. The results indicate the decrease in precipitation and temperature rise in both SDSM and LARS-WG models. Also, in the present study, the SDSM model showed more variations than the LARS-WG model. Finally, the results obtained in both statistical downscaling models indicate the decreased amount of runoff in the studied basin is in the future period. In the study of the effect of climate change on runoff in the studied area, according to the values of Nash-Sutcliff coefficient and the coefficient of determination obtained at the calibration step (0.63 and 0.779, respectively) and the verification step (0.61 and 0.61, respectively), it is observed that the SIMHYD model has acceptable performance in the studied basin. These results are consistent with the findings of Aghashahi et al. (2012), Rajabi et al. (2013), Zolgharnein et al. (2013), Zhang et al. (2014).
Behrooz Sari sarraf; Tahereh Jalali Ansaroodi
Volume 6, Issue 19 , September 2019, , Pages 163-185
Abstract
Introduction In the recent decades, the growth of the industrial activities and the increase in greenhouse gases have imbalanced the Earth's climate which is called the phenomenon of the climate change. This phenomenon directly affects the hydrological parameters. While climate change directly affects ...
Read More
Introduction In the recent decades, the growth of the industrial activities and the increase in greenhouse gases have imbalanced the Earth's climate which is called the phenomenon of the climate change. This phenomenon directly affects the hydrological parameters. While climate change directly affects surface water resources through changes in the major long-term climate variables such as air temperature, precipitation, and evapotranspiration, the relationship between the changing climate variables and groundwater is more complicated and difficult to quantify. The large amount of water is needed in different parts of arid and semi-arid regions provided through groundwater resources. In recent decades, the quantity and quality of water resources have been reduced by unprotected exploitation. In addition, climate change and global warming increase the severity of the problem. Therefore, the predicted effects of climate change on groundwater recharge play an important role in the management of these resources in the future. In this study, Global circulation models, HadCM3 under A2 and B2 scenarios, were used for investigating the impact of climate change on groundwater recharge rates between 2017 and 2030, in the Tasouj aquifer. Methodology In this study, to investigate the climate change in Tasouj basin, the required data were obtained from two sources including Global model output AOGCM which was based on the HadCM3 model and the observed data of the precipitation and temperature of Tabriz synoptic station with the statistical length of 1961 to 2016. To downscale the general circulation modal, the statistical method of SDSM was used. The Hydrologic Evaluation of Landfill Performance model (HELP) simulates all of the important processes in the hydrological cycle including surface runoff, evapotranspiration, vegetative growth, soil moisture storage, and vertical unsaturated drainage for each discrete layered soil column. In general, the modeled hydrologic processes by the program can be divided into two categories of surface and subsurface processes. The modeled surface processes are snowmelt, interception of rainfall by vegetation, surface runoff, and evaporation of water. The modeled subsurface processes are evaporation of water from the soil, plant transpiration, vertical unsaturated drainage. Vegetative growth and frozen soil models were also included in the program to aid modeling of the water routing processes. The required general data included growing season, average annual wind speed, average quarterly relative humidity, monthly normal mean temperatures, maximum leaf area index, evaporative zone depth and latitude. Result According to the simulation of Hadcm3 model, during the period of 2017-2030, the average monthly temperature in all months of the year will increase in the studied area. The highest amount of heating in the average temperature will happen in July about 2 degree Celsius. The highest decrease in precipitation will occur in April and May about 9 mm than the base period. The highest percentage of precipitation in Tasouj basin is used for evaporation. During 14 years of the prediction, the year 2020 has the highest and the year 2029 has the lowest amount of evaporation. In terms of runoff caused by precipitation, the year 2023 with 9.69 percent of precipitation will have the highest runoff. The lowest and highest amount of recharge will respectively happen in 2021 and 2027. The depth of water precipitation is significantly affected by soil moisture and with increasing soil moisture; the depth of water percolation to soil will decrease. The soil moisture content is negative in 2027. Consequently, the highest amount of recharge due to precipitation will happen in Tasouj basin. In the base period, the year 1990 had lowest precipitation and the year 1963 had the highest precipitation. Due to having a negative soil moisture storage in 1990, of 148 mm of annual precipitation, about 76.28 mm was spent for recharge. The amount of runoff is almost zero in this year and the rest of precipitation is evaporated. Despite the high annual precipitation in 1963, due to the high moisture content of the soil, the amount of recharge is only 4 percent of precipitation and most of the precipitation changes to runoff and evaporation. The status of evaporation, runoff and recharge in 2022, as the forecasted most precipitation year, is similar to 1963. Discussion and conclusion In recent years, the climate change has led to significant changes in the weather and the condition of surface and underground water resources in different locations. The response of the groundwater resources to drought and climate change is not as rapid as that of the surface water, but considering that the renewability of these resources takes much longer than that of the surface water, the impact of long-term drought on groundwater resources is much more serious than that of the surface water resources. Therefore, the monitoring of the condition and maintenance of the sustainability of these resources is important. In this way, by using a step by step approach, the impact of climate change on recharge, evaporate, and runoff for the 2017-2030 period was investigated and the simulation result showed that with increasing temperature and decreasing precipitation, of three parameters of evaporation, recharge, and runoff, the evaporation dominated the other parameters. But the high consumption of basin and the increase of temperature and precipitation decrease prevented Tasouj aquifer from returning to its balance. Therefore, a principle planning to control the harvest and treatment of aquifer by underground dam and artificial nourishment is necessary
