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 ...
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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
Reza Ghazavi; Maysam Nadimi; Ebrahim Omidvar; Rasul Imani
Volume 5, Issue 15 , October 2018, , Pages 54-79
Abstract
Abstract
Introduction
Information about river flow change and subsequent changes in water quality characteristics can help to manage and plan water resources. The environmental and socio-economic impacts of river flow changes are very important in an environmental water management. Climate change is an ...
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Abstract
Introduction
Information about river flow change and subsequent changes in water quality characteristics can help to manage and plan water resources. The environmental and socio-economic impacts of river flow changes are very important in an environmental water management. Climate change is an important challenge that should influence different parts of human life on earth such as rivers and lakes. The Evaluation of the impact of climate change phenomenon on the hydrological processes of rivers can decrease the challenges of managers and planners of water resources in the next period. The selection of suitable models is important for evaluation and prediction of the effects of climate changes on rivers and watershed discharge. Several hydrological models were used to evaluate the effects of climate change on a hydrological cycle. The Soil and Water Assessment Tool (SWAT) has been extensively used, mainly by hydrologists for watershed hydrology related subjects, since 1993. SWAT model should include both a forecasting model and weather generating model. This means that the generated weather data of the future should be presented to SWAT model for forecasting future rainfall and temperature. This is a new possibility for future river and watershed hydrology studies. The main aim of this study was to evaluate the effect of the future climate change on river discharge of the Heruchay River in Ardebil using SWAT model.
Methodology
In this study SWAT2009 model was used to in investigate and predict the quantitative changes of the discharge of the Heruchay River. For the period of 2014-2041, the daily rainfall and temperature data were predicted under three scenarios of A2, B1, and A1B, using LARS_WG climate model. The simulated data was used as the entered information of SWAT model and the model was implemented for 2014-2041 period.
SWAT is a river basin scale model that should work on a daily time-step. It was developed to predict the effect of the management decisions and climate change on the water cycle. In this study, SWAT model was used for its ability to simulate and forecast stream flow and evaluate the effect of climate change on river discharge.
A topographical map (Digital Elevation Model), climate data (daily rainfall, Maximum and minimum temperature), and soil and land use maps were prepared using GIS and measured data. As the precipitation is an important key input that influences flow and mass transport of the rivers, 5 rainfall gauging stations and 2 weather stations located in the study watershed were used.
Result and Discussion
The results of this study showed that SWAT model had an acceptable performance for discharge simulation during calibration and validation periods with coefficients of variation of 0.81 and 0.8 respectively for calibration and validation. Based on the results of A2 and B1 scenarios, the flow rate of the study river increased, whereas a decrease in the flow rate was predicated based on the results of the A1B scenario. The results of the climatic model indicated that the pattern of the rainfall should change in the prediction periods as the rainfall decreases in the winter and spring, while it increases in the summer.
Conclusion
This study offered a methodology for flow simulation and forecasting of future discharge via SWAT model. The effects of future climate change on flow quantity were examined. In this study, SWAT model was used to predict the impact of the future climate changes on river discharge. Model evaluation was done via Nash and Sutcliffe (NS), coefficients of determination (R2), P-factor, and R-factor. After model calibration, the predicted data under several climatic scenario were presented to the model. The results showed that the average of discharge will increase based on the A2 and B1 scenarios, while it will decrease under the A1B scenario. Therefore, it can be concluded that SWAT is a suitable model for discharge simulation in semi-arid areas. The results of this study also indicated that the combination of the results of LARS-WG and SWAT model should lead to an acceptable prediction of hydrological behavior of the rivers. It is important to notice that in this study only the effects of climate change on river discharge was evaluated. For a sustainable management strategy, other aspects of the watershed such as population pattern changes, land use change, and industrial development should be considered. The impact of the climate and land use change on water quality and soil erosion should also be investigated in the future studies.
