Ali Nasiri Khiavi; Ali Faraji; Raoof Mostafazadeh
Volume 6, Issue 21 , March 2020, , Pages 1-22
Abstract
1- IntroductionDetermining the sensitivity of streamflow to climate is necessary to make informed decisions to manage water resources and environmental systems for predicting hydro-climatic variability and climate change. Climate variability is considered as a key driver of hydrological processes. The ...
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1- IntroductionDetermining the sensitivity of streamflow to climate is necessary to make informed decisions to manage water resources and environmental systems for predicting hydro-climatic variability and climate change. Climate variability is considered as a key driver of hydrological processes. The sensitivity of streamflow to climate variables is predicted using a hydrological modeling procedure. In this regard, the results of streamflow modeling are comparing through the present and projected climate scenarios. Climate change in the last century has largely affected the processes of the water cycle and its components on different spatial scales. In recent years, the identification of effective factors and their impact on regional runoff changes has been widely explored by researchers in the field of hydrology. In the context of exploring water resources due to climate change, it is easy to estimate the impact of climate on political decision making and planning. Precipitation elasticity is defined as a tool to determine the rate of streamflow sensitivity regarding the precipitation variability. This study aims to calculate rainfall elasticity and variation of discharge in 20 watersheds using nonparametric elasticity estimation in the monthly timescale. 2- MethodologyIn this study, the sensitivity of rainfall to precipitation has been calculated using nonparametric estimation and a set of monthly data and precipitation data for Ardabil province. Climatic elasticity can be calculated by dividing the climatic variables such as rainfall, relative humidity, temperature, evapotranspiration, wind speed, specific radiation, etc. To estimate the Elasticity of precipitation (Ep), a non-parametric estimation of a set of average monthly discharge and rainfall data is required. At first, the monthly precipitation elasticity was calculated for 20 river gauge stations in the study area, and the median of these values was estimated as precipitation elasticity for the entire province in 12 months of the year. Then the Triple Diagram Model was used to assess the changes in the precipitation elasticity index with precipitation and discharge values. Also, based on the range of changes in the elasticity index, the hydrometric stations studied were classified into 3 categories and presented through a spatial map.3- ResultsThe results showed that the range of the elasticity index was between -2.21 to 3.96, which is related to Arbabkandi and Shamsabad stations, respectively. Based on the results of the Triple diagram model, the variability of the elasticity index is higher in the low discharges. Also, the value of the elasticity index is higher in the dry months, than the other months, which proves the greater impacts of precipitation on the river flow rising in dry months. There is also an inverse relationship between the elasticity index and the upland watershed area of each river gauge station. In watersheds located in upland parts of the area, the discharge shows fewer changes than precipitation, while in downstream watersheds, the discharge is changing more with precipitation variations. According to had the monthly elasticity-precipitation diagram, the calculated elasticity values had a higher amount in the range of medium values of precipitation (0-20 mm and 15-15 mm) in dry and wet months, respectively. 4- Discussion and conclusionThe results showed that the sensitivity of the elasticity index is higher at low discharge values, while in the higher values of the discharge, the elasticity index is less sensitive. According to the results, in the dry months, the value of elasticity index is higher than other months; in this case, it is possible to refer to the sensitivity of the change in rainfall to dry rainfall during the dry months. Changes in the values of the elasticity index in different rainfall indicate that the value of the low elasticity index was attributed to the precipitation occurs in the cold months of the year as a snowfall, which related to the delayed response of snow melting. In particular, due to snowmelt in upstream watersheds, this time delay reduces the elasticity index. It is also very difficult to distinguish the effects of human activities and changes using the employed approach. On the other hand, the sensitivity of the river flow varies over the study area, and it is always different considering the changes of climatic components, human exploitation, land use, geological characteristics, etc. In particular, calculating the elasticity index allows comparing the behavior of different rivers in terms of response to climate change changes. 5- References Chiew, F.H.S, Peel, M.C, Mcmohon, T.A, Siriwardena, L.W. (2006). Precipitation elasticity of streamflow in catchments across the world, Climate Variability and Change-Hydrological Impacts (Proceedings of the Fifth FRIEND World Conference held at Havana, Cuba, November 2006). IAHS Public. 308: 1-7.Mehri, S & Mostafazadeh, R. (2019). Comparing the variations in hydrologic response of Ardabil Province watersheds using precipitation-runoff polygons. Watershed Engineering and Management, 11(2), 381-391.Nasiri Khiavi, A & Mostafazadeh, R. (2018). Spatio-Temporal Assessment of River Flow Discharge Variability Indices in some Watersheds of Ardabil Province. Hydrogeomorphology, 17, 23-44.Nazari-Pouya, H., Kardovani, P & Farajirad, A.R. (2016). Investigation and Evaluation of Climate Change Impacts on Hydro-Climatic Parameters of Ekbatan Dam Basin (Hamadan Province). Ecohydrology, 3(2), 181-194.
Fariba Esfandyari Darabad; Raoof Mostafazadeh; Reza Shahmoradi; Ali Nasiri Khiavi
Volume 6, Issue 18 , June 2019, , Pages 57-77
Abstract
IntroductionThe ease of the use of river water resources has led to an extensive exploitation and, thus, the alteration flow regime. Although human manipulation on the river flows has social benefits, it alters natural ecosystems and threatens biodiversity by changing natural flow regimes. Hydrological ...
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IntroductionThe ease of the use of river water resources has led to an extensive exploitation and, thus, the alteration flow regime. Although human manipulation on the river flows has social benefits, it alters natural ecosystems and threatens biodiversity by changing natural flow regimes. Hydrological changes caused by dams and their related environmental problems have excited many concerns for hydrologists, ecologists, and policy-makers. The high number of constructed dams, the diversion of water, the exploitation of groundwater, the canalization of waterways and, the transfer of water into basins in the world have led to large-scale hydrological changes in the environment and aquatic ecosystems. The assessment of flow changes is important to understand and modify the considerable effects of dams on river systems. Therefore, the purpose of this study was to investigate the quantitative changes in hydrological parameters of the flow in four main groups including Low flows, Peak flows, Flow duration, and Flow variability in Zarrinehrood and Saruqchai Rivers in West Azerbaijan province.MethodologyIn this study, the percentage of changes of the Zarrinehrood and Saruqchai river flow regime, affected by the construction of dams, were evaluated. In addition, the daily discharge data from hydrometric stations were obtained. The recorded discharge data in the time periods of 1955 to 2012 were analyzed in this study. The values of 18 hydrological indicators categorized in four main groups including Peak flows, Low flows, Flow duration and Flow variability were calculated. In this regard, the percentage difference of each hydrologic index was calculated. Next, the hydrologic indices were plotted in the pre and post periods of the dam construction, and the results of the Sariqamish hydrometric station was presented as an example. Finally, the triple diagram model and the Surfer software were used to determine the variations of the percentage of difference in indicators against the mean discharge values over the study period.DiscussionAccording to the results, the Min and Q10 indices with values of 287.42 and -45.57%, had respectively the highest and the least changes The Q95 index and the rate of falling indicator showed an upward trend in the downside of the Miandoab hydrometric station. The highest percentage of difference of low flow group was related to the Miandoab hydrometric station, which indicated the increase of the minimum flow. The lowest percentage of difference was observed at the Alasaqqal-Chap hydrometric station. The Miandoab and Safakhaneh stations showed the highest and lowest percentage of differences in Peak flow group after dam construction. The changes of all hydrologic indices were small in low flow discharge and increased with greater amounts of river flow discharge in the Sariqamish hydrometric station, especially in discharge values of 0 to 20 cubic meters per second.The Miandoab hydrometric station also confirmed the previous results, which showed a decrease in the hydrological indexes of the arrinehrood River flow regime in 0-40 cubic meters per second over the study period, while the changes in the river flow regime had increased in the discharges intervals of more than 140 cubic meters per second.ConclusionTo summarize, the studied hydrological indices have been altered due to the dam construction. Indeed, they are decreasing or increasing based on the nature of indexes to characterize the flow variations. Also, according to the values of average difference percentage of indices in each main group, it can be said that the groups of Low flows, Peak flows, and Flow duration in the period after the construction of the dam compared to the period before the construction of the dam were respectively 303.37, 18.57 and 943.38% at the Miandoab river gauge station under the effect of Nowruzlu Dam. Also, triple diagram model confirmed that the difference in the flow regime indices were high in higher mean river discharge values. Considering the quantitative results related to the difference percentage in hydrologic indicators, the constructed dams considerably altered the natural flow regime of Zarrinehrood and Saruqchai Rivers. Therefore, it is necessary to consider the changes of hydrological regime resulting from the construction of dams to maintain the ecological flow requirements of the river ecosystem and ensure the use of surface water and healthy aquatic environmental condition.
Raoof Mostafazadeh; Ali Nasiri khiavi
Volume 5, Issue 17 , March 2019, , Pages 23-44
Abstract
Abstract
Introduction
The analysis of the temporal and spatial variations of surface runoff is one of the important issues in hydrology, water and soil resources management, and environmental science. Variability is an intrinsic component of environmental factors and elements. Today, the study of changes ...
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Abstract
Introduction
The analysis of the temporal and spatial variations of surface runoff is one of the important issues in hydrology, water and soil resources management, and environmental science. Variability is an intrinsic component of environmental factors and elements. Today, the study of changes in hydrological patterns and processes is one of the most important requirements for water and soil resources management. The temporal and spatial variations of runoff flow and discharge in terms of water use and exploitation have many economic effects, and this variability is the main cause of floods and droughts at different scales. In addition, hydrological processes, by changing the spatial and temporal scales, provide different responses that limit the repeatability of hydrological observations. In general, the tools of assessing changes in hydro-climatic time series include information theory and dominance measure. The first category indices include the Shannon Index and the Brillouin Index. While, the dominance measures include the Simpson index, the McIntosh index, and the Berger-Parger index, the indices of information theory measures have the best parameters. The Shannon index has a better distribution than Simpson or Berger Parker. While the Braillein index has a similar distribution to the Shannon index, it limits ranges from zero to one.
Therefore, the main purpose of this research was to evaluate the spatial and temporal changes of the Discharge Variability Indices (DVI) of surface runoff in some watersheds of Ardabil Province.
Methodology
Toward this attempt, the discharge variability indices of river flow fluctuations were calculated on a monthly time-scale including Shannon, Brillouin, Simpson, McIntosh, Berger-Parker, Index of Variability, Rainfall Anomaly Index, and Discharge Variability Index. For this puprpose, 22 river gauge stations in Ardabil Province were selected. First, the index values were calculated in the Excel software. After calculating these indices, their spatial variations were investigated in the studied area using the distance mapping method in ArcGIS 10.1. The spatial variations of the indices in the studied area were evaluated. In addition, the Triple Diagram Models were used to determine the temporal variation of the DVIs in relation to flow changes over the study time periods using Surfer software. Next, the Pearson correlation coefficient between the discharge variability indices were performed using R software.
Results and Discussion
The results showed that the variability of the DVIs were higher in the upstream regions than the downstream regions, which can be related to the less changes in river flow regimes and the limited interference caused by human utilizations. The highest and lowest values of the coefficient of variation were observed in the Macintosh and DAI+ indices respectively with the values of 195.55% and -567.06%. The results of the triple diagram models indicated that the variability of DVIs were higher in low river flow values. According to the interpolation results, the upstream stations were less variable, while in the downstream stations, the degree of variability was greater due to different human interactions. Based on the results of the triple diagram models, it can be said that the variability of Shannon, Simpson, Berger-Parker, McIntosh, and DVI indices was lower in low discharge values. Also, the DAI+ and DAI- indices were more variable in lower discharge values. The results also showed that there was a significant correlation between the Brillouin index and Index of Variability (-0.42), while the Berger index -Parker and Index of Variability had a positive correlation (0.91). Also, there was a significant positive correlation between RAI+ and RAI- indices (0.62) and the correlation between RAI- and DVI was significant (0.64). In addition, the degree of variability had decreased in recent years. Also, the correlation relationship of DVIs were tested using the R software.
Conclusion
Based on the results, in the upstream regions, the flow rate of the rivers was much lower than the downstream river gauge stations, which can be explained by the condition of the flow near the natural flow of the river. However, in the downstream stations on the main river (such as Samian and Arbab Kandi stations), the existence of Yamchi and Sabalan dams have been caused by a disruption and through the regulatory effect of the dam. In general, the Shannon index as an information-based index and Simpson (dominance-based index) yielded different results from other indicators. Most of the indices showed that the rate of variability in the low flow was higher than the high discharge values. In addition, in recent periods, the degree of variability of the flow has decreased based on most indices, although determining the cause of reducing the variability caused by climate change or human activities requires further studies. The assessment of the variability of the flow at the watershed scale allows the optimal utilization of surface water in the proper seasons and determines the effect of human activities on the river regime.
