Hydrogeomorphology
hasan Setayeshi Nasaz; sayyad Asghari Saraskanrood; Raoof Mostafazadeh; Aghil Madadi
Abstract
Rivers are very important in terms of human uses and ecological functions. In the present research, the environmental flow components of the Khiavchai River have been determined. Therefore, changes in the EFCs were determined using IHA software. According to the results, the values of low flows were ...
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Rivers are very important in terms of human uses and ecological functions. In the present research, the environmental flow components of the Khiavchai River have been determined. Therefore, changes in the EFCs were determined using IHA software. According to the results, the values of low flows were high in the first period (1988 to 2017), but decreased in recent periods. Also, the decrease in the discharge values of the maximum flow indicators and the increase in the number of days with zero discharge to the number of 174 days were also caused by the change of the river regime. The amount of peak rate and decline rate components has increased in recent periods. The values of low flow duration indicators and low flow frequency have increased. Based on the change of flow dispersion index, the occurrence of strong or very low flows in the river has been intensified. According to the FDCs, in the early periods of the river flow regime, river flow was higher than 0.01cms during the year, while in recent periods it has decreased to less than 0.001cms. Based on the changes in the duration of the flow in recent periods, the duration of the river has changed to 50-60% of the days of the year with a very low discharge. Overuse of river flow changes in the flow regime, and successive droughts have increased the severity of the change in the flow regime and the deviation of the river conditions from the normal state.
hydrogeology
Mousa Abedini; Sajjad Javadi; Raoof Mostafazadeh; AmirHesam Pasban
Abstract
Today, soil erosion is one of the major problems of watersheds and agricultural areas and natural resources, which causes land degradation and decreases soil fertility. Therefore, the purpose of this study is to investigate the relationship between vegetation and geomorphic indices with the values of ...
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Today, soil erosion is one of the major problems of watersheds and agricultural areas and natural resources, which causes land degradation and decreases soil fertility. Therefore, the purpose of this study is to investigate the relationship between vegetation and geomorphic indices with the values of erosion and sediment in the watershed of Koot-e-Tootraghi basin, which was done by using the capabilities of GIS to extract the geomorphic characteristics of the basin. For this purpose, erosion and sedimentation rates were calculated using the modified Psiac model (MPSIAC). Also, in order to extract physiographic and geomorphic features including: TWI topographic moisture layers, SPI current strength, SLOPE slope, domain curvature, profile curvature and sub-basin plan curvature, from the height digital model with a spatial accuracy of 30 meters, as well as other layers used in the MPSIAC model including1:25000 topographic maps, 1:100000 geological maps were used. According to the box diagram, the indices related to curvature have little changes in the studied area. Also, the indices related to curvature have little changes in the studied area. Based on the results, there is a positive and significant correlation of 0.47 (p-value less than 0.01) between the standard index of vegetation cover and topographic humidity index. In addition, there is a significant correlation (0.63) between waterway power index and slope. It was also found that the relationship between the slope and the normalized index of vegetation has an inverse and significant relationship (0.48) (p-value less than 0.01.).
Hydrogeomorphology
Vahideh Moradzadeh; Zeinab Hazbavi; Abazar Esmali Ouri; Raoof Mostafazadeh; Shirin Zarei; Nazila Alaei
Abstract
Ecological indicators have become important tools for evaluating and monitoring natural resources. Understanding the relationship between biological activities and ecological interactions is essential to their structure. On the other hand, human activities have significant effects on landscape evolution ...
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Ecological indicators have become important tools for evaluating and monitoring natural resources. Understanding the relationship between biological activities and ecological interactions is essential to their structure. On the other hand, human activities have significant effects on landscape evolution through changes in sediment production, transport, and storage. Therefore, this issue should be considered in the comprehensive management of different watersheds and ecosystems. Accordingly, the present study was conducted to evaluate the spatial heterogeneity of the hydro-sedimentologic disturbance index (HSDI) in the watershed located in the central part of Ardabil province. For this purpose, sediment transport (ST), hydrological stress (HS), recharge potential of groundwater (Rec), and soil erosion potential (SEP) were first calculated for 27 different sub-watersheds. Then, these factors were weighted using the Shannon entropy method. The hydro-sedimentologic disturbance index (HSDI) was calculated and zoned using the weighted average. The results showed that the mean, maximum and minimum values of the HSDI index in the Samian watershed were 10.17, 45.67, and 0.20, respectively. In addition, 87.67, 5.33, 5.32, and 1.68% of the watershed area were classified into very low, low, medium, and high levels of disturbances, respectively. Sub-watershed 19 located in the northern part, and sub-watersheds 20 and 21 located in the central part of the Samian watershed have the most disturbances, so they are prioritized for management actions. The present research framework can be used as a potential tool to support decisions that should focus on improving natural resource management.
hydrogeology
Sina Ziaye Shendershami; Abazar Esmali Ouri; Raoof Mostafazadeh; Ardavan Ghorbani
Abstract
The aim of this study was to investigate the factors affecting the decrease and change of groundwater level in Ardabil plain in two periods 1995 to 2005 and 2005 to 2015. The monthly precipitation data of Ardebil, Nir, Namin, Abi baglo, Hir, Samiyan stations in the Ardabil plain during the statistical ...
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The aim of this study was to investigate the factors affecting the decrease and change of groundwater level in Ardabil plain in two periods 1995 to 2005 and 2005 to 2015. The monthly precipitation data of Ardebil, Nir, Namin, Abi baglo, Hir, Samiyan stations in the Ardabil plain during the statistical period of 1995-2015 and monthly data of the height of the station in 24 Piezometric well ring were chosen for the plain. Landslide OLI and TM satellite imagery was used to prepare land use map for the target periods in June 1993, 2005, and 2015. The results of land use changes in the years 1993, 2005, and 2015 in the Ardabil plain showed the highest watery agriculture with 48156.26, 50678.66, and 58356.68 and area water level, respectively, were with 168.75 ,88.65 and 380.95 ha, lowest level Which indicates the high level of agricultural land involvement in the decline of agricultural land in the Ardebil plain. The study of the process of Piezometric Wells showed that in the plain of Ardabil, the maximum height of the surface of the station (1437 m) is related to the southern parts of the plains around the village - Noshahr-Kargan and the minimum height (1300 m) is related to the village of Khalifaulo Sheikh. The highest level of cultivation is also focused on user plans in these areas.
Ebrahim Asgari; abazar esmali; Raoof Mostafazadeh; Gholamreza Ahmadzadeh
Abstract
1- Introduction The comparison of different geological formations in term of sediment yield is one of the most important issues in many soil and water conservation studies. Moreover, the measurement of runoff production rate and sediment production is the prerequisite of watershed management. The potential ...
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1- Introduction The comparison of different geological formations in term of sediment yield is one of the most important issues in many soil and water conservation studies. Moreover, the measurement of runoff production rate and sediment production is the prerequisite of watershed management. The potential of a watershed toward erosion is the result of erosivity, erodibility of geological formations, slope gradient and land use types in the watershed. Accordingly, runoff is one of the important factors in the water erosion issues. Different geological formations depending on the rock composition, erosion and slope gradient, have a potential to produce sediment and play an important role in the amount of soil losses. The behavior of rocks and quaternary deposits against weathering and erosion depend on the nature of the rock and environmental affecting factors. Therefore, the main aim of the present study was investigating and comparing the geological formations regarding the runoff and sediment yield along with runoff threshold in Gharehshiran watershed of Ardabil province using a rainfall simulator measurement. 2- MethodologyBased on the geologic map of the studied area, the boundaries of different geological formations were defined and then according to the objectives of the present study, a field rainfall simulator (100 × 100 cm) with a height of one meter was used for field experiments. Theoretically, the use of rainfall simulator systems saves time and cost, which can be used for monitoring the amount of runoff and sediment along with all processes involved in erosion and sediment production. However, it should be noted that the use of rainfall simulators is also subject to limitations that can never fully create natural conditions. The plot scale measurements have been conducted through 45 samples in predefined geological formations of the studied area. The runoff threshold initiation time and the amount of runoff and sediment were recorded through field experiments. The runoff and sediment samples were collected in individually stored containers and were then, transferred to the laboratory. The values of runoff were measured and the samples were oven-dried for 24 hours at 105 °C and then the deposited amount of sediments were obtained. The amount of sediment in each sample was determined using a producer of precise weighting. Then, the normality of the data was analyzed using Kolmogorov-Smirnov test. The comparison of the geological formations was examined with respect to sediment amount, runoff, and initiation time threshold using One-way ANOVA method through SPSS software. Furthermore, the significant different in mean values of studied variables between geological formations were compared with Duncan's test. Then, the correlation between the studied variables in various geological formations was evaluated using Pearson correlation analysis in SPSS software. 3- Results and Discussion The results of one-way ANOVA test showed that there was no significant differences between different geological formations considering runoff and sediment yield (p < 0.05). While, there was a significant difference between geological formations with respect to the runoff threshold initiation time (p < 0.05). Comparison of the mean values of runoff threshold time using Duncan test indicated that the highest and lowest thresholds time of runoff production were observed in Qt2 (alluvial terraces) and Qb (basaltic lava) formations with the values of 8.28 and 2.28 minute, respectively. According to the results, there was an inverse relationship between runoff and sediment variables in different formations. Also, the correlation between the runoff threshold time and the amount of runoff was negative with -0.318 correlation coefficient (p < 0.05), while, correlation between the runoff threshold time and sediment yield values was positive (r=0.327) at 5% confidence level. 4- Conclusion Many of the geological formations in this area were related to Quaternary and Tertiary periods. Young alluvial terraces and upland terraces, along with marl, sand, conglomerate, and clay formations were related to the Quaternary period, which were the results of erosion from rock units of past periods. It is suggested that the effects of other effective factors on erosion and sediment production processes should be considered in future researches to make a better and comprehensive conclusion. In conclusion, it can be said that studied geological formations were assigned to the Quaternary era and had a similar behavior in term of runoff and sediment production, while the difference in composition and mineralogy of different formations led to differences in runoff threshold.
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.
Naser Ahmadi Sani; Karim Solaimani; Lida Razaghnia; Raoof Mostafazadeh; Jalal Zandi
Volume 5, Issue 16 , December 2018, , Pages 139-158
Abstract
Abstract Introduction Due to population growth and human activities and increasing water demand, water availability will be critical and water resource assessment and planning for sustainable use become more complex. The dynamic and long-term laws of runoff are important and have practical value for ...
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Abstract Introduction Due to population growth and human activities and increasing water demand, water availability will be critical and water resource assessment and planning for sustainable use become more complex. The dynamic and long-term laws of runoff are important and have practical value for the sustainable development and planning of water resources. On the other hand, the traditional methods of runoff estimation should be improved regarding the accuracy and spatial variations. The application of GIS extensions is needed to provide water resource assessment data. Therefore, the application of such new techniques has greatly increased in recent years to estimate the runoff characteristics. The SCS method is the most commonly used method for estimating surface runoff, whose accuracy has improved through employing advanced GIS-based tools. The applicability of Arc-CN Runoff tool was tested in different internal and external studies which emphasized the quantitative evaluation of the model results. Methodology In this study, the accuracy of runoff estimation by Arc-CN Runoff tool was evaluated based on the land use map in two different time periods (1996-2011). The Landsat satellite images of 1996 and 2011 were processed and analyzed for land use mapping. Map of soil hydrologic groups was prepared in GIS environment using slope and soil texture maps. The annual rainfall calculations were done using rainfall daily data of several years for stations within the basin. The curve number map was used to estimate runoff using SCS method within ArcCN-Runoff tool in GIS environment. The runoff observations of Karehsang Station were calculated using daily flow data and the base flow was separated. Finally, the accuracy of the estimated runoff was assessed by estimating the percent relative error. Results and Discussion According to the accuracy assessment of land use maps using the ground-based map, the best overall accuracy and kappa coefficient were respectively 90% and 88%. The results showed that the maximum likelihood algorithm and the combination of main and synthetic bands, classified the land use classes of the study area with an acceptable accuracy. The highest percentage of the area was classified as range and dry farming (62.74%) in 2011. The percentage of rangeland, dense forest, and water zones decreased in 2011 compared with 1996.The map of the hydrological groups shown in this study, consisted of groups B, C and D, respectively covering 15.5, 44.5 and 40% of the study area. The average CN in the years 1996 and 2011 was estimated to be around 79.6 and 81.6. The average estimated rainfall of the study area using the arithmetic mean, inverse distance weighting, and kriging methods in 1996 were respectively 486.24, 424.4 and 486.1 mm. The estimated annual rainfall values were equal to 521.5 (arithmetic mean), 514.6 (inverse distance weighting) and 521.5 (kriging) mm. Runoff height was the highest in bare lands and residential uses, and the minimum of runoff height values were estimated in good and medium rangelands. Conclusion The mean values of total runoff, base flow, and surface runoff have increased in 2011 compared to 1996. The highest CN values in both periods consisted of bare lands and residential area. The runoff height in different land uses and the total runoff height increased in 2011 (11.38 mm) compared to 1996 (8.8 mm), which can be partly due to the degradation and land use change. The results of this study showed that the ArcCN-Runoff tool improved the accuracy of potential runoff estimations, while the relative error of runoff estimation in both periods was relatively low and acceptable. Thus, the implemented tool can be used to assess and estimate runoff height. The results showed that the relative error of runoff estimation in both periods was in agreement and the error amount was relatively low (10%). In addition, the used methods and tools were evaluated with 90% accuracy in both periods and can be used for runoff estimation in data-scarce watersheds.
Khadijeh Haji; Shahnaz Mirzaei; Raoof Mostafazadeh; Habib Nazarnejad
Volume 4, Issue 13 , March 2018, , Pages 121-146
Abstract
Extended Abstract
Considering the relative stability of the physical characteristics of a watershed, the variability of the precipitation over space and time, and the direct relationship between rainfall and runoff, the variations of runoff can be expected and analyzed to understand the nature of variability. ...
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Extended Abstract
Considering the relative stability of the physical characteristics of a watershed, the variability of the precipitation over space and time, and the direct relationship between rainfall and runoff, the variations of runoff can be expected and analyzed to understand the nature of variability. Determining changes in the amount of runoff caused by rainfall and detecting the time of rivers' floods can provide a prediction of floods' occurrence and, consequently, reduce their damages. The increasing importance of water resources management in recent years, erosion, and sediment highlights the need for understanding the rivers' behavior and regimes. Regarding the changes in the river flow rate, estimating temporal and spatial variations of runoff changes can be effective in determining and controlling the dependent processes of soil erosion in a watershed and river bank, droughts, floods, and water quality and utilization. The analysis of the river flow variability, its duration and influencing factors, is necessary for an optimal river management/operation as the main sources of water uses.
Methodology
The monthly and annual runoff volumes of different stations were calculated based on the monthly discharge data in different years during the study period. Then, the variability indices were used to study the seasonal variations in the runoff volume at each hydrometric station. Next, using Annual Distribution of Regulating Coefficient and Concentration Rate indices, the seasonal variation in runoff volume of twenty river gauge stations located in Golestan Province were evaluated in 38 years. The values of Annual Distribution of Regulating Coefficient indicated the uniformity/ non-uniformity of changes in runoff volume at the studied river gauge stations. In addition, the annual variation of runoff volume was plotted in triple diagram models based on average runoff volume and time variables. The Kriging method was also used to draw the triple diagram models using two independent variables in a surfer environment. The Annual Distribution of Regulating Coefficient and Concentration Rate indices were considered as dependent variables. The variability of the implemented indices were analyzed over a time period of 38 years.
Results and Discussion
According to discharge data in different years, the monthly and annual runoff volumes of the stations were calculated during the study period. Based on the monthly spatial distribution, the results showed that the maximum amount of runoff volume of the stations were observed in March. The highest amount of surface runoff amounts occurred in Aghghala, Ghazagli, and Basirabad which respectively had an average annual runoff of 33.9, 33.5, and 32.6 million cubic meters. The highest uniformity in runoff occurrence was related to Nodehkhandoz, Tamar, Galikesh, and Gholitappeh stations, respectively with an annual Distribution of Regulating Coefficient of 0.19, 0.21, 0.23, and 0.24. The lowest Rate of runoff concentration was at Nodehkhandoz and Tamar stations respectively with 0.26% and 0.25%. The results also indicated a direct and significant relationship (R2 = 0.60) between Annual Distribution of Regulating Coefficient and Concentration Rate (p < .05). Ramian station had the highest Concentration Rate with a value of 0.62%. The highest significant decreasing and increasing trends, in Mann-Kendall test, were observed at Shirabad and Nodehkhandoz stations
Conclusions
According to the findings, there was a correlation between the annual distribution of regulating coefficient and the concentration rate. The higher values of the Annual Distribution of Regulating Coefficient and the Concentration Rate of runoff volume can be attributed to physiographic properties of watershed such as its slope, vegetation, and soil permeability. In other words, the process of changes in the runoff volume at these stations can indicate the temporal and spatial variations of precipitation, human protection measures such as dam construction in the basin, or the amount of permeability during the statistical period. In conclusion, with the non-uniform distribution of runoff volume in different months of the year, it can be expected that variations between the minimum and maximum values of runoff volume will also be high. Indeed, the higher the uniformity of the monthly distribution of runoff volume, the lower the variations between the minimum and maximum changes in the runoff volume. Variations in the amount of monthly runoff in the studied area can be related to the characteristics of the area, the hydrological response, and land use (agricultural land plowing season), as one of the main factors controlling runoff.
