base flow

Research on low flow is important, not only from a fundamental point of view but also in terms of sustainable water resource management. Optimum water resources management is one of the most crucial challenges of the 21st century, and due to population growth and climate change, water supply in the future will probably depend on sustainable water sources. The World Meteorological Organization (WMO) introduces low flow as a flow of rivers that continues during the dry period of the climate. Low flow is affected by climate changes, topography, geology, soil, and human activities. The geographical location and climatic conditions of Iran cause a lack of rainfall and water scarcity. Therefore, the recognition and analysis of sustainable water resources is the main component in the surface water resources management of Iran. This research has been done with the aim of investigating the characteristics of scientific publications regarding low flow research in Iran and the world and providing a perspective of the current situation and direction of future research.

The data relating to low flow research in environmental; agricultural and biological sciences were retrieved from the Science direct database in the period 1999 to 2022 and SCImago Journal Rank indicator (SJR) from https://www.scimagojr.com as well as scientific information database of Jihad Daneshgahi (SID) and data from Iranian Research Institute for Information Science and Technology (IranDoc). A total of 22875 publications were obtained and with following aspects analysed intensively:(1) Distribution of international low flow-related publications (2) low flow-related publications from Iran; (2) distribution of subject categories; (3) core journals; (4) distribution of Iranian articles related to low flow; (5) frequency of low flow-related articles in Middle East and countries around Iran; (6) research trends. Bibliometric techniques, including citation analysis, five-year impact factor, JCR classification, coverage period and h-index were used to evaluate and interpretation of the results.

The results showed that the general trend of global scientific publications in low-flow research was with a positive slope and a growth rate of 1.52%. Also, the trend of international publications from Iran had a positive slope with a 0.94 coefficient of determination and a growth rate of 1.60%. The results of the subject classification of publications at the global level showed that most publications with 85.75% belong to research papers and the least amount to conference papers and editorials. International papers originating from Iran were of the first order of importance to publications with 90.04%, which has a larger share of the total papers than global papers. The results of the analysis of the most important keywords related to low flow showed that more than 72% of the titles of papers and theses were assigned to "base flow" and "flow duration curve (FDC) keywords ".

This research is a systematic bibliographic analysis of texts related to low flow research publication. By summarizing and analysing the growth curve of publications, it can be concluded that the total number of international publications related to low flow research corresponds to the theoretical fitting line and shows the proportionality of the potential of low flow research in the world with the actual amount. The general result of the analysis of international publications from Iran shows a high potential for low flow research in Iran and indicates a change in the attention of the Iranian scientific community to the publication of articles on the topic of low flow at the international level.

Water balance and flow analysis within a basin is particularly important in terms of water development and utilization programs. Therefore, the purpose of this study is to evaluate and predict the outflow rate of Baghan watershed in Bushehr province. The data required for the implementation of the rainfall and discharge models were used to obtain the precipitation data of the Baghan Meteorological Station and the discharge of Baghan Hydrometric Station from 1981 to 2010. The Salas model is derived from a number of simple sub models that characterize different flow processes in the basin such as surface runoff, infiltration, evapotranspiration, deep infiltration and base flow. Error squares were used to calibrate the function model. The results of this study showed that the highest amount of rainfall in the basin was evacuated from the basin by evapotranspiration. The results showed Relative root mean square error before and after optimization of the coefficients of the four-variable Salas model decreased from 2.18% to 1.5% and the mean absolute error from 10.13 to 0.73. and mean error of the Salas four-variable model showed that in the years when the discharge value is almost average, the simulation value is very close to the observed value, and when the discharge value is much higher than the normal years, the simulation value is the less than its observed value.

Understanding the base flow can be useful in river flow analysis, rainfall-runoff modeling, calibration of models, water resource management in low flow conditions and determination of the amount of water storage in watershed. In this research, 22 stations were selected with the appropriate data and common period of the years of 1982-2012. The trend of flow changes during the months of the year was determined for all hydrometric stations in the study area and the driest month was determined. Then, the calibration of six recursive digital algorithms was performed using the long-term data of the driest month of the year and after obtaining optimal parameters of the models, the base flow separation for the whole period was performed. The performance evaluation of the models was done using root mean square error. The results showed that the major part of the river flow in the study area was related to the base flow and the minimum, maximum and average annual base flow index for the whole period was equal to 0.48, 0.62 and 0.56, respectively, representing more than 50% of ground water contribution to stream flow of the studied watersheds. Results of the evaluation of the models using the root mean square error showed that the mean error in the research area for all the methods ranged from 0.025 to 0.044. The minimum was related to Lynie and Holick, and the maximum related to the One-parameter digital filter. Over all, conclusion of the results of the calibration process and investing the correlation between calculated and measured data showed that there was a correlation with a coefficient of explanation of more than 80%. Calibration method with dry season data in the absence of tracer-based methods is suggested as the most suitable method for calibrating digital separation filters in the study area.

In this study, the seasonal variations of discharge and concentrations of soluble nitrite, nitrate, ammonium, orthophosphate and potassium and also the concentrations of these substances during baseflow and rainfall runoff in the seasonal and perennial rivers entering the Zarivar Lake were investigated. The results showed a great variation of discharge in the spring than the other months because of frequent rainfalls and the maximum discharge in this season. Despite the differences of the stream lake behavior and also the different nature of nutrients, generally, nutrients concentrations have different seasonally significant so that the maximum concentrations and the maximum concentration variations of soluble nitrite, nitrate, orthophosphate and ammonium were seen in summer. The results of the inter and intra storm variability analysis of nutrient concentrations indicated a significant differences between nitrite and nitrate during and between storm events with sig=0 and sig

In this study, daily rainfall-runoff simulation were discussed during 2000-2005 Khormaloo, Gharechay, Chehelchay Rivers in Golestan province using adaptive neuro-fuzzy inference system (ANFIS). First separate base and surface flow using a recursive digital filter. First separate base and surface flow using a recursive digital filter. Then using discharge in antecedent days and meteorological parameters such as temperature and rainfall, base and surface flow simulated separately using ANFIS and the best entries were determined. Total flow was determined by combination of best model of base and surface flow by ANFIS. The results of the combination of base flow and surface flow models and finally total flow modeling showed in all three stations, the model that combination of base flow and surface flow on before day has highest coefficient of determination and minimum error. Coefficient of determination in the test phase for Nodeh Khandooz, Ramian and Lazoore stations is 0.691, 0.991 and 0.999 respectively and error in stations is 1.413, 0.131 and 0.036 respectively. The results showed that the use of separation base flow technique increase the speed and accuracy of simulation and eliminates the problem of low speed execution in ANFIS and base and total flow predicted accurately.

Estimating the runoff coefficient that is influenced by morphometric, geologic and hydro climatologically factors are the most important issues in hydrology and information of its role in the planning and management of water resources is more important. In this research, twenty hydrometric stations with common period from 1974 to 1999were selected. Physiographic parameters of the catchments from the GIS environment were extracted. Run off coefficient was calculated and then base flow and related index were extracted from daily stream flow data using one parameter recursive digital filters. Lithological units using digital geological map, with the scale of 1: 250,000, based on expert opinion divided on two classes and area covered by each unit in each catchment were calculated. Factor analysis using 15 parameters were conducted and then the regional equations using linear regression at 1% significant level were determined. To compare and evaluate the accuracy and efficiency of the models, independence errors, colinerity and normal distribution of error were tested. Also the accuracy of the models and their estimation error using coefficient of determination, the standard error and the mean absolute error, were examined. Overall results showed that the estimated error rate for first homogeneous area 17.97 percent and for the second area 27.81 percent obtained

Grouping of similar watersheds using clustering methods helps to explain hydrological processes and regional water yields. In the present study, the daily discharge, base flow and Base Flow Index (BFI) and effective parameters including annual rainfall and physiographic characteristics (Area, Mean elevation, main stream length and drainage density) were analyzed using K-means and Hierarchical clustering algorithms over 22 sub-watersheds to determine the homogeneous groups in Ardabil Province. The Davies- Bouldin Index criterion was used to determine the optimal number of clusters over the study area. The base flow amount were separated from daily flow hydrographs by using One-Parameter algorithm through Excel programming. Then, the BFI values were calculated using the ratio of base flow and total amount of runoff. This K-means algorithm aims to find groups (clusters) of similar watersheds from a data set. Firstly, the watersheds were classified based on base flow and BFI and then other variables were used to cluster the studied watersheds. According to the results of K-Means clustering method considering base flow discharge the number of watersheds in first three groups were 4, 3 and 15, respectively. According to the results, the K-Means clustering methods detailed groups of watersheds compared with the Hierarchical method. Watershed grouping based on base flow and base flow index showed that the Arbabkandi and Gilandeh falls into a cluster, and Doostbeiglou, Pole-almas, Samian and Firozabad had similar characteristics. In general the Aladizgeh, Ahmadkandi and Baroogh watersheds had similar hydrologic response in terms of base flow, BFI and other physiographic and land-use related factors and classified into same group. Therefore, the homogeneous watersheds in terms of surface water and base flow variations had similar water yield and ecological flow behavior. Water resources planning and management of watersheds can be considered in homogeneous regions as planning unit.

Knowledge of river discharge and water-quality trend can be useful for planning and management of water resources. Due to the fact that the river base flow is supplied by ground water, considering of base flow for managing environmental demand. The Mann-Kendall's test is one of the approaches which is used for investigating of the trend in time series. In this study, the Mann-Kendall's test was used. For separating the base flow from daily discharge data, Hydro Office software was used. Then, after separating the base flow, monthly and annual time series have been formed. Also, the monthly and annual time series of water-quality characteristics including TDS, Ca, Mg, Na, SO4, CL, EC, PH, HCO3 and SAR of Arazkoose hydrometric station were formed to assess the trend of total flow, base flow and Water-quality characteristics data. Meaningful analysis of trend at the significant level of %5 indicates that, there is not any trend in total flow, base flow and Water-quality characteristics except PH in annual time scale. The result also shows that there is a fluctuating trend in monthly time scale.

When watershed input, evatransporation and ground water usage be limitated, recession curve showed storage–output relationship for basin. This relationship can help us in low flow forecasting, decision and management of water resources; hydrological models calibration and etc. In this study recession curve were modelled in Taleghan, Jajrod and Khoramdare rivers. At the first by consideration of annul hydrographs, recession lamb were separated then by doing some pre-processing recession curve get prepared for fitting various models. For each recession eight models were fitted. Result showed that for Jajrod and Talaghan, Barnes, Drogue, Coutagne and Wittenberg had better application, respectively. For Khoramdare river Horton, Barnes and Drogue had better performance with compared to others models. For Barnes model average value of K coefficient for Jajrod 0.97, 0.975 and 0.99, for Taleghan 0.967, 0.974 and 0.987 and for Khoramdare river 0.931, 0.945, 0.972 were obtained.

Base flow and related index is influenced by morphometric, geologic and hydroclimatological factors. As a result, it is precondition data for planning and water resources management. In this research, base flow and related index were extracted from daily stream flow data using one parameter recursive digital filter in eighteen hydrometric stations of the Caspian Basin. Physiographic, climatic, hydrological, and geological factors were calculated in GIS environment. Using factor analysis of the eighteen parameters, five factors were selected as independent factors. Statistical models were formulated to calculate several regressions between hydroclimatological and physiographic parameters. Further, residual analysis method was used to compare and evaluate the accuracy and efficiency of the models. Results showed that Hard Formations, the average height of basin, drainage density, and coverage of forest were the best predictors of the base flow index. Statistical models highlights importance of Q90/Q50 ratio as the suitable hydrologic index to estimate the base flow index. Besides, this model confirmed controlling role of Hard formations and the forest coverage on the base flow index.