Average Monthly Discharge Research Articles

The lake and groundwater interaction based on water balance in Dongting Lake, China

Study region: Dongting Lake (DTL), the second largest freshwater lake in China, plays a crucial role in regulating and storing water within the Yangtze River Basin.Study focus: The study utilized the water balance method to extensively investigate the exchange volume of groundwater and DTL from 2003 to 2020. Furthermore, we analyzed the impact of climate change and human activities on the interaction between groundwater and DTL.New hydrological insights for the region: Unlike previous studies, our study further included the ungauged runoff, providing a more comprehensive assessment of the water balance of DTL. From May to July, groundwater recharge from DTL, with an average monthly recharge of 0.71 km³. Conversely, groundwater discharges into DTL from August to April of the following year, with an average monthly discharge of 1.12 km³. The net groundwater discharge into the lake from 2003 to 2020 amounts to 7.98 km³/yr. Intriguingly, precipitation over the lake contributes a mere 0.6% to the total inflow, while lake evapotranspiration constitutes only 0.4% of the total outflow. Inflow runoff and outflow runoff play a leading role in the water balance of DTL, significantly influencing the exchange capacity between the lake and groundwater. Groundwater discharge into the lake serves as compensation for diminished runoff stemming from extreme climate occurrences, like droughts, and anthropogenic actions such as dam construction.

Sensitivity of small river channels in the North Carolina Piedmont to change in streamflow conditions, Atlantic Multi-decadal Oscillation, and land use/land cover change

Twenty-four years (1999–2022) of channel change is assessed using specific-gage analysis based on the United States Geological Survey (USGS) rating curve calibration data from thirteen sites (drainage area < 500 km2) to understand the sensitivity of discharge-specific stage (DSS) or its inverse, stage-specific channel capacity (SSCC) to streamflow regimes, hydroclimatological history, and land use in small Piedmont watersheds of North Carolina, USA. We compare observed channel changes to common streamflow and flood metrics, Atlantic Multi-decadal Oscillation Index (AMOI), and land use/land cover data using regression and correlation techniques to suggest drivers of change and infer sensitivity. In addition to interannual variability, our results at most sites reveal three coherent periods of DSS/SSCC variation at the sub-decadal scale as well as multidecadal trend variation. The magnitudes and frequencies of these changes indicative of potential sensitivity vary substantially amongst sites. The trendlines from the DSS plots for the full length of record indicate that six sites showed increased specific stage while the remaining seven sites showed either reduced or a near-zero change in specific stage. Coefficients of determination relating specific stage and the index of AMO are low (R2 = 0.14—0.38) with both positive and negative relationships exhibited. Multiple regression, coefficients of determination relating specific stage and average monthly discharge are more variable, ranging from 0.18 to 0.94. Both positive and negative correlations (r ≤ 0.7) are found between specific stage and basin land use/land cover intensity indices, although few are significant at 95 % confidence interval. Both qualitative observations and correlation analyses support inferences that drought and persistent low mean discharge conditions tend to increase discharge-specific stage values (decreasing SSCC), by aggradation of the bed and/or lower banks. At our sites, this may be responsible for a sub-decadal trend of increasing specific stage between roughly 2013 and 2018, followed by ongoing reductions over the subsequent period.

СВЕРХДОЛГОСРОЧНЫЙ ПРОГНОЗ СТОКА РЕК РОССИИ

The possibility of extended predictions of the Russian river streamflow is considered based on dynamic approach, in which the HBV-96 water-balance runoff formation model is used jointly with the extended ensemble meteorological forecast obtained with the INM5 model. Twelve river basins located in different climatic and physiographic zones of Russia were selected for analysis. The average annual and average monthly discharges, as well as the annual maximum streamflow, were predicted with a lead time of 1-5 years. The test on the reanalysis data for the period from 1980 to 2020 has shown that the applied dynamic approach makes it possible to adequately assess possible interannual fluctuations in the streamflow and its intraannual distribution. The ensemble of forecasts of the annual and maximum streamflow for the period 2023-2026 obtained using the HBV-96 and INM5 models is consistent with the data on the water regime of the analyzed rivers.

Modern changes in climatic characteristics and minimum flow of the rivers in the basin of lake Sevan

Formulation of the problem. Studies and data on modern changes in the winter minimum average monthly flow of the rivers of the Lake Sevan basin and their climatic characteristics have acquired great practical importance and considerable interest due to the increased use of water resources for the purposes of various types of economic activities, in particular, in connection with the development of the economy, hydropower, irrigation, population growth and rising living standards. Especially relevant are the calculations of the minimum flow in relation to solving the problems of water supply for settlements, industrial enterprises. The aim of the work. Assessment of modern changes in the winter minimum average monthly runoff of rivers in the Lake Sevan basin and their climatic characteristics. Methods. The following methods were used in the work: mathematical-statistical, extrapolation, interpolation, spatial analysis, analogy, correlation and cartography. Results. A physical map has been compiled with a network of meteorological stations and hydrological posts in the Lake Sevan basin. Close correlations were obtained between the values of the winter minimum average monthly runoff and the average runoff of the winter period for a hydrological year. These dependences can be used for preliminary estimates of the minimum runoff of the winter low-water period of unstudied rivers in the territory under consideration. In the course of the research, the winter minimum average monthly discharges were calculated by months and for the entire observation period, the average value of the minimum runoff for the winter low water, and the linear trend of the climatic characteristic. Based on the obtained results, a map of the distribution of the modul of the average minimum runoff of the winter low-water period and the coefficients of the linear trend of the winter air temperature were constructed. Examples of curves of long-term changes in precipitation amounts for the autumn and winter periods, the sum of positive temperatures and the number of days with a positive average daily air temperature in the winter period for a series of meteorological stations in the study area are presented. The rivers of the Lake Sevan basin are characterized by an uneven spatio-temporal distribution of winter minimum runoff and climatic characteristics, changes in the winter average monthly minimum runoff, precipitation amounts for the autumn and winter periods are multidirectional, and air temperature changes are only an upward trend. In the area under consideration, there is mainly (by 8 out of 12 stations under study) a tendency to decrease in the values of the minimum average monthly river flow. The conducted studies lead us to the conclusion that the main factor causing changes in the low-water runoff of the rivers in the Lake Sevan basin in winter is the air temperature, or rather, its increase. It follows from this that when calculating and forecasting winter runoff, it is necessary to relate the values of runoff and air temperature.

ASSESSMENT OF DROUGHT INDICES AND WATER AVAILABILITY USING STATISTICAL Z-SCORE AND MOCK MODEL

The phenomenon of drought and water scarcity due to climate change is a major problem in many countries. Assessing drought conditions and water availability in a watershed helps the government and communities implement sustainable watershed management. The study was conducted in Krueng Jreue Sub Watershed, Krueng Aceh Watershed, Aceh Province, Indonesia. The meteorological and hydrological indices in the watershed were analyzed using statistical Z-Score for Precipitation (ZSP) and Discharges (ZSD). Discharges originated from Mock model was used to examine the water availability in a watershed. The results showed the ZSP and ZSD indices from 2008 to 2017 were almost categorized as normal. In certain months, drought indices with the criteria of extreme wet (EW), very wet (VW), and severe drought (SD) also occurred. In general, the ZSP and ZSD indices were consistent, but for certain months (April 2008, November 2010, and March 2017) inconsistencies were found due to differences in signs and index classes. The Mock model parameters for the proportion of surface soil uncovered by vegetation (m), infiltration factor (IF), initial soil moisture (ISM), and flow reduction coefficient (Rc) were 20 %, 0.4, 200 mm month-1, and 0.6, respectively. The average monthly discharge during the period of 2008-2017 ranged from 3.16-31.18 m3s-1. The total water needs of 5.041 m3 s-1 per month. The water availability per month was surplus in the rainy season (October-April), but deficit in the dry season (May-September). This research not only contributes to enriching references for similar research in Krueng Aceh Watershed, Indonesia but can also be applied to other watersheds according to the current conditions of watershed characteristics.

Minimum Instream Environmental Flow in Shatt Al-Hillah River

To maintain river flows necessary to meet social and ecological objectives, instream environmental flows are frequently used as a strategy. The capability of three alternative historical flow approaches to protect against low flows is shown in this study using gage stations in the Shatt Al-Hillah River in Iraq. The extension of the Shatt al-Hillah River is the focus of this research discussion on environmental flow assessment. The available data on discharge in this research were adopted for ten years from 2012-2021. Different flow methods were adopted to establish a minimum environmental flow in the Shatt Al-Hillah River. Three hydrological-based approaches: Tennant, modified Tennant, and low-flow metrics like 7Q10, were used to compare the results of the methods with the provision of a minimal environmental flow. The Tennant method relies on 30 % of the annual discharge rate as the minimum environmental instream flow. The modified Tennant method is based on 30% of the monthly average discharge rate as a minimum environmental instream flow. The 7Q10 method is based on the lowest daily discharge rate in 7 consecutive days for ten years. The results showed that the minimum instream environmental flow given by the Tennant method is 42.26 m3/s while the lowest value of the minimum instream environmental flow obtained from modified Tennant was 37.2 m3/s in January, and the largest value was 47.22 m3/s in August. The one obtained by the 7Q10 method was 50 m3/s in this research.

Increasing Alaskan river discharge during the cold season is driven by recent warming

Arctic hydrology is experiencing rapid changes including earlier snow melt, permafrost degradation, increasing active layer depth, and reduced river ice, all of which are expected to lead to changes in stream flow regimes. Recently, long-term (>60 years) climate reanalysis and river discharge observation data have become available. We utilized these data to assess long-term changes in discharge and their hydroclimatic drivers. River discharge during the cold season (October–April) increased by 10% per decade. The most widespread discharge increase occurred in April (15% per decade), the month of ice break-up for the majority of basins. In October, when river ice formation generally begins, average monthly discharge increased by 7% per decade. Long-term air temperature increases in October and April increased the number of days above freezing (+1.1 d per decade) resulting in increased snow ablation (20% per decade) and decreased snow water equivalent (−12% per decade). Compared to the historical period (1960–1989), mean April and October air temperature in the recent period (1990–2019) have greater correlation with monthly discharge from 0.33 to 0.68 and 0.0–0.48, respectively. This indicates that the recent increases in air temperature are directly related to these discharge changes. Ubiquitous increases in cold and shoulder-season discharge demonstrate the scale at which hydrologic and biogeochemical fluxes are being altered in the Arctic.

Floodwater harvesting of the Arghastan River basin of Kandahar in Afghanistan

Climate change and population growth are the important factors that place additional pressures on water resources, and generally, predictions indicate that these pressures are increasing continuously, so it is necessary to regulate surface water sources. Afghanistan has a semiarid climate and already received worse effects of climate change; therefore, there is an extremely needed regulation of river flow across the country. Arghastan River is in the southernwest parts of the country, thousands of cubic kilometers of water in this river are wasted annually, and drought and floods are the main problems of the residents due to nonmanagement of river flow. The main objective of the study conducted by GIS was to find a dam site along the river for proper water management. A contour map was created for the entire watershed by using 5-meter DEM, that the most suitable site for the dam is at the coordinate of 66°48'34.468"E 31°35'4.512"N, it is possible to build up to 170-meter-high dam. The purpose site of the reservoir has the capacity to store about 1700 million cubic meters of water at an elevation of 170 meters, while the average monthly discharge of the Arghastan River up to the specific point of the investigation is about 38.6 m3/s. Suppose the floodwater of this River basin is harvested. In that case, it will provide the chance for residents to rescue their property from flood hazards during the rainy season, and they will have enough water for irrigation purposes during the summer season.

Evaluation of Potential Changes in Extreme Discharges Over Some Watersheds in Côte d’Ivoire

Climate change has had strong impacts on water resources over the past decades in Côte d’Ivoire, but these impacts on hydrological extremes remain largely unknown in most watersheds. Thus, this work aimed to evaluate the trends and breakpoints in extreme discharge characteristics of five watersheds in Côte d’Ivoire over the period 1970 to 2017. Seven indexes were selected, namely the 5-day maximum flow (QX5-days), peak discharge (Qmaxan), maximum monthly discharge (VCX30), annual minimum discharge (Qminan), average monthly discharge (QMNA), discharge day rate (VCN7), and characteristic of low discharge (WFD). The analysis was done using the modified Mann–Kendall (MMK) test and the standard normal homogeneity test at a 5% significance level for heterogeneous and homogeneous periods of data. The results for the heterogeneous and homogeneous periods were similar, with a predominance of non-significant trends for high discharge, except for the VCX30 index, which showed a significant upward trend at Kahin station. A decreasing trend for QX5-days was found at Loboville station. The variables Qminan, QMNA, VCN7, and WDF show significant upward trends of 33%, 16%, 50%, and 33% for the heterogeneous stations, respectively. A significant breakpoint in almost all variables was obtained, with a strong decrease after 2008. Some differences between the results from the heterogeneous and homogeneous periods of data were found and discussed. This study can help in understanding the behaviour of past hydrological extremes in the study area and in planning for further studies in the future.

Spatial dynamic model of land use land cover change on hydrological response characteristics in the Upper Ciliwung Sub-Watershed

Ciliwung Watershed is one whose state is critical. This condition causes the expansion of residential areas upstream of Ciliwung. Land use and land cover change affect a region’s hydrological characteristics. As a hydrological model, the SWAT (Soil and Water Assessment Tools) can predict the hydrological watershed characteristics affected by land use. This study aims to assess the land use change influence on hydrological characteristics and variations in inflow and outflow to develop the ideal recommendations for land use in the Ciliwung sub-watershed using system dynamics. The main river channel is constructed based on the watershed delineation process results, the watershed boundary consisting of 27 sub-watersheds. Due to average monthly discharge, the impact of land use change on hydrological characteristics in 2011, 2016, and 2020 were 65.01, 63.59, and 64.31 m3/second, respectively. The hydrological characteristics of all HRUs generated revealed that the Q max was 13,09 m3/s, and the Q min was 0.18 m3/s. In upstream Ciliwung, based on an inflows and outflows analysis, there were variations in 2011-2016 and 2016-2020. Based on the calibrated simulation results, the coefficient of determination (R2) was 0.8, and NSE was 0.78. The resulting R2 and NSE values indicate excellent model performance in the validation results. The ideal scenario is the intervention scenario on land use and population demography since it can reduce runoff. Runoff is the water that flows over the surface because the soil has reached its maximum infiltration capacity.

ДИНАМИКА ИЗМЕНЕНИЯ РЕСУРСОВ РЕЧНОГО СТОКА ТОБЫЛ -ТОРГАЙСКОГО ВОДОХОЗЯЙСТВЕННОГО БАССЕЙНА

The study presents results of assessing the resources of the river flow of the Tobyl - Torgai water management basin. The purpose of the work is to update the previously developed methodology for assessing the annual runoff resources of individual rivers and river runoff resources of the considered water management basin of the Republic of Kazakhstan. The calculations used the average monthly and average annual water discharge of the main rivers. Methods have been developed for determining and restoring the observed and natural runoff, long-term statistical characteristics and its values of probability of exceeding. The equations for determining the water resources of local runoff and water resources coming from other regions are obtained. As a result of the work done on the preliminary calculation, the total surface water resources for the Tobyl – Torgai water management basin, formed in Kazakhstan and coming from the territory of the Russian Federation for a long-term period from 1931 to 2019, on average amount to 1,67 km3, of which: resources formed within Kazakhstan - 1,33 km3, inflow – 0,34 km3. The runoff formed in the territory of the basin, for the disturbed period, relative to the conditionally natural period, decreased by 8%, the runoff coming from the Russian Federation decreased by 12%, and the total water resources by 9%

Statistical Assessment of the Runoff Variability of Small Rivers in the Middle Zeravshan Basin

The article deals with the issues of statistical assessment of the variability of the runoff of small rivers in the Middle Zeravshan basin. For this purpose, the average monthly and annual water discharges were used, taken into account at 11 hydrological stations located on small rivers and water resources in the Middle Zeravshan basin. Calculations to estimate the coefficient of variability of river runoff were carried out for two periods: the first calculation period includes the base climatic period (1961-1990), and the second calculation period includes 1991-2018. Based on the analysis of the results obtained, an increase in the value of the coefficient of variation (Cv) in the second calculation period relative to the first calculation period was revealed.

Study of Rainfall and Water Discharge Spatial Variability Using Exploratory Spatial Data Analysis Method in Bondowoso Regency

The difference in rainfall intensity affects the hydrological cycle as a process that greatly determines the amount of water discharge. Thus, in water resources management, it is important to determine the distribution pattern of rainfall and discharge. By studying the characteristics of rainfall distribution patterns and water discharge, the potential of water resources can be illustrated well. This study uses the Exploratory Spatial Data Analysis method to examine spatial variability of rainfall intensity and water discharge in Bondowoso Regency. Rainfall and discharge data are collected from 35 rain stations and 227 weirs in 2008 until 2018. This study produces monthly average rainfall distribution values between 190 mm / month with monthly average discharge between 7300lt/sec/month. Meanwhile, the obtained average annual rainfall distribution values are between 2300 mm/year with annual average discharge values between 105000 lt/sec/month. The spatial distribution map using IDW method produces information on the potential of water resources as follow: the higher the height of a place, the higher the average monthly rainfall, while the lower the height of a place, the higher the average monthly discharge. As for the obtained correlation value between rainfall and discharge is R² = 0.665.

Assessment of the Rural Water Supply Potential by Mechanical Wind Pumping Around the Floodplains of Lake Chad

In the present work, an assessment of the rural water supply potential by mechanical wind pumping around the floodplains of Lake Chad has been considered. Inside the floodplains around Lake Chad, available surface water is largely contaminated and represents health hazards to populations. Access to underground and clean water has increasingly become rare. Moreover, clean water scarcity has led to conflict and territorial pressures, which are contributing factors to poverty in the considered area. Four localities, Baga, Baga-Sola, Makari and Nguigmi, respectively, in Nigeria, Chad, Cameroon and Niger have been selected inside the floodplains around Lake Chad, to evaluate the potential of wind power and prospects of windmills development to provide safe drinking-water supply, livestock watering and small-scale irrigation. Long-term satellite-derived data, obtained through the Prediction of Worldwide renewable Energy Resources have been considered suitable and viable alternative to missing site-specific data from ground stations. Windmill of Multi-blade driven piston pump is the preferred water pumping option for this study because of its higher overall system efficiency. The results of this study indicate that mean wind speeds, at 10 m height above ground level, are 4.64 m/s for Baga, 4.76 m/s for Baga-Sola, 4.32 m/s for Makari and 4.44 m/s for Nguigmi. In addition, wind speeds for Baga, for instance, are in the range of 2.5–10 m (working range of a wind pump), at 10, 15, 20 and 25 m height agl, for 79.64, 82.80, 84.79, and 86.19 per cent of the time. Corresponding values for Baga-Sola, Makari and Nguigmi are in the range of 80.50–87.76 per cent, 76.86–85, 58 per cent, 77.92–86.21 per cent, respectively. For a Windmill with a 2 m-blade, a 25 m-height tower and considering a total dynamic head of 30 m, average monthly discharges for the dry season are 1,330, 1,374, 1,200 and 1,199 m3, respectively for Baga, Baga-Sola, Makari and Nguigmi. Furthermore, corresponding costs of water are 9.53, 9.23, 10.56 and 10.57 XAF/m3, for Baga, Baga-Sola, Makari and Nguigmi, in that order.

ДОСЛІДЖЕННЯ ДЕФІЦИТІВ ВОДНОСТІ ТА ІНДЕКСІВ ПОСУХИ ДЛЯ ЗОНИ НЕДОСТАТНЬОЇ ВОДНОСТІ УКРАЇНИ

The study of the formation of water deficits on rivers in the zone of the insufficient water content of Ukraine is presented in the article. To determine the deficits, the “threshold” method was used, which involves comparing the daily water discharges in the low water period with the values of the minimum runoff of a given probability of exceeding. Long-term data of average daily and average monthly minimum water discharges during the winter and summer-autumn period on rivers located in different areas of river basins and significantly differing in the catchment area, namely the Southern Bug River – Oleksandrivka (A = 46200 km2), Kinska River – Pologi (A = 353 km2), Obitichna River – Primorsk (A = 1300 km2) for the observation period from 1953 to 2018 inclusive was used. In cases where runoff values ​​were less than Q90% or Q97%, they were considered deficient (90%) or extremely deficient (97%). The dynamics of deficits in time are analyzed, and the number of such events by decades, frequency, average volume, duration, and intensity are determined. The chronological course of runoff volumes and deficits (90%) is graphically presented. Analyzing the obtained diagrams, it can be noted that naturally, the largest water deficit was observed in low-water years (below normal), and accordingly, the lack of deficit is characteristic of multi-water periods (above normal). Additionally, extreme deficits were also estimated (97%) for the Southern Bug River – Oleksandrivka township. The study also presents the results of the calculation of various drought indices. For the rivers of the study area, using the DrinC drought calculator were calculated – the river runoff drought index (SDI), standardized precipitation index (SPI), agricultural standardized precipitation index (aSPI), drought research index (RDI), effective drought research index (eRDI) , and its relationship with water discharges during the summer-autumn period was analyzed. Long-term data of average monthly water discharges at 6 hydrological gauge (Kodyma river – Katerynka river, Ingul river – Novogorozhene river, Ingul river – Sednivka village, Kinska river – Polohy town, Kilchen river- Oleksandrivka Persha village, Kalchyk river – Kremenivka village) were used as initial information and as also average monthly air temperature and monthly precipitation at 6 meteorological stations (Odessa, Kherson, Kropyvnytskyi, Zaporizhia, Dnipro, and Mariupol). Analyzing the obtained results, it can be noted that drought indices provide an opportunity to study climatic and hydrological trends, characterize drought, assess the severity of drought, and promote early assessment of the effects of drought. In particular, the SDI index correlates well with water discharges, which opens up opportunities for forecasting runoff in the dry period.

Determination of the amount of Sanitary Water Flow from Dams based on the Quality of Drinking Water: A Case Study, Taleghan River, Iran

Background: Given the crisis of water shortage and the industrial development in Iran, comprehensive water-resource management and planning to handle the water quality of the rivers are the critical issues to tackle with. The concentration of river pollutants is a function of both the quantity and quality of the river flow regime. In this regard, the construction of large dams leads to quantitative and qualitative changes in downstream rivers. These changes are effective in the health of the river water for uses such as drinking, agriculture, and industry. Therefore, in addition to the quantity of water needs of rivers, their quality needs to be also considered. Objectives: This study aimed to analyze issues related to the sanitary water flow of large dams. Our case study was the Taleghan River dam, Alborz Province, Iran, on which Taleghan reservoir was built to supply some part of the water needed by Greater Tehran, Iran. Methods: This study examined a 22-km long section of the river at the riffle of Taleghan Dam in Alborz Province (103 km from Karaj), Iran. The average annual and monthly discharges of the river in four 6-km-apart stations were estimated. The statistics of eight hydrometric stations and a discharge-surface method were used to calculate the average annual discharge of each sub-basin downstream of Taleghan Dam. Moreover, the discharge non-dimensionalization method, along with the observational statistics of the index station, was used to calculate the average monthly discharge in the examined stations. The Hydrologic Engineering Centers River Analysis System (HEC-RAS) software (version 4.0) was then utilized to determine the values ​​of river flow rates hydraulically. Additionally, water quality parameters were compared with the standard concentrations proposed by the World Health Organization (WHO) for drinking-water quality to examine possible changes in pollutant concentrations during the study. Correlation and regression statistical tests in SPSS software (version 24) were then used to analyze the relationship between discharge and pollutant concentration. Results: The experimental equation of Q = 0.0372A0.8641 was obtained to estimate the discharge based on the sub-basins area using the discharge-surface method. The average annual discharge at stations 2, 3, and 4 (B, C, and D) were estimated at 1.39, 2.11, and 3.39 m3/s, respectively, using this equation. Subsequently, the average monthly discharges in the studied stations in September were calculated at 0.21, 0.29, and 0.46 m3/s, respectively. Afterward, the discharge was measured using HEC-RAS software (version 4.0) in the same month at 0.34, 0.44, 0, and 0.62 m3/s, respectively. The examination of water quality values from ​​among the 17 water quality parameters revealed that physicochemical elements, pH concentration, lead (Pb), and electrical conductivity were higher than the standard concentration of drinking water proposed by the WHO. Conclusion: A model was presented to estimate sanitary water flow by performing correlation tests and linear regression calculations between the river discharge at the dam downstream and the concentration of water quality parameters. According to the proposed model, the minimum flow of sanitary water was estimated at 1.82 m3/s to be considered to release from the dam in the driest month of the year. Therefore, the release of water as the minimum flow of sanitary water less than 1.82 m3/s was not allowed in any other month of the year.

Determination of the amount of Sanitary Water Flow from Dams based on the Quality of Drinking Water: A Case Study, Taleghan River, Iran

Introduction: Given the crisis of water shortage and the industrial development in Iran, comprehensive water-resource management, planning, and serious handling of water quality of the rivers in Iran are the critical issues to tackle with. The concentration of river pollutants is a function of both the quantity and quality of the river flow regime. In this regard, the construction of large dams leads to quantitative and qualitative changes in downstream rivers. These changes are effective in the health of the river environment for such uses as drinking, agriculture, and industry. Accordingly, it is essential to consider the quality of river water in addition to the amount of river water needs. Materials and Methods: This study examined a 22-km long section of the river at the riffle of Taleghan Dam in Alborz Province (103 km from Karaj), Iran. The average annual and monthly discharges of the river in four 6-km-apart stations were estimated. The statistics of eight hydrometric stations and a discharge-surface method were used to calculate the average annual discharge of each sub-basin downstream of Taleghan Dam. Moreover, the discharge non-dimensionalization method, along with the observational statistics of the index station, was used to calculate the average monthly discharge in the examined stations. The Hydrologic Engineering Centers River Analysis System (RAS-HEC) software was then utilized to determine the values ​​of river flow rates hydraulically. Additionally, water quality parameters were compared with the standard concentrations proposed by the World Health Organization (WHO) for drinking-water quality to examine possible changes in pollutant concentrations during the study. Correlation and regression statistical tests in SPSS software (version 24) were then used to analyze the relationship between discharge and pollutant concentration. Results: The experimental equation of Q = 0.0372A0.8641 was obtained to estimate the discharge based on the sub-basins area using the discharge-surface method. The average annual discharge at stations 2, 3, and 4 (B, C, and D) were estimated at 1.39, 2.11, and 3.39 m3/s, respectively, using this equation. Subsequently, the average monthly discharges in the studied stations in September were calculated at 0.21, 0.29, and 0.46 m3/s, respectively. Afterward, the discharge was measured using HEC-RAS software in the same month at 0.34, 0.44, 0, and 0.62 m3/s, respectively. The examination of water quality values from ​​among the 17 water quality parameters revealed that physicochemical elements, pH concentration, lead (Pb), and electrical conductivity were higher than the standard concentration of drinking water proposed by the WHO. Conclusion: A model was presented to estimate sanitary water flow by performing correlation tests and linear regression calculations between the river discharge at the dam downstream and the concentration of water quality parameters. According to the proposed model, the minimum flow of sanitary water was estimated at 1.82 m3/s to be considered to release from the dam in the driest month of the year. Therefore, the release of water as the minimum flow of sanitary water less than 1.82 m3/s was not allowed in any other month of the year.

მდინარის ჩამონადენის განსაზღვრა ჰიდროლოგიური მონაცემების დეფიციტის პირობებში მდ. მტკვრის ჰესების კასკადის მაგალითზე

The article discusses a method for determining water discharge at intake points under the conditions of lack of hydrological data. As an example is given the calculation of the river flow at intake points of the hydroelectric power chain cascade on the river Mtkvari (Chitakhevi HPP, ZAHPP, Ortachala HPP). The data taken from the hydrological stations of ,,Likani,, and „Tbilisi“ are multiplied by the adaptation coefficient, which is obtained by dividing catchment areas of Chitakhevi HPP ZAHPP and Ortachala HPP. The method allows to receive continuous average monthly and annual water discharge at the intake points of Chitakhevi HPP, ZAHPP, Ortachala HPP, instead of incomplete hydrological data. Additionally, the impact of Zhinvali reservoir is taken into account in the calculation of river flow at intake points of the ZAHPP and Ortachala HPP. Also its effect on natural water inflow of river Mtkvari is established. The calculation results show that since of the operation of Zhinvali HPP the average annual water inflow of the river Mtkvari is decreased by 10% at the intake points of the ZAHPP and Ortachala HPP. Using the calculation results it is possible to determine the river flow for existing and planned HPPs on the section of Chitakhevi-Ortachala. The method also helps to determine the design parameters of these HPPs more accurately that is important for effective and safe operation of HPPs on the river Mtkvari during different levels of water flow.

ANALYSIS OF SUSTAINABLE WATER RESOURCES MANAGEMENT BASED ON THE POTENTIAL WATER AVAILABILITY IN THE SEMI-ARID AREA OF KUPANG, INDONESIA

Aims: This study discusses water resources management based on water discharge potential of the Oebobo-Liliba watershed in Kupang City, East Nusa Tenggara, Indonesia. Methodology and Results: River water discharge was analyzed based on hydrological data of a span of 10-years. Average rainfall was calculated using the arithmetic mean method, and potential evapotranspiration (ETo) was calculated through Penman Modification with CROPWAT 8.0. The discharge analysis was conducted through a Mock method. Change in land cover was rendered using related land maps from year 2008 and 2018. Management of agricultural land was discussed through a descriptive analysis. The results showed an average monthly discharge of 0.667 m3/sec. The need for clean water is rendered to be 170 liters/person/day, and the discharge requirement of 90% = 281 liters/sec is concluded to be able to meet the community's clean water needs which amounts to 142,569 people. The total area of paddy fields is 5.38 Ha with water requirements of 1.5 liter/sec/ha, where 80% or 348 Liter/sec can be used to irrigate 232 hectares of paddy. Further results show that land cover in dryland forests decreased from 15% to 10%, settlements increased from 20% to 49%, and shrubs diminished from 20% to 0%. Conclusion, significance and impact study: The minimum debit trend shows a declining trend, while the maximum discharge trend shows an inclining trend. This research concludes that water discharge is adequate to meet community needs yet requires proper water resources management strategy from upstream to downstream of the watershed.

Картографирование современного состояния и трансформации водного режима рек Европейской территории России

Water regime of rivers is an important characteristic of the surface land waters as a natural environment component and object of economic use. The reaction of the rivers’ water regime to the climatic changes, including the case of extreme hydro-meteorological events, has not been studied carefully yet. It is necessary to adapt the water part of national economy to the current trends and characteristics of rivers’ water and ice regime. The analysis and inventory of these trends are required to make appropriate decisions. The authors present the methodology and the results of mapping the current European Russia rivers’ water regime and its modern transformation. The resulting map series includes the maps of the season beginning months, the coefficient of natural flow regulation, the average runoff depth for the "historical" period, extreme monthly equal discharge rate, the ratio of average monthly discharge between seasons, the runoff depth in the "modern" period and its change compared to the "historical" one, a map of water regime transformation, as well as a number of supplementary climatic maps reflecting changes in temperature and precipitation regime. The obtained maps allowed revealing numerous spatiotemporal tendencies, including intensification of the hydrological cycle; the increase in the annual runoff depth in the middle of the East European Plain; increase of absolute unevenness of summer low-water runoff and decrease of relative unevenness; the decrease of maximum discharge; significant change of the ratio of discharge components for the most rivers of the European Russia, the most important feature of which is decreasing the share of snowmelting component.