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Downstream impacts of large hydropower dams are often neglected or underestimated, especially for areas situated at long distances from a dam. Naturalization of the flow hydrograph is an important step in assessing hydro‐ecological and socio‐economic impacts of regulation. Using reservoir inflows, a recently developed, lagged‐flow naturalization method is applied to the lower portion of the regulated Peace River, which forms the northern boundary of the Peace‐Athabasca Delta (PAD). The PAD is a Ramsar wetland of international importance that depends on overland flooding for recharge of its high‐elevation or "perched" basins. Such flooding can be caused by ice jams during the spring breakup of the ice cover or by exceptionally high runoff during open‐water flow conditions. Herein, the focus is on the latter type of event and the resulting recharge of basins located within the Peace sector of the PAD. For the period 1972–2017, regulation has reduced open‐water flow peaks by ~4100 m3/s on average, while limiting the possibility of overbank flooding from the Peace River during the summer. Consistent with earlier findings on spring breakup flows, naturalized open‐water peaks do not exhibit a temporal trend. Recharge of non‐perched basins can also occur with moderately high flows that cause no overland flooding but generate flow reversals in Peace River tributaries. In turn, this mechanism can deliver river water to various basins either directly or via connecting channels. Our results show that flow‐based variables that index the hydrological sustenance of non‐perched basins have been significantly reduced by regulation. [ABSTRACT FROM AUTHOR]

Due to developing abstractions and their impacts on surface runoff, the recorded flow has been changed by human activities in most water gauging stations. Therefore, there is not found natural regime in the catchments. Accordingly, the objective of naturalization is to remove the effect of human activity factors and determine the actual amount of the river flow before the abstraction and the upstream development. Researchers have presented different methods that are mainly based on volume budget. In this way, this research presented the conventional methods as well as investigated their weak points. These new and innovative methods have been applied based on the available data. The methods have been planned based on the net consumption in which, the different types of water demands related to the upstream of each hydrometric station, are estimated for each month of a long-term series. Then, the amount of natural flow is determined by adding them to the observed flow. The accuracy and validation of the results are investigated by comparing the observed and calculated flow. As a case study, this method was utilized and implemented for Tireh and Marbareh sub-basins in Dez as well as Solgan and Beheshtabad sub-basins in the Karun basin. The results showed the role of the human activity factors decreasing the long-term outflow in the Tireh basin a 23.2%, in the Marbareh basin a 28.7%, in the Vanak watershed a 26%, and in the Beheshtabad basin a 9.5%. The results validation indicated the appropriate compatibility of the observational and estimated data for the control points (the stations). In this research, natural flow is obtained by presenting a practical method based on available information in the country. The proposed method has been in the preliminary stages. To verify and comprehend it, it should be used in future research on the interaction of surface and underground water and the use of new technologies such as remote sensing.

Olt River represents one of the most complex hydrographic system, both in terms of the natural factors of the flow and the uses that influence the natural flow. Hydrometric stations on the main course provide good monitoring of the runoff. The most important uses are water supplies and reservoirs. The analysis refers to the degree of runoff influence and the type of influenced runoff. The degree of runoff influence is analysed at all seven hydrometric stations in absolute and relative values. The type of flow affected indicates relative constancy and does not change along the main course.

The goal of this study is to evaluate the performance of the National Water Model (NWM) in time and space across the contiguous United States. Retrospective streamflow simulations were compared to records from 3260 USGS gauging stations, considering both regulated and natural flow conditions. Statistical metrics, including Kling–Gupta efficiency, Percent Bias, Pearson Correlation Coefficient, Root Mean Squared Error, and Normalized Root Mean Squared Error, were employed to assess the agreement between observed and simulated streamflow. A comparison of historical trends in daily flow data between the model and observed streamflow provided additional insight into the utility of retrospective NWM datasets. Our findings demonstrate a superior agreement between the simulated and observed streamflow for natural flow in comparison to regulated flow. The most favorable agreement between the NWM estimates and observed data was achieved in humid regions during the winter season, whereas a reduced degree of agreement was observed in the Great Plains region. Enhancements to model performance for regulated flow are necessary, and bias correction is crucial for utilizing the NWM retrospective streamflow dataset. The study concludes that the model-agnostic NextGen NWM framework, which accounts for regional performance of the utilized model, could be more suitable for continental-scale hydrologic prediction. [ABSTRACT FROM AUTHOR]

Due to developing abstractions and their impacts on surface runoff, the recorded flow has been changed by human activities in most water gauging stations. Therefore, there is not found natural regime in the catchments. Accordingly, the objective of naturalization is to remove the effect of human activity factors and determine the actual amount of the river flow before the abstraction and the upstream development. Researchers have presented different methods that are mainly based on volume budget. In this way, this research presented the conventional methods as well as investigated their weak points. These new and innovative methods have been applied based on the available data. The methods have been planned based on the net consumption in which, the different types of water demands related to the upstream of each hydrometric station, are estimated for each month of a long-term series. Then, the amount of natural flow is determined by adding them to the observed flow. The accuracy and validation of the results are investigated by comparing the observed and calculated flow. As a case study, this method was utilized and implemented for Tireh and Marbareh sub-basins in Dez as well as Solgan and Beheshtabad sub-basins in the Karun basin. The results showed the role of the human activity factors decreasing the long-term outflow in the Tireh basin a 23.2%, in the Marbareh basin a 28.7%, in the Vanak watershed a 26%, and in the Beheshtabad basin a 9.5%. The results validation indicated the appropriate compatibility of the observational and estimated data for the control points (the stations). In this research, natural flow is obtained by presenting a practical method based on available information in the country. The proposed method has been in the preliminary stages. To verify and comprehend it, it should be used in future research on the interaction of surface and underground water and the use of new technologies such as remote sensing. [ABSTRACT FROM AUTHOR]

The most commonplace natural flow inside one-ended inclined pipes today is water heating systems. In this study, a model was created for the estimation of the pipe outlet temperature of the fluid with the energy balance for the inside of the tank, flow rate calculation of natural circulation, and other thermal calculations in a one-ended inclined pipe. In addition, this model has been compared with the Li model in the literature, and it is easier and more successful. 100 W, 200 W, 400 W, 600 W, and 800 W thermal power was applied to a one-ended inclined pipe, and the temperature values were recorded in five minute periods in the experiments that lasted a total of six hours. As the average of the experiments, the estimation results for the current model and the Li model are: the average percent relative error rates are 6.02 and 15.1 and the coefficient of determination, R², are 0.9865 and 0.9683, respectively. [ABSTRACT FROM AUTHOR]

The San Francisco Estuary and its upstream watershed have been highly altered by human development following the California Gold Rush in the mid-19th century. In this paper, we explore the inter- and intra-annual variability of freshwater flow to this estuary and the resulting salt intrusion under scenarios that represent pre-development and contemporary conditions. To place this comparison in context with the advent of systematic and accurate flow and salinity measurements in the estuary, we consider an additional “pre-project” scenario that represents early 20th-century water management (circa 1920), after major flood control and reclamation but before the introduction of large water storage, diversion, and export operations. We use an observed climate record that spans 82 years to compare freshwater flow associated with the scenarios’ landscape and water use characteristics. Using published relationships between flow and salt intrusion length developed from three-dimensional hydrodynamic modeling, we evaluate the effect of these flow alterations as well as estuarine geometry modifications and historically-observed sea-level rise on salt intrusion. We conclude that the pre-development estuary exhibited a more seasonally-variable salinity regime, resulting from a more variable inflow regime from the upstream watershed.

Olt River represents one of the most complex hydrographic system, both in terms of the natural factors of the flow and the uses that influence the natural flow. Hydrometric stations on the main course provide good monitoring of the runoff. The most important uses are water supplies and reservoirs. The analysis refers to the degree of runoff influence and the type of influenced runoff. The degree of runoff influence is analysed at all seven hydrometric stations in absolute and relative values. The type of flow affected indicates relative constancy and does not change along the main course. [ABSTRACT FROM AUTHOR]

To examine the hybrid nanomaterial transportation within a permeable region, a numerical approach was applied. The permeable domain was filled with a mixture of water with hybrid nanomaterial (Fe3O 4 + MWCNT). The wavy below wall experiences uniform flux but the top circular wall maintains at cold temperature. Magnetic field in x -direction was applied and non-Darcy formulation was applied for applying permeability effect. Gravity forces help the transportation of hybrid nanomaterial and magnetic forces reduce the speed of nanomaterial. Imposing nanomaterial can decline the irreversibility. For simulation of equations, CVFEM was applied and Bejan and Nu numbers were calculated. Verification test depicts the nice agreement and contours for irreversibility have been presented. By imposing Ha, the Be augments about 4.36% while Nu declines around 13.32%. By selecting greater Da, the Nu intensifies around 8.95% while Be declines about 4.35%. Nu elevates around 93.78% with an augment of Ra while Be drops around 52.75%. [ABSTRACT FROM AUTHOR]

Hydrological modeling is nowadays critical for evaluating the status, past trends, and future perspectives of water availability at the global, regional, and local scales. The Iberian Peninsula is registering more frequent and severe droughts and water scarcity caused not only by extreme meteorological events, but also by increased demand for water for urban, industrial, and agricultural supplies. Better simulation models are thus needed for accurately quantifying the availability of local water resources. In this study, the natural flow regime in different watersheds of the Iberian Peninsula was simulated using the process-based, fully distributed, MOHID-Land model from 1979 to 2013. Streamflow results were compared with measurements at 73 hydrometric stations not influenced by reservoirs, and with the data available in the management plans of each hydrographic region. The results showed a high dispersion of the goodness-of-fit indicators, with the coefficient of determination (R2) ranging between 0 and 0.91, and the modeling efficiency (NSE) being higher than 0.35 at only 22 (calibration) and 28 (validation) hydrometric stations. Considering the scale of application, results were acceptable but evidenced the difficulties in simulating streamflow in watersheds using a coarse resolution. As such, this paper further deals with the difficulties and challenges of the adopted modeling approach. Nevertheless, this study constitutes a further step towards the more accurate assessment of water resources availability at the Iberian Peninsula scale using process-based modeling. [ABSTRACT FROM AUTHOR]

Natural earth-bounded channel flows usually subject to various sidewall turbulences, i.e. in the form of secondary currents, due to non-constant channel shapes at different sections. This paper investigates an improved Shiono-Knight model (SKM) by combining it with a Multi-Zonal (MZ) method (proposed by Pu, 2019) to represent lateral flow turbulence and secondary currents in different shapes of open channel, i.e. rectangular and trapezoidal. By applying the proposed analytical model to both rectangular and trapezoidal channel flows, we have inspected different streamwise velocity characteristics across transverse direction generated by their sidewalls in order to provide crucial fundamental understanding to real-world natural flow system. The proposed model has also been validated via various experimental data conducted in national UK Flood Channel Facility (UK-FCF). It has been observed that the trapezoidal channel has created a larger sidewall zone where secondary current can affect flow velocity; however, the intensity of the secondary flow in trapezoidal channel has been found lesser than that of the rectangular channel. By improving the modelling of natural flow at sidewall, the studied approach could be adapted into different existing analytical models to improve their accuracy. [ABSTRACT FROM AUTHOR]

In this paper, an improved Shiono–Knight model (SKM) has been proposed to calculate the rectangular compound open channel flows by considering a multi-zonal (MZ) approach in modelling turbulence and secondary flows across lateral flow direction. This is an effort to represent natural flows with compound shape more closely. The proposed model improves the estimation of secondary flow by original SKM model to increase the accuracy of depth-averaged velocity profile solution formed within the transitional region between different sections (i.e. between main-channel and floodplain) of compound channel. This proposed MZ model works by sectioning intermediate zones between floodplain and main-channel for running computation in order to improve the modelling accuracy. The modelling results have been validated using the experimental data by national UK Flood Channel Facility. It has been proven to work reasonably well to model secondary flows within the investigated compound channel flow cases and hence produce better representation to their flow lateral velocity profile. [ABSTRACT FROM AUTHOR]

ABSTRACT In a watershed there is space and climate variability within its catchment area, causing changes in water qualitative and quantitative characteristics. Thus, the hydrological data collected from a specific basin may be extrapolated to neighboring basins with similar physical characteristics, using techniques of hydrological regionalization. This study developed the flow regionalization in the Teles Pires Basin, using historic series and probabilistic models to verify the data adherence through the regression equations adjustment according to the hydrologically homogeneous regions. The linear and power regression models were tested, employing physical and climatic characteristics and then the best adjustments were selected based on coefficients of determination, adjusted coefficient of determination, significance by F-test and small number of variables in the equation. The physical characteristics of the basin, drainage area and mainstream length, and the climatic variable, annual total precipitation showed higher adjustments. These equations can provide subsidy for decision making in the process of water resource management.

Abstract: An estimate of a river's natural flow regime is useful for water resource planning and ecosystem rehabilitation by providing insight into the predisturbance form and function of a river. The natural flow regime of most rivers has been perturbed by development during the 20th century and in some cases, before stream gaging began. The temporal resolution of natural flows estimated using traditional methods is typically not sufficient to evaluate cues that drive native ecosystem function. Additionally, these traditional methods are watershed specific and require large amounts of data to produce accurate results. We present a mass balance method that estimates natural flows at daily time step resolution for the northern branch of the Rio Grande, upstream from the Rio Conchos, that relies only on easily obtained streamflow data. Using an analytical change point method, we identified periods of the measured flow regime during the 20th century for comparison with the estimated natural flows. Our results highlight the significant deviation from natural conditions that occurred during the 20th century. The total annual flow of the northern branch is 95% lower than it would be in the absence of human use. The current 2 year flood has decreased by more than 60%, is shorter in duration, and peaks later in the year. When compared to unregulated flows estimated using traditional mass balance accounting methods, our approach provides similar results. [ABSTRACT FROM AUTHOR]

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