scholarly journals Alluvial evidence for major climate and flow regime changes during the middle and late Quaternary in eastern central Australia

Geomorphology ◽  
2008 ◽  
Vol 101 (1-2) ◽  
pp. 109-129 ◽  
Author(s):  
Gerald C. Nanson ◽  
David M. Price ◽  
Brian G. Jones ◽  
Jerry C. Maroulis ◽  
Maria Coleman ◽  
...  
Keyword(s):  
Flow Regime ◽  
Late Quaternary ◽  
Regime Changes ◽  
Central Australia

scholarly journals Potential impacts to freshwater ecosystems caused by flow regime alteration under changing climate conditions in Taiwan

2008 ◽  
Vol 5 (6) ◽  
pp. 3005-3032 ◽  
Author(s):  
J.-P. Suen
Keyword(s):  
Climate Change ◽  
Flow Regime ◽  
River Flow ◽  
Aquatic Organisms ◽  
Freshwater Ecosystems ◽  
Climate Conditions ◽  
Regime Changes ◽  
Changing Climate ◽  
Extreme Flood ◽  
Precautionary Measures

Abstract. Observed increases in the Earth's surface temperature bring with them associated changes in precipitation and atmospheric moisture that consequentially alter river flow regimes. This paper uses the Indicators of Hydrologic Alteration approach to examine climate-induced flow regime changes that can potentially affect freshwater ecosystems. Analyses of the annual extreme water conditions at 23 gauging stations throughout Taiwan reveal large alterations in recent years; extreme flood and drought events were more frequent in the period after 1991 than from 1961–1990, and the frequency and duration of the flood and drought events also show high fluctuation. Climate change forecasts suggest that such flow regime alterations are going to continue into the foreseeable future. Aquatic organisms not only feel the effects of anthropogenic damage to river systems, but they also face on-going threats of thermal and flow regime alterations associated with climate change. This paper calls attention to the issue, so that water resources managers can take precautionary measures that reduce the cumulative effects from anthropogenic influence and changing climate conditions.

scholarly journals Development of an eco-geomorphic modeling framework to evaluate riparian ecosystem response to flow-regime changes

2018 ◽  
Vol 123 ◽  
pp. 112-126 ◽  
Author(s):  
Rebecca M. Diehl ◽  
Andrew C. Wilcox ◽  
David M. Merritt ◽  
Dustin W. Perkins ◽  
Julian A. Scott
Keyword(s):  
Flow Regime ◽  
Ecosystem Response ◽  
Modeling Framework ◽  
Riparian Ecosystem ◽  
Regime Changes

scholarly journals On the Relationship between Experimental and Numerical Modelling of Gravel-Bed Channel Aggradation

Hydrology ◽  
2019 ◽  
Vol 6 (1) ◽  
pp. 9
Author(s):  
Barbara Zanchi ◽  
Matteo Zucchi ◽  
Alessio Radice
Keyword(s):  
Numerical Model ◽  
Numerical Modelling ◽  
Boundary Conditions ◽  
Flow Regime ◽  
Model Calibration ◽  
Water Regime ◽  
Morphological Changes ◽  
Regime Changes ◽  
Laboratory Flume ◽  
The Relationship

This communication explores the use of numerical modelling to simulate the hydro-morphologic response of a laboratory flume subject to sediment overloading. The numerical model calibration was performed by introducing a multiplicative factor in the Meyer–Peter and Müller transport formula, in order to achieve a correspondence with the bed and water profiles recorded during a test carried out under a subcritical flow regime. The model was validated using a second subcritical test, and then run to simulate an experiment during which morphological changes made the water regime switch from subcritical to supercritical. The “relationship” between physical and numerical modelling was explored in terms of how the boundary conditions for the two approaches had to be set. Results showed that, even though the first two experiments were reproduced well, the third one could not be modeled adequately. This was explained considering that, after the switch of the flow regime, some of the boundary conditions posed into the numerical model turned out to be misplaced, while others were lacking. The numerical modelling of hydro-morphologic processes where the flow regime is trans-critical in time requires particular care in the position of the boundary conditions, accounting for the instant at which the water regime changes.

Changing low flow seasonality in Central European headwaters

2021 ◽  
Author(s):  
Vojtech Vlach ◽  
Ondrej Ledvinka ◽  
Milada Matouskova
Keyword(s):  
Flow Regime ◽  
R Package ◽  
Hydrological Drought ◽  
Low Flow ◽  
Significant Shift ◽  
Regime Changes ◽  
Seasonality Index ◽  
Long Term Trends ◽  
Summer Minimum ◽  
Hydrological Droughts

<p>In the environment of the changing climate in Central Europe, the seasonality and magnitude of low flow events and hydrological droughts are projected to change in the near future. Ongoing increases in the air temperature, rates of evaporation and decreasing snow cover will significantly affect the summer deficit volumes even in the rivers of humid montane and highland areas in mid-latitudes. However, what if the significant changes have already been happening during the last decades? Therefore, this research is focused on analysis of the variability and seasonality of low flow events and hydrological drought events in fifteen near-natural catchments along the Czech–German and Czech–Polish national borders. To quantify the low flow regime changes of the study regions in the last 52 years (1968–2019), we applied tools from the R package lfstat. The 30-year moving averages of seasonality ratio (SR) and the seasonality index (SI) were derived to address the degree of change in each catchment. Moreover, the 7-day and 30-day mean summer minimum discharges were computed, as well as the streamflow deficit volumes for every episode of hydrological drought. The results showed a continual increase in the proportion of summer low flow and drought events during the study period along with a significant shift in the average date of low flow occurrence towards the beginning of the year. The most marked shifts in low flow seasonality were found mainly in catchments with the average altitude 800–1000 m a. s. l. Conversely, the low flow regime in catchments above 1000 m a. s. l. and also in the catchments below 800 m a. s. l. remained nearly stable throughout the 1968–2019 period. Moreover, the analysis of 7- and 30-day mean summer minimum discharges indicated a much-diversified pattern in the behavior of long-term trends than it was expected.</p>

scholarly journals Flow regime changes at hydraulic jumps in an open Venturi channel for Newtonian fluid

2017 ◽  
Vol 9 (4) ◽  
pp. 169-179 ◽  
Author(s):  
Prasanna Welahettige ◽  
Bernt Lie ◽  
Knut Vaagsaether
Keyword(s):  
Flow Regime ◽  
Newtonian Fluid ◽  
Triple Point ◽  
Hydraulic Jump ◽  
Experimental Results ◽  
Hydraulic Jumps ◽  
Flow Depth ◽  
Supercritical Flow ◽  
Subcritical Flow ◽  
Regime Changes

The aim of this paper is to study flow regime changes of Newtonian fluid flow in an open Venturi channel. The simulations are based on the volume of fluid method with interface tracking. ANSYS Fluent 16.2 (commercial code) is used as the simulation tool. The simulation results are validated with experimental results. The experiments were conducted in an open Venturi channel with water at atmospheric condition. The inlet water flow rate was 400 kg/min. The flow depth was measured by using ultrasonic level sensors. Both experiment and simulation were done for the channel inclination angles 0°, −0.7°, and −1.5°. The agreement between computed and experimental results is satisfactory. At horizontal condition, flow in the channel is supercritical until contraction and subcritical after the contraction. There is a hydraulic jump separating the supercritical and subcritical flow. The position of the hydraulic jump oscillates within a region of about 100 mm. Hydraulic jumps coming from the contraction walls to the upstream flow are the main reasons for the conversion of supercritical flow into subcritical flow. An “oblique jump” can be seen where there is a supercritical flow in the contraction. There is a triple point in this oblique jump: the triple point consists of two hydraulic jumps coming from the contraction walls and the resultant wave. The highest flow depth and the lowest velocity in the triple point are found at the oblique jump.

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