Non-stationarity of low flows and their relevance to river modelling during drought periods

2017 ◽  
Vol 68 (12) ◽  
pp. 2306 ◽  
Author(s):  
David W. Rassam ◽  
Daniel Pagendam ◽  
Mat Gilfedder ◽  
Lu Zhang
Keyword(s):  
Regression Analysis ◽  
River Flow ◽  
Low Flow ◽  
Flow Conditions ◽  
Low Flows ◽  
River Modelling ◽  
Quantile Regression Analysis ◽  
River Models ◽  
Groundwater Contribution ◽  
Ltb Metric

Changes in groundwater storage lead to a reduction in groundwater contribution to river flow and present as non-stationarity, especially during low-flow conditions. Conventional river models typically ignore this non-stationarity, and, hence, their predictions of declines in low flows during drought periods are likely to be compromised. The present study assesses non-stationarity and highlights its implications for river modelling. A quantile regression analysis showed non-stationarity of low flows in the Namoi catchment (Australia), with statistically significant downward trends in the 10th percentile of log-transformed baseflow (10-LTB). This highlighted the usefulness of the 10-LTB metric to identify non-stationarity and, hence, alert modellers to the importance of adopting models that explicitly account for groundwater processes when modelling such river systems.

scholarly journals Lithological and Tectonic Control on Groundwater Contribution to Stream Discharge During Low-Flow Conditions

Water ◽  
2020 ◽  
Vol 12 (3) ◽  
pp. 821 ◽  
Author(s):  
Stefanie Wirth ◽  
Claire Carlier ◽  
Fabien Cochand ◽  
Daniel Hunkeler ◽  
Philip Brunner
Keyword(s):  
Water Resources ◽  
Stream Flow ◽  
Low Flow ◽  
Limited Information ◽  
Flow Conditions ◽  
Stream Discharge ◽  
Low Flows ◽  
Dry Spells ◽  
Deep Boreholes ◽  
Groundwater Contribution

Knowing how stream discharge in an ungauged catchment reacts to dry spells is a major challenge for managing water resources. The role of geology on these dynamics is poorly understood. For the Swiss Molasse basin, we therefore explored how the geology influences the groundwater contribution to stream flow during low-flow conditions. Using existing data from geological reports and maps as well as from deep boreholes, we constructed a basin-wide overview of the hydrogeological quality of the bedrock and investigated five catchments in 3D. We found that catchments with the most permeable sedimentary bedrock are least sensitive to low flows (marine sandstone, K = 10−4 to 10−5 m/s, Peff = 5–10%). In contrast, if bedrock K is low (K < 10−6 m/s), the presence of a productive Quaternary volume becomes decisive for groundwater contribution to stream flow. Limitations exist due to a restricted database for K and Peff values of the Molasse and limited information on continuation of lithologies with depth. This emphasizes the need for more hydrogeologically relevant data for the future management of water resources. Our results highlighting what lithotypes favor groundwater contribution to stream flow are valid also in other regions for the assessment of a catchment’s sensitivity to low flows.

Sources of Chlorophenolic Compounds to the Fraser River Estuary

1988 ◽  
Vol 23 (1) ◽  
pp. 55-68 ◽  
Author(s):  
J. H. Carey ◽  
J. H. Hart
Keyword(s):  
River Flow ◽  
River Estuary ◽  
Low Flow ◽  
Fraser River ◽  
Pulp Mills ◽  
Flow Conditions ◽  
Downstream Site ◽  
Upstream Site ◽  
The North ◽  
Main River

Abstract The identity and concentrations of chlorophenolic compounds in the Fraser River estuary were determined under conditions of high and low river flow at three sites: a site upstream from the trifurcation and at downstream sites for each main river arm. Major chlorophenolics present under both flow regimes were 2,4,6-trichlorophenol (2,4,6-TCP), 2,3,4,6-tetrachlorophenol (2,3,4,6-TeCP), pentachlorophenol (PCP), tetrachloroguaiacol (TeCG) and a compound tentatively identified as 3,4,5-trichloroguaiacol (3,4,5-TCG). Under high flow conditions, concentrations of the guaiacols were higher than any of the Chlorophenols and concentrations of all five chlorophenolics appeared to correlate. Under low flow conditions, concentrations of chloroguaiacols were higher than Chlorophenols at the upstream site and at the downstream site on the Main Arm, whereas at the downstream site on the North Arm, concentrations of 2,3,4,6-TeCP and PCP were higher than the chloroguaiacols in some samples. Overall, the results indicate that pulp mills upstream from the estuary are important sources of chlorophenolics to the estuary under all flow conditions. Additional episodic inputs of 2,3,4,6-TeCP and PCP from lumber mills occur along the North Arm. When these inputs occur, they can cause the concentrations of Chlorophenols in the North Arm to exceed provisional objectives. If chloroguaiacols are included as part of the objective, concentrations of total chlorophenolics in water entering the estuary can approach and exceed these objectives, especially under low flow conditions.

scholarly journals A large sample analysis of European rivers on seasonal river flow correlation and its physical drivers

2019 ◽  
Vol 23 (1) ◽  
pp. 73-91 ◽  
Author(s):  
Theano Iliopoulou ◽  
Cristina Aguilar ◽  
Berit Arheimer ◽  
María Bermúdez ◽  
Nejc Bezak ◽  
...  
Keyword(s):  
River Flow ◽  
Frequency Estimation ◽  
Low Flow ◽  
Time Lags ◽  
Low Flows ◽  
Flow Formation ◽  
Gaussian Probability Distribution ◽  
High Flows ◽  
Seasonal Correlation ◽  
Seasonal Streamflow

Abstract. The geophysical and hydrological processes governing river flow formation exhibit persistence at several timescales, which may manifest itself with the presence of positive seasonal correlation of streamflow at several different time lags. We investigate here how persistence propagates along subsequent seasons and affects low and high flows. We define the high-flow season (HFS) and the low-flow season (LFS) as the 3-month and the 1-month periods which usually exhibit the higher and lower river flows, respectively. A dataset of 224 rivers from six European countries spanning more than 50 years of daily flow data is exploited. We compute the lagged seasonal correlation between selected river flow signatures, in HFS and LFS, and the average river flow in the antecedent months. Signatures are peak and average river flow for HFS and LFS, respectively. We investigate the links between seasonal streamflow correlation and various physiographic catchment characteristics and hydro-climatic properties. We find persistence to be more intense for LFS signatures than HFS. To exploit the seasonal correlation in the frequency estimation of high and low flows, we fit a bi-variate meta-Gaussian probability distribution to the selected flow signatures and average flow in the antecedent months in order to condition the distribution of high and low flows in the HFS and LFS, respectively, upon river flow observations in the previous months. The benefit of the suggested methodology is demonstrated by updating the frequency distribution of high and low flows one season in advance in a real-world case. Our findings suggest that there is a traceable physical basis for river memory which, in turn, can be statistically assimilated into high- and low-flow frequency estimation to reduce uncertainty and improve predictions for technical purposes.

scholarly journals Calibration of hydrological models for ecologically relevant streamflow predictions: a trade-off between fitting well to data and estimating consistent parameter sets?

2020 ◽  
Vol 24 (3) ◽  
pp. 1031-1054 ◽  
Author(s):  
Thibault Hallouin ◽  
Michael Bruen ◽  
Fiachra E. O'Loughlin
Keyword(s):  
Flow Regime ◽  
River Flow ◽  
Freshwater Ecosystems ◽  
Living Environment ◽  
Rate Of Change ◽  
Low Flow ◽  
Hydrological Models ◽  
Flow Conditions ◽  
Local Flow ◽  
Trade Off

Abstract. The ecological integrity of freshwater ecosystems is intimately linked to natural fluctuations in the river flow regime. In catchments with little human-induced alterations of the flow regime (e.g. abstractions and regulations), existing hydrological models can be used to predict changes in the local flow regime to assess any changes in its rivers' living environment for endemic species. However, hydrological models are traditionally calibrated to give a good general fit to observed hydrographs, e.g. using criteria such as the Nash–Sutcliffe efficiency (NSE) or the Kling–Gupta efficiency (KGE). Much ecological research has shown that aquatic species respond to a range of specific characteristics of the hydrograph, including magnitude, frequency, duration, timing, and the rate of change of flow events. This study investigates the performance of specially developed and tailored criteria formed from combinations of those specific streamflow characteristics (SFCs) found to be ecologically relevant in previous ecohydrological studies. These are compared with the more traditional Kling–Gupta criterion for 33 Irish catchments. A split-sample test with a rolling window is applied to reduce the influence on the conclusions of differences between the calibration and evaluation periods. These tailored criteria are shown to be marginally better suited to predicting the targeted streamflow characteristics; however, traditional criteria are more robust and produce more consistent behavioural parameter sets, suggesting a trade-off between model performance and model parameter consistency when predicting specific streamflow characteristics. Analysis of the fitting to each of 165 streamflow characteristics revealed a general lack of versatility for criteria with a strong focus on low-flow conditions, especially in predicting high-flow conditions. On the other hand, the Kling–Gupta efficiency applied to the square root of flow values performs as well as two sets of tailored criteria across the 165 streamflow characteristics. These findings suggest that traditional composite criteria such as the Kling–Gupta efficiency may still be preferable over tailored criteria for the prediction of streamflow characteristics, when robustness and consistency are important.

River flow abstraction due to hydraulic storage at freezeup

2009 ◽  
Vol 36 (3) ◽  
pp. 519-523 ◽  
Author(s):  
Spyros Beltaos
Keyword(s):  
Water Quality ◽  
River Flow ◽  
Ice Cover ◽  
Low Flow ◽  
Flow Data ◽  
Flow Conditions ◽  
Ice Concentration ◽  
Cover Thickness ◽  
Water Quality And Quantity

A hydrologic extreme that can be partly generated by ice effects is low winter flow, which is known for potential impacts on water quality and quantity of rivers receiving effluent discharges or industrial withdrawals. Flow abstraction caused by hydraulic storage during the upstream propagation of an ice cover is quantified using the equations of continuity for ice and water. The flow abstraction is shown to increase with increasing ice concentration, but to decrease with increasing ice cover thickness. Numerical values are consistent with winter abstractions indicated by flow data from Canadian hydrometric stations. The present results further suggest that low-flow conditions in winter should generally improve, or at least not deteriorate, under a warmer climate.

scholarly journals The effects of climatic anomalies on low flows in Switzerland

2019 ◽  
Author(s):  
Marius G. Floriancic ◽  
Wouter R. Berghuijs ◽  
James W. Kirchner ◽  
Peter Molnar
Keyword(s):  
River Flow ◽  
Potential Evapotranspiration ◽  
Weather Conditions ◽  
Climatic Conditions ◽  
Low Flow ◽  
Weather Forecasts ◽  
Environmental Consequences ◽  
Low Flows ◽  
Insight Into ◽  
Seasonal Weather

Abstract. Large parts of Europe have faced extreme low river flows in recent summers (2003, 2011, 2015, 2018) with major economic and environmental consequences. Understanding the origins of extremes like these is important for water resources management. To reveal how weather drives low flows, we explore how deviations from mean seasonal climatic conditions (i.e. climatic anomalies) of precipitation and potential evapotranspiration shaped the occurrence and magnitude of the annual 7-day lowest flows (Qmin) across 380 Swiss catchments from 2000 through 2018. Most annual low flows followed periods of below average precipitation and above average potential evapotranspiration, and the most extreme low flows resulted from both of these drivers acting together. Extremely dry years saw simultaneous drought conditions across large parts of Europe, but low flow timing during these years was still spatially variable across Switzerland. Longer climatic anomalies led to lower low flows. Most low flows were typically preceded by climatic anomalies lasting up to two months, whereas low flows in the extreme years (2003, 2011, 2015, 2018) were associated with much longer-lasting climatic anomalies. Weather conditions on even longer time scales have been reported to sometimes affect river flow. However, across Switzerland, we found that precipitation totals in winter only slightly influenced the magnitude and timing of summer and autumn low flows. Our results provide insight into how precipitation and potential evapotranspiration jointly shape summer and winter low flows across Switzerland, and could potentially aid in assessing low-flow risks in similar mountain regions using seasonal weather forecasts.

ANALYSIS OF LOW-FLOW CONDITIONS IN A HETEROGENEOUS KARST CATCHMENT AS A BASIS FOR FUTURE PLANNING OF WATER RESOURCE MANAGEMENT

2020 ◽  
Author(s):  
Klaudija Sapač ◽  
◽  
Simon Rusjan ◽  
Nejc Bezak ◽  
Mojca Šraj ◽  
...  
Keyword(s):  
Water Resources ◽  
Water Use ◽  
Water Resource Management ◽  
Flow Characteristics ◽  
Low Flow ◽  
Flow Conditions ◽  
Discharge Data ◽  
River Catchment ◽  
Low Flows ◽  
Recession Curves

Understanding and prediction of low-flow conditions are fundamental for efficient water resources planning and management as well as for identification of water-related environmental problems. This is problematic especially in view of water use in economic sectors (e.g., tourism) where water-use peaks usually coincide with low-flow conditions in the summer time. In our study, we evaluated various low-flow characteristics at 11 water stations in the non-homogenous Ljubljanica river catchment in Slovenia. Approximately 90% of the catchment is covered by karst with a diverse subsurface, consisting of numerous karst caves. The streams in the remaining part of the catchment have mainly torrential characteristics. Based on daily discharge data we calculated and analyzed values of 5 low-flow indices. In addition, by analyzing hydrograph recession curves, recession constants were determined to assess the catchment’s responsiveness to the absence of precipitation. By using various calculation criteria, we analyzed the influence of individual criteria on the values of low-flow recession constants. Recession curves are widely used in different fields of hydrology, for example in hydrological models, baseflow studies, for low-flow forecasting, and in assessing groundwater storages which are crucial in view of assessing water availability for planning water resources management. Moreover, in the study we also investigated the possible impact of projected climate change (scenario RCP4.5) on low-flow conditions in two sub-catchments of the Ljubljanica river catchment. For the evaluation we used the lumped conceptual hydrological model implemented in the R package airGR. For periods 2011-2040, 2041-2070, and 2071-2100 low-flow conditions were evaluated based on flow duration curves compared with the 1981-2010 period. The lowest discharges at all water stations in the Ljubljanica river catchment occur mostly during the summer months. Our results for the future show that we can expect a decrease of the lowest low-flows in the first two 30-year periods, while in the last one low-flows could increase by approx. 15%. However, the uncertainty/variability of the results is very high and as such should be taken into account when interpreting and using the results. This study demonstrates that evaluation of several low-flow characteristics is needed for a comprehensive and holistic overview of low-flow dynamics. In non-homogeneous catchments with a high karstic influence, the hydrogeological conditions of rivers should also be taken into account in order to adequately interpret the results of low-flow analyses. This proved to be important even in case of neighboring water stations.

scholarly journals Mekong River flow and hydrological extremes under climate change

2016 ◽  
Vol 20 (7) ◽  
pp. 3027-3041 ◽  
Author(s):  
Long Phi Hoang ◽  
Hannu Lauri ◽  
Matti Kummu ◽  
Jorma Koponen ◽  
Michelle T. H. van Vliet ◽  
...  
Keyword(s):  
Climate Change ◽  
River Flow ◽  
High Flow ◽  
Mekong River ◽  
Low Flow ◽  
Future Climate Change ◽  
Climate Projections ◽  
Low Flows ◽  
Hydrological Extremes ◽  
Hydrological Impact

Abstract. Climate change poses critical threats to water-related safety and sustainability in the Mekong River basin. Hydrological impact signals from earlier Coupled Model Intercomparison Project phase 3 (CMIP3)-based assessments, however, are highly uncertain and largely ignore hydrological extremes. This paper provides one of the first hydrological impact assessments using the CMIP5 climate projections. Furthermore, we model and analyse changes in river flow regimes and hydrological extremes (i.e. high-flow and low-flow conditions). In general, the Mekong's hydrological cycle intensifies under future climate change. The scenario's ensemble mean shows increases in both seasonal and annual river discharges (annual change between +5 and +16 %, depending on location). Despite the overall increasing trend, the individual scenarios show differences in the magnitude of discharge changes and, to a lesser extent, contrasting directional changes. The scenario's ensemble, however, shows reduced uncertainties in climate projection and hydrological impacts compared to earlier CMIP3-based assessments. We further found that extremely high-flow events increase in both magnitude and frequency. Extremely low flows, on the other hand, are projected to occur less often under climate change. Higher low flows can help reducing dry season water shortage and controlling salinization in the downstream Mekong Delta. However, higher and more frequent peak discharges will exacerbate flood risks in the basin. Climate-change-induced hydrological changes will have important implications for safety, economic development, and ecosystem dynamics and thus require special attention in climate change adaptation and water management.

Synchrony in population dynamics of juvenile Atlantic salmon: analyzing spatio-temporal variation and the influence of river flow and demography

2021 ◽  
Author(s):  
Colin Bouchard ◽  
Mathieu Buoro ◽  
Clément Lebot ◽  
Stephanie M Carlson
Keyword(s):  
Atlantic Salmon ◽  
Environmental Conditions ◽  
River Flow ◽  
Multiple Scales ◽  
Low Flow ◽  
Moran Effect ◽  
Spatial Synchrony ◽  
Flow Conditions ◽  
Spatio Temporal ◽  
Regional Synchrony

Dispersal and shared environmental conditions can both synchronize the dynamics of local populations, but disentangling their relative influence on dynamics is challenging. We used a Bayesian approach to estimate the synchrony of a metapopulation of Atlantic salmon composed of 18 populations in Brittany, France, including a 24-year time-series of the abundances of juveniles. We estimated the spatial synchrony at a regional and local spatial scale over the study period. We found a strong regional synchrony despite spatio-temporal variability of local synchrony in the abundance of juveniles. We then explored the drivers of synchrony, including environmental conditions (aspects of river flow) and abundance of adult breeders. This revealed that summer low-flow conditions seemed to synchronize the abundances of juveniles more than the synchrony in the abundance of adult breeders, suggesting a Moran effect. Given that drought conditions are expected to become more common with climate change, our work highlights the potentially strong synchronizing effect of summer low-flow on the dynamics of local salmon populations and the benefits of considering synchrony at multiple scales.

Geochemistry of Cu, Zn and Fe in the Tambo River, Australia II. Field investigation under low-flow conditions

2008 ◽  
Vol 59 (1) ◽  
pp. 80 ◽  
Author(s):  
Barry T. Hart ◽  
Tina Hines ◽  
Bruce A.W. Coller
Keyword(s):  
River Flow ◽  
Field Investigation ◽  
Low Flow ◽  
Flow Conditions ◽  
Study Region ◽  
Hydrous Iron Oxide ◽  
Input Region ◽  
Flow Filtration ◽  
Colloidal Fraction ◽  
Cu And Zn

The behaviour of Fe, Cu and Zn, added to the upper Tambo River (Victoria, Australia) via a metal-enriched groundwater input, was studied during a period of very low river flow. Water samples were collected over a 1.3-km section of the river located immediately downstream of the spring input. Heavy metals were separated into three fractions (dissolved, colloidal and particulate) using tangential flow filtration. Within the ‘input region’, the pH was low (5.1–5.8) and sulphate (306–359 mg L–1), total Fe (2.81 mg L–1), total Cu (19.7 mg L–1) and total Zn (24.1 mg L–1) concentrations all increased significantly. Subsequently, the total metal concentrations reduced with distance downstream of the input, and approached values similar to those recorded upstream of the input region at the end of the study region. Most of the Fe was oxidised before it entered the river as a thick hydrous iron oxide floc that travelled downstream close to the riverbed. The remaining dissolved Fe (mainly Fe(II)) that entered the river largely controlled the behaviour of Cu and Zn in the ‘active region’ (75–400 m). This Fe(II) was rapidly oxidised to Fe(III), which then removed large amounts of the dissolved Cu (65%) and Zn (55%) into the colloidal fraction. Processes such as settling of particles, dilution by groundwater inputs and sorption of dissolved Cu and Zn onto sediments removed the remainder of the Cu and Zn.

Sign in / Sign up

Export Citation Format

Share Document