A large-scale hydroclimatological perspective on western European river flow regimes

2012 ◽  
Vol 44 (5) ◽  
pp. 809-833 ◽  
Author(s):  
Donna Wilson ◽  
David M. Hannah ◽  
Glenn R. McGregor
Keyword(s):  
Large Scale ◽  
Western Europe ◽  
River Flow ◽  
Flow Regimes ◽  
Climatic Conditions ◽  
Low Flow ◽  
Annual Rainfall ◽  
Time Variability ◽  
Runoff Generation

A novel flow regime classification scheme was applied to 141 river basins across western Europe, providing more robust analysis of space–time variability in regimes and their driving hydroclimatological processes. Regime shape (timing) and magnitude (size) were classified to regionalise long-term average flow regimes and to quantify year-to-year variation in regimes for each basin. Six long-term regime shape regions identified differences in seasonality related to latitude and altitude. Five long-term magnitude regions were linked to location plus average annual rainfall. Spatial distribution of long-term regimes reflected dominant climate and runoff generation processes. Regions were used to structure analysis of (relative) inter-annual regime dynamics. Six shape and five magnitude inter-annual regimes were identified; and regime stability (switching) assessed at pan-European, regional and basin scales. In some years, certain regime types were more prevalent, but never totally dominant. Regime shape was more stable at higher altitude due to buffering by frozen water storage-release (cf. more variable rainfall-runoff at lower altitudes). The lower inter-annual magnitude regimes persisted across larger domains (cf. higher magnitude) due to the more widespread climatic conditions generating low flow. Notably, there was limited spatio-temporal correspondence between regime shape and magnitude, suggesting variations in one attribute cannot be used to infer the other.

scholarly journals Incorporating large-scale atmospheric variables in long-term seasonal rainfall forecasting using artificial neural networks: an application to the Ping Basin in Thailand

2016 ◽  
Vol 48 (3) ◽  
pp. 867-882 ◽  
Author(s):  
M. S. Babel ◽  
T. A. J. G. Sirisena ◽  
N. Singhrattna
Keyword(s):  
Climate Change ◽  
General Circulation ◽  
Large Scale ◽  
Resource Planning ◽  
Seasonal Rainfall ◽  
Annual Rainfall ◽  
Rainfall Forecasting ◽  
Artificial Neural ◽  
Atmospheric Variables

Understanding long-term seasonal or annual or inter-annual rainfall variability and its relationship with large-scale atmospheric variables (LSAVs) is important for water resource planning and management. In this study, rainfall forecasting models using the artificial neural network technique were developed to forecast seasonal rainfall in May–June–July (MJJ), August–September–October (ASO), November–December–January (NDJ), and February–March–April (FMA) and to determine the effects of climate change on seasonal rainfall. LSAVs, temperature, pressure, wind, precipitable water, and relative humidity at different lead times were identified as the significant predictors. To determine the impacts of climate change the predictors obtained from two general circulation models, CSIRO Mk3.6 and MPI-ESM-MR, were used with quantile mapping bias correction. Our results show that the models with the best performance for FMA and MJJ seasons are able to forecast rainfall one month in advance for these seasons and the best models for ASO and NDJ seasons are able do so two months in advance. Under the RCP4.5 scenario, a decreasing trend of MJJ rainfall and an increasing trend of ASO rainfall can be observed from 2011 to 2040. For the dry season, while NDJ rainfall decreases, FMA rainfall increases for the same period of time.

Using a long-term climate simulation to address future changes in Western Europe precipitation regimes due to global warming

2020 ◽  
Author(s):  
Pedro M. Sousa ◽  
Alexandre M. Ramos ◽  
Ricardo M. Trigo ◽  
Christoph C. Raible ◽  
Martina Messmer ◽  
...  
Keyword(s):  
Global Warming ◽  
Moisture Transport ◽  
Large Scale ◽  
Western Europe ◽  
Warming Trend ◽  
Water Vapor Transport ◽  
Climate Simulation ◽  
Wet Season ◽  
Precipitation Regimes

<p>Moisture transport and Atmospheric Rivers (ARs) over the Northeastern Atlantic are a very relevant process for the inter-annual variability of precipitation over Western Europe. Based on a long-term transient simulation (850-2100CE) from the CESM model, we have showed that moisture transport towards Western Europe (using the vertically integrated horizontal water vapor transport, IVT) has been increasing significantly since pre-industrial period, in a clear association with the global warming trend. Both current and projected changes (using RCP 8.5) significantly exceed the range given by inter-annual to inter-decadal internal/external variability observed during the last millennium.</p><p>We have checked the emergence of the temperature, IVT and precipitation signals in Iberia and the UK, showing that while the first two have now clearly emerged from the pre-warming state, precipitation series are still slightly below that threshold. Nevertheless, projections clearly show an increase in rainfall at higher latitudes (i in phase with a warmer and moister atmosphere); and a decrease at lower latitudes decoupled from the overall increase in moisture availability. Additionally we have explored the role played by large-scale circulation and atmospheric dynamics for these contrasting projections. Overall, results show that a poleward migration of moisture corridors and ARs explain a significant fraction of these projected trends. Based on the Clausius–Clapeyron relation we have separated the thermodynamical from dynamical changes. We also show how that a significant increase in subtropical anticyclonic activity over Iberia is responsible for: i) dynamical circulation changes; ii) a shortening of the wet season; iii) to less efficient precipitation regimes in the region. These results highlight the urge to adapt to a drying trend in Mediterranean-type climates, as a consequence of Global Warming.</p><p> </p><p>The financial support for this work was possible through the following FCT project: HOLMODRIVE - North Atlantic Atmospheric Patterns influence on Western Iberia Climate: From the Lateglacial to the Present [PTDC/CTA-GEO/29029/2017]</p>

scholarly journals Variability of seasonal and annual rainfall in the River Nile riparian countries and possible linkages to ocean–atmosphere interactions

2015 ◽  
Vol 47 (1) ◽  
pp. 171-184 ◽  
Author(s):  
Charles Onyutha
Keyword(s):  
Large Scale ◽  
Equatorial Region ◽  
Annual Rainfall ◽  
River Nile ◽  
Short Term ◽  
Ocean Atmosphere ◽  
Data Points ◽  
The Difference ◽  
Term Data

Variability analyses for the rainfall over the Nile Basin have been confined mostly to sub-basins and the annual mean of the hydroclimatic variable based on observed short-term data from a few meteorological stations. In this paper, long-term country-wide rainfall over the period 1901–2011 was used to assess variability in the seasonal and annual rainfall volumes in all the River Nile countries in Africa. Temporal variability was determined through temporal aggregation of series rescaled nonparametrically in terms of the difference between the exceedance and non-exceedance counts of data points such that the long-term average (taken as the reference) was zero. The co-occurrence of the variability of rainfall with those of the large-scale ocean–atmosphere interactions was analyzed. Between 2000 and 2012, while the rainfall in the equatorial region was increasing, that for the countries in the northern part of the River Nile was below the reference. Generally, the variability in the rainfall of the countries in the equatorial (northern) part of the River Nile was found to be significantly linked to occurrences in the Indian and Atlantic (Pacific and Atlantic) Oceans. Significant linkages to Niño 4 regarding the variability of both the seasonal and annual rainfall of some countries were also evident.

scholarly journals Impact of climate change on freshwater ecosystems: a global-scale analysis of ecologically relevant river flow alterations

2010 ◽  
Vol 14 (5) ◽  
pp. 783-799 ◽  
Author(s):  
P. Döll ◽  
J. Zhang
Keyword(s):  
Climate Change ◽  
River Discharge ◽  
River Flow ◽  
Flow Regimes ◽  
Freshwater Ecosystems ◽  
Land Area ◽  
Impact Of Climate Change ◽  
Water Withdrawals ◽  
The Impact

Abstract. River flow regimes, including long-term average flows, seasonality, low flows, high flows and other types of flow variability, play an important role for freshwater ecosystems. Thus, climate change affects freshwater ecosystems not only by increased temperatures but also by altered river flow regimes. However, with one exception, transferable quantitative relations between flow alterations and ecological responses have not yet been derived. While discharge decreases are generally considered to be detrimental for ecosystems, the effect of future discharge increases is unclear. As a first step towards a global-scale analysis of climate change impacts on freshwater ecosystems, we quantified the impact of climate change on five ecologically relevant river flow indicators, using the global water model WaterGAP 2.1g to simulate monthly time series of river discharge with a spatial resolution of 0.5 degrees. Four climate change scenarios based on two global climate models and two greenhouse gas emissions scenarios were evaluated. We compared the impact of climate change by the 2050s to the impact of water withdrawals and dams on natural flow regimes that had occurred by 2002. Climate change was computed to alter seasonal flow regimes significantly (i.e. by more than 10%) on 90% of the global land area (excluding Greenland and Antarctica), as compared to only one quarter of the land area that had suffered from significant seasonal flow regime alterations due to dams and water withdrawals. Due to climate change, the timing of the maximum mean monthly river discharge will be shifted by at least one month on one third on the global land area, more often towards earlier months (mainly due to earlier snowmelt). Dams and withdrawals had caused comparable shifts on less than 5% of the land area only. Long-term average annual river discharge is predicted to significantly increase on one half of the land area, and to significantly decrease on one quarter. Dams and withdrawals had led to significant decreases on one sixth of the land area, and nowhere to increases. Thus, by the 2050s, climate change may have impacted ecologically relevant river flow characteristics more strongly than dams and water withdrawals have up to now. The only exception refers to the decrease of the statistical low flow Q90, with significant decreases both by past water withdrawals and future climate change on one quarter of the land area. However, dam impacts are likely underestimated by our study. Considering long-term average river discharge, only a few regions, including Spain, Italy, Iraq, Southern India, Western China, the Australian Murray Darling Basin and the High Plains Aquifer in the USA, all of them with extensive irrigation, are expected to be less affected by climate change than by past anthropogenic flow alterations. In some of these regions, climate change will exacerbate the discharge reductions, while in others climate change provides opportunities for reducing past reductions. Emissions scenario B2 leads to only slightly reduced alterations of river flow regimes as compared to scenario A2 even though emissions are much smaller. The differences in alterations resulting from the two applied climate models are larger than those resulting from the two emissions scenarios. Based on general knowledge about ecosystem responses to flow alterations and data related to flow alterations by dams and water withdrawals, we expect that the computed climate change induced river flow alterations will impact freshwater ecosystems more strongly than past anthropogenic alterations.

scholarly journals EVALUATION OF POSSIBLE CHANGES IN THE RIVER LINE OF THE OKA BASIN FOR THE COMING PERIOD OF THE FIRST HALF OF THE XXI CENTURY

2020 ◽  
Vol 1 (5) ◽  
pp. 71-75
Author(s):  
G. Kh. Ismaiylov ◽  
◽  
N.V. Muraschenkova ◽  
Keyword(s):  
River Basin ◽  
21St Century ◽  
River Runoff ◽  
River Flow ◽  
Climatic Conditions ◽  
Global Changes ◽  
The Future ◽  
Seasonal Runoff ◽  
The City

A retrospective analysis and assessment of long-term changes in the annual and seasonal runoff of the Oka River basin over a long 131-year observation period (1881 / 1882–2011/2012) was performed. The changes in the annual distribution of the Oka river runoff over the seasons of the year (spring flood, summer-autumn and winter low water) from its annual value for the selected time periods (before and after 1976/1977) are considered. It has been noted that over the past decades, river runoff has been formed in new climatic conditions associated with global changes and, as a result, regional climate. The assessment of possible changes in the annual and seasonal runoff of the Oka River basin (to the final alignment – the city of Kaluga, with a basin area of 54,900 km2 ) in the first half of the 21st century is carried out. In assessing changes in the river flow of the Oka basin for the future period, the method of trends (trends) is used, based on the identification of cycles in fluctuations in hydrological characteristics and unidirectional trends (trends) inherent in individual phases (ups and downs) of these cycles, as well as to the establishment of functional (correlation) relationships between environmental factors (climatic, anthropogenic) and the nature of the response (river flow). In this case, the trend model serves as an alternative to the homogeneity hypothesis of long-term fluctuations in river flow. The change in the future values of the river flow of the Oka basin was estimated using averaged data of 30-year periods of time characterized by relative stationarity of climatic and hydrological conditions. The dynamics of the average 30-year values of the annual runoff in the upper reaches of the Oka River (the closure target is the city of Kaluga for the period 1881/1882–2011/2012) is considered. Possible forecasted mean annual values of the annual flow of the Oka River for the first half of the 21st century are obtained

scholarly journals Long term prediction of flood occurrence

2016 ◽  
Vol 373 ◽  
pp. 189-192 ◽  
Author(s):  
Cristina Aguilar ◽  
Alberto Montanari ◽  
María José Polo
Keyword(s):  
Flow Regime ◽  
River Flow ◽  
Research Question ◽  
Flood Frequency ◽  
High Flow ◽  
Low Flow ◽  
Physical Explanation ◽  
Po River ◽  
Flood Season

Abstract. How long a river remembers its past is still an open question. Perturbations occurring in large catchments may impact the flow regime for several weeks and months, therefore providing a physical explanation for the occasional tendency of floods to occur in clusters. The research question explored in this paper may be stated as follows: can higher than usual river discharges in the low flow season be associated to a higher probability of floods in the subsequent high flow season? The physical explanation for such association may be related to the presence of higher soil moisture storage at the beginning of the high flow season, which may induce lower infiltration rates and therefore higher river runoff. Another possible explanation is persistence of climate, due to presence of long-term properties in atmospheric circulation. We focus on the Po River at Pontelagoscuro, whose catchment area amounts to 71 000 km2. We look at the stochastic connection between average river flows in the pre-flood season and the peak flows in the flood season by using a bivariate probability distribution. We found that the shape of the flood frequency distribution is significantly impacted by the river flow regime in the low flow season. The proposed technique, which can be classified as a data assimilation approach, may allow one to reduce the uncertainty associated to the estimation of the flood probability.

scholarly journals Restoration ecologists might not get what they want: Global change shifts trade-offs among ecosystem functions

2020 ◽  
Author(s):  
Sebastian Fiedler ◽  
José A.F. Monteiro ◽  
Kristin B. Hulvey ◽  
Rachel J. Standish ◽  
Michael P. Perring ◽  
...  
Keyword(s):  
Climate Change ◽  
Plant Species ◽  
Plant Diversity ◽  
Large Scale ◽  
Plant Traits ◽  
Climatic Conditions ◽  
Ecosystem Functions ◽  
List Type ◽  
Trade Offs

ABSTRACTEcological restoration increasingly aims at improving ecosystem multifunctionality and making landscapes resilient to future threats, especially in biodiversity hotspots such as Mediterranean-type ecosystems. Successful realisation of such a strategy requires a fundamental mechanistic understanding of the link between ecosystem plant composition, plant traits and related ecosystem functions and services, as well as how climate change affects these relationships. An integrated approach of empirical research and simulation modelling with focus on plant traits can allow this understanding.Based on empirical data from a large-scale restoration project in a Mediterranean-type climate in Western Australia, we developed and validated the spatially explicit simulation model ModEST, which calculates coupled dynamics of nutrients, water and individual plants characterised by traits. We then simulated all possible combinations of eight plant species with different levels of diversity to assess the role of plant diversity and traits on multifunctionality, the provision of six ecosystem functions (covering three ecosystem services), as well as trade-offs and synergies among the functions under current and future climatic conditions.Our results show that multifunctionality cannot fully be achieved because of trade-offs among functions that are attributable to sets of traits that affect functions differently. Our measure of multifunctionality was increased by higher levels of planted species richness under current, but not future climatic conditions. In contrast, single functions were differently impacted by increased plant diversity. In addition, we found that trade-offs and synergies among functions shifted with climate change.Synthesis and application. Our results imply that restoration ecologists will face a clear challenge to achieve their targets with respect to multifunctionality not only under current conditions, but also in the long-term. However, once ModEST is parameterized and validated for a specific restoration site, managers can assess which target goals can be achieved given the set of available plant species and site-specific conditions. It can also highlight which species combinations can best achieve long-term improved multifunctionality due to their trait diversity.

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.

scholarly journals Many-year Fluctuations of River Runoff in South-taiga Subzone of the Western Siberia

2013 ◽  
pp. 34-45
Author(s):  
Keyword(s):  
Western Siberia ◽  
River Flow ◽  
Atmospheric Precipitation ◽  
Southern Taiga ◽  
Low Flow ◽  
Groundwater Levels ◽  
Level Regime ◽  
Southern Taiga Subzone ◽  
Bog Water

A detailed analysis of river flow long-term changes in the Southern taiga subzone of Western Siberia has been carried out with the Chaya River basin as an example. Causal statistical analysis of changes in groundwater levels, bog water level, air temperature and atmospheric precipitation has been performed. The conducted studies revealed a statistically significant trend in the increase of surface runoff in the winter low flow of the Chaya River and its large tributaries (the Iksa and the Parbig), as well as the underground runoff component for virtually the entire year. An ambiguous regularity has been observed in the change of the level regime of rivers. The main reason for the observed changes in the water regime of the said territory is the redistribution of atmospheric moisture and shifting of the boundaries of hydrological seasons.

scholarly journals FACTORS INFLUENCING ESTUARY SEDIMENT DISTRIBUTION

1976 ◽  
Vol 1 (15) ◽  
pp. 120 ◽  
Author(s):  
Mary P. Kendrick ◽  
B.V. Derbyshire
Keyword(s):  
River Flow ◽  
Saline Water ◽  
Climatic Conditions ◽  
Seasonal Fluctuations ◽  
Short Term ◽  
Sediment Distribution ◽  
Sea Levels ◽  
Subsequent Period ◽  
Estuary Sediment

Many factors combine to determine the way in which sediments are distributed throughout an estuary. Most fundamental are those which produce the natural rhythm of diurnal (or semi-diurnal), bi-monthly and seasonal fluctuations due to predictable variations in tide and weather. This group includes tidal discharge, fresh river flow and the resultant distribution of saline water. When considered together with such factors as the availability and properties of sediments within and beyond the landward and seaward limits of an estuary, they determine how the available material shall be eroded, transported and deposited during the course of the natural cycle. Superimposed on these regular fluctuations are the effects of other factors which may or may not be predictable, are not necessarily regular in occurrence and may be either natural or man-made. These include secular trends, such as long-term adjustments in land/sea levels or climatic conditions, which have a small but continuing effect on some of the factors in the first group. They also include sudden, short-term events like earthquakes or hurricanes which impose a shock to the system that may involve the movement of large quantities of material during the subsequent period of readjustment.

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