scholarly journals Longer Growing Seasons Cause Hydrological Regime Shifts in Central European Forests

Forests ◽  
2021 ◽  
Vol 12 (12) ◽  
pp. 1656
Author(s):  
Petr Kupec ◽  
Jan Deutscher ◽  
Martyn Futter
Keyword(s):  
Regime Shift ◽  
Hydrological Regime ◽  
Annual Runoff ◽  
Order Effects ◽  
Runoff Generation ◽  
Central European ◽  
European Forests ◽  
Water Limitation ◽  
Growing Seasons

In this study, we present evidence for a hydrological regime shift in upland central European forests. Using a combination of long-term data, detailed field measurements and modelling, we show that there is a prolonged and persistent decline in annual runoff: precipitation ratios that is most likely linked to longer growing seasons. We performed a long term (1950–2018) water balance simulation for a Czech upland forest headwater catchment calibrated against measured streamflow and transpiration from deciduous and coniferous stands. Simulations were corroborated by long-term (1965–2018) borehole measurements and historical drought reports. A regime shift from positive to negative catchment water balances likely occurred in the early part of this century. Since 2007, annual runoff: precipitation ratios have been below the long-term average. Annual average temperatures have increased, but there have been no notable long term trends in precipitation. Since 1980, there has been a pronounced April warming, likely leading to earlier leaf out and higher annual transpiration, making water unavailable for runoff generation and/or soil moisture recharge. Our results suggest a regime shift due to second order effects of climate change where increased transpiration associated with a longer growing season leads to a shift from light to water limitation in central European forests. This will require new approaches to managing forests where water limitation has previously not been a problem.

Long-term effects of liming on the species composition of the herb layer in temperate Central-European forests

2019 ◽  
Vol 437 ◽  
pp. 49-58 ◽  
Author(s):  
Frank M. Thomas ◽  
Katharina Krug ◽  
Jörg Zoldan ◽  
Hans-Werner Schröck
Keyword(s):  
Species Composition ◽  
Herb Layer ◽  
Long Term Effects ◽  
Central European ◽  
European Forests

scholarly journals Estimation of annual runoff by exploiting long-term spatial patterns and short records within a geostatistical framework

2020 ◽  
Vol 24 (8) ◽  
pp. 4109-4133
Author(s):  
Thea Roksvåg ◽  
Ingelin Steinsland ◽  
Kolbjørn Engeland
Keyword(s):  
Missing Values ◽  
Mean Squared Error ◽  
Interpolation Method ◽  
Predictive Performance ◽  
Annual Runoff ◽  
Climatic Conditions ◽  
Kriging Interpolation ◽  
Runoff Generation ◽  
Kriging Interpolation Method

Abstract. In this article, we present a Bayesian geostatistical framework that is particularly suitable for interpolation of hydrological data when the available dataset is sparse and includes both long and short records of runoff. A key feature of the proposed framework is that several years of runoff are modelled simultaneously with two spatial fields: one that is common for all years under study that represents the runoff generation due to long-term (climatic) conditions and one that is year-specific. The climatic spatial field captures how short records of runoff from partially gauged catchments vary relative to longer time series from other catchments, and transfers this information across years. To make the Bayesian model computationally feasible and fast, we use integrated nested Laplace approximations (INLAs) and the stochastic partial differential equation (SPDE) approach to spatial modelling. The geostatistical framework is demonstrated by filling in missing values of annual runoff and by predicting mean annual runoff for around 200 catchments in Norway. The predictive performance is compared to top-kriging (interpolation method) and simple linear regression (record augmentation method). The results show that if the runoff is driven by processes that are repeated over time (e.g. orographic precipitation patterns), the value of including short records in the suggested model is large. For partially gauged catchments the suggested framework performs better than comparable methods, and one annual observation from the target catchment can lead to a 50 % reduction in root mean squared error (RMSE) compared to when no observations are available from the target catchment. We also find that short records safely can be included in the framework regardless of the spatial characteristics of the underlying climate, and down to record lengths of 1 year.

scholarly journals Ecological Degradation of the Yangtze and Nile Delta-Estuaries in Response to Dam Construction with Special Reference to Monsoonal and Arid Climate Settings

Water ◽  
2021 ◽  
Vol 13 (9) ◽  
pp. 1145
Author(s):  
Zhongyuan Chen ◽  
Hao Xu ◽  
Yanna Wang
Keyword(s):  
Regime Shift ◽  
Yangtze Estuary ◽  
Anthropogenic Sources ◽  
Arid Climate ◽  
Dam Construction ◽  
Nutrient Inputs ◽  
The Yangtze Estuary ◽  
Ecological Degradation ◽  
Phytoplankton Communities

This study reviews the monsoonal Yangtze and the arid Nile deltas with the objective of understanding how the process–response between river-basin modifications and delta-estuary ecological degradation are interrelated under contrasting hydroclimate dynamics. Our analysis shows that the Yangtze River had a long-term stepwise reduction in sediment and silicate fluxes to estuary due to dam construction since the 1960s, especially after the Three Gorges Dam (TGD) closed in 2003. By contrast, the Nile had a drastic reduction of sediment, freshwater, and silicate fluxes immediately after the construction of the Aswan High Dam (AHD) in 1964. Seasonal rainfall in the mid-lower Yangtze basin (below TGD) complemented riverine materials to its estuary, but little was available to the Nile coast below the AHD in the hyper-arid climate setting. Nitrogen (N) and phosphate (P) fluxes in both river basins have increased because of the overuse of N- and P-fertilizer, land-use changes, urbanization, and industrialization. Nutrient ratios (N:P:Si) in both delta-estuaries was greatly altered, i.e., Yangtze case: 75:1:946 (1960s–1970s), 86:1:272 (1980s–1990s) and 102:1:75 (2000s–2010s); and Nile case: 6:1:32 (1960s–1970s), 8:1:9 (1980s–1990s), and 45:1:22 (2013), in the context of the optimum of Redfield ratio (N:P:Si = 16:1:16). This led to an ecological regime shift evidenced by a long-term change in phytoplankton communities in the Yangtze estuary, where silicious algae tended to lose dominance since the end of the 1990s, when more toxic dinoflagellates began to emerge. In the Nile estuary, such a regime shift was indicated by the post-dam dramatic reduction in zooplankton standing crop and fish landings until the early 2000s when biological recovery occurred due to nutrient inputs from anthropogenic sources. Although the Yangtze had higher human impacts than the Nile in terms of population, industrialization, and fertilizer application, N concentrations in the Nile estuarine waters surpassed the Yangtze in recent decades. However, eutrophication in the Yangtze estuary is much more intensive than in the Nile, leading to the likelihood of its estuarine water becoming more acidic than ever before. Therefore, ecological degradation in both delta-estuaries does not follow a linear trajectory, due not only to different climate dynamics but also to human forcings. The comparative insights of this study should be incorporated into future integrated coastal management of these two important systems.

scholarly journals Long-term changes of river discharge regime in Latvia

2008 ◽  
Vol 39 (2) ◽  
pp. 133-141 ◽  
Author(s):  
Maris Klavins ◽  
Valery Rodinov
Keyword(s):  
Climate Variability ◽  
River Discharge ◽  
Water Resource Management ◽  
Regional Climate ◽  
Hydrological Regime ◽  
High Water ◽  
Regime Changes ◽  
Long Term Changes ◽  
Discharge Regime

The study of changes in river discharge is important for regional climate variability characterization and for development of an efficient water resource management system. The hydrological regime of rivers and their long-term changes in Latvia were investigated. Four major types of river hydrological regimes, which depend on climatic and physicogeographic factors, were characterized. These factors are linked to the changes observed in river discharge. Periodic oscillations of discharge, and low- and high-water flow years are common for the major rivers in Latvia. A main frequency of river discharge regime changes of about 20 and 13 years was estimated for the studied rivers. A significant impact of climate variability on the river discharge regime has been found.

Runoff generation processes in permafrost-influenced area of the Heihe River Headwater

2021 ◽  
Author(s):  
Fan Zhang ◽  
Xiong Xiao ◽  
Guanxing Wang
Keyword(s):  
Soil Water ◽  
Stream Water ◽  
Hydrological Regime ◽  
Summer Rainfall ◽  
Frozen Soil ◽  
Heihe River ◽  
The Tibetan Plateau ◽  
Permafrost Degradation ◽  
Runoff Generation ◽  
Spring Snowmelt

<p>Permafrost degradation under global warming may change the hydrological regime of the headwater catchments in alpine area such as the Tibetan Plateau (TP). In this study, he runoff generation processes in permafrost-influenced area of the Heihe River Headwater were investigated with the following results: 1) The observed stable isotope values of various water types on average was roughly in the order of snowfall and snowmelt < bulk soil water (BSW) < rainfall , stream water, mobile soil water (MSW) , and lateral subsurface flow. The depleted spring snowmelt and enriched summer rainfall formed tightly bound soil water and MSW, respectively. The dynamic mixing between tightly bound soil water and MSW resuted in BSW with more depleted and variable stable isotopic feature than MSW. 2) Along with the thawing of the frozen soil, surface runoff and shallowsubsurface flow (SSF) at 30−60 cm was the major flow pathway in the permafrost influenced alpine meadow hillslope during spring snowmelt and summer rainfall period, reapectively, with the frozen soil maintaining supra-permafrost water level. 3) Comparison between two neighouring catchments under similar precipitation conditions indicated that streamflow of the lower catchment with less permafrost proportion and earlier thawing time has larger SSF and higher based flow component, indicating the potential changes of hydrological regims subject to future warming.</p>

scholarly journals A long-term multi-proxy record of varved sediments highlights climate-induced mixing-regime shift in a large hard-water lake ~5000 years ago

2014 ◽  
Vol 73 (2) ◽  
Author(s):  
Walter Finsinger ◽  
Thierry Fonville ◽  
Emiliya Kirilova ◽  
Andrea Lami ◽  
Piero Guilizzoni ◽  
...  
Keyword(s):  
Regime Shift ◽  
Hard Water ◽  
Proxy Record ◽  
Varved Sediments ◽  
Water Lake ◽  
Mixing Regime

scholarly journals Exploring and Quantifying River Thermal Response to Heatwaves

Water ◽  
2018 ◽  
Vol 10 (8) ◽  
pp. 1098 ◽  
Author(s):  
Sebastiano Piccolroaz ◽  
Marco Toffolon ◽  
Christopher Robinson ◽  
Annunziato Siviglia
Keyword(s):  
Water Temperature ◽  
River Water ◽  
Thermal Response ◽  
Hydrological Regime ◽  
Management Policy ◽  
Extreme Weather Events ◽  
Thermal Dynamics ◽  
Depth Analysis ◽  
River Water Temperature

Most of the existing literature on river water temperature focuseds on river thermal sensitivity to long-term trends of climate variables, whereas how river water temperature responds to extreme weather events, such as heatwaves, still requires in-depth analysis. Research in this direction is particularly relevant in that heatwaves are expected to increase in intensity, frequency, and duration in the coming decades, with likely consequences on river thermal regimes and ecology. In this study we analyzed the long-term temperature and streamflow series of 19 Swiss rivers with different hydrological regime (regulated, low-land, and snow-fed), and characterized how concurrent changes in air temperature and streamflow concurred to affect their thermal dynamics. We focused on quantifying the thermal response to the three most significant heatwave events that occurred in Central Europe since 1950 (July–August 2003, July 2006, and July 2015). We found that the thermal response of the analyzed rivers contrasted strongly depending on the river hydrological regime, confirming the behavior observed under typical weather conditions. Low-land rivers were extremely sensitive to heatwaves. In sharp contrast, high-altitude snow-fed rivers and regulated rivers receiving cold water from higher altitude hydropower reservoirs or diversions showed a damped thermal response. The results presented in this study suggest that water resource managers should be aware of the multiple consequences of heatwave events on river water temperature and incorporate expected thermal responses in adaptive management policy. In this respect, additional efforts and dedicated studies are required to deepen our knowledge on how extreme heatwave events can affect river ecosystems.

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