Effects of hydropeaking waves offsets on growth performances of juvenile Salix species

Alexandre Buttler, Lorenzo Gorla, Paolo Perona, Constant Signarbieux, Pascal Turberg
Elsevier, 2015
Article

Résumé

Hydropower production and other human activities change the natural flow regime of rivers (e.g., hydropeaking effects), in turn, impacting the riparian environment. Here we present an experiment conceived to investigate the response of forced offsets in water table dynamics on the temperate flood-plain riparian vegetation species of Salix viminalis. Three specific water level regimes, simulating daily hydropeaking effects in terms of daily water table variations and offsets, were applied to three batteries of Salix cuttings growing outdoors in plastic pots. All pots initially were provided the same unlimited water supply. Then the dynamics were changed to include 90-cm daily oscillations of water table. The transitory responses of the cuttings were quantified with measurements of continuous sap flow and water potential. We regularly monitored growth parameters, leaf water potential, and gas exchange measurements, and took pictures of each plant. At the end of the experiment, all cuttings were removed and the biomass, from both above and below ground, analyzed. The 3D root structure was investigated using high-resolution computed tomography. Our results showed a clear link between root distribution and water regime. The strong offset of water table dynamics was followed by root system adjustment and plant adaptation to the new conditions. Macroscopic effects in terms of growth parameters corresponded with water pressure and transpiration measurements, strengthening our interpretation of the results. Daily hydropeaking offset appeared to have only a minor impact on the development and photosynthesis of S. viminalis cuttings, and can probably be neglected in real cases of dam regulation. On the other hand, weekly periodicity (e.g., weekend periods of dryness) could have harsher impacts, and should be evaluated in future studies. (C) 2015 Elsevier B.V. All rights reserved.

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Alexandre Buttler, Lorenzo Gorla, Paolo Perona, Constant Signarbieux, Pascal Turberg
Elsevier, 2015
Article

Résumé

Official source

https://infoscience.epfl.ch/record/204671?ln=fr

À propos de ce résultat

Concepts associés (23)

Concepts associés

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Publications associées (11)

Publications associées

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Experimental response of Salix cuttings to different flow regimes due to human activities

Alexandre Buttler, Lorenzo Gorla, Paolo Perona, Constant Signarbieux, Pascal Turberg

Hydropower production and other human activities change the natural flow regime of rivers, in turn impacting the riparian environment. The main challenge in order to define eco-sustainable flows is to quantify the effects in terms of geomorphology and ecosystem adaptation. We present 2-years controlled experiments to investigate riparian vegetation (Salix Viminalis) response to forced water table changing dynamics, from one water regime to another, in a temperate region (Switzerland). Three synthetic flow regimes have been simulated and applied to three batteries of Salix cuttings growing outdoor within plastic pots, each about 1 meter tall. In 2012 one treatment simulated a minimal flow policy for small run-of-river hydropower plants, which drastically impacts the low and the medium-low components of the hydrograph, but not the extremes. In 2013 we confirmed and completed some of 2012 results, by reproducing typical hydropeaking effects due to dam management and focusing on daily water table variations and offsets. For both the seasons, after an initial period where all pots undergone the same oscillations in order to uniform the plants initial conditions, the experiment started, and the water dynamic was changed. Cuttings transitory response dynamics has been quantified by continuous sap flow and water potential measurements, and by regularly collecting growth parameters, as well as leaves photosynthesis, fluorescence, and pictures of each plant. At the end of the experiment, all cuttings were carefully removed and the both above and below ground biomass analyzed in detail. Particularly, the 3D root structure was obtained by High Resolution Computer Tomography. Our analyses revealed a clear dependence between roots distribution and water regime reflecting the need for adaptation, in agreement with field observations of Pasquale et al. (2012). In particular, an initial strong difference in terms of stress and growth performances was then followed by a later adjustment in the roots system, notably detected from tomographic images. Macroscopic effects in terms of growth parameters at weekly time step have found correspondence at higher time resolution in terms of sap flow and stem pressure, strengthening our results interpretation. REFERENCES - Pasquale et al. "Effects of streamflow variability on the vertical root density distribution of willow cutting experiments." Ecological Engineering 40 (2012): 167-172. - Gorla et al., "Transient response of Salix cuttings to changing water level regimes", WRR, accepted.

2014

Chargement

Experimental response of Salix cuttings to sudden water table changing dynamics

Alexandre Buttler, Lorenzo Gorla, Paolo Perona, Constant Signarbieux, Pascal Turberg

Hydropower production, agriculture and other human activities change the natural flow regime of rivers, in turn impacting the riparian environment. Inadequate flow rules (e.g., minimal or residual flows) reflecting our limited understanding of eco-hydrological processes have thus been applied since decades. The main challenge for an eco-sustainable water management is to quantify the effects of flow regulation on channel morphodynamics and biological processes. We present a controlled laboratory experiment to investigate riparian vegetation (Salix Viminalis) response to forced water table changing dynamics, from one water regime to another, in a temperate region (Switzerland). Three synthetic flow regimes have been simulated and applied to three batteries of Salix cuttings (60 in total) growing outdoor within plastic pots, each about 1 meter tall. After an initial period where all pots undergone the same oscillations in order to uniform the plants initial conditions, the experiment started, and the water dynamic was changed for two out of three batteries. In particular, one treatment simulated a minimal flow policy, which drastically impacts the low and the medium-low components of the hydrograph, but not the extremes. The other treatment reproduced only the low frequencies corresponding to the seasonal trend of the natural flow regime, still applied on the third battery. Cuttings transitory response dynamics has been quantified by continuous sap flow and water potential measurements, and by regularly collecting growth parameters, as well as leaves photosynthesis, fluorescence, and pictures of each plant. At the end of the experiment, all cuttings were carefully removed and the both above and below ground biomass analyzed in detail. Particularly, the 3D root structure was obtained by High Resolution Computer Tomography. Our analyses reveal a clear dependence between roots distribution and water regime reflecting the need for adaptation, which are also in agreement with field observations of Pasquale et al. (2012, in press). In particular, an initial strong difference in terms of stress and growth performances was then followed by a later adjustment in the roots system, notably detected from tomographic images. Roots tropic response resulted in spatial reallocation, which likely allowed survivors to adapt to new conditions. Macroscopic effects in terms of growth parameters at weekly time step have found correspondence at higher time resolution in terms of sap flow and stem pressure, strengthening our results interpretation. Other interesting effects detected by sap flow meters and psychrometers in the transition time, even if coherent to water regimes, have not led to macroscopic effects. A discussion with data from a parallel field installation along the Thur River (Switzerland) is also made.

2013

Chargement

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Dams and water management for hydropower production, agriculture and other human activities alter the natural flow regime of rivers. The new river hydrograph components depend on the type of impoundment and the policy of regulation but such a different flow regime will likely affect the riparian environment. The main challenge in order to define sustainable flow releases is to quantify hydrological effects in terms of geomorphology and ecosystem response. A considerable lack of knowledge still affects the link hydrology-ecology and inadequate flow rules (e.g., minimal or residual flows) are consequently still widespread: further research in this direction is urgently required. We present an experiment, which aims to investigate the effects of different water stage regimes on riparian vegetation (salix Viminalis cuttings) development in a temperate region (Switzerland). This work describes the installation setup, together with the first results concerning the first of the two scheduled seasons of campaign. Sixty Salix cuttings were planted in non-cohesive sandy-gravel sediment within 1 meter tall plastic pots in- stalled outside in the EPFL campus. After grouping them in three batteries, the water level within them has been varying following three river regimes simulated by adjusting the water level within the pots by means of an automatic hydraulic system. The three water level regimes reproduce a natural flow regime, a minimum residual flow policy, which only conserves peaks during flooding conditions, and an artificial regime conserving only low frequencies (e.g., seasonality) of the natural dynamic. The natural flow regime of the first battery has been applied for two months to the entire system; the three regimes above said started in June 2012. This triggered a plant response transitory regime, which we monitored by measuring plant growth, soil and atmospheric variables. Particularly, measures concern with branches development leaves photosynthesis and fluorescence, together with pictures of each plant. Sap flow was measured for thirty cuttings using a time resolution of thirty minutes, whereas psychrometers measuring the water potential were sampling data every fifteen minutes. Soil moisture and meteo data have also been collected as essential drivers of plant response: these data as well as sap flow measurements can be later compared to a similar field installation along Thur River (Switzerland). After the first season of measurement, in 2012, part of the cuttings have been carefully removed and further analyzed as far as the below ground biomass is concerned. Strong differences in terms of stress and growth performances were observed in correspondence of the transitional phase, following the alterations of the natural flow regime. A later adjustment in the roots distribution allowed survivors to re-sprout and to withstand new conditions

2013

Chargement

Experimental response of Salix cuttings to different flow regimes due to human activities

Alexandre Buttler, Lorenzo Gorla, Paolo Perona, Constant Signarbieux, Pascal Turberg

2014

Experimental response of Salix cuttings to sudden water table changing dynamics

Alexandre Buttler, Lorenzo Gorla, Paolo Perona, Constant Signarbieux, Pascal Turberg

2013

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2013