Global Change Abstracts The Swiss Contribution - SCNAT

132 Global Change Abstracts – The Swiss Contribution | Oceans and Fresh Water Systems
08.1-248
The GLOWA Jordan river project: Integrated
research for sustainable water management
Drexler C, Tielbörger K
Switzerland, Germany
Water Resources , Hydrology
Mountain Research and Development, 2007, V27,
N3, AUG, pp 274-275.
08.1-249
Hydropower production and river rehabilitation:
A case study on an alpine river
Fette M, Weber C, Peter A, Wehrli B
Switzerland
Hydrology , Marine & Freshwater Biology , Ecology
Despite the numerous benefits of hydropower production,
this renewable energy source can have serious
negative consequences on the environment.
For example, dams act as barriers for the longitudinal
migration of organisms and transport of
particulate matter. Accelerated siltation processes
in the receiving river reduce the vertical connectivity
between river and groundwater. Hydropeaks,
caused by short-term changes in hydropower
operation, result in a negative impact on both
habitat and organisms, especially during winter
months when natural discharge is low and almost
constant. In this study, we report the current deficits
present in the River Rhone from two different
scientific perspectives - fish ecology and hydrology.
Potential rehabilitation solutions in synergy
with flood protection measures are discussed. We
focus on the effects of hydropeaking in relation to
longitudinal and vertical dimensions and discuss
local river widening as a potential rehabilitation
tool. The fish fauna in the Rhone is characterized
by a highly unnatural structure (low diversity,
impaired age distribution). A high correlation between
fish biomass and monotonous morphology
(poor cover availability) was established. Tracer
hydrology provided further details about the reduced
permeability of the riverbank, revealing a
high degree of siltation with K values of about 4.7
x 10 (-6) m s(-1). Improving the hydrologic situation
is therefore essential for the successful rehabilitation
of the Rhone River. To this end, hydropeaks
in the river reaches must be attenuated. This
can be realized by a combination of different hard
technical and soft operational measures such as
retention reservoirs or slower up and down ramping
of turbines.
Environmental Modeling Assessment, 2007, V12,
N4, NOV, pp 257-267.
08.1-250
Effects of alpine hydropower operations on
primary production in a downstream lake
Finger D, Bossard P, Schmid M, Jaun L, Müller B,
Steiner D, Schäffer E, Zeh M, Wüest A
Switzerland
Limnology , Hydrology , Marine & Freshwater Biology
, Ecology , Water Resources
During the past century, the construction of hydropower
dams in the watershed of Lake Brienz
has significantly altered the dynamics of turbidity,
which has important implications for lake
productivity. To assess these effects, we measured
in situ carbon assimilation rates and ambient
light intensities over 18 months. Based on experimental
data, a numerical model was developed
to assess gross primary production under present
light conditions and those under a hypothetical
case without upstream dams. Light conditions
for the hypothetical ‘no-dam’ situation were estimated
from pre-dam Secchi depths and simulated
‘no-dam’ particle concentrations. Current gross
primary production is low (similar to 66 gC m(-2)
yr(-1)), and could increase similar to 44% if the lake
was less turbid. Disregarding nutrient retention
in reservoirs, we estimate gross primary production
would be similar to 35% lower in summer and
similar to 23% higher in winter in the absence of
reservoirs. The annual primary production (similar
to 58 gC m(-2)yr(-1)) would decrease similar to
12% compared to the current primary production
with dams. According to model calculations, hydropower
operations have significantly altered
the seasonal dynamics, but have little effect on
annual primary production in Lake Brienz.
Aquatic Sciences, 2007, V69, N2, JUN, pp 240-256.
08.1-251
Comparing effects of oligotrophication and
upstream hydropower dams on plankton and
productivity in perialpine lakes
Finger D, Schmid M, Wüest A
Switzerland
Modelling , Hydrology , Water Resources , Marine
& Freshwater Biology
In recent decades, many perialpine lakes have
been affected by oligotrophication due to efficient
sewage treatment and by altered water turbidity
due to upstream hydropower operations. Such
simultaneous environmental changes often lead
to public debate on the actual causes of observed
productivity reductions. We evaluate the effects
of those two changes by a combined approach
of modeling and data interpretation for a case
study on Lake Brienz (Switzerland), a typical oligotrophic
perialpine lake, located downstream