Download Task 5.3.5

RL5 Kick-Off Meeting
WP3 Variations in the terrestrial component of water cycle
Task 5.3.5
Effects of climate and hydrological changes on the thermal structure and water
storage in sub-alpine lakes and temperature related production/respiration
variations
Gianni Tartari & Diego Copetti
Bologna, 2007, May 2nd
Lake responses to climate change:
•
Modification thermal stratification (TEMPERATURE),
•
Lake hydrodynamics (RIVERS INFLOW, WIND) and large-scale
circulation (CURRENTS),
•
Chemical/trophic water quality (HYDROLOGY, POLLUTANT
TRANSPORT),
•
Ecological quality (BIOCENOSYS MODIFICATIONS)
Lake responses to climate change
Effects on shallow lakes
• higher temperatures give longer thermal stability with reduction of sediments
resuspension but, on the contrary, the increasing of oxygen depletion in the
hypolimnion will increments the phosphorous internal loads in eutrophic water
bodies;
• lower nutrient input and lower water levels may stimulate the growth of
submerged macrophytes with positive feedback effects on the ecological state
• warmer summers favouring zooplanktivores cyprinid fish at the expense of
piscivores fish;
• changes to smaller average size of fish may directly or indirectly (by affecting
grazers) favour phytoplankton growth and dominance of potential toxic
cyanobacteria;
• enhanced risk of fish kill due to cyanobacteria and anoxic conditions;
• higher salinity and droughts may be detrimental to the ecological status and
reduce biodiversity;
• increase in salinity will also exacerbate eutrophication because key-grazers of
phytoplankton are affected and because of increased top-down control in such
lakes.
Lake responses to climate change
Effects on deep lakes
• higher temperatures during spring and autumn will prolong the stratification
period;
• in nutrient-rich lakes, this may enhance the risk of oxygen depletion in the
bottom water (hypolimnion) and lead to higher phosphorous release from the
sediment, just as it may change the biomass, composition and distribution of
phytoplankton in time and space;
• a temperature increase will mediate a shift in fish composition and fish size,
resulting in enhanced predation on zooplankton and thus reduced grazing on
phytoplankton. Like in shallow lakes, improvements are expected in the
Mediterranean area due to the reduced loading, though this may be
counterbalanced by increased dominance of potential toxic cyanobacteria;
• the reducing hydraulic loading will icrease the retention and accumulation of
nutrients in southern lakes.
Task 5.3.5 Effects of climate and hydrological changes on the thermal
structure and water storage in sub-alpine lakes and temperature
related production/respiration variations
Modelling and experimental activities will be carried out in two sub-alpine lakes:
Lake Pusiano (mid shallow) and Lake Como (large deep).
Aim
To build up a model-based tool for predicting long-term scenarios of variations in
thermal structure and water storage in lakes and to infer about possible
temperature related changes in the lake production/respiration budget
Approach
To combine the results of hydrological and hydrodynamics models using
meteorological scenarios as result of other RLs/tasks of the project.
Sub-task
TS1
1. data collection (meteorological, hydrological, lake level, temperature etc. (6 month);
2. model calibration (24 months);
3. long term scenarios on hydrological and hydrodynamics lake evolution (9 months).
TS2
4. lake water temperature scenarios will be used to infer on the effects on lake biology
(production/respiration rate).
Lake Pusiano
Catchment
Area
94.8
km²
Maximum altitude
1453
m
Average altitude
638
m
Lake
Area
4,99
km²
Volume
69.2106
m³
Avarege altitude
259
m a.s.l
Maximum depth
24
m
Average depth
14
m
Theoretical water
renewal time
0.8
year
Lake Pusiano is
eutrophic
Lake Pusiano
Climatological variables
Hydrology
Rivers water quality
Lake level
Thermal profile
GIS
Chemistry:
 Nutrients;
 Main ions.
Land use
Anthropization
Geology etc.
Biology:
 Phytoplankton;
 Zooplankton.
SWAT
QUAL 2E
Catchment
Daily
inflow
Nutrient
loads
Hydrodynamic: DYRESM
Ecological: CAEDYM
Lake
Lake Como
Catchment
Area
4508
km²
Maximum altitude
4050
m
Como
Lake
Area
145
km²
Volume
22.5
km³
Avarege altitude
198
m a.s.l
Maximum depth
425
m
Average depth
155
m
Theoretical water
renewal time
4.4
year
Pusiano
Lake Como is
mesotrophic
Lake Como
LDS Network
Water level
Climatological variables
Hydrology
Rivers water quality
Chemistry:
 Nutrients;
 Main ions.
GIS
Biology:
 Phytoplankton;
Land use
Anthropization
Geology etc.
Annual/monthly inflow
Nutrient
loads
Catchment
Hydrodynamic: DYRESM
Ecological: CAEDYM
Lake
LDS Network on Lake Como
LDS2
425 m
LDS3
LDS1
The hydrodynamic model
DYRESM
(DYnamic Reservoir Simulation Model)







Input file:
configuration,
meteorological forcing,
lake morphometry,
Inflows,
outflow,
initial profile,
hydrodynamic parameters.
LWR
Inflow
SWR
Momentum
LWR
Outflow
Epi
Meta
Hypo
The ecological model
CAEDYM
(Computational Aquatic Ecosystem DYnamics Model)
Solar radiation
Gas exchange (e.g. O2, CO2, NOx)
Inflow
Up take
Sedimentation
Resuspension (e.g. POP, PON)
Dissolved flux (e.g. PO4, NH4)
Outflow
Gen-Mar
Gen-Mar 2005
2007
Lake Como
Different interannual response of lake water surface temperature
Jan-Mar 2005-2006-2007
Lake Como
Effects of the thermal stability on ecological state
Possible scenarios
• Oxygen depletion in the hypolimnion and consequent nutrient release at
the water-sediment interface;
• Sediments resuspension,
• Effects of nutrient load change on the lake production (chlorophyll a)
• Possible shift from green algae to cyanobacteria.
Links whit other CIRCE’s RLs&WPs
RL2 - The Mediterranean Region and the Global Climate System
Li Laurent (CNRS/IPSL), Silvio Gualdi (INGV)
WP2.4: Coordination on production of scenarios and distribution of datasets
Responsible: Li Laurent (CNRS/IPSL)
RL3 - Radiation, clouds, aerosols and climate change
Le Treut Herve (CNRS/LMD-IPSL), Lelieveld Jos (MPICH )
WP3.3: Impacts of future climate change on the surface radiation
Responsible: Lelieveld Jos (MPICH)
RL5 - Water Cycle
Alpert Pinhas (TAU), Vurro Michele (IRSA-CNR)
WP5.1: Analysis of changes in Atmospheric water budget
Responsible: Alpert Pinhas (TAU)
WP5.2: Variations in the precipitation component of the water cycle in the Mediterranean Region
Responsible: Trigo Ricardo (ICAT-UL)
RL7 - Impacts of Global Change on Ecosystems and the services they provide
Valentini Riccardo (UNITUSCIA), Holger Hoff (PIK)
WP7.5: Climate impacts on biogeochemical cycling
Responsible: Reichstein Markus (MPIBGC)