WP3 Variations in the terrestrial component of water cycle

Task 5.3.5Effects of climate and hydrological changes on the thermal structure and water

storage in sub-alpine lakes and temperature related production/respiration variations

Bologna, 2007, May 2nd

RL5 Kick-Off Meeting

Gianni Tartari & Diego Copetti

Physical state of la

kes

Trophic state of lakes

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)

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.

Lake responses to climate change

Sub-taskTS11. 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).TS24. lake water temperature scenarios will be used to infer on the effects on lake biology

(production/respiration rate).

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

ApproachTo combine the results of hydrological and hydrodynamics models using meteorological scenarios as result of other RLs/tasks of the project.

Lake Pusiano

Catchment

Area 94.8 km²

Maximum altitude 1453 m

Average altitude 638 m

Lake

Area 4,99 km²

Volume 69.2106 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

Catchment Lake

Climatological variables Hydrology Rivers water quality

SWATQUAL 2E

Dailyinflow

Chemistry: Nutrients; Main ions.

Biology: Phytoplankton; Zooplankton.

Hydrodynamic: DYRESMEcological: CAEDYM

Land useAnthropizationGeology etc.

GIS

Nutrientloads

Lake levelThermal profile

Lake Como

Catchment

Area 4508 km²

Maximum altitude 4050 m

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

Lake Como is mesotrophic

Como

Pusiano

Lake Como

Catchment Lake

Climatological variables Hydrology Rivers water quality

Annual/monthly inflow

Chemistry: Nutrients; Main ions.

Biology: Phytoplankton;

Hydrodynamic: DYRESMEcological: CAEDYM

Land useAnthropizationGeology etc.

GIS

Nutrientloads

LDS NetworkWater level

LDS Network on Lake Como

425 m

LDS1

LDS3

LDS2

DYRESM(DYnamic Reservoir Simulation Model)

SWR

LWR

Momentum

LWR

Epi

Hypo

Meta

Input file:configuration, meteorological forcing,lake morphometry, Inflows,outflow, initial profile, hydrodynamic parameters.

The hydrodynamic model

Inflow Outflow

CAEDYM(Computational Aquatic Ecosystem DYnamics Model)

Inflow OutflowGas exchange (e.g. O2, CO2, NOx)

Dissolved flux (e.g. PO4, NH4)

Resuspension (e.g. POP, PON)

Up take

Solar radiation

Sedimentation

The ecological model

Gen-Mar 2005Gen-Mar 2007

Lake Como

Different interannual response of lake water surface temperatureJan-Mar 2005-2006-2007

Lake Como

• 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.

Effects of the thermal stability on ecological state

Possible scenarios

RL2 - The Mediterranean Region and the Global Climate SystemLi Laurent (CNRS/IPSL), Silvio Gualdi (INGV)WP2.4: Coordination on production of scenarios and distribution of datasetsResponsible: Li Laurent (CNRS/IPSL)

RL3 - Radiation, clouds, aerosols and climate changeLe Treut Herve (CNRS/LMD-IPSL), Lelieveld Jos (MPICH )WP3.3: Impacts of future climate change on the surface radiationResponsible: Lelieveld Jos (MPICH)

RL5 - Water CycleAlpert Pinhas (TAU), Vurro Michele (IRSA-CNR)WP5.1: Analysis of changes in Atmospheric water budgetResponsible: Alpert Pinhas (TAU)WP5.2: Variations in the precipitation component of the water cycle in the Mediterranean RegionResponsible: Trigo Ricardo (ICAT-UL)

RL7 - Impacts of Global Change on Ecosystems and the services they provideValentini Riccardo (UNITUSCIA), Holger Hoff (PIK)WP7.5: Climate impacts on biogeochemical cyclingResponsible: Reichstein Markus (MPIBGC)

Links whit other CIRCE’s RLs&WPs