WP3 Variations in the terrestrial component of water cycle

1. 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

2. Trophic state of lakes Physical state of lakes

3. 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)

4. 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.

5. 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.

6. 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 • data collection (meteorological, hydrological, lake level, temperature etc. (6 month); • model calibration (24 months); • long term scenarios on hydrological and hydrodynamics lake evolution (9 months). • TS2 • lake water temperature scenarios will be used to infer on the effects on lake biology (production/respiration rate).

7. Catchment Lake Area 4,99 km² Area 94.8 km² Volume 69.2106 m³ Maximum altitude 1453 m Avarege altitude 259 m a.s.l Average altitude 638 m Maximum depth 24 m Average depth 14 m Theoretical water renewal time 0.8 year Lake Pusiano Lake Pusiano is eutrophic

8. Lake Pusiano Climatological variables Hydrology Rivers water quality Lake level Thermal profile • Chemistry: • Nutrients; • Main ions. • Biology: • Phytoplankton; • Zooplankton. GIS Land use Anthropization Geology etc. Daily inflow Hydrodynamic: DYRESM Ecological: CAEDYM SWAT QUAL 2E Nutrient loads Catchment Lake

9. Catchment Lake Area 145 km² Area 4508 km² Volume 22.5 km³ Maximum altitude 4050 m Avarege altitude 198 m a.s.l Maximum depth 425 m Average depth 155 m Theoretical water renewal time 4.4 year Lake Como Como Pusiano Lake Como is mesotrophic

10. Lake Como Climatological variables Hydrology Rivers water quality LDS Network Water level • Chemistry: • Nutrients; • Main ions. • Biology: • Phytoplankton; GIS Annual/monthly inflow Land use Anthropization Geology etc. Hydrodynamic: DYRESM Ecological: CAEDYM Nutrient loads Catchment Lake

11. LDS2 425 m LDS3 LDS1 LDS Network on Lake Como

12. SWR Momentum LWR LWR Outflow Inflow Epi Meta Hypo The hydrodynamic model DYRESM (DYnamic Reservoir Simulation Model) • Input file: • configuration, • meteorological forcing, • lake morphometry, • Inflows, • outflow, • initial profile, • hydrodynamic parameters.

13. The ecological model CAEDYM (Computational Aquatic Ecosystem DYnamics Model) Solar radiation Gas exchange (e.g. O2, CO2, NOx) Outflow Inflow Up take Sedimentation Resuspension (e.g. POP, PON) Dissolved flux (e.g. PO4, NH4)

14. Gen-Mar 2007 Gen-Mar 2005 Lake Como

15. Different interannual response of lake water surface temperature Jan-Mar 2005-2006-2007 Lake Como

16. Effectsof 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.

17. 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)