LAKE TRASIMENO BETWEEN PAST AND FUTURE. Alessandro Ludovisi.

Transcription

1 UNIVERSITA DEGLI STUDI DI PERUGIA DIPARTIMENTO DI CHIMICA, BIOLOGIA E BIOTECNOLOGIE LAKE TRASIMENO BETWEEN PAST AND FUTURE Alessandro Ludovisi alessandro.ludovisi@unipg.it

2 Lake Trasimeno

3 The past

4 Copper Age (5000 y b.c.) Bronze Age (3500 b.c.) Etruscan-Roman Period Century VII b.c V A.D. XI XII Century Present XIV Century XV - XIX Century Water levels of Lake Trasimeno from the Copper Age to present, based on archeological data (Gambini, 2002) and relation with climate Climate cold warm wet dry

5 1420 Emperor Claudius (41-54 d.c.) Hystorical water management in Lake Trasimeno Braccio Fortebraccio da Montone Burzigotti et al., modified

6 Consorzio Bonifica del Trasimeno Pope Sisto V Hystorical water management in Lake Trasimeno Burzigotti et al., modified

7 Altitude (m a.s.l.) Average lake depth (m) Hydrometric level and average depth of Lake Trasimeno during the last century Outlet restructuring Withdrawal licensing Outlet threshold

8 LAKE TRASIMENO 1958 La crisi del

9 THE ARTIFICIAL LOWERING OF LAKE WATERS IN THE FIRST HALF OF THE 20 th CENTURY CAUSED A PROGRESSIVE (AND IRREVERSIBLE ) SHIFT TOWARDS A CONDITION OF SHALLOW LAKE! affecting, in particular: Water column stratification and mixing, and thus: Water transparency and colour Amount of suspended solids in the water column Bottom oxygenation Nutrients cycling Trophic state Sedimentation rates Salt accumulation Macrophyte coverage..and thus, the whole lake biocoenosys!

10 TSS (mg l -1 ) a Average lake depth (m) SEDIMENT RESUSPENSION IN SHALLOW WATERS Shallow lakes 4 a=surface lake fraction subjected to resuspension (Carper & Bachman, 1984) a=f(d, W, A) D=average depth W=wind speed (10 Km h -1 ) A= winf fetch Gaino et al. (2012) Hydrobiologia Estimated historical trends of the theoretical fraction of the lake surface subject to resuspension and Total Suspended Solids (TSS ) in a central site exposed to a wind of 3 m s -1

11 Consorzio Bonifica del Trasimeno Ministero dei Lavori Pubblici Hystorical water management in Lake Trasimeno Burzigotti et al., modified

12 Altitude (m a.s.l.) Average lake depth (m) Hydrometric level and average depth of Lake Trasimeno during the last century Outlet restructuring Withdrawal licensing Restriction rules for withdrawals Catchment basin enlargment Outlet threshold maximum level minimum level

13 LAKE TRASIMENO 2003

14 HISTORICAL DATA SERIES Sampling site ARPA Umbria Water quality data collected monthly since 1990 Hydrobiological Station - Università di Perugia Daily meteorological data since 1955 Water quality data collected in several monthly sampling surveys since1958 S.I.G.L.A. meteorological stations managed by the Province of Perugia Half-hourly data collected since 1988

15 mm PRECIPITATION Annual value linear trend Critical precipitation (Dragoni, 1982) Hydrological crisis Ludovisi & Gaino (2010) Journal of Limnology

16 C AIR TEMPERATURE ΔT= +1.4 C ~ C/decade Ludovisi & Gaino (2010) Journal of Limnology

17 Water conductivity at 25 C (ms cm -1 ) WATER QUALITY CHANGES Total Dissolved Solids (kg 10 6 ) SALINITY Annual value Maximum Mean Minimum R 2 = 0.77 p< Periods with water levels under the outlet threshold YEAR Accumulation rate = tons year -1 Ludovisi & Gaino (2010) Journal of Limnology

18 Total Alkalinity ( mg L -1 CaCO 3 ) WATER QUALITY CHANGES ALKALINITY SO [ Polynomial Regression for Data1_Alcmin: Y = A + B1 * X 0.75 Cl Parameter Value Error A B R-Square(COD)SD N P < Annual value Maximum Average Minimum YEAR Ludovisi & Gaino (2010) Journal of Limnology Polynomial Regression for Data1_Alcmed: Y = A + B1 * X Parameter Value Error A B R-Square(COD)SD N P E-4 HCO CO 3 2- Polynomial Regression for Data1_Alcmax: Y = A + B1 * X Parameter Value Error The change in the ionic A B balance due to salt R-Square(COD)SD N P accumulation has caused an increase in alkalinity

19 ph WATER QUALITY CHANGES D.O. (mg l -1 ) ph Annual value Maximum Mean Minimum Polynomial Regression for Data1_pHmed: Y = A + B1 * X Weight given by Data1_pHerr error bars. Parameter Value Error A B R-Square(COD)SD N P Maximum 16 Polynomial Regression for Data1_pHmax: Mean Y = A + B1 * X Minimum Parameter Value Error A B R-Square(COD)SD N P Polynomial Regression for Data1_pHmin: Y = A + B1 * X Parameter Value Error A B R-Square(COD)SD N P DISSOLVED OXYGEN

20 SRP (mg L -1 ) Secchi depth (m) Total Phosporous (mg l -1 ) Chlorophyll a ( g l -1 ) WATER QUALITY CHANGES Annual value Maximum Mean Minimum Eutrophy Mesotrophy Annual value Maximum Average Minimum TROPHIC STATE AND TRANSPARENCY Annual Value Maximum Mean Minimum Eutrophy Mesotrophy Mesotrophy Eutrofphy Annual value Maximum Mean Minimum Ludovisi & Gaino (2010) Journal of Limnology

21 SEDIMENT RESUSPENSION AND WATER TRANSPARENCY Secchi depth (m) Average lake depth (m) TSS (mg l -1 ) a=surface lake fraction subjected to resuspension (Carper & Bachman, 1984) a=f(d, W, A) D=average depth W=wind speed (10 Km h -1 ) A= winf fetch Gaino et al. (2012) Hydrobiologia Annual value Maximum Mean Minimum

22 THE FUTURE SCENARIOS

23 IPCC Assessment Report 2007 (AR4) Average changes for temperature ( C) and precipitation (%) projections from a set of 21 global models for the A1B scenario. Predicted differences are for the period with respect to the averages

24 SOUTHERN EUROPE / MEDITERRANEAN IPCC Assessment Report 2007 (AR4) IPCC Report 2007: Regional averages of changes for temperature ( C) and precipitation (%) projections from a set of 21 global models for the A1B scenario. Predicted differences are for the period with respect to the averages The signal is assumed to increase linearly with time.

25 SOUTHERN EUROPE / MEDITERRANEAN IPCC Assessment Report 2013 (AR5) IPCC Assessment Report 2013 (AR5): Regional averages of changes for temperature ( C) and precipitation (%) projections from a set of 42 global models for the RCP4.5 scenario. Predicted differences are with respect to the averages

26 Temperature ( C) THE FUTURE SCENARIOS T_observed T_IPCC_50 T_IPCC_min T_IPCC_max TEMPERATURE Observed ( ) and simulated ( ) scenarios for air temperature at Lake Trasimeno The reference period ( ) (+ climate signal) is replicated several times in the future Ludovisi A., Gaino E., Bellezza M., Casadei S. (2013) Aquatic Ecosystem Health & Management

27 Precipitation (mm year -1 ) THE FUTURE SCENARIOS P_observed P_IPCC_50 P_IPCC_min P_IPCC_max PRECIPITATION Observed ( ) and simulated ( ) scenarios for precipitation at Lake Trasimeno The reference period ( ) (+ climate signal) is replicated several times in the future Ludovisi A., Gaino E., Bellezza M., Casadei S. (2013) Aquatic Ecosystem Health & Management

28 THE FUTURE SCENARIOS THE WATER BALANCE MODEL (LUMPED) Ludovisi A., Gaino E., Bellezza M., Casadei S. (2013) Aquatic Ecosystem Health & Management V ( mm / month) = ( P s S s P b S S b s C ) V d V a E Precipitation on the lake surface Precipitation on the catchment basin Runoff coefficient Outflows from the artificial outlet Withdrawals for agriculture and civil uses Evaporation (Visentini equation) Calibrated from observed data ( ) E=f(T)

29 C MODEL CALIBRATION 0.5 Average monthly runoff coefficient in the calibration period ( ) (annual average) Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Month

30 Water level ( m a. s. l. ) THE FUTURE SCENARIOS WATER LEVELS Observed Scenario 1 (IPCC_P50_T50) Scenario 2 (IPCC_Pmax_Tmin) Scenario 3 (IPCC_Pmin_Tmax) LAKE BOTTOM! OUTLET THRESHOLD Ludovisi A., Gaino E., Bellezza M., Casadei S. (2013) Aquatic Ecosystem Health & Management

31 WATER FROM MONTEDOGLIO Since 2012 : 1-2 Mm 3 year 1 to agriculture DIRECT INPUT TO THE LAKE??

32 Water level ( m a. s. l. ) THE FUTURE SCENARIOS (with strong mitigation) Observed Scenario 1 (IPCC_P50_T50) + 10 Mm -3 /year Abolition of abstraction licensing +10 Mm 3 year 1 of water input from external basins. Scenario 3 (IPCC_Pmin_Tmax) + 10 Mm -3 /year LAKE BOTTOM! OUTLET THRESHOLD Ludovisi A., Gaino E., Bellezza M., Casadei S. (2013) Aquatic Ecosystem Health & Management

33 LAKE TRASIMENO May 2014 the water level exceeds the outlet threshold after 25 years!