Lake Tegel and Schlachtensee: Past and Future

1. Lake Tegel and Schlachtensee:Past and Future Dr. Inke Schauser and Dr. Ingrid Chorus, German Environmental Agency

2. Berlin: Lake Tegel and Schlachtensee Lake Tegel Lake Tegel (Main basin) Area 3.060.379 m2 Volume 23.148.783 m3 Max. depth 16 m Water retention time ~ 75 d Schlachtensee Area 420100 m2 Volume 1971000 m3 Max. depth ~ 9 m Water retention time ~ 210 d Schlachtensee

3. Past Problems High P Load High Chlorophyll-a concentrations Low Secci depths Danger for use as drinking water reservoir and recreation site Past Measures P Elimination Plants at Inflow (8-16 cent/m3) Aeration at Lake Tegel Hypolimnion Withdrawal at Lake Schlachtensee Re-establishment of makrophytes and reed Past Problems, Past Measures

4. Wasser direkt aus dem Tegeler See 1983

5. 1 / 40 P Fracht Berlin: Lake Tegel and Schlachtensee PEP Lake Tegel Lake Tegel (Main basin) Area 3.060.379 m2 Volume 23.148.783 m3 Max. depth 16 m Water retention time ~ 75 d PEP since 1985 Schlachtensee Area 420100 m2 Volume 1971000 m3 Max. depth ~ 9 m Water retention time ~ 210 d PEP since 1981 Schlachtensee PEP 1 / 100 P Fracht PEP = Phosphorus Elimination Plant

6. Lake Tegel: Aeration since 1979

7. Schlachtensee: Hypolimnetic withdrawal 1981-1996

8. 100.0 10.0 External P load [g m-2 yr-1] 1.0 0.1 1980 1982 1984 1986 1988 1990 1992 1994 1996 1998 2000 2002 Schlachtensee Lake Tegel Reduction of External Load

9. 400 300 0-8 m lake depth 200 100 TP [mg m-3] 0 100 100 80 200 60 8-15 m lake depth Estimated Intensity of Aeration [%] 300 40 400 20 500 0 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 TP PO4-P Aeration Lake Tegel: Effect of Aeration

10. 10000 1000 100 10 1 0 1980 1982 1984 1986 1988 1990 1992 1994 1996 1998 2000 2002 2004 P in the lake [kg] P withdrawn [kg a-1] external P load [kg a-1] Schlachtensee: Effect of HW

11. Lake Tegel, 1 m Activation of PEP Tegel 1000 250 800 200 600 TP [µg L-1] 150 400 200 100 Chl-a [µg L-1] 0 50 0 1984 1986 1988 1990 1992 1994 1996 1998 2000 2002 2004 Schlachtensee, 1 m Activation of PEP Beelitzhof 1000 250 800 200 1980 1982 1984 1986 1988 1990 1992 1994 1996 1998 2000 2002 2004 600 TP [µg L-1] 150 400 200 Chl-a [µg L-1] 100 0 50 0 TP and Chlorophyll-a

12. Biovolumen [cm3/m3] Tegeler See 1 - 5 m Schlachtensee 0 - 4 m

13. 100 1980 1984 2006 Chlorophyll a in 1 m depth [µg L-1] 10 Schlachtensee ('80-'06) 2006 Lake Tegel ('84-'06) 1 10 100 1000 Total phosphorus in 1 m depth [µg L-1] Annual mean of TP and Chlorophyll-a

14. Lake Tegel External load of River Havel (10  80 %) Schlachtensee Shoreline over use and erosion Both Money! Public participation Lake Tegel Higher Runoff of PEP (> 2,2 m/s) Schlachtensee Rising public awareness Both Rising politics awareness Rising public awareness  How??? Current Problems, Future Solutions

16. Nearby Future  Workshop 8./9.11.2007: “Perspectives of Lake Modeling towards Predicting Reaction to Trophic Change”  Scientific Publication in Lake and Reservoir Management, November 2007: “Assessment of internal and external lake restoration measures for two Berlin lakes „ • Publication for broad public, schools and interested persons: „Lake Tegel and Schlachtensee: two examples of successfull lake restoration“