Mecklenburg-Western (23.182 km²)

Schwerin

(ca. 96.000 residentes)

Germany The Redevelopment and Restoration Programme of the Lakes in Mecklenburg – ()

Jürgen Mathes - Ministry of Agriculture, Environment and Consumer Protection Mecklenburg-Western Pomerania

• Introduction • The redevelopment and restoration programme in Mecklenburg-Western Pomerania • Examples of restoration actions • Conclusions

Workshop WG2 at 06.05. – 08.05.2009 in Keszthely/Hungary Lakes in Mecklenburg-Western Pomerania

2036 Lakes> 1 ha, thereof 622 artificial thereof 557 Lakes> 10 ha, thereof 60 artificial thereof 185 Lakes* > 50 ha, thereof 7 artificial thereof 103 Lakes> 100 ha thereof 10 Lakes > 1.000 ha thereof 1 Lake >10.000 ha (Müritz)

(updated in March 2009)

* in connection with EU’s Water Framework Directive Mecklenburg-Western Pomerania

Number of lakes: 2036 Area [km²]: 739 Surface percentage [%]: 3,1

Rostock

Schaalsee (72,3 m deep) Müritz (107 km²) Schwerin Problem: Trophic situation of the lakes

Low trophic level : phytoplankton low, macrophytes low, clear water

High trophic level : high density of phytoplankton and macrophytes, turbid water, floating blue-green algae Trophic situation of lakes in Mecklenburg-Western Pomerania

LAWA – directive (1999):

Trophic • oligotrophic Trophic Classification situation • mesotrophic reference situation • eutrophic 1 • Total phosphorus • eutrophic 2 • lake basin morphology Criteria • Water transparency • polytrophic• 1 natural potential of • Chlorophyll a • polytrophic 2 inflow phosphorus • hypertrophic - 1 Trophic classes 1 - 7 Trophic classes 1 - 7 - 2 - 3 - 4 Evaluation - 5 - 6 (Difference between trophic and trophic reference situation) - 7 Evaluation classes 1 - 7 Trophic situation of lakes in Mecklenburg-Western Pomerania

More than 80% of the lakes in Mecklenburg- Western Pomerania are eutrophic or their tropic level is even higher. Most of the lakes are classified at least 1 class above their potential natural situation. Oligotrophic lakes are extremely rare. Poly- und hypertrophic waters are anthropogenic.

According § 1 WHG, alike § 3 LWaG M-V as well as the EU-WFD: „ ...the water quality must be protected and reconstructed when derogated.” Consequence :

• Redevelopment and restoration of lakes in Mecklenburg- Western Pomerania • Protection of especially valuable mesotrophic lakes with municipal importance Redevelopment and restoration programme of lakes in Mecklenburg -Western Pomerania

Redevelopment = lake external measures, decreasing nutrient input into the waters by closing cycles of matter onshore. As a result of redeveloping the catchment area, causes of eutrophication are removed or minimized.

Restoration = lake internal measures, that support self regulation of waters and improve reaction time to redevelopment measures.

General note :

• Redevelopment prior to restoration • Combination of redevelopment and restoration only by prospective of redevelopment or when the costs of residual redevelopments are unjustified • Sustainable measures (or combinations) are preferred for restoration Criteria of rank order

• Evaluation of trophic state acc. to LAWA (=Confirmation for need of action) • State of preliminary studies • Territorial relevance • Morphometry of lake • Catchment area (area quotient) • Engagement of user • Cost/benefit analysis

„Measurement for need of action“ ranking list Redevelopment and Restoration Programme of lakes in Mecklenburg -Western Pomerania

ranking list

targeted monitoring programmes

feasibility study

strategy of treatment, planning, implementation

redevelopment restoration protection

accompanying monitoring programmes

documentation Redevelopment and restoration programmes of lakes in Mecklenburg-Western Pomerania

updated Februar 2009 Finished projects

Schmachter See Conventer See Stralsund

Rostock See bei Stresow Buggenhagener See

Kirch Rosiner See Siedenbollentiner See Schwandter See Cossensee Tiefwarensee Neubrandenburg Schwerin Möllener See Damm- Pragsdorfer See Jabeler See see Probst Jesarer See Neustädter See Schmaler Luzin Gr. Weißer See

Glambecker See Redevelopment and restoration programmes of lakes in Mecklenburg-Western Pomerania

asupdated atFebruar February 2009 2009 Current projects

Stralsund

Rostock

Tressower See

Neubrandenburg Schwerin Tollensesee

Feldberger Haussee

Schloßsee Penkun Dabelowsee Redevelopment and restoration programmes of lakes in Mecklenburg-Western Pomerania

updated February 2009 Future projects (Selection)

Stralsund

Eixener See Sildemower See Rostock Duckwitzer See Satower See Teterower See Ivenacker See

Neubrandenburg Schwerin Melzer See Crivitzer See

Feldberger Haussee Zierker See Measures for restoration

• Measures, in order to achieve an export of phosphorus (removal of causes) • Measures to achieve fixation of phosphorus (elimination of effect) • Measures to influence the structure of organisms (bio-manipulation) Measures for restoration

• Measures, in order to achieve an export of phosphorus (removal of causes) - sediment excavation - draining of depth water - extraction of depth water - plants to eliminate phosphorus Foto: Spieker , KJS Foto: Walter, 2005

Foto:Rost, 2005 Example: Excavation (polymictic lake)

Schloßsee (polymictic) Schloßsee Buggenhagen • area: 9,8 ha; catchment area: 1,0 km² • until 1994: huge problems with water quality and accumulation of mud (max. water depth: 0,6 m!) • 1990: Shutdown of a big cowshed nearby • 1994 – 1996: Elimination of liquid manure inflows, modernization of a communal purification plant Concurrent restoration : excavation: averaged water depth of 0,83 m / max. water depth: 2,9 m • draining of mud waters out of the catchment area • agricultural use of sediments

Foto : Nagel, 19.06.2003 Schloßsee near Buggenhagen (potentially eutrophic)

excavation

100 250 Chl-a [µg/l] 80 200 TP [µg/l] (summer) 60 150 (spring)

40 100

20 50

0 0

1,5 250 SECCHI- 200 TP [µg/l] 1,0 depth [m] (summer) (summer) 150 100 0,5 v i e w v i e w v i e w v i e w v i e w

ground- 50 ground- ground- ground- ground- 0,0 0 1996 1997 1998 1999 2003 2006 2007 2008 1996 19973 2006 1998 2007 1999 2008 200

trophic-index: 4,2 3,9 3,0 3,0 4,0 3,9 3,5 3,3 classification: p 2 p 1 e 2 e 1 p 1 p 1 p 1 e 2 evaluation: 5 3 2 1 3 3 3 2 1996 1997 1998 1999 2003 2006 2007 2008 2003 1996 1997

Dominance of phytoplankton

2006 2007 2008 1999 1998

Dominance of macrophytes Foto: bioplan, Sommer 2007 Measurements for restoration

• Measures to achieve a fixation of phosphorus (eliminate effect) - aeration of the hypolimnion - precipitation - destratification - sediment covering Quelle: Hupfer, IGB Installation of the TIBEAN-plant on the Tiefwarensee

Foto: IGB

Foto: IGB

Foto: IGB Foto: bioplan, 2006 Example: P-precipitation (dimictic lake)

Großer Weißer See Morphometric values: Großer Weißer See

N Tief nan aben [m] • lake area: 27,4 ha 0 bis 1 • max. depth: 12,2 m 1 bis 3 W O • medium depth: 6,1 m 3 bis 5 • shore length: 2240 m 5 bis 7 S • catchment area: 2,0 km² 7 bis 9 9 bis 11 11 bis 13 • clear water until the 1960´s (skin-diving contests!) • intensive carp production lead to decrease in water quality (blue-green algae, SECCHI depths in summer less than 0,5 m) • strong recreational interest (swimming, skin-diving etc.) • Jan. 2002: P-precipitation with aluminium sulphate via aeroplane on the frozen lake - 95 starts und landings - application of 47 t granulate (Al-content: 9%) • additional measures to decimate non predative fishes and increase population of predative fishes ( pikes) Großer Weißer See (potentially mesotrophic)

Precipitation

25 100 20 Chl-a [µg/l] 80 TP [µg/l] 15 (summer) 60 (spring) 10 40 5 20 0 0

5 100 4 80 TP [µg/l] SECCHI- (summer) 3 depth [m] 60 2 (summer) 40 1 20 0 0 1996 2000 2001 2002 2003 2004 2005 20061996 2000 2001 2002 2003 2004 2005 2006

trophic-Index: 2,9 2,8 3,1 2,1 2,1 2,0 2,0 1,8 1,9 1,9 classification: e 1 e 1 e 2 m m m m m m m evaluation: 2 2 3 1 1 1 1 1 1 1 1996 2000 2001 2002 2003 2004 2005 2006 2007 2008 Measurements for restoration

• Measures to achieve a fixation of phosphorus (eliminate of effect) - aeration of the hypolimnion - precipitation - destratification - sediment covering Example: Covering of sediment (dimictic lake)

Siedenbollentiner See • poor water quality (due to blue-green algae, problems with oxygen balance) • utilisation (swimming, fishing) • 2001 – 2003: research-project on the potential to improve the ecological state of lakes using minerals of clay (for example attempts of enclosures using materials of the lake) Oct. 2006: covering of the sediment using 980 t of clay-mineral in total • possible additional P-precipitation with aluminium sulphate is still under debate

• lake area: 5,8 ha • max. depth: 10,3 m • medium depth: 4,5 m • shore length: 989 m • catchment area: 3,9 km²

Großer Siedenbollentiner See (potentially mesotrophic)

Sediment covering

Chl a [µg/l] 100 (summer) 500 80 400 TP [µg/l] 60 300 (spring) 40 200 20 100 0 0

1,5 SECCHI- 500 depth [m] 400 1,0 (summer) 300 TP [µg/l] (summer) 200 0,5 100 0,0 0

1999 2001 2002 2006 2007 2008 1999 2001 2002 2006 2007 2008

trophic-index: 3,7 3,9 3,7 3,7 2,9 3,2 classification: p 1 p 1 p 1 p 1 e 1 e 2 evaluation: 4 4 4 4 2 3 1999 2001 2002 2006 2007 2008 Summary: measures in stratified lakes

☺

Summary: measures in non-stratified lakes

Dominancedominance of of Bistability macrophytesplankton ? ☺ Conclusions

Measures for redevelopment and restoration are necessary in order to improve the ecological state of lakes effectively within the EU-WFD standards. The success of the measures taken is more likely the better the measures are determined by systematically collected preliminary data (especially from longitudinal studies). Most quality improvements of lakes in Mecklenburg-Western Pomerania can be attributed to the implementation of redevelopment and restoration programmes. Best results were not achieved by relatively expensive excavation works, but by adapting precipitation techniques to each lake. Despite enormous advances in techniques for restoration within the last years, the possibilities to restore shallow polymictic lakes are still restricted in comparison to deep and stratified lakes. Many thanks for your attention!

Workshop WG2 at 06.05. – 08.05.2009 in Keszthely/Hungary