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Clearwater Lakes in The Netherlands:

Clearwater Lakes in The Netherlands:. I - strategy, status and trends II - shallow lakes network. Budapest, 12 October 2007. harry.hosper@rws.nl Centre for Water Management. Characteristics of lakes Ecosystem approach in restoration What are the results sofar?

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Clearwater Lakes in The Netherlands:

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  1. Clearwater Lakes in The Netherlands: I - strategy, status and trends II - shallow lakes network Budapest, 12 October 2007 harry.hosper@rws.nl Centre for Water Management

  2. Characteristics of lakes • Ecosystem approach in restoration • What are the results sofar? • Prospects for 2015?

  3. The Netherlands: delta of rivers Rhine and Meuse

  4. The Netherlands: 30% below sea level

  5. Artificial water bodies

  6. Heavily modified water bodies

  7. River IJssel Former Southern Sea 1932 Afsluitdijk 1930 IJsselmeer Markermeer 1976 1968 1942 1957

  8. Volkerakmeer

  9. Volkerakmeer

  10. Daphnia: filterfeeders

  11. Zebra mussels: filterfeeders Dreissena polymorpha

  12. cormorants: fish-eaters

  13. mute swans: plant-eaters

  14. tufted ducks: mussel-eaters

  15. commercial fisheries

  16. Objectives shallow lakes (1-3 m) Clear water Biodiversity: plants, fish, birds, .. People: swimming, boating, fishing, landscape, .. TP 0.09 mg/l CHL 23 mg/m3 Secchi 0.90 m

  17. 'hysteresis' TP standard

  18. nutrient management P-inflow P-lake hydro- morphology fisheries management algae turbidity

  19. TP in River Rhine Total Phosphorus Rhine at D/NL border

  20. Trends 100 lakes NL median values TP TN CHL Secchi

  21. CHL TP Means apr-sep 2000-2005

  22. Zwarte meer Veluwemeer Wolderwijd Gooimeer Eemmeer

  23. enclosure studies

  24. Secchi

  25. Zwarte Meer: 1973-2005 Dreissena Fisheries 400 m-2 mg.m-3 secchi in mm 100 m-2

  26. Veluwemeer: 1969-2000 Fisheries Bream kg.ha-1 mussel N.m-2

  27. fishery - bream disturbance sediment Dreissena mussels Charabeds + + - turbidity After Lammens et al. (2004)

  28. Charophytes "ecosystem engineers": - sediment fixation - habitat creation - clearing lakes

  29. Clear water in the lakes Veluwemeer and Wolderwijd

  30. Conditions today: • positive trends in P, N, CHL and Secchi • some clear water, macrophyte-dominated lakes • still many turbid water lakes, no macrophytes • Short-term action: • Sewage: • 4-th step in treatment plants in some catchments • Agriculture: • reduce surface run off by smart agr practices • Fishery: • reduce bream to help macrophytes & mussels Conclusions 1

  31. Conclusions 2 • Clear water lakes 2015? • Yes, … if bream fishery is accepted as management tool • Long-term perspectives? • Natural water levels • Flooding of adjacent land areas • (following sea level rise) • Letting the sea back in?

  32. Shallow Lakes Network = learning company • Mission: • learning, inspiration, helping, .. Integrating water policy, lake science and lake management, .. • Organization: • - 140 members on list • - national/local government, consultancy, universities, stake holders • informal platform, no membership dues, free meetings/lunches (rotating hosts pay for that) • programme committee (<0.5 ftu), administration by CWM (Centre for Water Management, = ex RIZA)

  33. Shallow Lakes Network (2) = learning company • Activities: • meetings 2x per year, field excursions • international excursions (Broads UK, Müritzsee D, Jutland DK?) • sounding board for case studies/restoration plans • national eutrophication survey • website (www.shallowlakes.net, under restoration)

  34. SLN: excursion to Müritz national park (D)

  35. SLN: Spring meeting

  36. Lake Restoration Academy • EU network of national networks • Social network & virtual network • Sowing the seeds for: • European Lake Management Society (ELMS)? • First EU Lake Management Conference 2010? • See also: • www.nalms.org

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