Heldere meren in Friesland in 2015: droom of werkelijkheid? Clearing Lakes Revisited; 1 December 2011 Theo Claassen & Roelof Veeningen

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1 Heldere meren in Friesland in 2015: droom of werkelijkheid? Clearing Lakes Revisited; 1 December 2011 Theo Claassen & Roelof Veeningen

2 Clear lakes in Friesland in 2015: dream or reality? Clearing Lakes Revisited; 1 December 2011 Theo Claassen & Roelof Veeningen tclaassen@wetterskipfryslan.nl rveeningen@wetterskipfryslan.nl

3 Wadden Sea Lake IJsselmeer

4 The Netherlands in the delta s of four rivers Friesland in the northern River Rhine delta Ems Rhine Scheldt Meuse

5 Wadden Sea Leijen Chain arranged interconnected lakes Fl-He Slotermeer Lake IJsselmeer Average depth 1-2 m Distance to IJsselmeer 4 to 54 km Fluessen-Heegermeer 2300 ha Slotermeer 1120 ha Leijen 300 ha Hydrology bifurcated: Summer in Winter out

6 Many cows and pumping engines

7 Ongoing water quality problems, as well as problems for related functions Algae blooms Bergumermeer 2009 Recreation Low transparency Bank erosion Fisheries Bream dominated Cattle drinking Fish kill

8 Harry s life-work began 40 y ago Waarom gebeurt dit alles in onze maatschappij? En vooral: Waartegen moeten wij onze akties richten? Fosfaten vervuilen het milieu, we weten het nu wel allemaal. Waarom is fosfaat nu zo in het bijzonder van belang? Fosfaten geven algengroei. Dat blijkt niet zo n prettig effect te hebben: stank, vissterfe en soms ook vergiftiging.

9 Aktie Strohalm. Uitgave van de Luide Lach, 1971; prijs ƒ 2,50 Dank aan alle medewerkers en met name aan: Harry Hosper (fosfaatgedeelte).

10 Harry s life-work began 40 y ago Explanation of eutrophication Limiting factors P loads for The Netherlands P standards for shallow lakes mg/l Measures to be taken Occupy movement s reflection PN

11 Clear lakes in Friesland in 2015: dream or reality? 2007 H 2 O 40 (18): 31-33

12 Clear lakes in The Netherlands in 2015: dream or reality? Hosper et al., 2007 H 2 O 40 (18): Yes, a realistic perspective, because: Improving waste water purification Decreasing nutrient concentrations Allowing water level fluctuations Fisheries on benthivorus fish Share knowledge Start pilots

13 Stability of the clear water state in the 1930s and 1940s Factors favoring the clear water state Low nutrient loading Natural water level dynamics High fishing on planktivores / benthivores Flushing Frisian main water system Major role Major role Major role Moderate role Alde Feanen Minor role High role Moderate role Clearing Lakes. Hosper, H., 1997

14 Strategies and this presentation focused on Reduction of emissions of nutrients Water level management Fish stock management Flushing with Lake IJsselmeer water

15 nutrient management P-inflow hydromorphology Hosper P-lake algae turbidity fisheries management Well, this is what we call the ecosystem approach in lake restoration. First of all..nutrient control. In addition to that.. fisheries management and hydrology/morphology measures, if necessary.

16 Measures against eutrophication source measures: Reduction of emissions of nutrients system measures: Water level management Flushing internal measures: Fish stock management

17 This presentation History of the Frisian lakes district Measures taken from 1970 onwards Developments in water quality Perspectives for 2015, 2021 and 2027

18 Friesland omstreeks 900

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20 Fryslân before 1920 Dokkumer Nieuwe Zijlen Friese Sluis Zoutkamp Harlingen Makkum Workum Hindeloopen Stavoren Lemmer Waterafvoer via sluizen

21 Fryslân present day Dokkumer Nieuwe Zijlen Friese Sluis Zoutkamp Gaarkeuke Harlingen J.L. Hooglandgemaal Tacozijl ir. D.F. Woudagemaal Teroelsterkolk Waterafvoer via sluizen Wateraanvoer via sluize Waterafvoer via gemale

22 Average water level in 1876 en 1976

23 Decreasing water table fluctuations last century Ontwikkeling peilverloop Friese boezem ( ) Woudagemaal Afsluitdijk Teroelsterkolk -0.2 m + NAP Hooglandgemaal Lauw ersmeer huidig boezemstreefpeil (NAP-0,52 m) verordening 1987 peilbesluit jaar Target level m NAP Based on interests of agriculture and boat traffic, neither ecology nor water quality

24 Still decreasing helophyte vegetation reed die-back and shore protection

25 In 1876 flooded area 13 th Februari 1910, Sad situation Enclosure dam Lauwersmeer discussed in The Lords

26 Floodplain area decreased with 98 % discharging polder area increased in proportion

27 This presentation History of the Frisian lakes district Measures taken from 1970 onwards Developments in water quality Perspectives for 2015, 2021 and 2027

28 Sanitation efforts and emission reduction before and after 1970 Bucket system of feces collection Wastewater treatment plants Urban sewerage systems Disconnection of rainwater

29 Wwpt s treat over 95% of waste all water

30 Reduction of P from wwtp s Fosfaat Jaar P-influent P-effluent Rendement P Vracht (kg/d) Verwijderingsrendement (%)

31 Reduction of N from wwtp s Stikstof N-totaal influent N-totaal effluent Rendement N Jaar Vracht (kg/d) Verwijderingsrendement (%)

32 P load form wwtp s, IJsselmeer, polders and precipitation bronnen P: ; jaarbasis ton P/jaar neerslag ton P/jr polder ton P/jr IJsselmeer ton P/jr RWZI ton P/jr '80 '

33 Measures taken so far Emission reduction Reed bed purification Dredging Hydrological isolation Enlarging flood plain areas Nature friendly bank constructions Pilot-scale experiments water plants Fish migration facilities Removal of fish (Bream) Source system internal measures

34 This presentation History of the Frisian lakes district Measures taken from 1970 onwards Developments in water quality Perspectives for 2015, 2021 and 2027

35 Classification and assessment according to the WFD - all Frisian lakes are heavily modified - Natuurlijke watertypen Referentie condities of Zeer Goede Ecologische Toestand Goede Ecologische Toestand (GET) Matig Ontoereikend Sterk veranderde & Kunstmatige watertypen Goed ecologisch potentieel (GEP) Matig Ontoereikend Slecht Slecht

36 ,7 0,6 0,5 0,4 0,3 0,2 0, gem P 1981 Phosphorus mg P/l

37 Average summer concentrations zomergemiddelde mg P/l zomergemiddelde tot N ,7 0,6 0,5 0,4 0,3 0,2 0,1 0, ,0 4,5 4,0 3,5 3,0 2,5 2,0 1,5 1,0 0,5 0,

38 Average summer concentrations Chlorofyl Doorzicht boezemmeren , , ,50 0,40 0,30 0,20 0, ,

39 Trend: phosphorus OK, chlorophyll not OK strategy: additional measures Hosper et al., 2011 H 2 O 44 (7): Trend type 2

40 Trends in water quality in lake Leijen A nitrogen B phosphorus C transparency D chlorophyll N-totaal (mg/l) Doorzichtl (cm) N-tot = -0,16 Jaar R 2 = 0, A Zicht = 0,694 Jaar R² = 0, Jaar C P-totaal (mg/l) Chlorofyl-a ( µg/l) ,1 0, logP = -0,0391 Jaar + 77,529 R 2 = 0, B Chl = -2,93 Jaar R 2 = 0, Jaar D Grontmij & Natuur en Water, 2010

41 Actual P load (mgp/m 2 /d) in Lake Leijen: still higher than critical load helder en plantenrijk fisheries management troebel 10,6 lage P-belasting 3,9 6,4 hoge P-belasting

42 Total P and total N in Bergumermeer Bergumermeer midden totaal stikstof 6 5 t-n KRW-norm t-n gehalte (mg/l) 1 0 jan-11 jan-10 jan-09 jan-08 jan-07 datum Bergumermeer midden totaal fosfaat t-p KRW norm t-p gehalte (mg/l) jan-11 jan-10 jan-09 jan-08 jan-07 datum

43 Assessment of water bodies according to Frisian WFD-goals Waterlichaam Algen (EKR) 0.5 Water planten (EKR) 0.4 Macro fauna (EKR) 0.5 Vissen (EKR) 0.3 Fosfaat (mg/l) 0.09 Stikstof (mg/l) 1.3 Door zicht (cm) 65 Overige meren 0,30 0,187 0,44 0,23 0,10 2,0 40 Sneekermeer e.o. 0,43 0,03 0,45 0,15 0,05 1,8 57 Fluessen e.o. 0,22 0,18 0,40 0,15 0,06 1,8 41 Alde Feanen 0,39 0,10 0,34 0,51 0,07 2,0 46 Grote Wielen 0,24 0,1535 0,35 0,23 0,08 1,6 38

44 Assessment system macrophytes Assessment system fishes Doelrealisatie in % tov GEP: waterplanten Doelrealisatie in % tov GEP: Vissen Groote Wielen Groote Wielen Alde Feanen Alde Feanen Fluessen e.o. Sneekermeer e.o. Overige meren Fluessen e.o. Sneekermeer e.o. Overige meren normstelling normstelling 0% 20% 40% 60% 80% 100% 0% 20% 40% 60% 80% 100%

45 This presentation History of the Frisian lakes district Measures taken from 1970 onwards Developments in water quality Perspectives for 2015, 2021 and 2027

46 - Main conclusions (1) Improvement in nutrient levels, but last years stagnation Actual P load still higher than critical load Not yet a switch in ecosystem composition Climate change is stimulating eutrophication

47 - Main conclusions (2) Further reduction in nutrient concentrations heavy and costly task A more natural water level regulation not (yet) feasible Fish stock management a bridge to far Physical disturbance in lakes is high

48 + Main conclusions (3) WFD measures: natural banks, improving fish migration, retention area in main water system and in polders Small plots of macrophytes recovered Increasing N/P ratio and P becoming limiting for blue green algae Fish stock biomass is decreasing Small scale measures (e.g. spawning area for fish, restocking macrophytes and Dreissena)

49 Trends in phytoplankton samples Ordination DCA with Canoco Axis Axis Scores van de monsters op de eerste twee assen van de ordinaties groene punten zijn monsters uit periode 81-90, rode uit periode 91-95, blauwe uit periode zwarte uit periode Van Dam et al., 2007

50 Two gradients in Alde Feanen A isolated peat diggings B main water system

51 Coverage percentage of vegetation in Izakswiid (A) and Skrome lân (B) drijvend submers A1 A2 A3 A4 A5 B1 B2 B3 B4 B5

52 Total P concentration in Izakswiid (A) and Skrome lân (B) totp (mg/l) 0,3 0,25 0,2 0,15 0,1 0,05 0 A1 A2 A3 A4 A5 B1 B2 B3 B4 B5

53 Enclosures and row of pillows in Morfologisch: Lake Leijen Oeverbescherming/inrichting en beplanting

54 Transparency (cm) in Frisian lakes, related to lake IJsselmeer water IJsselmeer Wijde Ee Sneekermeer Langw eer Grote Brekken dz 121 dz 0090 Jan to Oct dz 0053

55 Spawning area for fish Aqualân

56 Fish stock in spawning area Aqualân August ; spwaning species in blue Baars Perca fluviatilis Blankvoorn Rutilus rutilus Bittervoorn Rhodeus sericeus amarus Brasem Abramis brama Driedoornige stekelbaars Gasterosteus aculeatus Giebel Carassius auratus gibeilo Kleine modderkruiper Cobitus taenia Kolblei Abramis bjoerkna Paling Anguilla anguila Pos Gymnocephalus cernuus Riviergrondel Gobio gobio Ruisvoorn Scardinius erythrophthalmus Snoek Esox lucius Tiendoornige stekelbaars Pungitius pungitius Vetje Leucaspius delineatus Zeelt Tinca tinca Totaal n n individuals Aantal soorten n species Aantal soorten broed n 0+ species

57 Fish stock composition (biomass) in Lake Leijen raoch bream 2002 raoch bream w hite bream w hite bream ruffe ruffe pike perch pike perch perch perch smelt smelt eel eel pike pike 2011 baars brasem blankvoorn karper kolblei kleine modderkruiper aal/paling pos snoekbaars rivierdonderpad riviergrondel rietvoorn/ruisvoorn spiering zeelt snoek

58 Fish biomass in Lake Leijen jaartal totale visbiomassa (kg/ha) biomassa brasem (kg/ha) aandeel brasem (%) * * * visbiomassa na uitvoering van uitdunningsvisserijen in voorafgaande winter

59 Landsat true color remote sensing images showing within lake and between lake variation, as well as in time

60 Two alternative stable states, or more? Scheffer et al., 1993

61 or a stepwise restoration process of the Frisan lakes? Frisian variant on: Hosper, 1997

62 Clear lakes in Friesland in 2015: dream or reality? The answer Question is not if, but when, where and how extensive Many indications and signs of being close to a switch Hard to predict which factor triggers to a switch (dry winter: P and N; strong winter: algae; dry spring: transparency; decreasing trend: algae; time: bream collapse, )

63 Clear lakes in Friesland in 2015: dream or reality? % clear water total clear present policy total clear additional fisheries % clear water in the boezem % 6 %

64 Invitation to Harry for a boat trip in 2015