harry.hosper@rws.nlCentre for Water Management

Budapest, 12 October 2007

• Characteristics of lakes

• Ecosystem approach in restoration

• What are the results sofar?

• Prospects for 2015?

River IJssel

1932 Afsluitdijk

19421957

1968

1976

1930IJsselmeer

Markermeer

P-inflow

P-lake

algae

turbidity

nutrient management

hydro- morphology

fisheries management

0

0,2

0,4

0,6

0,8

1

1,2

1,4

1,6

1,8

2

1967 1971 1976 1981 1986 1991 1996 2001 2006

TP

in m

g/l

Total PhosphorusRhine at D/NL border

0,00

0,05

0,10

0,15

0,20

0,25

0,30

0,35

1980 1985 1990 1995 2000 2005

tota

al-P

(m

g/l

)

0

20

40

60

80

100

120

140

1980 1985 1990 1995 2000 2005

chlo

rofy

l-a

(mg

/l)

0,00

0,50

1,00

1,50

2,00

2,50

3,00

3,50

4,00

4,50

1980 1985 1990 1995 2000 2005

tota

al-N

(m

g/l

)

0,00

0,10

0,20

0,30

0,40

0,50

0,60

0,70

0,80

0,90

1,00

1980 1985 1990 1995 2000 2005

do

orz

ich

t (m

)

1

10

100

1000

0.01 0.10 1.00 10.00

totaal-P (mg/l)

chlo

rofy

l-a (u

g/l)

A (n=13)

D (n=49)C (n=22)

B (n=2)

Means apr-sep 2000-2005

0

0,2

0,4

0,6

0,8

1

1,2

1,4

1980 1985 1990 1995 2000 2005 2010

do

orz

ich

t (m

)

Wolderwijd Veluwemeer Eemmeer

Gooimeer Zwarte Meer norm

0

100

200

300

400

500

600

700

800

900

1000

TP

CHL

Secchi

100 m-2

400 m-2

Dreissena

m

g.m

-3

se

cchi in

mm

Fisheries

0

50

100

150

200

250

300

350

1969 1972 1975 1978 1981 1984 1987 1990 1993 1996 1999

0

0,2

0,4

0,6

0,8

1

1,2

1,4

1,6

Se

cc

hi

(m)

bream mussel Secchi

Veluwemeer 1969-2000

Bre

am k

g.h

a-1

mu

ssel

N.m

-2

Fisheries

fishery

bream

disturbance sediment

turbidity

Chara beds Dreissenamussels

After Lammens et al. (2004)

+

+-

-

0

200

400

600

800

1000

1200

1400

1600

1969 1974 1979 1984 1989 1994 1999

Inte

rnal

cov

erag

e (h

a, 1

00%

den

sity

)

0,0

2,0

4,0

6,0

8,0

10,0

12,0

14,0

Sec

chi (

dm)

Chara spp.

Potamogeton perfoliatus

Potamogeton pectinatus

transparency

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

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?

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)

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)

- 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