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The impact of climate change on lakes in the Netherlands: a review

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Climate change will alter freshwater ecosystems but specific effects will vary among regions and the type of water body. Here, we give an integrative review of the observed and predicted impacts of climate change on shallow lakes in the Netherlands
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  The impact of climate change on lakes in the Netherlands: a review Wolf M. Mooij 1, *, Stephan Hu ¨lsmann 1,3 , Lisette N. De Senerpont Domis 1 , Bart A.Nolet 1 , Paul L. E. Bodelier 1 , Paul C. M. Boers 2 , L. Miguel Dionisio Pires 1 , Herman J.Gons 1 , Bas W. Ibelings 1 , Ruurd Noordhuis 2 , Rob Portielje 2 , Kirsten Wolfstein 2 andEddy H. R. R. Lammens 2 1 NIOO-KNAW, Centre for Limnology, Rijksstraatweg 6, 3631 AC Nieuwersluis, The Netherlands;  2 RIZA,P.O. Box 17, 8200 AA Lelystad, The Netherlands;  3 Insititute of Hydrobiology, Dresden, University of Technology, 01062 Dresden, Germany; *Author for correspondence (e-mail: w.mooij@nioo.knaw.nl; phone:+31-294-239352; fax: +31-294-232224) Received 21 April 2004; accepted in revised form 29 June 2005 Key words:  Biodiversity, Carrying capacity, Invading species, Nuisance species, Temperature,Transparency Abstract Climate change will alter freshwater ecosystems but specific effects will vary among regions and the type of water body. Here, we give an integrative review of the observed and predicted impacts of climate change onshallow lakes in the Netherlands and put these impacts in an international perspective. Most of these lakesare man-made and have preset water levels and poorly developed littoral zones. Relevant climatic factors forthese ecosystems are temperature, ice-cover and wind. Secondary factors affected by climate include nutrientloading, residence time and water levels. We reviewed the relevant literature in order to assess the impact of climate change on these lakes. We focussed on six management objectives as bioindicators for the func-tioning of these ecosystems: target species, nuisance species, invading species, transparency, carryingcapacityand biodiversity. We conclude that climate change will likely (i) reduce the numbers of several targetspecies of birds; (ii) favour and stabilize cyanobacterial dominance in phytoplanktoncommunities; (iii) causemore serious incidents of botulism among waterfowl and enhance the spreading of mosquito borne diseases;(iv) benefit invaders srcinating from the Ponto-Caspian region; (v) stabilize turbid, phytoplankton-domi-nated systems, thus counteracting restoration measures; (vi) destabilize macrophyte-dominated clear-waterlakes; (vii) increase the carrying capacity of primary producers, especially phytoplankton, thus mimickingeutrophication; (viii) affect higher trophic levels as a result of enhanced primary production; (ix) have anegative impact on biodiversity which is linked to the clear water state; (x) affect biodiversity by changing thedisturbance regime. Water managers can counteract these developments by reduction of nutrient loading,development of the littoral zone, compartmentalization of lakes and fisheries management. Introduction Global average surface temperatures on earth haveincreased by approximately 0.6   C over the lastcentury. The past two decades were the warmestsince 1861 (Houghton et al. 2001). Without proper action against anthropogenic greenhouse effectsthe Intergovernmental Panel on Climate Change(IPCC) predicts increases in global average surfacetemperature of 1.4 to 5.8   C for the year 2100 Aquatic Ecology (2005) 39:381–400    Springer 2005DOI 10.1007/s10452-005-9008-0  (Houghton et al. 2001). Northern Europe willexperience an increase in the frequency andintensity of precipitation. However, regional cli-mate changes are harder to predict as small spatialfluctuations in climate patterns have far-reachingconsequences for regional climate.Ecological responses to recent climate changehave been demonstrated across different naturalsystems (Walther et al. 2002; Parmesan and Yohe2003). Long time series analyses of physical andbiological characteristics of fresh water ecosystemsin Northern Europe have shown that climatechange affects the winter concentration of nitratenitrogen (George et al. 2004), the concentration of dissolved reactive phosphorus (George et al.2004), and the timing of seasonal succession eventsof phytoplankton and zooplankton (Mu ¨ller-Navarra et al. 1997; Weyhenmeyer et al. 1999;George 2000; Gerten and Adrian 2000; Straile2000; Straile and Adrian 2000; Straile 2002;Carvalho and Kirika 2003; George et al. 2004).However, differences in lake morphometry andsite specificity result in differences in the relativeeffect of climate change on ecosystem variables(Gerten and Adrian 2001; George et al. 2004). Because of their smaller volume and absence of stratification in summer, shallow water bodies areless influenced by meteorological conditions in thepreceding winter than deeper waterbodies, andrespond more directly to the prevailing weatherconditions (Gerten and Adrian 2000, 2001). Theimportance of morphometry and site specificity,added to the strong deviations of local climatefrom global climate, imply that specific predictionson the effects of climate change can only be madewith a specific type of ecosystem and a specificregion in mind.Here, we focus specifically on large, shallow lakeecosystems in the Netherlands. Several parametersof climate change are relevant to these ecosystems:changes in temperature, ice-cover, wind and pre-cipitation. Secondary effects of climate changemay include changes in nutrient loading, residencetime and water level. In contrast to other large,shallow European lakes, the Dutch shallow lakeshave a poorly developed littoral zone partly due totheir non-natural srcin and partly due to contin-uous mixing and high turbidity. Furthermore, thehighly controlled hydrology of Dutch lakes resultsin their water level to be unnaturally stable. Thecombined effect of the absence of a true littoralzone, and the non-natural stable water levels mightrender the Dutch lakes less resilient to externalstress factors (Scheffer et al. 2001a, 2001b) – such as climate change – than other lakes in Europe.In this paper, we will give a state-of-the-artreview of the observed, predicted and potentialeffects of climate change on shallow lakes in theNetherlands, using proven bioindicators for thefunctioning of these freshwater ecosystems.The potential deleterious effects of climate changewill be judged by indicators at the species level, i.e.target species, nuisance species and invadingspecies, and by indicators at the ecosystem level,i.e. transparency (in principle a physical parameterbut used here as an indicator of the associatedecosystem state), carrying capacity and biodiver-sity. First, we describe the general characteristicsof shallow lakes in the Netherlands as compared toshallow lakes in other parts of Europe. Next, wediscuss the projected climate change scenarios forthe Netherlands and how each of the indicators of the functioning of shallow lakes in the Netherlandsis affected by climate change. In the discussion weintegrate these findings into an impact assessment,put them into an international perspective, andevaluate their implications for management. Shallow lakes The main Dutch freshwater lakes (Table 1) areshallow, varying in depth from 1 to 5 m (Gulatiand Van Donk 2002). They are located in thelower catchment area of the river Rhine and rangein size from a few hectares to more than100,000 ha. Sand, clay and peat are the mainsubstrate types and the water residence time inlakes varies from 1 to 14 months. Most of theDutch lakes are man-made and lack a well-devel-oped littoral zone. Water levels are regulated suchthat water tables are kept relatively low in winterto facilitate run off of surplus water and relativelyhigh in summer to facilitate drainage of waterto agricultural land, i.e. the regulation leads toreversal of the natural regime. Due to theircontrolled hydrology and poorly developed littoralzone, the Dutch lakes are rather difficult to com-pare with many other shallow lakes in Europe. In amore natural situation, most of these lakes wouldbe comparable with: Lake Peipsi (Russia/Estonia),Lake Vo˜rtsja ¨rv (Estonia), Lake Uluabat (Turkey),382  Loch Leven (Scotland) and Lake Balaton(Hungary) (Table 2).Being shallow, all of these lakes are permanentlymixed (polymictic) and the sediments are regularlydisturbed by wind action. Consequently, there isno stratification of temperature or oxygen. In theNetherlands, water temperature shows annualmaximum of 20–22   C at the beginning of Augustand a minimum of 2–4   C at the end of January(Mooij and Van Tongeren 1990). Most of theDutch lakes indirectly receive eutrophic water(total P, 150–300  l g l ) 1 ; total N, 4–9 mg l ) 1 ) fromthe river Rhine. The chlorophyll- a  levels in thelakes range between 25 and 90 l g l ) 1 , total Pbetween 100 and 300 l g l ) 1 and total N between 2and 3.5 mg l ) 1 (Portielje and Van der Molen1998). The biomass of the phytoplankton in thesemesotrophic to eutrophic systems may often belimited by underwater light rather than P or N.Temperate shallow lakes have been consideredto be in one of two alternative stable states, a clearmacrophyte-dominated state or a turbid phyto-plankton-dominated state (Scheffer et al. 1993).Due to eutrophication, the majority of the Dutchshallow lakes have become turbid, with transpar-encies ranging from 0.25 to 0.5 m, so that macro-phytes are suppressed by light limitation. Similartrends can be observed in large shallow lakes inother parts of Europe (Table 2). Biomanipulationcan cause a switch from the turbid to the clear stateand thus enhance macrophyte growth (Van Donket al. 1990; Meijer 2000). When Sechhi-disc trans-parency depth exceeds about 1 m, enough lightreaches the bottom in large areas of most lakes andmacrophytes have the potential to develop as theydid in the 1990s in ca. 70–90 % of the area in lakesVeluwemeer and Wolderwijd (Lovvorn and Gill-ingham 1996; Portielje and Rijsdijk 2003).The food webs in these eutrophic lakes in theturbid state are relatively simple as the speciesdiversity in the lakes is low. Phytoplankton isdominated during the largest part of the summer(or even year round) by cyanobacteria withconcentrations of chlorophyll- a  ranging between50 and 150 l g l ) 1 (Van der Molen and Portielje1999). Zooplankton is represented by a fewcladoceran species (mainly  Bosmina longirostris , Daphnia galeata  and  Chydorus spaericus ) andcyclopoid copepods, usually with spring peaks of several hundred ind. l ) 1 and low concentrationsduring the summer (Vijverberg and Boersma 1997).      T    a     b     l    e     1 .     S   o   m   e   g   e   n   e   r   a    l   c    h   a   r   a   c   t   e   r    i   s   t    i   c   s   o    f   t    h   e   m   a    j   o   r   s    h   a    l    l   o   w    l   a    k   e   s    i   n   t    h   e    l   o   w   e   r   c   a   t   c    h   m   e   n   t   o    f   t    h   e   r    i   v   e   r    R    h    i   n   e .    W   a   t   e   r    l   e   v   e    l    T   r   a   n   s   p   a   r   e   n   c   y    (   c   m    )    C    h    l   o   r   o   p    h   y    l    l    (      l    g    l    )             1     )    P    V    I    (      %     )    R   e   s    i    d   e   n   c   e   t    i   m   e    (   y   e   a   r    )    B   o   t   t   o   m   s   u    b   s   t   r   a   t   e    D   e   p   t    h    (   m    )    S   u   r    f   a   c   e   a   r   e   a    (    h   a    )    R   e    f   e   r   e   n   c   e   s    L   a    k   e    V   o    l    k   e   r   a    k    C   o   n   s   t   a   n   t    8    0  –    1    2    0    2    0  –    5    0    1    0    0 .    1    6    S   a   n    d    5 .    2    4    5    0    0    B   r   e   u    k   e   r   s   e   t   a    l .    (    1    9    9    7    ) ,    L   a   m   m   e   n   s   e   t   a    l .    (    2    0    0    2    )    L   a    k   e    I    J   s   s   e    l    C   o   n   s   t   a   n   t    4    0  –    6    0    4    0  –    8    0    2 .    1    0 .    3    3    S   a   n    d    4 .    5    1    2    0 ,    0    0    0    L   a   m   m   e   n   s    (    1    9    9    9    ) ,    L   a   m   m   e   n   s   a   n    d    V   a   n    d   e   n    B   e   r   g    (    2    0    0    1    ) ,    I    b   e    l    i   n   g   s   e   t   a    l .    (    2    0    0    3    )    L   a    k   e    V   e    l   u   w   e    C   o   n   s   t   a   n   t    5    0  –    1    2    0    1    0  –    4    0    8    9    0 .    1    5    S   a   n    d    1 .    5    3    4    0    0    L   a   m   m   e   n   s   e   t   a    l .    (    2    0    0    2    ) ,    P   o   r   t    i   e    l    j   e   a   n    d    R    i    j   s    d    i    j    k    (    2    0    0    3    )    L   a    k   e    W   o    l    d   e   r   w    i    j    d    C   o   n   s   t   a   n   t    5    0  –    9    0    1    0  –    4    0    7    0    0 .    3    5    S   a   n    d    1 .    9    2    5    0    0    P   o   r   t    i   e    l    j   e   a   n    d    R    i    j   s    d    i    j    k    (    2    0    0    3    )    L   a    k   e    M   a   r    k   e   n    C   o   n   s   t   a   n   t    3    0  –    5    0    4    0  –    6    0    4 .    8    1 .    2    C    l   a   y    3 .    5    6    7 ,    0    0    0    L   a   m   m   e   n   s    (    1    9    9    9    )    L   a    k   e    L   o   o   s    d   r   e   c    h   t    C   o   n   s   t   a   n   t    3    0  –    4    0    5    0  –    1    0    0    5    1    P   e   a   t    1 .    8    1    5    0    0    M   o   s   s   e   t   a    l .    (    2    0    0    3    b ,    P   e    l   e   t   a    l .    (    2    0    0    4    )    L   a    k   e    T    j   e   u    k   e   m   e   e   r    C   o   n   s   t   a   n   t    3    0  –    4    0    5    0  –    1    0    0    1    0 .    3    5    S   a   n    d    /   p   e   a   t    1 .    5    2    2    0    0    L   a   m   m   e   n   s   e   t   a    l .    (    2    0    0    2    )    L   a    k   e    E   e   m    C   o   n   s   t   a   n   t    2    5    1    0    0    1    0 .    0    8    C    l   a   y    /   s   a   n    d    1 .    7    1    5    0    0    P   o   r   t    i   e    l    j   e   e   t   a    l .    (    2    0    0    1    )    A    l    l    l   a    k   e   s   g    i   v   e   n   a   r   e    l   o   c   a   t   e    d    i   n   t    h   e    N   e   t    h   e   r    l   a   n    d   s   a   n    d   m   a   n  -   m   a    d   e    b   y   c    l   o   s   u   r   e   o    f   s   e   a  -   a   r   m   s   a   n    d   p   e   a   t   e   x   c   a   v   a   t    i   o   n .    T    h   e   y    l   a   c    k   a   n   a   t   u   r   a    l    h   y    d   r   o    l   o   g    i   c   a    l   r   e   g    i   m   e .    M   o   s   t   o    f   t    h   e    l   a    k   e   s   a   r   e    i   n   t    h   e   t   u   r    b    i    d   p    h   y   t   o   p    l   a   n    k   t   o   n  -    d   o   m    i   n   a   t   e    d   s   t   a   t   e .    D   a   t   a   o   n   t   r   a   n   s   p   a   r   a   n   c   y ,   c    h    l   o   r   o   p    h   y    l    l   a   n    d    P    V    I    (    P   e   r   c   e   n   t   a   g   e    V   o    l   u   m   e    I   n    f   e   s   t   e    d    b   y   m   a   c   r   o   p    h   y   t   e   s    )   r   e   p   r   e   s   e   n   t   a   n   n   u   a    l   a   v   e   r   a   g   e   s   o   v   e   r   t    h   e   p   a   s   t    d   e   c   a    d   e . 383  In some lakes the zooplankton community isdominated by rotifers (Gulati and Van Donk2002). Zoobenthos is dominated by chironomidsand oligochaetes with biomasses of 1–10 g freshweight m ) 2 (Lammens et al. 1985). The fish aremainly represented by cyprinids, particularlybream  Abramis brama  and the fish standing cropamounts from 100 to 200 kg ha ) 1 (Lammens et al.2002). This low diversity occurs in the turbid state.At total-P levels of 50–150  l g l ) 1 a switch can occurto a clear vegetation-rich state with a high diversity(Scheffer 1998) as was observed in Veluwemeer andWolderwijd after a drastic reduction of the breampopulation amongst other restoration measures.Also, an increase of the zebra mussel populationmay have contributed to the return of the clear-water phase in some lakes (Lovvorn and Gilling-ham 1996; Portielje and Rijsdijk 2003). Climate change In the Netherlands, in the past century an increaseof 0.8   C can be noted in yearly averages of airtemperature (Klein Tank 2004). This increase iscorrelated with an increase in world average tem-perature of 0.6   C. Further analysis of the histor-ical data showed that the strongest temperatureincreases could be observed during late winter andearly spring (Oldenborgh and Van Ulden 2003).Since 1901, an increase in average winter precipi-tation has been observed (Oldenborgh and VanUlden 2003). Based on the findings of the thirdIPCC report (Houghton et al. 2001) the KNMI (the Royal Netherlands Meteorological Institute)developed three climate scenarios for the Nether-lands for the 21st century (Table 3). There isconsiderable uncertainty in these climate projec-tions concerning the changes in the amount of precipitation, the influence of cloud cover, theinfluence of ocean circulation on the regional cli-mate and the changes in climate variability (e.g.the frequency of events such as storms, extremewarm winters or extreme wet years). Temperature and ice cover The KNMI scenarios predict temperatureincreases varying from 1 to 6   C (Table 3). Watertemperature in shallow lakes, which are polymic-tic, is tightly coupled to air temperature: any dif-      T   a     b     l   e     2 .     G   e   n   e   r   a    l   c    h   a   r   a   c   t   e   r    i   s   t    i   c   s   o    f   a   n    d   o    b   s   e   r   v   e    d   e   c   o    l   o   g    i   c   a    l   r   e   s   p   o   n   s   e   o   n   c    l    i   m   a   t   e   c    h   a   n   g   e   o    f    l   a   r   g   e   s    h   a    l    l   o   w    l   a    k   e   s    i   n    N   o   r   t    h   e   r   n    E   u   r   o   p   e .    W   a   t   e   r    l   e   v   e    l    T   r   a   n   s   p   a   r   e   n   c   y    (   c   m    )    C    h    l   o   r   o   p    h   y    l    l    (      l    g    l    )             1     )    P    V    I    (      %     )    R   e   s    i    d   e   n   c   e   t    i   m   e    (   y   e   a   r    )    B   o   t   t   o   m   s   u    b   s   t   r   a   t   e    D   e   p   t    h    (   m    )    S   u   r    f   a   c   e   a   r   e   a    (    h   a    )    E   c   o    l   o   g    i   c   a    l   r   e   s   p   o   n   s   e   t   o   c    l    i   m   a   t   e   c    h   a   n   g   e    S   o   u   r   c   e    L   a    k   e    P   e    i   p   s    i    (   s   e   n   s   u    l   a   t   o    ) ,    E   s   t   o   n    i   a    /    R   u   s   s    i   a    U   n   r   e   g   u    l   a   t   e    d    2    0    0    2    0    1    1 .    1    P   e   a   t    7 .    1    3    5    5 ,    5    0    0    D   e   c   r   e   a   s   e   o    f   v   e   n    d   a   c   e    (      C   o   r   e   g   o   n   u   s   a     l     b   u     l   a     )    N   o   g   e   s   e   t   a    l .    (    1    9    9    6    ) ,    V   a   n    E   e   r    d   e   n   a   n    d    L   a   m   m   e   n   s    (    2    0    0    1    )    L   a    k   e    B   a    l   a   t   o   n ,    H   u   n   g   a   r   y    R   e   g   u    l   a   t   e    d    4    0  –    7    0    1    0  –    3    0    1  –    3    3  –    8    S    i    l   t    3 .    2    5    5    9 ,    3    0    0    C   y   a   n   o    b   a   c   t   e   r    i   a    b    l   o   o   m   s    S   p   e   c   z    i   a   r   a   n    d    B    i   r   o    (    1    9    9    8    ) ,    K   o   v   a   c   s   e   t   a    l .    (    2    0    0    3    )    L   a    k   e    V   o    ˜   r   t   s    j   a    ¨   r   v ,    E   s   t   o   n    i   a    U   n   r   e   g   u    l   a   t   e    d    1    1    0    2    2    1    1    S   a   n    d    G   r   a   v   e    l    C    l   a   y    P   e   a   t    2 .    8    2    7 ,    0    0    0    C    h   a   n   g   e    i   n   w   a   t   e   r    l   e   v   e    l   s ,    C   y   a   n   o    b   a   c   t   e   r    i   a    b    l   o   o   m   s    H   a    b   e   r   m   a   n   a   n    d    L   a   u   g   a   s   t   e    (    2    0    0    3    ) ,    M   o   s   s   e   t   a    l .    (    2    0    0    3    b    ) ,    N   o   g   e   s   e   t   a    l .    (    2    0    0    3    ) ,    K    i   s   a   n    d   a   n    d    N   o   g   e   s    (    2    0    0    4    )    L   a    k   e    U    l   u   a    b   a   t ,    T   u   r    k   e   y    R   e   g   u    l   a   t   e    d    4    0  –    1    6    0    2    0  –    8    0    3    0  –    5    0    C    l   a   y    2 .    5    1    9 ,    9    0    0    W   a   t   e   r    l   e   v   e    l   c    h   a   n   g   e   s    L   a   m   m   e   n   s   e   t   a    l .    (    2    0    0    1    )    L   o   c    h    L   e   v   e   n ,    S   c   o   t    l   a   n    d    U   n   r   e   g   u    l   a   t   e    d    2    0  –    4    0    0 .    4    3    S   a   n    d   s   t   o   n   e    3 .    9    1    3    3    0    S    h    i    f   t   s    i   n   p    l   a   n    k   t   o   n   p    h   e   n   o    l   o   g   y    C   a   r   v   a    l    h   o   a   n    d    K    i   r    i    k   a    (    2    0    0    3    )    A    l    l    l   a    k   e   s   g    i   v   e   n   a   r   e    l   o   c   a   t   e    d   o   u   t   s    i    d   e   t    h   e    N   e   t    h   e   r    l   a   n    d   s .    D   a   t   a   o   n   t   r   a   n   s   p   a   r   a   n   c   y ,   c    h    l   o   r   o   p    h   y    l    l   a   n    d    P   e   r   c   e   n   t   a   g   e    V   o    l   u   m   e    I   n    f   e   s   t   e    d    (    P    V    I    b   y   m   a   c   r   o   p    h   y   t   e   s    )   r   e   p   r   e   s   e   n   t   a   n   n   u   a    l   a   v   e   r   a   g   e   s   o   v   e   r   t    h   e   p   a   s   t    d   e   c   a    d   e . 384  ference between air temperature and water tem-perature is reduced by 50 %  within three days(Mooij and Van Tongeren 1990; Gerten andAdrian 2001). Given the tight relationship betweenair temperature and water temperature, anychange in the former will mostly result in a cor-responding change in the latter. In about 50 %  of the winters, the Dutch lakes have a partial orcomplete ice cover for a few days to a few weeks. Aclimate-related rise in temperature would cause adrop in the frequency, extent and duration of periods with ice cover. Precipitation The projected increase in precipitation will be aug-mented by periods with extreme precipitationresulting in an increased frequency of so-called ‘wetyears’ (Table 3). The predicted changes in precipi-tation and evaporation in Europe (Houghton et al.2001) will increase discharges of the river Rhineduring winter and spring (Middelkoop 2000),whereas extended periods with low water dischargemay be expected in summer and autumn (Loaicigaet al. 1996). As a result, winter water levels wouldincrease whereas lower levels are likely in summer,potentially leading to drying of the shallowest partsof the lakes. Also, water residence time of shallowlakes is expected to decrease in winter and toincrease in summer. Wind/waves The extent of changes in wind and changes thefrequency of storm events due to climate change isstill highly uncertain. In the past 41 years, thefrequency of storms has decreased in the Nether-lands (Klein Tank et al. 2002). Wind speeds in theNetherlands are sufficient to homogenize the waterin lakes up to some 10 km 2 in surface area. Sig-nificant wind resuspension of sediment occursabout every second day in a medium-sized ‘peatlake’ in summer, and resuspension of >50 % of thelake area is not exceptional. Wind-induced resus-pension markedly increases vertical light attenua-tion, and thus directly limits primary production(Gons et al. 1991). Despite the observed decreasein the number of storms, climate scenarios predictonly a 2 % increase in the maximum wind speed in25 yrs (Dorland et al. 1999). Consequences for nutrient loading Climate change will affect nutrient loading of lakesin the Netherlands in different ways. Changes inwater supply may have an effect on the waterchemistry of lakes, as the increased water supply of riverine origin (carrying high loads of nitrogencompounds, chloride and sulphate) will affect localwater quality. Furthermore, an increase of netprecipitation in winter, and especially an increasein extreme rainfall events, will tend to increase theP-loading of lakes. The P-loading from smallerstreams is to a large extent determined by peakdischarges following heavy rainfalls. In streamcatchments with agricultural land-use and a historyof fertilization, P-saturation is higher in the top soillayer. Thus, higher groundwater levels will result inhigher concentrations in the water that is dis-charged to surface water (Van der Molen et al.1998). In their study on four lakes in the EnglishLake district, George et al. (2004) recorded highersoluble reactive phosphorus concentrations after Table 3.  KNMI climate change scenarios for the Netherlands in the year 2100 based on the 3rd IPCC report.Low estimation Medium estimation High estimationTemperature +1   C +2   C +4–6   CAverage summer precipitation +1 %  +2 %  +4 % Summer evaporation +4 %  +8 %  +16 % Average winter precipitation +6 %  +12 %  +25 % Intensity of extreme rainfall events +10 %  +20 %  +40 % Frequency of extreme rainfall events 47 yrs 25 yrs 9 yrsSea level rise + 20 cm + 60 cm + 110 cmThe sea level rise is corrected for lag and subsidence (source KNMI/IPCC). 385
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