TABLA DE VENCIMIENTOS DE DERIVADOS POR AÑO

Bas W. Ibelings1, Jasper M. Stroom2, Miquel F.L.L.W. Lürling3,1 & W. Edwin A. Kardinaal4

1

Netherlands Institute of Ecology (NIOO-KNAW) – Department of Aquatic Ecology, Droevendaalsesteeg 10, 6708 PB Wageningen, The Netherlands ([email protected]

) and Institute FA Forel, University of Ge-

neva, Switzerland;

2

Waternet, PO Box 94370, 1090 GJ Amsterdam, The Netherlands;.

3

Wageningen University – Aquatic Ecology & Water Quality Management Group, PO Box 47, 6700 AA Wageningen, The Netherlands;

4

KWR Watercycle Research Institute, Groningerhaven 7, 3433 PE Nieuwegein, The Netherlands

Introduction

God created the earth, but the Dutch created Holland. This old proverb nicely emphasises the crucial role of water management in The Netherlands. Protection against flooding has always been essential for survival of the country. The earliest regional water boards were already founded in the 14th century. Traditionally the focus of water management has been purely on management of water quantity, but since 1970 water quality management was added to the responsibilities. The current central aim of water management in The Netherlands has been described as: “to obtain and maintain a safe country and to preserve and strengthen healthy, resilient water systems that ensure sustainable use of water”(Nationaal Waterplan 2009-2015). Water management more and more is aimed at closing the water-cycle and reflecting this by integrating groundwater, sewerage, surface- and drinking water all in one organisation. All func- tions of water systems (e.g. production of drinking water, shipping, recreation, nature) are weighed and balanced. Although 40 % of the drinking water consumed in the Netherlands is abstracted from surface water-bodies, cyanobacteria and cyanotoxins are of no concern, since several steps in the production processes are efficient barriers for cells and toxins (Vernooij et al, 2011). Subject of this paper is the use of surface waters for recreation. Recreational use is thus only one of a number of functions of lakes and rivers in the Netherlands.

The overall responsibility for the safety of recreational waters, as well as the formal decision to issue warnings and such lies with the provinces and not with the water management authority. The appropriate water management authority has the responsibility to carry out the monitoring and investigate water quality and sources of pollution. In inland small(er) water bodies this is the responsibility of the water boards. The larger lakes and bathing locations along the main rivers fall under the responsibility of the Directorate-General for Public Works & Water Management, the executive arm of the Ministrty of Infrastucture and the Environment. As regulated by the EU bathing water directive and its Dutch legal implementation, the water management authority needs to examine causes of water quality exceedances (reported in bathing water profiles) and propose measures to comply with the standards of the bathing water directive. This does not necessarily mean that implementation and financing of all measures is a responsibility of the water management authority. Implementation depends on the type of measure and the impor- tance of the bathing location to other stakeholders such as the provinces, local municipality and care-takers of bathing areas. The above applies to faecal pollution which is EU-standardized. For cyanobacteria the situation is even less clear since in the EU Water Framework Directive nor the Bating Water directive nor any Dutch legislation imposes an obligation to take specific

from the Bathing Water Directive varies with the level of local ambitions. In most cases the ap- proach of controlling cyanobacteria follows the fecal approach. Nevertheless in Dutch waters the problems and costs of cyanobacterial measures by far outweigh the costs of measures con- cerning fecal pollution.

Most of the lakes in the Netherlands are man-made. In the densely populated western part of the country many shallow lakes are the result of extensive peat-digging in the 19th century, with deeper lakes being of more recent date and resulting from sand and gravel extraction. Yet oth- ers, like the large lake IJsselmeer are closed-off former estuaries. Almost all of these lakes are still eutrophic and ecological quality needs further improvement, despite the fact that large and costly efforts have brought down the concentrations of nitrogen and phosphorous. Lake restora- tion has been successful in some cases, but many lakes are still turbid and without the exten- sive submerged vegetation that once characterized them. The Ecological Quality Ratio of the Water Framework Directive shows an upward trend over 1987-2008, but this is based upon a general trend of decreasing chlorophyll-a, whilst there is no significant improvement in the de- creased occurrence of nuisance algal blooms (Hosper et al., 2011). Indeed blooms of cyano- bacteria are a conspicuous attribute of many of the lakes in the Netherlands, and concentrations of microcystin often reach high levels (see Fig. 1). Trends seem to indicate that microcystin lev- els have increased rather than decreased over recent years. In short it is clear that the potential for recreational exposure to (toxic) cyanobacteria in the Netherlands is rather large. We have numerous lakes that are eutrophic and support blooms of cyanobacteria in a densely populated country with a high demand for water related recreational activities (see Fig. 2a). In 2009, the Netherlands had 553 official inland freshwater bathing sites, of which 524 were located at vari- ous lakes. In fresh and brackish waters nearly 50 % of these official bathing waters experience the presence of nuisance cyanobacterial blooms (Fig. 2b).

Controlling cyanobacterial blooms is a serious responsibility for water management in the Neth- erlands, visit http://www.stowa.nl/Thema_s/Cyanobacteri_n/index.aspx for an overview of activi- ties. The general public is relatively well informed about the health risks of recreation (e.g. swimming, (wind)surfing, waterskiing, diving) in lakes. There are special hotlines where informa- tion about the water quality of specific water bodies can be obtained (‘Zwemwatertelefoon’) and there are dedicated websites (e.g. http://www.waterland.net/zwemwater) with clickable maps of the provinces, showing whether swimming is unsafe in particular water bodies. Most warnings and almost all closure of lakes are related to blooms of toxic cyanobacteria. In the following we discuss regulations with respect to cyanobacteria and their toxins which have been developed in the Netherlands. We further present how the procedures and guidelines have evolved over the years from a simple protocol, based purely on microcystin measurements to a more com- plex protocol, which is based upon cyanobacterial biomass. Furthermore, the implementation of the EU Bathing Water Directive (DIRECTIVE 2006/7/EC) in Dutch legislation is addressed.