Eutrophication Case Study

Abstract

Tamar Lakes is comprised of two reservoirs, which are located in South West England and in the headwaters of River Tamar at approximately 135 m above ordnance datum. Upper Tamar Lake (UTL) is a direct feed source reservoir of potable water in North Cornwall. Immediately following completion in 1975, UTL was subject to intense blue-green algal blooms that continue to the present. These blooms create operational problems for water treatment, especially in hot-dry years. Lower Tamar Lake (LTL) was constructed as a water supply reservoir in 1819 and became obsolete following UTL coming on-line. Detailed water quality investigations over a period of some 28 years have confirmed the source of nutrient enrichment that fuels the algal blooms to be agriculturally derived, corresponding with a substantial increase in livestock farming. Associated poor land management practices, such as extensive field drainage and inappropriate slurry disposal to land, are linked with substantial elevations in organic contaminants such as ammonia, biochemical oxygen demand (BOD) and suspended solids (SS) during rainfall events. Evidence demonstrates that both reservoirs act as primary treatment lagoons, substantially reducing the worst of these pollutants and providing significant environmental gain. The implications of the Common Agricultural Policy (CAP), the Water Framework Directive (WFD) and regulatory monitoring are discussed in relation to resource management.

Rönne å catchment area is a river watershed located in Southern Sweden and includes lakes (e.g. Ringsjön), rivers (Rönne å) and marine coastal areas (Kattegatt). Institutions in Swedish water governance is complex with multiple actors and frameworks on all scales: local (water councils, municipalities), regional (county administrative boards, water authorities), national (Swedish jurisdiction) and EU (water framework directive). This calls for knowledge about social-ecological complexity, best-practice water governance, and how cross-sector collaboration (or lack thereof) might influence environmental problems and essential ESS. In particular, Case Study 6 looks at the process of eutrophication and restoration of good water quality and their implications for the provision of ecosystem services along the Rönne å catchment.

Freshwater is the bloodstream of the biosphere and provides ecosystem services that are essential for human-being (Folke, 2003). However, mismanagement has previously caused trade-offs in ecosystem services with distinguished winners and losers (Hower et al., 2014), which highlights the importance of a sustainable and holistic governance to ensure the resilience of ecosystem services.

Institutional and governance challenges are a particular issue in the Rönne catchment, site of Case Study 6. When implementing the WFD, Sweden introduced water councils in the catchments. However, the legal role / structure of water councils differs between catchments. Whereas in a neighbouring catchment (KRC), cooperation between the municipalities and councils was settled with a contract, this is lacking for the Rönne Å catchment. Additionally, water council participants (the most local institution for the WFD) often lack a legal mandate to foster decisions and restoration activities, which limits decisions and implementation. To combat these issues, there are discussions and conflicting opinions if two water councils in the catchment should potentially merge: RRC - Rönne Å River Council and the council for Lake Ringsjön. This might extend the comparatively strong restoration activities around the lake to the whole catchment where those activities where less prominent in the past.

Case Study 6 is based on the science of Social-Ecological Systems and the resilience principles. Through stakeholder engagement and workshops, it considers options to improve the governance of the Rönne catchment. These workshops and stakeholder groups also consider management options to improve local water quality and ecosystem service provision. They include management of the turbid lake Ringsjön through biomanipulation and municipal sewage plans to decrease eutrophication from private sewage treatment. Changing the dynamics in lake Ringjsön through biomanipulation will have benefits for recreational fishing and tourism stakeholders in the future, but is very costly for the adjacent municipalities now. Upgrading private sewage systems is very costly for house owners and the benefits therefrom are difficult to visualize. The Case Study also aims to collaborate with stakeholders to identify win-win solutions or to reconcile perceived trade-offs.

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