Lake Management, Criteria

Lakes are of importance for their heritage, ecological, and aesthetical value. However, lakes are subjected to enormous stress from industry emissions, sewage, agricultural run-off, hydrological modifications, and human-induced climate changes. The six major pressures affecting lakes today are (1) eutrophication; (2) hydromorphological modifications; (3) acidification; (4) alien species; (5) hazardous substances; and (6) climate changes. Effective management is therefore of critical importance for lake preservation and restoration as both a heritage asset and also as a resource benefiting the human population and it requires a focus on ecosystem elements indicative of these pressures. Having a comprehensive suite of ecosystem quality indicators at a lake manager's disposal will allow the evaluation of the extent of pressure affecting a lake and its influence on the ecosystem's structure and functioning. There are still significant knowledge gaps in our understanding on how lakes respond to certain pressures and in particular to combination of pressures. To resolve the problem, managers may need to define a hierarchy among these to identify priority actions at the appropriate geographical scale. The appropriate unit for management of water quality is at watershed level and it is in this context that assessment criteria for indicators relating to pressures in lakes should be incorporated into a decision support system to allow interpretation regarding their influence on the structure and functioning of lake ecosystems. The usefulness of criteria should be reevaluated both in context of their ability to reflect pressure and also their relevance to lake biota.