Deliverable 3.13

Review on processes and effects of changes in water level and salinity in lakes and threats due to climate change on current adaptive management and restoration efforts

Link http://www.refresh.ucl.ac.uk/webfm_send/2400

Abstract According to the Intergovernmental Panel on Climate Change (IPCC) released in September 2013, an unprecedented change in temperature and precipitation patterns has been globally recorded in the recent few decades and further change is predicted to occur in the near future mainly as the result of human activity. In particular, the available projections show that the Mediterranean climate zone will be markedly affected with significant implications for lake water levels and salinity. This may be exacerbated by increased demands for irrigation water. Based on long-term data from seven lakes covering a geographical gradient of fifty two degrees of latitudes and a literature review, we discuss how changes in water level and salinity related to climate warming and water abstraction impact on the ecosystem structure, function, biodiversity and ecological state of the lakes. We provide guidelines for mitigation of the negative effects on the ecological state of lakes that are likely to result from changes in climate and water abstraction practices.
Some of the negative cascading effects on lake ecosystems resulting from water level reductions and salinity increases may be counteracted by integrated water resource management. This should encompass reshaping of planning processes, coordinating land and water use, recognising water quantity and quality linkages, conjunctive use of surface water and groundwater, protecting and restoring natural systems, and enhancing inland water retention time. Win-win measures include those promoting sustainable water use, such as water pricing and water use prioritisation, control over abstraction of surface and ground water, implementation of safety water technologies, efficient usage and conservation technologies and reduction of water loss and water friendly farming. Further win-win measures are those that improve the storage capacity of water in the drainage basin such as reforestation and controlled drainage, and in some areas use of desalinised sea water.

To compensate for enhanced eutrophication due to global warming, attention should also be directed at reducing the external loading of nutrients and sediment to the lakes via changes in land management and agricultural practices. This may include measures to reduce soil erosion, application of fertilisers in accordance with the soil retention capacity and crop needs, leading to less intensive land use in catchments with sensitive fresh waters, (re)-establishment of riparian vegetation to buffer nutrient transfers to water bodies and improved design of sewage works to cope with the consequences of flood events and low flows in receiving waters. In-lake measures may include sediment removal, sediment capping (chemical treatment of the sediment) and/or biomanipulation.
Finally, we highlight research steps required to improve knowledge of the impacts of anthropogenically induced changes to lake water level and salinity. Special emphasis should be directed at research into

  • effects of changes in water level on stratification, boundary mixing, nutrient exchange over boundaries, resuspension and the sediment–water exchange of nutrients,
  • effects of extreme variations in water level and salinity on the resistance and resilience of lake ecosystems due to extreme climate events,
  • improved understanding of the coupling of the littoral, benthic and pelagic systems related to water level fluctuations,
  • role and extent of water level fluctuations in promoting macrophyte species richness,
  • interactive effects of water level fluctuations, temperature and nutrients for phytoplankton, phytobenthos and macrophyte growth,
  • ecosystem responses (e.g. macrophyte growth) to water level fluctuations in lakes with different basin morphometry,
  • the ranges of salinity changes likely to induce major ecosystem changes and interactive effects of salinity, nutrients and temperature on the lake ecosystems,
  • interaction of salinity with other stressors (e.g. temperature) and their ecological effects,
  • physiological studies on the effect of salinity and different ionic composition on individual organisms,
  • impact of water level changes and salinisation on ecosystem goods and services.

To handle these challenges, multi-faceted approaches are needed, including establishment of long-term monitoring sites (there are currently very few of these), analyses of existing time series and snapshot data, experiments, palaeoecological analysis and modelling.

Link http://www.refresh.ucl.ac.uk/webfm_send/2400

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