New Climate Model Predicts Major Changes in River Flow and Water Temperature

A series of high-resolution computer models to assist land-use and fisheries managers in coping with the effects of climate change on sensitive peat land river catchments have been developed as part of the NDP funded RESCALE project (Review and Simulate Climate and Catchment Responses) at Burrishoole, Co Mayo. The research was led by the Department of Geography at the National University of Ireland, Maynooth with project partners from the Marine Institute, Newport and the School of Natural Sciences, Trinity College, Dublin. In an Irish context this is the first time that Global Climate Models have been downscaled to a catchment scale and the work has clearly shown that in addition to milder winters and warmer summers we can also expect more frequent flood events in the west of Ireland, with so called 50 year flood events occurring every 7 to 9 years by the 2080s.

The core of the RESCALE project is to adapt current large scale computer models, designed to study and predict the worldwide effects of global climate change, for use as high definition models for smaller local river catchments, such as the Burrishoole. What makes the Burrishoole an ideal subject for study is the fact that an unbroken record of information on water temperature, air temperature, river discharge, rainfall and a host of other factors exists for this catchment dating back to the 1950s. This information collected at the Furnace facility and the neighbouring Met Eireann synoptic station, is invaluable as a resource, not only for measuring physical change over the past sixty years, but also as a proven yardstick to ‘ground-truth’ any computer-generated models describing the likely effects of global warming.

“Under our Sea Change strategy the Institute identified climate change as a priority area for research over the period 2007 to 2013,” says Dr Peter Heffernan, chief executive of the Marine Institute. “Together with two earlier reports arising from the programme, on the status and impacts of climate change in our marine environment, the RESCALE report adds significantly to our understanding of what is going on in our oceans, rivers and streams. New evidence is emerging that the changes we are seeing in marine and freshwater biological systems are associated with rising water temperatures, as well as related changes in salinity, dissolved oxygen and the circulation of water.”

According to the RESCALE report, high water temperatures in late winter and early spring can have negative impacts on the survival of salmon eggs and young fish, while extreme high temperatures and low water levels during summer can increase the number of deaths in returning adult salmon. Other factors related to the changing climate impacting on salmon and trout survival and the quality of freshwaters are dissolved oxygen, acidity and the amount of dissolved carbon, or colour, in the water.

While increased water temperatures can have negative impacts on fish such as salmon and trout, their effect can be positive for other species, such as eels, which may benefit from raised water temperatures during the freshwater phase of their life cycle.

The study was primarily concerned with the aquatic environment and the migratory fish in particular but the predicted changes also have major implications for agricultural and forestry practices these catchments, from now until the turn of the century. The overall changes predicted in air temperature and the changes in the frequency and intensity of flood and precipitation events will need to be taken into account when planning forestry and agricultural programmes well into the future.

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