New research is assessing how climate change will affect our lakes and streams, writes Dick Ahlstrom
More heavily polluted drinking water, washed-out bridges and river banks, destroyed salmon and trout spawning beds, increasingly silted lake beds. These are just a few of the predicted results of climate change on our inland waterways.
The Marine Institute and Trinity College in Dublin have joined an EU initiative called Climate and Lake Impacts in Europe, or Clime, to assess how our lakes and rivers might be affected in light of rapid climate change.
"Regardless of the international protocols like Kyoto, we are going to see climate change in the next 30 to 40 years," says Dr Russell Poole of the Marine Institute's aquaculture and catchment management services. "This is regardless of what we do with carbon-dioxide emissions. We are going to have to cope with it. We have made our bed and we will have to lie on it."
Clime is an attempt to plug live environmental data into powerful computer models to gain insights into how changing climate might affect us, explains Poole. The three-year project, supported by the European Commission's environment and sustainable-development programme, involves 10 EU states applying a great deal of expertise to the problem.
Each participant will contribute to the very large data stream, he says. The institute will step up its already extensive monitoring of Lough Feeagh and the Burrishoole catchment, adjacent to its lab in Newport, Co Mayo. It will also measure dissolved organic carbon (DOC) levels in Dublin's main reservoir, Poolaphouca. Trinity will measure nitrogen and phosphorus in the lakes of Killarney and also do some modelling.
Poole, Brendan O'Hea, an institute colleague, and Dr Norman Allott of Trinity's department of zoology are the leading Irish participants in Clime. The team already has a good idea of what to expect given that change is already under way, says Poole.
Most predictions, including work done at NUI Maynooth, point to a huge, 25 per cent drop in summer rainfall but increased rain during the winter. "The east coast will be hit more in the summer deficit than the west and the west would get an increased risk of flooding in the winter," he says. "You are not talking 200 years from now, you are talking about 30 to 50 years."
There are signs already of this greater seasonality in rainfall, he believes. The initial risk is caused by the erosive force of these flash floods, which can dig out and collapse bridges and waterside construction and also wash out embankments.
Soil lifted by the fast-moving water will increase silting of the gravel spawning beds favoured by trout and salmon. What you will probably see, he says, is fish community change, with coarse fish such as pike and roach replacing trout. "We are certainly seeing an increase in sediment deposition in lakes."
Drier summers and wetter winters will also have a strong influence on DOC, he believes. "Some of this is happening already. A bog is naturally anoxic and self-preserving, but if it dries out and is open to the air it breaks down. When it gets wet again, material leaches out." The result is higher levels of "humic organic acids" in the water.
This will accelerate the natural process already seen near boglands, the discolouration of local watercourses. "It is the orange colour you typically see," says Poole. Although not toxic, high levels of discolouration can inhibit ultraviolet water sterilisation systems, he says, adding to the costs of making the water fit to drink. Higher water acidity also means more dissolved metals in the water, such as iron, manganese and aluminium.
The ten square kilometre Burrishoole catchment will provide a focus for the research, he says. "We are using climate data we have collected and the environmental data we are collecting in the catchment for the last few years."
The centrepiece of the catchment is Lough Feeagh, a four-kilometre-long lake and its associated 30 miles of feeder and discharge streams. The Newport-based lab is using automated monitoring systems to collect vast amounts of data, some of it recorded every 15 minutes and most of it several times a day. "It is very high resolution, very intensive monitoring," says Poole.
The team records temperature, rainfall, evaporation, cloud cover, wind speed and direction, lake and stream water levels, suspended solids and sedimentation, DOC, nitrogen and phosphorus. There are temperature sensors every 200 yards or so in watercourses.
Poole and his colleagues are finding huge differences between streams to the west and east of a slope. There can be 200 per cent differences in rainfall within this confined area, he says.