ForSite | Nutrient exchanges | Drainage

Nutrients leave forests in the liquid phase by overland flow and soil throughflow, exiting to surface-runoff channels and groundwater. The amount of water leaving the site can be calculated as precipitation minus evapotranspiration. The mean precipitation in Ireland is about 1000 mm/year, with perhaps 600 mm accounted for by evapotranspiration. Total soil percolation varies from about 400 mm/year in the drier east midlands to over 2 m/year in the mountains of the west of Ireland.Map of leaching, or soil-throughflow amount. Where low values occur in high-rainfall areas (peatlands of the west), the water output is chiefly in surface runoff rather than soil throughflow.

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