Bishop, K; Hauhs, M; Nyberg, L; Seibert, J; Moldan, F; Rodhe, A; Lange, H; Lischeid, G: The Hydrology of the Covered Catchment: Water Storage, Flowpaths and Residence Times in Hultberg,H and Skeffington,RA (eds.): Experimental Reversal of Acid Rain Effects: The Gardsjön Project, John Wiley & Sons Ltd., 109-135 (1998)
Abstract: The hydrology of the G1 ROOF catchment was analysed using a variety of hydrometric and tracer techniques that sought to identify flowpaths and residence times. These studies found that runoff response to precipitation was rapid once a water storage threshold is passed (200 mm). Water storage within the catchment varied from 125-245 mm, with a 3 year average of 191 mm. The proportion of this storage which was held in the unsaturated zone above the water tabie went from over 90 % at low flow to a minimum of 40 % at peak flow. Much of the runoff was transmitted in the upper three decimetres of the soil. Some tracer studies found that the residence time of water within the catchment can be described by an exponential distribution. The mean residence time varies from 5 days at the highest observed flow rates to 175 days at the lowest observed flow rates. A small portion of the water can move at rates of several metres per hour during periods of high flow. The spatial pattern of residence times within the catchment, as observed from a step-shift of the d18O in precipitation after the roof was built, was consistent with the general picture of flowpaths arrived at from hydrometric measurements.While these investigations have identified many hydrological features typical of Fenno-Scandian till catchments, the shallow soils, high organic matter content in the B horizon, and strong lateral concentration of flow across the concave topography of the catchment are important to bear in mind when generalizing the hydrochemical response of the Covered Catchment Experiment to other catchments.