Accumulation of water and generation of leachate in a young landfill

Seven-year-old pilot-scale landfills were investigated with respect to operation of the soil cover, accumulation of water and rainfall-leachate Bur relationship. The annual soil moisture fluctuation in the soil cover was of the order of 120 mm. Given an average precipitation of 580 mm, the net water input into the landfill, split into storage and leachate discharge, was on average 250 mm annually. The portion that becomes leachate increased from zero to about half during 6.5 years. The storage increase was about 180 mm/m during this period. Fair agreement between the calculated storage and the moisture content in solid waste samples was observed, A 1-2 month time lag in the net water input-leachate discharge relation was observed. It is suggested that the observed short leachate flux response to a period of infiltration may indicate that a large part of the water is retained by surface tension as thin films in restricted channels, which is overcome by gravity when the input is suddenly increased. The storage-leachate flux relationship was quantified and was found to consist of a family of curves depending on the storage and the rise or decline of leachate flux. (C) 1997 Elsevier Science B.V.