HOW TÓTHIAN CONCEPTS INFLUENCED THE MODERN UNDERSTANDING OF PEATLAND HYDROLOGY

Long after the appearance of Jozef Tóth's seminal paper on groundwater flow in 1963, peatland scientists still believed that the deeper pore waters remained immobile under the topographic highs and lows of raised bogs and adjacent fens. The few hydrological studies done during this period either used simple Darcian or Dupuit-Forscheimer analytical approaches assuming only lateral flow in the uppermost layers of undecomposed peat that contains the living biomass of the vegetation. As late as 1981 this conceptualization remained entrenched in the ecological literature and dominated thinking on interactions among climate, hydrology, and carbon cycling in peatlands.

This concept of lateral flow dominated peatland hydrology was challenged by Siegel (1981,1983) who published the first numerical model simulations of groundwater flow in a large peat basin. He based his conceptual model on one of Tóth's analytical examples showing local groundwater flow cells developing under sinusoidal groundwater mounds on a gentle regional hydraulic gradient. This work suggested that groundwater flow could penetrate deep below the peat veneer under raised bogs in the Glacial Lake Agassiz peatlands of Minnesota.

The results of subsequent field work there and in the Hudson Bay Lowland (Canada)broadly agreed with results of this numerical model but posed new problems: under some large raised bogs, deep recharge cells did not occur. Reeve et al. (2000;2001) investigated the cause of these differences with a more detailed numerical analysis that showed sand and gravel under some bogs focused deep local recharge. All these studies,fundamentally based on of Toth's concepts, helped change the paradigm of modern peatland hydrologeology.

Siegel, D.I., 1981, Hydrogeologic setting of the Glacial Lake Agassiz Peatland, northern Minnesota: U.S. Geological Survey Water-Resources Investigations 81-24, 32 p.

Siegel, D.I., 1983, Groundwater and evolution of the Glacial Lake Agassiz: Journal of Ecology, vol. 71, p. 913-921.

Reeve, A.S., Siegel, D.I., and Glaser, P.H., 2000, Simulating vertical flow in large peatlands, Journal of Hydrology, vol. 227, p.207-217.

Reeve, A.S., Warzocha, J., Siegel, D.I., and Glaser, P.H., 2001,Regional ground-water flow modeling of the glacial lake Agassiz peatlands, Minnesota, J. Hydrology, vol. 243, pp 91-100