From Fishpond to Farmland – The Transformation of Lake Lorsch

As part of the project “The River Weschnitz Fluvioscape and its Interaction with the Lorsch Abbey”, a focal point is an artificial fish pond situated within the natural floodplain, used from 1474-1718/20. Located south of Lorsch in the present-day Hessian Ried, the pond—known as Lake Lorsch—is notable not only for its size, nearly four square kilometers, but also for the minimal construction required for its creation and maintenance. As Henselowsky et al. (2025) demonstrate, favorable environmental conditions—a high groundwater table, sedimentological sealing, and a location below the receiving water body, the River Weschnitz—enabled the project with little structural intervention.

Later anthropogenic modifications—particularly post-use terraforming—have obscured original features such as inflow and outflow channels, hatching ponds, and bank reinforcements. The initial phase of this study therefore focuses on identifying and isolating these later impacts, especially dense drainage networks and current turf and agricultural use, to better reconstruct the late medieval fluvial landscape.

Geophysical methods (ERT, EMI and core analysis) have confirmed the presence of structures derived from historical cartography and archival documentation. Nonetheless, sedimentological evidence is limited: lacustrine horizons are absent, phosphorus levels only slightly elevated, and fine-grained fluvial deposits minimal. This reflects the lake’s unique operational history; archival records show it was periodically and deliberately drained, sometimes remaining dry for months or years. While intended to boost nutrient availability and fish productivity, this practice prevented the long term development of lacustrine soils and stratigraphy in general.