Development of Field-Scale Lysimeters to Assess Management Impacts on Runoff

Most empirical studies of field management effects on runoff water quality rely on edge-of-field monitoring, which is generally unreplicated and prone to high variances, or small plots, which constrain the use of conventional farm equipment and can hinder insight into landscape processes that drive hydrology. We sought to develop field-scale lysimeters that were sufficiently large to support assessment of landscape processes but also replicated to allow quantitative comparisons of hydrologic processes. A hillslope underlain by limestone bedrock with a recent history of hydrologic observation was selected in central Pennsylvania. Twelve 15 m x 27 m plots were established and defined by earthen berms on all sides to isolate and collect overland flow, along with tile drains to collect shallow lateral flow. Over three years, considerable variability in site hydrology was observed between lysimeters, highlighting differences in the extent of hydrologic isolation of some lysimeters as well as in flows that potentially bypassed our collection infrastructure. Even so, clear patterns were observed in surface and subsurface flow that enabled grouping of plots based on hydrologic similarities. Results illustrate the experimental opportunities and limitations of developing field-scale lysimeters for agronomic inference.