Coupling land use and groundwater models to map land use legacies: Assessment of model uncertainties relevant to land use planning

Groundwater models coupled with GIS analyses can be used to estimate the time for groundwater and solutes to be transported from each location across a watershed to surface water bodies. Coupled to backcast land use models, these estimates can be used to create land use “legacy” maps that quantify the contribution of historic land uses to the groundwater signal arriving at streams. However, groundwater models and backcast land use models contain uncertainties inherent to each model. These uncertainties may affect the outcome of the coupled model and hence their reliability to natural resource and land use planning.In this paper we demonstrate how a simple spatially explicit, multi-uncertainty metric can be used to assess uncertainties from our backcast land use change and groundwater travel time model. We couple five variants of groundwater travel time (GWTT) simulations with 12 variants of historic land uses, and analyze the resulting 60 realizations of land use legacy maps using a spatially explicit, multi-metric uncertainty score. We apply this approach to the Muskegon River Watershed in Michigan, where groundwater flow provides the vast majority of streamflow. Our results indicate that despite uncertainties inherent in both models, townships located in the north-central portion of the study watershed can benefit from using legacy maps as planning tools despite a wide range of evaluated uncertainties.

► A backcast land use model and a groundwater travel time model are coupled.
► Sixty land use legacy maps are created from these coupled models varying parameters.
► Uncertainty in coupled models are assessed for planning units in a regional watershed.
► Simulating urban change and value of conductivity are greatest sources of uncertainty.
► We show that many planning units can use the coupled model despite uncertainties.