资源环境科技发展态势分析平台

Groundwater discharge zones connect aquifers to surface water, generating baseflow and serving as ecosystem control points across aquatic ecosystems. The influence of groundwater discharge on surface flow connectivity, fate and transport of contaminants and nutrients, and thermal habitat depends strongly on hydrologic characteristics such as the spatial distribution, age, and depth of source groundwater flowpaths. Groundwater models have the potential to predict spatial discharge characteristics within river networks, but models are often not evaluated against these critical characteristics and model equifinality in regards to discharge processes is a known challenge. We quantify discharge characteristics across a suite of groundwater models with commonly used frameworks and calibration data. We developed a base model (MODFLOW‐NWT) for a 1570 km² watershed in the northeastern United States and varied the calibration data and settings; control of river‐aquifer exchange directionality; and resolution. Most models (n = 11 of 12) fit similarly to calibration metrics, but patterns in discharge location, flowpath depth, and subsurface travel time varied substantially. We found 1) a 15% difference in the percent of discharge going to 1^st order streams, 2) three‐fold variations in flowpath depth, and 3) seven‐fold variations in the subsurface travel times. We recalibrated three models using a synthetic discharge location dataset. Calibration with discharge location data reduced differences in simulated discharge characteristics, suggesting an approach to reduced equifinality based on widespread field‐based mapping of discharge zones. Our work quantifying variation across common modeling approaches is an important step toward characterizing and improving predictions of groundwater discharge characteristics.