USING MULTIPLE CONCEPTUAL MODELS TO UNDERSTAND TRANSBOUNDARY GROUNDWATER FLOWS IN RED CLIFF RESERVATION, WI

Interactions between surface water and groundwater play a crucial role in water resources management. Understanding recharge dynamics in the vicinity of surface water bodies has important implications for stream ecology. A comprehensive approach is required to quantify recharge, defined as the entry of water into the saturated zone. The objective of this study is to investigate the transboundbary water impacts on groundwater-fed streams in Red Cliff reservation in northern Wisconsin under different recharge scenarios.

A modified Thornthwaite-Mather Soil-Water-Balance code (USGS, 2010) which takes spatially variable factors including climate, land cover and topography into consideration to estimate the spatially- variable recharge rate, is used in this study. The main objective of this study is to understand the probable extent of groundwater recharge areas that contribute to the streams of the Red Cliff Reservation. Stream baseflows and the water configuration can be estimated using the groundwater flow model developed using MODFLOW (Harbaugh, 2005; Harbaugh et al., 2000). Three groundwater models, forced by three conceptual models representing different assumptions about estimated recharge and aquifer hydrological properties, are calibrated through PEST (Doherty, 2010a, b) to obtain a plausible model with the best match between simulated observations (heads and stream flows) and corresponding field observations. Capture zones are then delineated by using backward transport of particles through numerical flow modeling with MODPATH (Pollock, 1994). Different conceptual models give similar range of recharge rate throughout the peninsula, while SWB-based recharge show a better estimation. The recharge at this site appears to be predominantly controlled by soil types and land cover. Existing high- capacity wells don’t impact streamflows or recharge to the Red Cliff reservation.