Regional groundwater flow model construction and wellfield site selection in a karst area, Lake City, Florida

摘要

The city of Lake City is in the process ofexpanding their water supply facilities by 45420 m3day-1(12MGD) to meet future demands. One portion of wellfield siteselection addressed here includes analysis of ambientgroundwater quality and its potential for contamination, thisstudy also addresses the potential impacts of groundwaterwithdrawals to existing legal users, wetlands, surface waters andspring flows. A regional groundwater flow model (MODFLOW)was constructed using existing hydrogeologic data from state andfederal agencies in order to simulate the existing hydrologicconditions of this karst area and to predict withdrawal impacts.The model was calibrated by matching potentiometric surfacemaps and spring flows to within reasonable ranges. Drawdownsin the Floridan and surficial aquifers predicted by the model showminimal impacts to existing legal users and only a 5% reductionin the flow at Ichetucknee Springs ca 21km (13 miles) away. Dueto the karstic nature of the Floridan aquifer here, the equivalent-porous-medium flow model constructed would not beappropriate for contaminant transport modeling. Thegroundwater flow model is, however, appropriate to representhydraulic heads and recharge/discharge relationships on a regional scale.