Application of isotopic tracers to determine water residence times in multi-scale water management

Abstract

Sustainable use and management of aquifers and their interaction with rivers and lakes requires qualitative and quantitative assessment of aquifer hydrogeology and dynamics, and the use of conceptual and/or hydrologic models. Hydrologic observations in addition to estimation of aquifer properties are needed for numerical groundwater models. Recently, isotope techniques such as groundwater age dating (where "age" is the time between recharge and sampling), are being used to develop conceptual models of groundwater flow and provide information for model calibration. A wide number of isotopes can be used to estimate groundwater ages ranging from decades to thousands of years, and each tracer has advantages and disadvantages. Field sampling requirements for different tracers, as well as the model assumptions and corrections necessary to estimate groundwater ages, are non-trivial, especially when applied in different climatic and hydrogeological settings. The goal of this project is to combine the expertise of the University of Nebraska-Lincoln Water Cluster research group (UNL-WC) in age-dating "young" groundwater with the expertise of scientists at Universidade Estadual Paulista (UNESP) in age-dating "old" groundwater to improve ongoing studies (including FAPESP-funded research). We will also conduct workshops in Nebraska and Brazil, and seek to develop collaborative proposals related to water management in two globally important aquifers the Guarani Aquifer (Brazil) and the High Plains Aquifer (USA) (AU)