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Key challenges facing the application of the conductivity mass balance method: a case study of the Mississippi River basin

“…Given the importance of baseflow, many methods have been proposed for baseflow separation. Although these methods can be categorized according to various conditions (Stewart et al, 2007;Zhang et al, 2013;Miller et al, 2014;Lott and Stewart, 2016), they can generally be divided into two groups, namely non-tracer-based and tracer-based separation methods (Li et al, 2014). Non-tracer methods mainly include graphical and low-pass filter methods which only require stream discharge data (Nathan and McMahon, 1990;Eckhardt, 2008).…”

“…The advantage of these methods relates to their use of site-specific variables, such as concentrations of chemical constituents, which are a function of actual physical processes and flow paths in the basin responsible for generation of different flow components. Therefore, chemical mass balance estimates of baseflow are often considered to be more reliable than those from graphical hydrograph separation estimates (Stewart et al, 2007). The principal disadvantage of mass-balance methods relates to their requirements of both observed discharge and chemical concentration data, which are not widely available, especially over a long period.…”

“…In an analysis of hydrograph separation conducted using different geochemical tracers, Caissie et al (1996) demonstrated that SC was the most effective single variable for quantifying the runoff and groundwater components of total streamflow since SC is a natural environmental tracer that can be inexpensively measured concurrently with streamflow (Kunkle, 1965;Matsubayashi et al, 1993;Arnold et al, 1995;Caissie et al, 1996;Cey et al, 1998;Heppell and Chapman, 2006;Stewart et al, 2007;Pellerin et al, 2008).…”

“…The conductivity mass balance (CMB) method converts specific conductance to a baseflow value using a twocomponent mass balance calculation (Pinder and Jones, 1969;Nakamura, 1971;Stewart et al, 2007):…”

“…These questions have been partially answered by past studies. Miller et al (2014) concluded that the CMB method was successful in quantifying baseflow in a variety of stream ecosystems, including snowmelt-dominated watersheds (Covino and McGlynn, 2007), urban watersheds (Pellerin et al, 2008) and a range of other settings (Stewart et al, 2007;Sanford et al, 2011;Lott and Stewart, 2016). However, most chemical hydrograph separation studies have been conducted in small watersheds and for short durations (Miller et al, 2014).…”