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

Abstract

Abstract. The conductivity mass balance (CMB) method has a long history of application to baseflow separation studies. The CMB method uses site-specific and widely available discharge and specific conductance data. However, certain aspects of the method remain unstandardized, including the determination of the applicability of this method for a specific area, minimum data requirements for baseflow separation and the most accurate parameter calculation method. This study collected and analyzed stream discharge and water conductivity data for over 200 stream sites at large spatial (2.77 to 2 915 834 km2 watersheds) and temporal (up to 56 years) scales in the Mississippi River basin. The suitability criteria and key factors influencing the applicability of the CMB method were identified based on an analysis of the spatial distribution of the inverse correlation coefficient between stream discharge and conductivity and the rationality of baseflow separation results. Sensitivity analysis, uncertainty assessment and T test were used to identify the parameter the method was most sensitive to, and the uncertainties of baseflow separation results obtained from different parameter determination methods and various sampling durations were compared. The results indicated that the inverse correlation coefficient between discharge and conductivity can be used to quantitatively determine the applicability of the CMB method, while the CMB method is more applicable in tributaries, headwater reaches, high altitudes and regions with little influence from anthropogenic activities. A minimum of 6-month discharge and conductivity data was found to provide reliable parameters for the CMB method with acceptable errors, and it is recommended that the parameters SCRO and SCBF be determined by the 1st percentile and dynamic 99th percentile methods, respectively. The results of this study can provide an important basis for the standardized treatment of key problems in the application of the CMB.

Optimal Baseflow Separation Through Chemical Mass Balance: Comparing the Usages of Two Tracers, Two Concentration Estimation Methods, and Four Baseflow Filters

“…Studies have found that the effectiveness of using tracers in baseflow separation depends on the correlation between SEC and streamflow rate of the catchment system. Catchments with a higher magnitude of the correlation are more likely to have better performance (Guo et al., 2022; Lyu et al., 2020; Tunqui Neira, Tallec, et al., 2020). Therefore, this study applies a Spearman Correlation Coefficient (SCC) of −0.3 as the threshold to filter the catchments following Lyu et al.…”

“…Therefore, this study applies a Spearman Correlation Coefficient (SCC) of −0.3 as the threshold to filter the catchments following Lyu et al. (2020). For turbidity a threshold of 0.3 is used as it is positively correlated with streamflow (Tilahun et al., 2013; Zarnaghsh & Husic, 2021).…”

“…The selection of 1 year as the threshold is based on the findings from Lyu et al. (2020) and Li et al. (2014), which shows that a minimum length of 6‐month is sufficient to guarantee stable performance.…”

“…Therefore, there is a need to compare the performance of using the power-law function relationship and the interpolation method. (Stewart, 2015); SMM/SMM-modified, the smooth minima method (Gustard et al, 1992) and its modified version (Aksoy et al, 2008) Eckhardt (2005) or the Lyne and Hollick (1979) filters (abbreviated as "E-RDF" and "LH-RDF" in the table). Three studies modeled baseflow and SEC using two-or three-parameter power functions.…”

Roles of forest disturbance and climate variability on streamflow components in snow‐dominated paired watersheds at multiple temporal scales

“…This might introduce uncertainties in the monthly analysis. However, we adopted two methods in assessing annual (3) In this study, although baseflow was separated using the combined baseflow separation method with high accuracy at the annual time scale, there were biased estimations for seasonal baseflow (Lyu et al, 2020;Zhang et al, 2013).…”