MIX (2003, 2013)
Mixing calculations involve computing the ratios in which two or more end-members are mixed in a sample. Mixing calculations are useful for a number of tasks in hydrology, such as hydrograph separation, water or solute mass balances, and identification of groundwater recharge sources. Most methods available for computing mixing ratios are based on assuming that end-member concentrations are perfectly known, which is rarely the case. Often, end-members cannot be sampled, and their concentrations vary in time and space. Still, much information about them is contained in the mixtures. To take advantage of this information, we present here a maximum likelihood method to estimate mixing ratios, while acknowledging uncertainty in end-member concentrations. Given that the software was developed in FORTRAN, it requires one input file and generates two output ones, both files being very long. The input file contains information about the water samples (which can be split into “Sources” or “Wells”), their end-member concentration values and covariance. Additional information such as restrictions or initial conditions can also be set.
