Effects of sampling frequency on estimates of dissolved silica export by streams: The role of hydrological variability and concentration-discharge relationships

[1] Accurate estimates of solute export are critical for mass balance studies of elemental flux. We explored how variation in hydrology (e.g., flashiness) and concentrationdischarge relationships modulate the effect of solute sampling frequency on bias and precision associated with estimates of dissolved silica export in rivers. Dissolved silica concentration and discharge data from 14 rivers were used to parameterize a nonlinear concentration-discharge model, which was used to generate simulated data for daily dissolved silica concentration for 20 rivers. We determined how solute sampling at various intervals affects bias, precision, and root-mean-square error of export estimates. Bias and coefficient of variation of dissolved silica export increased with coarser sampling intervals. Flashiness and the coefficient of variation of daily discharge typically explained 90% or more of the variation in bias and precision of dissolved silica export, particularly at finer sampling intervals. Our analysis should be useful to researchers and land managers who are planning or evaluating sampling programs to determine solute flux or who seek error estimates for solute export.