Modeling of nutrient and sediment concentrations and loads for Clear Lake California, using RLOADEST

Models of daily mass loads of nutrient species constituents and suspended sediment at tributary locations using water quality measurements and stream discharge from river gauging stations were developed to estimate nutrient and suspended sediment mass loads flowing into the Clear Lake watershed. Mass loads are calculated by multiplying stream discharge, measured as volume per time, by constituent concentration, measured in mass per volume. River Load Estimation (rloadest) models were used to complete a regression analysis of the natural logarithm of nutrient concentration as a function of either flow, the square of flow, decimal time, seasonality, or some combination of these terms. The code for rloadest in R is available at: (Lorenz and others, 2017). Rloadest models of daily concentration and daily loads were attempted for the nutrient constituents, and suspended sediment, at 10 sites in the Clear Lake watershed. Rloadest model output includes the daily predicted concentration, in milligrams per liter, and the daily predicted mass load, in kilograms of constituent per day. Loads are aggregated by the model so that monthly or yearly loads are also calculated.