Phosphorus Models Applied to New Mexico Reservoirs

Abstract

Many empirical, mass balance phosphorus models have been developed and tested on northern temperate lakes. Sixteen published models were tested on New Mexico reservoirs to determine their usefulness in simulating reservoir behavior in the Rio Grande basin. The models overpredicted measured, seasonal phosphorus concentrations in the reservoirs. Models with settling velocities that varied with selected hydrologic variables performed better than models with constant settling velocities. Model predictions were improved by establishing a relationship between removal rates of phosphorus and certain hydrologic variables. The relationship between settling velocity of phosphorus and reservoir flushing rate was the most significant. Flushing rate also was significantly correlated with the loading rate of total suspended solids. This helps to explain the removal rates observed in the reservoirs. High flushing rates bring in high loads of suspended solids, which may combine with phosphorus and remove it from the water column as the solids settle.