Twenty-three softwater lakes in British Columbia, Canada, were sampled before fall overturn to assess thein situconditions associated with internal phosphorus loading. Hypolimnetic sediment and water results were correlated with physical and morphological characteristics of each lake. The concentration of soluble reactive phosphorus (SRP) measured 1 m above the sediment–water interface was strongly correlated with the oxidation reduction potential (ORP) measured at the same depth. Above 0 mV, soluble reactive phosphorus was below 3 μgL−1at 1 m above the sediment–water interface. Below 0 mV, soluble reactive phosphorus concentrations increased exponentially with decreasing oxidation reduction potential. A model using sediment loss on ignition (LOI) and spring overturn phosphorus (SOP) can predict the hypolimnetic oxidation reduction potential. Lakes with areal water loading values < 10 m yr−1typically had higher loss on ignition and spring overturn phosphorus concentrations. High loss on ignition and spring overturn phosphorus concentrations will cause anoxic conditions in the hypolimnion and internal phosphorus loading if the oxidation reduction potential drops below 0 mV at the sediment–water interface. Using the relationships presented, the impact of watershed development and lake restoration projects on internal phosphorus loading can be predicted.