Dissolved Phosphorus Dynamics in Headwater Streams

Abstract

A comparative study of seven headwater streams was undertaken to evaluate the relative importance of land use, water discharge, water temperature, solar irradiance, and stream sediment resuspension on levels of dissolved phosphorus (DP). In six of the streams, [DP] increased from early spring to late summer. Nutrient-rich streams are temporally more variable than nutrient-poor ones. Average DP concentrations were not related to the proportion of forest cover but showed a correspondence with underlying geology. Despite the restricted geographical area, relationships between [DP] and water discharge varied in magnitude and in direction among the streams. Simple hydrological models treating the catchments as two-reservoir systems accounted for the different behaviors and performed satisfactorily when the effect of temperature was considered. The residual variance showed no seasonal trends but was significantly correlated with daily solar irradiance for one of the seven streams. Finally, the hypothesis that resuspension of stream sediments affects soluble phosphorus concentration was experimentally rejected.