Phosphorus balance in reservoirs of seasonal and long-term regulation

Abstract

The results of model simulation of the phosphorus regime and balance in the Ivankovo, Mozhaisk and Istra reservoirs, which carries out seasonal regulation of the Upper Volga runoff and long-term regulation of the Moskva and Istra rivers, are presented. The components of phosphorus balance were calculated using 2-D box model of heat and mass transfer which provides for day-by-day calculation of spatio-temporal distribution of water quality parameters. Phosphorus balance equation accounts for phosphorus input along the rivers and from the side watershed area, phosphorus regeneration from the bottom sediments, water release to the lower pool, and phosphorus removal through water discharge from the Ivankovo reservoir to the Moscow Canal, as well as the annual increase or decrease of phosphorus mass. Calculations refer to an average water year. A comparative analysis of phosphorus balance components in the Ivankovo reservoir and in the reservoirs near Moscow shows that the processes of sedimentation and regeneration of phosphorus from sediments are more intensive in the Ivankovo reservoir. The main discharge of phosphorus to the lower pool is during the spring flood period in the reservoir of seasonal regulation and during the low-water period in the reservoirs of longterm regulation. Scenario calculations provided graphs of the values of phosphorus retention in a reservoir depending on the increasing external phosphorus load.