Seal of Newport News, Virginia

Dock at Lee Hall Reservoir

Problem  

     The City of Newport News, Virginia, provides treated water for public supply to many of the communities of the lower York-James Peninsula. Raw water is obtained from a combination of surface-water and ground-water sources and is pumped into Harwoods Mill and Lee Hall Reservoirs (the terminal reservoirs). The water is subsequently withdrawn and treated. Although the primary purpose of these reservoirs is water supply, the reservoirs are also used for recreational fishing and other non-contact, water-based activities.

     Although concentrations of dissolved phosphorus in the reservoirs are low, sufficient phosphorus appears to be available to stimulate algal growth. Abundant algae in the water make it difficult to treat the water and increase treatment costs. Consequently, the city routinely applies copper sulfate to the reservoirs to control algal growth. Such treatment, however, can have undesirable effects because copper has a maximum concentration allowable in public drinking-water supplies and can accumulate in bed sediment. Phosphorus also can accumulate in bed sediment and then can be released back into the water column to subsequently stimulate additional algal growth. The City of Newport News, therefore, is assessing its algal management strategy and is identifying possible alternative strategies for the control of algal growth. To develop a long-term strategy to manage algal growth, the city must better understand phosphorus sources and cycling in the reservoirs.

Objectives

     The objectives of this project are to: 

• evaluate the role of phosphorus sources and cycling in stimulating algal growth in the terminal reservoirs and 
•  identify and assess potential alternatives for managing phosphorus and algal growth in the reservoirs.

Relevance and Benefits

     Information on phosphorus sources and cycling in the terminal reservoirs will help the City of Newport News better manage the reservoirs for public-supply and recreational purposes. In doing so, the city can better provide a consistently potable water supply at a reasonable cost to the public. The public will benefit by 

• having a water supply with fewer taste and odor problems at a reasonable cost and 
• having improved recreational opportunities.

Approach

     The study will evaluate the role of phosphorus sources and cycling in stimulating algal growth in the terminal reservoirs by evaluating the relative contribution of different phosphorus sources. To accomplish this, the project will evaluate five main components that affect phosphorus sources and cycling:  

• the natural inflow of phosphorus from the reservoir watersheds, 
• the hydraulic characteristic of the reservoirs and quality of water in the water column of the reservoirs (including the effects of pumpage from outside sources and the phosphorus contained in settling sediment),
• the composition and distribution of reservoir bed sediment, 
• the pore-water quality, and 
• the transport of phosphorus from bed sediment.