Apply a Particle Tracking Model to Analyze Impacts of Water Intake on Ichthyoplankton Mortality in Tidal Freshwater Region of the Rappahannock River Grant uri icon

abstract

  • Caroline County, Virginia, is seeking to develop a new water supply source in the upstream Rappahannock River that will include the construction of a new water intake. The currently proposed intake is sized to meet the average daily water demand of 7.9 million gallons per day (mgd) and a maximum daily demand of 13.9 mgd, based on projected water demands for the planning year 2035. The proposed intake location is approximately 30 km upstream of the Route 301 bridge over the Rappahannock River near Port Royal. The location of the water intake is influenced by tide, the impacts of the intake on the mortality of ichthyoplankton and the ecosystems in the tidal freshwater region of the Rappahannock River are not well known. Because of the interaction of tide and freshwater discharge, it creates a difficult situation for accurate analyses of environmental impacts of the intake if the impacts are only evaluated locally. One of the key potential impacts of the intake operation on marine resources is causing an increase in the mortality of fish eggs and larvae. Because of the complex geometry and large variations of freshwater discharge in this tidal freshwater region, the tidal flow can transport ichthyoplankton back and forth and increase mortality. However, ichthyoplankton transport pathways and retention time in this region are unknown. It is unclear if ichthyoplankton spawned in this freshwater region will be affected by the intake. To provide sound scientific-based information for the environmental assessment, a numerical modeling approach can be used to simulate ichthyoplankton dispersion and changes in mortality caused by the intake.The Virginia Institute of Marine Science (VIMS) will support Caroline County in conducting the modeling study. We propose to develop a fine-resolution model to simulate tidal flow and larval transport processes. With the use of the model, the changes in hydrodynamic conditions in terms of currents and water exchange can be evaluated, which will provide good information for understanding the impacts of intake on the ecosystems of the adjacent region and ichthyoplankton transport. We will use a particle tracking model to simulate the movement of fish eggs and larvae and to accurately evaluate probabilistic increases of mortality due to the intake under different hydrological conditions. The model results can provide information for an accurate risk assessment.

date/time interval

  • March 2021 - February 2022

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