**Shwet Prakash, Venkat Kolluru and Carol Young**

**Abstract:** Ballast water systems in large LNG carriers are essential for proper operations and stability. Water withdrawn from the surrounding environment to supply to the ballast can pose entrainment and impingement risk to the resident fish population. Quantification of these risks and the net effect on population is usually quite challenging and complex. Various methods over the last several decades have been developed and are available in the literature for quantification of entrainment of mobile and immobile lifestages of resident fish. In this study, a detailed 3-dimensional model was developed to estimate the entrainment of ichthyoplankton (fish eggs and larvae) and fish from an estuarine environment during the repeated short-term operation of a ballast water intake for an LNG carrier. It was also used to develop a zone of influence to determine the ability of mobile life stages to avoid impingement. The ichthyoplankton model is an Equivalent Adult Model (EAM) and assesses the number of breeding adults lost to the population. The EAM incorporates four different methods developed between 1978 and 2005. The study also considers the uncertainty in estimates for the lifestage data and, as such, performs sensitivity analyses to evaluate the confidence level achievable in such quantitative estimates for entrainment.

Reprinted from *J. Mar. Sci. Eng.* Cite as: Prakash, S.; Kolluru, V.; Young, C. Evaluation of the Zone of Influence and Entrainment Impacts for an Intake Using a 3-Dimensional Hydrodynamic and Transport Model. *J. Mar. Sci. Eng.* **2014**, *2*, 306-325.

#### **1. Introduction**

Intake systems are used throughout the world for a variety of reasons including: ballast water systems, cooling water systems, drinking water systems and industrial use systems. In all of these intake systems, water is withdrawn from the surrounding surface waters and can entrain ichthyoplankton (IP) and other life stages. Quantification of entrainment and the resulting effect on a population is usually quite challenging and complex. Various methods over the last several decades have been developed and are available in the literature for quantification of entrainment of mobile and immobile lifestages of resident fish. However, accurate estimation relies heavily on field sampling, understanding of the fish population and the choice of appropriate methodologies. Due to the differences in volitional movement, planktonic stages must be evaluated differently than swimming life stages.

Typically the risks to fishes associated with intake operations can be categorized into the following main impacts:


Figure 1 shows a conceptual model of the various capture zones.

**Figure 1.** Conceptual model of capture zones for planktonic and mobile life stages.
