Water Nuggets Practice Exam 2025 – Complete Study Resource

Maintaining dissolved oxygen (DO) concentration in a thermally stratified reservoir is essential for the health of aquatic ecosystems. The correct answer involves destratification and hypolimnetic reaeration. This method addresses the challenges that arise when a reservoir undergoes thermal stratification, forming layers that can hinder the natural mixing of waters.

During stratification, the upper layer (epilimnion) is warmer and more oxygen-rich, while the lower layer (hypolimnion) can become depleted of oxygen, especially if organic matter decomposes at the bottom. Destratification helps mix these layers, allowing oxygen-rich water from the surface to reach the bottom layer. This process can be accomplished through mechanical methods, such as using aerators or mixers that physically disrupt the stratified layers. Hypolimnetic reaeration specifically refers to the infusion of oxygen into the deeper water layer, vital for maintaining aquatic life and reducing the risk of fish kills due to low oxygen levels.

The other methods listed, such as adding copper sulfate, bluestone, or alum, are not suitable for maintaining DO concentration. They may serve different purposes, such as controlling algae growth or clarifying water, but do not directly address the oxygen depletion that can occur in stratified