Water Flow
The flow of water through the Chesapeake Bay has a large impact on the period of low dissolved oxygen in the Bay. Events that occur in the spring set up conditions that affect conditions in the Bay throughout the rest of the year.
| In the spring, snow melt and spring rains create a high rate of water flow into the Bay over a 2-week period called the freshet. In years when this flow is very high, the area of low dissolved oxygen in the Bay is larger and more severe. |  |
| This water flow creates stratification, or layering, in the Bay. Dense salty water from the ocean flows in on the bottom of the Bay while the less-dense fresh river water flows out over it, creating a wedge. This layering creates a barrier between the upper area of the water column and the lower area. |  |
| The barrier prevents movement of oxygen from the surface to the bottom of the Bay, which results in hypoxia, or low dissolved oxygen, because oxygen is consumed at a greater rate below the barrier than it can be replenished from above. |  |
Explore these and other related processes in greater detail in the presentation below.