Energy: Conowingo Dam

Here we are at the Conowingo Dam in Darlington, Maryland. The dam, built in 1928, sits near the mouth of the Susquehanna river. About 50% of the freshwater entering the Chesapeake comes from the River, so that’s quite a bit that passes through the dam before entering the Bay. You can see how the dam may play a pretty impactful role in the health of the Chesapeake. So, coming here, I wanted to take a closer look at that role and explore the good and the bad.

Let’s start with the good…

For myself, the most important benefit from the dam is that it is a “clean” source of renewable energy. It runs on water and gravity. No burning of gas, coal, or any fossil fuels are needed to create energy. Over the course of a decade the dam will provide as much energy as burning 7.5 million tons of coal. Each year it prevents about 880,000 tons of greenhouse gases from entering the atmosphere, and is the source of about 55% of Maryland's renewable energy. And on average it powers about 165,000 homes. It’s also a favorite spot for birdwatchers as bald eagles are seen here in large groups from the fall to spring. It’s an easy spot for them to catch fish and for the bird watchers to take pictures (the dam even has a photography competition on site to see who takes the best bald eagle picture).

Now with all of that said, the dam does have it’s problems.

The most pressing issue? Nutrients entering the bay. The problem is that the reservoir behind the dam has filled up with sediment. What used to be a gate to hold back nutrients like phosphorus and nitrogen from entering the bay, is now essentially wide open. This harms the Bay greatly, as those nutrients fuel algae growth. These algae blooms can block light from reaching the bottom of the Bay, impacting submerged aquatic vegetation. They also deplete the water of oxygen, creating dead zones. Nutrient reduction is essential and at the center of Bay restoration. In fact, in 2014, the Bay watershed states signed the Chesapeake Bay Watershed Agreement with the EPA promising to reduce these nutrients. It wasn’t just a signed promise though, it was a legal binding agreement with specific and measurable goals. With the states working towards reducing nutrients to the Bay, and the Conowingo Dam’s lost trapping capacity, analysis shows that an additional 6 million pounds of nitrogen and 260,000 pounds of phosphorus need to be reduced in order to mitigate the dam’s lost ability to hold back nutrients.

In the 2014 agreement, each state was to provide its own watershed implementation plan to show how they’d reduce nutrients. The Conowingo Dam plays such a critical role in this reduction that the dam itself has its own watershed implementation along with the states. Overall, the big issue is the dam can no longer trap nutrients from entering the Bay. This is especially true during heavy rainfall when settled nutrients are flushed out of the reservoir. Not just that, but debris and garbage are also washed into the Bay causing a headache of a cleanup. Now, the Dam does have skimmer boats that collect debris before it enters the Bay. In 2018 alone, they collected over 4,000 tons. But during heavy rain when the reservoir begins to overflow, the gates of the Dam are opened and all debris and nutrients are washed downstream where it becomes someone else's problem.

In 2019, there was a $200 million settlement made with Maryland that would require the dam to further contribute to the Bay’s restoration. A 50 year contract renewal in 2021 also included provisions that required the Dam to provide an additional $700 million into Bay restoration efforts. With that money, Exelon (the company that owns the dam) has promised enhancements to water quality below the dam, improved fish and eel passage, aquatic habitat restoration efforts, and debris removal. $700 million dollars is a ton of money (Exelon had over 33 billion dollars in revenue in 2020), but many environmentalists didn’t think the 2021 contract with the state went far enough. They say it left the dam off the hook. Some suggesting that instead of actually working on the issues at the dam, Exelon just sends the money to organizations that provide clean up once the damage is already done.

The Conowingo Dam has some benefits for sure, but there’s a lot of issues that it isn’t necessarily improving when it comes to Chesapeake restoration and health. No matter where you stand on the issues with the dam, most parties agree that work needs to be done on reducing nutrients from their original sources (runoff from agriculture, urban areas, or water treatment plants just to name a few). Phosphorus and nitrogen aren’t coming from or created by the dam itself. They’re coming from the thousands of miles upstream that lead to the dam. The only guaranteed fix seems to be reducing the nutrients from the source, which the dam makes sure to point out in their watershed implementation plan. What are your thoughts on the Dam and what do you think needs to be done? What are some options that can be implemented upstream that would help reduce nutrients from passing through the Conowingo Dam? Sound off below. Thanks.