The Potomac River spills over Great Falls west of Washington, D.C.. Marli Miller/UCG/Universal Images Group via Getty ImagesAs climate change warms rivers, they are losing dissolved oxygen from their water. This process, which is called deoxygenation, was already known to be occurring in large bodies of water, like oceans and lakes. A study that colleagues and I just published in Nature Climate Change shows that it is happening in rivers as well. We documented this change using a type of artific