Probably just winter draw down in case of large amount of rainfall. Corp of Engineers has a website to check it out.

compared to historical average that it seemed to be something else.

Another DUer said they are still working on the emergency spillway so its likely being managed extra prudently

OROVILLE — Two years ago today, about 188,000 people were ordered to evacuate for fear the damaged Oroville Dam spillway would fail.

While the worst fears never materialized, the incident had impacts still felt in the community. It also spawned new legislation related to dam safety, a modern rebuild of the spillway, and many lawsuits against the state Department of Water Resources.

This is by no means a comprehensive summary, but below are some major updates related to the spillway crisis.

Reconstruction continues

Both the main and emergency spillways are still under reconstruction.

DWR said the main spillway was ready to be used again by its Nov. 1, 2018, deadline. However, some minor work there is still ongoing, including site clean-up and sidewall backfill. Contractors are also working to bring the hillside back to its natural state by grading and hydroseeding. That work will be ongoing “well into spring 2019,” according to DWR.

Work on the emergency spillway continues as well. Currently construction crews are placing a concrete cap on top of a new buttress made of roller-compacted concrete.

https://www.times-standard.com/2019/02/12/oroville-dam-two-years-after-the-mass-evacuation-heres-where-we-are/?utm_content=tw-eurekaTS&utm_source=twitter.com&utm_medium=social&utm_campaign=socialflow

They are still working on it ...

it makes sense that they are managing it conservatively since it still under repair