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Why did early estimates of the Deepwater Horizon oil leak differ from later estimates?

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Fireboats battle a blaze on the Deepwater Horizon drilling rig in the Gulf of Mexico, April 2010. — Deepwater Horizon oil spill Fireboat response crews attempt to extinguish the blaze aboard the Deepwater Horizon oil rig in the Gulf of Mexico, April 21, 2010.

Early estimates of the Deepwater Horizon oil leak differed from later assessments primarily due to the difficulty of measuring the flow from a damaged well located nearly 5,000 feet below the ocean surface.12

Initially, BP estimated that approximately 1,000 barrels of oil were leaking per day. However, as the disaster unfolded and monitoring efforts intensified, these figures were revised significantly upward. By late April 2010, the National Oceanic and Atmospheric Administration (NOAA) estimated the leak at 5,000 barrels per day, and by late May, the U.S. Department of the Interior’s Flow Rate Technical Group determined the rate was actually between 12,000 and 19,000 barrels per day. U.S. government officials eventually suggested that the flow had peaked at more than 60,000 barrels per day.12

These discrepancies highlight the immense technical challenges in quantifying subsea discharges, as the initial estimates were based on limited data that failed to capture the true scale of the rupture.12