Well, we warned ya. That estimate didn’t last very long.

Yesterday the government released new estimates of how much oil was spewing on a daily basis from BP’s Macondo well into the Gulf of Mexico, based on much better data and hi-def video. It’s worse than we thought: initially the well was gushing oil at a rate of 2.6 million gallons (62,000 barrels) per day. At the time, BP and the Coast Guard claimed the spill rate was 62 times smaller than that — 42,000 gallons (1,000 barrels) per day.

Eight days into the spill, NOAA got involved and raised the estimate to 210,000 gallons (5,000 barrels) per day. BP grudgingly accepted this, and it remained the official estimate of the spill rate – more than 10 times too small, we now know – until May 27, more than a month after the disaster began.

Working with BP as a consultant back in the 1990s, I interacted with some of the smartest geologists and reservoir engineers I’ve known. How could they get this so very wrong, knowing the bottomhole pressure of the well, the size of the reservoir, and the relative percentage of oil to natural gas? And how could the US Coast Guard – the agency that responds to oil and hazardous materials spills of all kinds and sizes – not know that they were dealing with a spill 10 times larger than the official estimate?

As the well leaked oil and natural gas, pressure in the reservoir below gradually lessened, so the flow rate of oil declined to 2.2 million gallons (53,000 barrels) per day. The well was capped on July 15, totally shutting off the flow of oil and gas.

Bottom line: using these new government numbers, and the estimate in a previous Washington Post article that about 33.6 million gallons were diverted from the leaking well and never entered the Gulf, we come up with a total spill of 172.2 million gallons (4.1 million barrels) – more than 15 times the official size of the Exxon Valdez oil spill in 1989.