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And sure enough, they show the arrival of the river.

Now, what we've been doing is we've been going out and collecting bivalves from along our delta area, live bivalves, and then analyzing them. We're looking at their isotopic profiles. And sure enough, they show the arrival of the river. They show the influence of the fresh water and what's really neat is that the US Bureau of Reclamation of course keeps exact numbers on how much water they're releasing from those dams. So we know exactly how much water was flowing into the delta at that time, so again, we can equate the certain amount of isotopic variation with a given amount of fresh water flow.

This is a preliminary picture of the results we've been getting. We have more data points now. This is a comparison of the flow volumes that we've been calculating from the fossils versus the flow volumes the flow volumes recorded in that short historical period before Hoover Dam went up. And what's we'll notice and you'll see what additional data points are telling us, they form a pretty nice distribution of flows from very low, pretty non-existent to reasonably high.

However, as we continue to fill this in, the fossil flows are tending to fall into this region. What this is telling us is that on average, the historical record, the last 100 years in the Southwest United States has been on the really wet side. This is a conclusion that other paleoclimatologists, tree ring scientists and so on have already suggested on the basis of much shorter records. And what we're doing is we pushed this back to the 2,000 year mark now and we're tending to agree with them. So, basically our historical record, which is a record upon which we base all of our plans for development of the Southwest, our international agreements about how much water we keep in the United States and how much water goes to Mexico, is based on a biased sample of the distribution of flows from the Colorado River or a biased sample of the distribution of precipitation in the Southwest. This is, we think, a very significant finding and a reasonably unpopular one, also.

What we're working on now is filling this in. These are all readings from the first 1,000 years. We have funding to go back to the previous 1,000 years. We don't think we can push it back much further because the amino acid aging method becomes quite inaccurate as you go back to 3,000 years or so. But perhaps we'll come up with an alternative way of doing that. Now, another aspect of this work is to ask what are the ecological implications of this picture. What are the ecological implications of this picture, what are the ecological implications of the turn off of the river?


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