From the April 2007 newsletter:

Here is a NOAA website you can use to gauge the flood conditions at the range before driving over. CLICK HERE

Here are Bob Zander and Doc's observations on flood levels:

If water is at 9 feet above normal level (bottom line on the graph), then water is in front of the 200 yard berm.
At 15 feet above normal level water is in front of the 100 yard berm, so anything above 10 feet above normal level at Spencer
indicates a good chance part or all of the range may be closed.