For those who are interested, the formal reference is:

Irrigation Systems for the 21st Century, Proceedings of a Conference
sponsored by the Irrigation and Drinage Division of the American Society
of Civil Engineers and the Oregon Section, ASCE, July 28-30, 1987.

It's published by ASCE - I looked it up on the ASCE website &, as it
happens, it's available but being cleared out, & is being offered at
$9.00 for U.S. sales, $10.80 for international sales, marked down from
$72.00. You can find it at:

http://www.pubs.asce.org/BOOKdisplay.cgi?8703953

Cheers,
Thomas H. Walker, P.G.
twalker@ffeng.com