1. Graduate Student, Dept. of Earth Science, Univ. of California, Santa Barbara, CA 93106; presently, School of Earth and Space Exploration, Arizona State Univ., Tempe, AZ 85282.
2. Assistant Professor, Dept. of Earth Science, Univ. of California, Santa Barbara, CA 93106; presently, Dept. of Geography and Environmental Sciences, Tel Aviv Univ., Tel Aviv, 69978 Israel.
3. Chief Hydrogeologist, Water Replenishment District of Southern California, 4040 Paramount Blvd., Lakewood, CA 90712.
4. Professor, Dept. of Earth Science, Univ. of California, Santa Barbara, CA 93106 (corresponding author).