[1] Univ Wyoming, Dept 3925, Laramie, WY 82071 USA
[2] Colorado State Univ, Dept Agr & Resource Econ, Ft Collins, CO 80523 USA
[3] Utah State Univ, Dept Appl Econ, Logan, UT 84322 USA
[4] CH2MHill Inc, Wilmington, DE 19803 USA
[5] Utah Dept Environm Qual, Div Water Qual, Salt Lake City, UT 84114 USA