WMOD00595

• Title: Lake Oroville Runoff Enhancement Project - Final Report
• Date: 9/1/1995
• Weather Modification - Doc Type: Report

1. INTRODUCTION

The LOREP lLake Oro~ille Runoff Enhancement Project) was a randomized \\-inter cloud
seeding demonstration project that was conducted by the California D\\~ (Department of
Water Resources). The LOREP was located in the :Nliddle Fork Feather River watershed in
northern California. The Drought Relief Act of 1991 authorized the Bureau of Reclamation
to support the transfer of weather modification technology to the States and to participate
with the States on a matching funds basis for a 5-year period. In November 1991, a joint
EIR/EIS (Environmental Impact R.eview and Environmental Impact Statement) was approved
by the U.S. Forest Senice, Plumas National Forest, which allowed the demonstration project
to begin in the 1991-92 winter season. Although the \\-inter of 1991-92 marked the first year
of the 5-year program to quantifY precipitation increases possible from cloud seeding, DWR
had been testing the required program equipment and facilities since 1988. The project plan
was for randomized cloud seeding experiments, using liquid propane as the seeding agent,
to be conducted during five consecutive winter seasons. Through a Cooperative Agreement
between DWR and Reclamation (Bureau of Reclamation), DW""R provided funds to
R.eclamation for technical assistance on this project.

The purpose of the project was to increase snowpack runoff to Lake Oroville, the main
reservoir of the State \Vater Project located in northem California. The goal of the project
was to demonstrate through physical and statistical analyses the increases in winter
sno~vpack obtainable by seeding \\inter storms \\-ith liquid propane. The project was hoped
to provide additional water to help alleviate drought and provide a working t.echnology for
other \Vestern States that need additional water supplies (Sward, 1991).

Propane was tested as the seeding agent instead of the more conventional AgI (silver iodide)
because measurement of mountaintop icing showed more hours of SL \V (supercooled liquid
water) in the -1 to -5 "C temperature window than at the colder temperatures (~-5 OC) where
AgI is more effective. The use of ground-based liquid propane dispensers is believed to have
a better chance to ma.ximize precipitation, given the warm temperature of California storms.
This cloud-seeding project is the first of its kind in the country that has used liquid propane
to seed winter clouds to increase snowfall (Sward, 1991). The process involved releasing
pressurized propane into cold clouds moving up the slope of the Sierra Crest. As propane
evaporates, it lowers the surrounding air temperature to well below -40 oC (-40 OF), producing
billions of tiny ice crystals. These crystals grow in size at the expense of cloud droplets and
eyentually form snO\vfl~kes. Propane works well because it can drop the ambient air
temperature to -100 OF without freezing itself. R.eynolds (1989, 1991, 1992a) describes the
original design, development and testing of the remote, ground-based liquid propane
dispenser used as the seeding de\ice on this project. R.eynolds' calculations estimating
increased runoff from an augmented snowpack in the study area are included as appendix D.

The LOREP was suspended after completion of only 3 }T of the intended 5-}T project. D\VR
management suspended this project prematurely because of three overriding considerations.
First, the Reclamation project scientist who designed and implemented LOREP took a new
position with the Kational \Veather Service. This move was in response to R.eclamation's new
commitment to transform from a water resources development agency to a premier wat.er
resources management agency. Consequently, Reclamation work on research programs t-o
develop water resources, such as weather modification, will be phased out. Secondly, the
three winter seasons completed have been extreme, either excessively dry as in 1991-92 and