An Update on the North Dakota Cloud Modification Project

Abstract

Operational cloud seeding has been conducted over parts of western North Dakota since the 1950’s. Operations began with ground based seeding in the early years, but by the early 1960’s airborne delivery of seeding agents became the preferred method. Currently, a combination of cloud base and cloud top seeding is employed on the North Dakota Cloud Modification Project (NDCMP) using an acetone-based AgI solution, end-burning AgI flares, ejectable AgI flares, and dry ice pellets  (CO2) as seeding agents. The goals of the dual-purpose project are to increase growing season precipitation and reduce crop and property damage caused by hail. The project is funded by county tax levies and limited state cost-sharing. Operations are conducted from June 1 through August 31 each year, twenty-four hours a day, seven days a week. Every evaluation of the project has indicated beneficial results, but with varying statistical confidence. Rainfall increases on the order of 7 to 15% have been realized in and slightly downwind of the target counties. Crop-hall damage as been reduced by 45% and wheat yields have increased by 5.9%. A benefit-to-cost ratio of 35:1 has been realized for wheat production alone.