New Water for Northern Plains

Current research follows a plan to progress from experimental projects on individual clouds (or areas less than 1,000 sq miles) to pilot projects involving several thousand square miles to operational projects over areas which could involve tens of thousands of square miles. Research to date has shown that individual clouds exist that can be made to produce additional precipitation by seeding, and a beginning has been made on defining the meteorological conditions for which cloud seeding can produce additional useable precipitation. Results of cloud seeding for hail suppression are mixed. Pilot project extending over several thousand square miles are now needed to determine whether the effects found on experimental projects can be extended to larger areas. There is a need to leave a limited number of cases (randomly selected) unseeded as controls to monitor the effects of the weather modification treatment. It is proposed that the fraction left unseeded change from 50% for experimental projects to 25% for pilot projects to 10% for operational projects.