Feasibility/Design Study for a Cloud Seeding Program in the Yadkin River Basin, North Carolina

Abstract

North American Weather Consultants (NAWC) was contracted by Cube Hydro Partners, LLC with headquarters in Bethesda, Maryland, to conduct a cloud seeding feasibility/design study for the Yadkin River Basin located in North Carolina. This study was prepared in conformance with American Society of Civil Engineer’s Guidelines and Standards. The goal of the program would be to augment precipitation over the Yadkin River Basin to increase streamflow into a series of Cube Hydro reservoirs along the Yadkin River. This increased streamflow would then be used to generate additional hydropower (clean energy) from facilities installed on project dams. NAWC compiled a site-specific climatology for this Basin. Both ground-based and airborne seeding was considered, but only airborne seeding was recommended due to the lack of significant topographic features in the Basin and the rather high average height of the -5° C level in potentially “seedable” storms (630 mb), as well as other meteorological factors. Regression equations relating precipitation to streamflow suggest that seeding only during the cool season produces streamflow increases not only during the cool season, but would also have a residual effect that increases streamflow throughout the remainder of the year. Overall, cool-season seeding is likely to have about 1.4 times as much impact on total streamflow as warm-season seeding (assuming the same increase percentage-wise in precipitation), with the cool season increase more evenly distributed throughout the year in terms of the resultant streamflow. Therefore, only a cool season program was recommended. Detailed examination of a 3-year cool season storm climatology in the Yadkin Basin suggest that aircraft-based cloud seeding during the cool season could enhance precipitation by 4.1%, resulting in an estimated 5.2% increase in annual streamflow (109,200 acre-feet). Cost estimates were prepared for a seasonal program. Once the estimated costs were established, NAWC was able to develop benefit/cost ratio estimates. Using information provided by Cube Hydro, NAWC calculated a potential benefit/cost ratio of 5/1. NAWC concluded that the proposed program was feasible based upon both technical and economic considerations as recommended in the “Guidelines for Cloud Seeding to Augment Precipitation”, Third Edition by the American Society of Civil Engineers (ASCE,2016).