Precipitation Enhancement Program

The Edwards Aquifer Authority has operated a Precipitation Enhancement Program (PEP) since 1999 through a “turn-key” contract with a private contractor. This program cost the Authority approximately $500,000 per year and this program continued through the end of the 2001 PEP season. In an effort to enhance services and reduce costs, the Authority contracted with the South Texas Weather Modification Association (STWMA) of Pleasanton, Texas, and the Southwest Texas Rain Enhancement Association (SWTREA) of Carrizo Springs for its 2002 Precipitation Enhancement Program (PEP).

The Authority renewed contracts with STWMA and SWTREA in 2003.The cost for the Authority to run the 2003 PEP programs is $124,776, at a cost of approximately $0.4 per acre within the service area. In 2002 and 2003 the service area includes Bandera, Bexar, Medina and Uvalde counties. The STWMA is responsible for cloud-seeding over Bandera, Bexar and Medina counties and the STWMA is responsible for cloud-seeding over Uvalde County for the Authority.

A licensed meteorologist monitors clouds that may be candidates for seeding. Once a cloud is selected, a pilot flies above it or under it and burns a flare containing tiny particles of silver iodide and moisture accumulates around the particles forming raindrops. Clouds only have about a 20-30 minute life span, however, research indicates that seeded clouds have double the life span; therefore, increasing rainfall.

Research funded by the Authority indicates that precipitation enhancement can result in increased rainfall of about 20% to 50% with the later figure now appearing to be the most probable. The present benefit of the PEP program is increased rainfall and recharge to the Edwards Aquifer. Additional benefits would be seen even if the rain doesn’t fall over the aquifer’s Recharge Zone because rainfall keeps homeowners from having to water lawns and farmers from having to irrigate crops.