Harvesting the Texas Skies in 2015 - A Summary of Rain Enhancement (Cloud Seeding) Operations in Texas
Projects in Texas
West Texas Weather Modification Association (WTWMA)
South Texas Weather Modification Association (STWMA)
Edwards Aquifer Authority (EAA)
Panhandle Groundwater Conservation District
Trans Pecos Weather Modification Association
City of Wichita Falls
Rolling Plains Project
Texas has a lengthy history of using cloud seeding to lessen the impact of periodic, often severe, droughts. Numerous “rainmaking” efforts sprouted during the epic drought of the 1950s, and some continued into the 1960s, giving impetus to the Texas Legislature to adopt a law, in 1967, governing the use of weather modification technologies. In ensuing years, both the State and federal governments provided funds for both cloud seeding research and assessing the impact of commercial weather modification projects.
With more substantive evidence that cloud seeding, when performed in timely and appropriate ways, could invigorate convective clouds, promoting their growth and capacity to produce rainwater, a coordinated, State-funded program began in earnest in the latter half of the 1990s. Today, with drought a pending, if not ever present, threat to the economy and well-being of Texans, rain enhancement projects flourish within large areas of Northwest, West, and South Texas. In fact, the seven cloud seeding projects today cover about 31 million acres (or about one-sixth of the land area of the state). When drought was a greater threat a decade ago, as many as 51 million acres were included in cloud seeding “target” areas in the state.
Texas’ present-day cloud seeding efforts are much more than well-considered responses to drought, however. They are also concerted efforts, using the latest technological tools and understanding, to replenish fresh-water supplies in aquifers and reservoirs as well as to help meet the growing needs of agriculture, industry, and municipalities for fresh water. Political subdivisions like water conservation districts and county commissions have embraced the technology of rain enhancement as one element of a long-term, water-management strategy designed to ensure a growing population has enough water to meet its future needs.
Each of the cloud seeding projects uses specially-equipped aircraft designed to place seeding materials (in the form of pyrotechnic devices, or flares, containing silver iodide and other compounds) into convective towers (turrets of growing thunderstorms) to induce them to expand and process more atmospheric water. The seeding is achieved by burning flares either mounted on the wings of single and twin-engine aircraft or held in racks, and dropped (ejected), from the underside of the aircraft fuselage. Pilots in the aircraft are directed to convective clouds believed by the meteorologist to be treatable with the seeding agent. Timing and targeting are the two critical factors in successful seeding of young thunderstorms. The concerted efforts of both pilot(s) and meteorologist are designed to give the growing cloud a “nudge” to enable it to be more efficient in the way it uses available cloud droplets to grow raindrops.
Projects in Texas
As each of the rain enhancement projects became established in recent years, State matching funds were allocated to the sponsoring groups to enable them to procure needed hardware such as specially-equipped aircraft and ground-based radar systems. Each project initially constructed its program, either leasing or purchasing aircraft, at a cost of 8 to 9 cents per acre, with the State assuming up to 4.5 cents of that cost. Eventually, the State share of the cost declined, such that today no residual State funds are used to sustain these programs. From the time the State began paying in part for the programs (1997) until State funds were exhausted (2004), the State contributed about $11.7 million. An additional $1.5 million in State funds was spent during that time to assess the projects’ performance.
No State funds are available for the current biennium (which began on September 1, 2014) for any cloud seeding operations in Texas.
Each year an independent analyst at Texas Tech University uses Doppler weather radar data from the National Weather Service network to assess the impact of these rain-enhancement projects on seasonal rainfall within the projects’ target areas. The analysis of cloud-seeding operations conducted by these projects in 2014 showed that, on average, individual seeded thunderstorms lived 19 minutes longer (or 45 percent longer) than untreated storms in the vicinity and covered some 47 percent more area than the unseeded ones. Rain output from seeded storms, on average, was nearly one and one-half times (140 percent more) than that from nearby untreated storms. The total number of single, isolated thunderstorms that were seeded produced an estimated 122,914 acre-feet above and beyond what could have been expected without intervention. More complex thunderstorm clusters that were seeded yielded an estimated 1,996,821 additional acre-feet of rainwater. The cost to produce this additional rainwater was estimated at less than $11 an acre-foot.
The following is a description, by project, of rain enhancement operations being conducted during 2015 in Texas.
West Texas Weather Modification Association (WTWMA)
This project, based in San Angelo, is now in its 19th consecutive year of operation. Its target is the third largest in the state---some 6.4 million acres in west central Texas between Midland and San Angelo. The WTWMA employs a full-time meteorologist and pilots using Doppler weather radar data produced by the National Weather Service. The meteorologist is based at Mathis Field, while aircraft are located at the San Angelo airport as well as several other locations within the target area.
The project has a dual purpose: Permits are held by the WTWMA for both rain enhancement and hail suppression operations. The way in which the Association obtained its aircraft and radar, and hired its permanent staff, in 1997-98, to become self-contained as a project served as a prototype for other rain enhancement programs that materialized in Texas in subsequent years. The staff of the WTWMA can provide more information about this project (325-949-1950; http://wtwma.com).
The project with its base of operations in Pleasanton (south of San Antonio) is also in its 19th consecutive year of operation, having been established in 1997 to seed clouds over a target area extending from the base of the Edwards Plateau to near the coastal bend area of Texas. The STWMA is an alliance of two water districts (Evergreen Underground Water Conservation District and the Live Oak Underground Water Conservation District) and a county commission. Seeding activities are directed by a staff meteorologist working with National Weather Service Doppler weather radar data from the airport in Pleasanton. Because the STWMA has ownership of all of the resources (technical and human) needed to perform rain enhancement operations at any time, the weather modification project runs on a year-round basis.
In 2002 the STWMA expanded its target area to absorb three of the counties previously in the cloud seeding target area of the rain enhancement program of the Edwards Aquifer Authority (EAA). The EAA reduced the size of its target area (now the primary drainage area for the Edwards Aquifer) and enlisted existing rain enhancement projects based in Pleasanton and Carrizo Springs to provide aerial and technical coverage for its newly-redefined target. As a result, the target area of the STWMA expanded by some 2.2 million acres, to nearly 6 million, making it the state’s second largest weather modification target. The EAA contracts with the STWMA for cloud seeding services in Bandera, Bexar, and Medina counties. More information on this project can be obtained by contacting the STWMA staff (830/569-4186; http://southtexasweathermodification.com.)
Edwards Aquifer Authority (EAA)
The EAA first initiated its own rain enhancement effort in 1998, using an out-of-state contractor for seeding operations based in Hondo. Since its inception, the aim of the project has been to put additional water on the ground, and into the aquifer that is the primary source of water for several million people living in South Central Texas, including the metropolis of San Antonio. After four years of contracted services, the EAA in 2003 assigned portions of its “old” target area to two well-established and independently-run cloud seeding projects nearby. Since then, three of the counties in its redefined target have been served by the South Texas Weather Modification Association. The EAA office in San Antonio (800/292-1047; www.edwardsaquifer.org) can supply more information about its rain enhancement effort.
One of the largest water conservation districts in Texas also conducts cloud seeding operations to enhance rainfall and, thus, augment groundwater recharge over the Ogallala Aquifer in the state’s northern extremity. This project of the PGWCD, after being served in its initial year by a contractor, followed the path taken by earlier projects in Texas and in 2001 procured its own aircraft, radar, office facility, and support personnel. The PGWCD project has access to cloud systems moving out of Oklahoma into its target area, which currently consists of nearly 4.1 million acres in the eastern sector of the Texas Panhandle. The staff of the PGWCD (806/883-2501; www.pgcd.us/programs/precipitation_enhancement.php ) can provide additional information about this project.
Trans Pecos Weather Modification Association (TPWMA)
Cloud-seeding has been underway west of the Pecos River since May 2003. The TPWMA consists of the Ward County Irrigation District and other political subdivisions within Culberson, Loving, Pecos, Reeves, and Ward counties. Its target area in that part of Texas along and west of the Pecos River consists of 5.1 million acres. TPWMA aircraft are based at the airport in Pecos, and seeding missions are directed by a meteorologist based in San Angelo. Additional information is available about this project through the Ward County Irrigation District in Barstow (432/445-6834.
Two new rain-enhancement projects began operations in 2013 for the first time, with plans to cloud seed again in 2014. Both projects contract for cloud seeding services, which are carried out on behalf of the City of Wichita Falls and a group of counties in the Rolling Plains region. A meteorologist directs an aircraft, based in Wichita Falls, on seeding missions over the watersheds of three reservoirs that furnish water for the city of Wichita Falls: Arrowhead, Kemp, and Kickapoo. The permitted area for seeding flights covers a large area extending from the headwaters of Lake Kemp to the drainage basin for Arrowhead.
Several counties joined together to sponsor several months of cloud seeding in 2014 in a Rolling Plains target from near Abilene north and eastward toward the Red River valley. Six counties made up that target of 3.487 million acres, and three additional counties to the west and southwest were added to allow for an adequate “buffer” in which aircraft could operate to seed storms moving northeastward into the target. In all, the Rolling Plains project encompassed 5.247 million acres. Plans are underway to reinstate rain-enhancement operations in the spring of 2015 in the region.
Each of the projects described above is permitted by TDLR, with each permit extending over a 4-year period. The project sponsor, or contractor, is also required to keep current a Texas weather modification license, which is renewable annually.
Individuals, or organizations, representing areas of the state not now engaged in cloud seeding but with an interest in doing so should contact George Bomar (512/936-4313; e-mail: firstname.lastname@example.org) of the TDLR about any, and all, weather modification permitting and licensing matters or for general information about cloud seeding technology.