Plumbing new irrigation

opportunities frim gas drilling

By Steve Werblow

Special to the Journal

Innovative irrigation studies may help High Plains farmers and ranchers enjoy an extra benefit from coal bed methane (CBM) wells--free irrigation water.

Scientists are investigating ways to use groundwater from gas wells to improve rangeland or irrigate crops. such as alfalfa, rather than having to collect it, pump it back into the ground, or direct it into a nearby stream.

In many areas, groundwater that is pumped out of coal bed deposits to release trapped natural gas is soft--high in sodium and other minerals, notes Kevin Harvey, soil scientist for Cascade Earth Science (CES), in Bozeman, MT. CES, an earth sciences engineering firm that specializes in wastewater treatment systems, is conducting the irrigation studies with Williams Production Company, one of the nation's leading natural gas companies.

Using special forms of elements, such as calcium and sulfur, the CES team is finding ways to mitigate the effects of ions in the CBM water, making it suitable for irrigation. Without treatment, the mineral-rich water could disrupt natural soil structure, creating sticky mud in wet conditions and hard crusts in dry weather. By treating the soil--and/or the water--the scientists can protect the field from damage and allow landowners to benefit from the extra water.

The CES trials also are designed to explore optimum timing for irrigation sets using CBM water. The most successful CBM irrigation systems utilize center pivots, notes Jake LaRue, a project development engineer with CES, based in Valley, NE. "Pivots operate 24 hours a day, seven days a week, just like gas wells," LaRue says. "They require very little labor on anybody's part to operate. And you can be much more precise in your application than you can with flood irrigation, for instance."

Precision is important for two reasons, notes LaRue. The first helps protect the soil from crusting over. "Pivots can be designed to apply small droplets," he explains. "The smaller the droplet is, the lighter it is, and the less kinetic energy it has when it hits the soil. We want to minimize soil particle dispersion."

The second role of precise irrigation revolves around managing minerals from the water, explains LaRue. By managing the irrigation application depth with a system that provides optimum uniformity, irrigators can flush salts away from the root zone, but keep them above the water table. Where salts are naturally present in the upper soil profile, irrigation schedules can be set to avoid flooding the field and drawing those buried salts to the surface. CES has employed pivot management very successfully in hundreds of irrigation systems designed to utilize wastewater from food processing plants, industrial sites and municipal water treatment systems, points out LaRue.

The Wyoming test sites are showing promising results. Mack White, district conservationist for the Natural Resources Conservation Service (NRCS), in Gillette, WY, has observed the trials.

"I saw vegetation growing on a site that I didn't know existed up there--grasses that came up and other plants that I haven't seen in this area," White says. "For instance, there was a little serviceberry plant that some deer had grazed down. I only have found serviceberry in one other place, in this county, in 20 years of being here."

Improving rangeland in the gas-rich Powder River Basin of Wyoming and Montana--where the tests are being conducted--can significantly enhance conditions for livestock and wildlife. White points out that some ranchers, in the area, also have found grassed pipeline rights-of-way installed by the gas companies to be beneficial, as they yield more vegetation than native rangeland. And irrigating with CBM water could ultimately yield profitable cropping opportunities, especially with salt-tolerant grasses, such as tall wheatgrass. "Where water quality is pretty respectable and there are suitable soils, it is a possibility," White says.

Talk with the gas company officials to see if they might be interested in working out a win-win irrigation arrangement, suggests LaRue, as the use of CBM water for irrigation means they don't have to seek permits for year-round disposal. Permits for wintertime flow into constructed ponds or nearby streams are likely to be all that is necessary where irrigation can account for CBM water the rest of the year.

CBM wells produce significant amounts of water for the first year or two of operation, says Harvey. Water yield tapers off for the balance of the well's operating life, which can range from five to 15 years. Harvey notes that gas companies can connect a series of wells to an irrigation system, maintaining a substantial amount of output from the pivot for many years.

The key to gaining profitable water opportunities during those years, says hydrogeologist Ray Murphy with Williams, is to be sure to ask gas company representatives to work with you on developing a system, if irrigation could suit your operation.

Date: 3/18/02