KEENESBURG — While farmers around him give up control over water used for a century to irrigate crops, Marc Arnusch is crouching in a thick cornfield inspecting blue digits on his new sensor. The third-generation farmer installed it to measure exactly the level of moisture in soil right at the roots of his corn. He’s also considering underground tubes that emit water only upon contact by roots.

This technology, made for farming in the Israeli desert,

enables precision for applying only as much water as necessary to maximize production of sugar beets, onions and corn.

Agriculture across Colorado and the West continues to use 85 percent of total water supplies. But growing numbers of farmers are shifting toward greater efficiency, replacing ditch-and-flood irrigation with center-pivot sprinklers and tubes that emit tiny drops.

Colorado officials say they’re counting on such increased efficiency and conservation as the state readies for an increase in people and industry — with a projected annual shortfall of 163 billion gallons.

State water planners anticipate farmers will be able to transfer more of their huge share of water to meet intensifying demands of Front Range industry and housing developers.

“Basically, we’re going to ask the agricultural community to do what the municipal community has already done: Let technology work for you,” said James Eklund, director of the Colorado Water Conservation Board.

Greater efficiency irrigating crops means farmers could grow more and make more water available to companies and cities, Eklund said.

“You can do right by your business and attract new people,” he said, “and at the same time you can be freeing up water that otherwise would have been lost.”

But the rising expectations for agricultural water worries Arnusch, 42, who is a Colorado Farm Bureau board member.

“Efficiency doesn’t necessarily translate to using less volume of water,” he said. “We want to retain that ownership. Then we control the future of the water.”

Agricultural ownership control over water rights, Colorado Farm Bureau leaders contend, is crucial. Farmers currently appear to be losing ground as some willingly sell water rights, like 401(k) accounts for rural families, via brokers who transfer them to cities.

In the South Platte River Basin, state data show loss of water reduced 1.1 million acres of agricultural land during the past three decades to 813,000 acres. That decrease of nearly 300,000 acres adds to large losses in southeastern Colorado after sales by farmers to cities in the 1970s shifted 14.6 billion to 19.5 billion gallons of water.

In southeastern Weld County, traditionally one of the nation’s biggest agricultural producers due to heavy irrigation, farmers said one-third of water rights have been sold since 2009.

Some went to companies involved in the oil and gas boom. Others went to expanding cities.

Gov. John Hickenlooper has declared “buy and dry” must end. Hickenlooper’s senior water adviser, John Stulp, said in a recent interview that, given food and environmental benefits of agriculture, the notion that agriculture’s 85 percent share of water should shrink is unrealistic.

Yet Colorado will encourage Alternative Transfer Mechanisms for shifting water to cities — with farmers leasing water temporarily while retaining ownership — aiming to move 16.2 billion gallons a year. Stulp said any ATM deals will be voluntary.

“There is no mandate to agriculture,” he said. “No one is asking growers to give up ownership of that water.”

Bigger challenges

The rising competition for water that affects Arnusch also increasingly challenges farmers around the West from Colorado to California.

In the 19th century, geologist John Wesley Powell, exploring the West for the government, declared it arid and mostly unsuitable for agriculture, and warned “there is not sufficient water to supply the land.”

Yet federal authorities directed huge expenditures to divert water from rivers and install reservoirs — enabling agriculture. This enabled the settlement that has led to the nation’s fastest-growing populations. Colorado’s population of 5.4 million, concentrated along the Front Range, is growing by 1.6 percent a year, twice the national rate.

Farmers statewide say they’re wrestling with the full implications for people and land.

“Should we be planting cities in desert areas? Who should go — the farmers or the city dwellers?” said Paul Kehmeier, who grows alfalfa, oats and other crops 50 miles southeast of Grand Junction in western Colorado.

To do that, he diverts water from a river into ditches, managing a homestead his great-grandfather started 120 years ago on land where Ute Indians once thrived.

“Certainly, our farm needs to be irrigated. Otherwise, it would be sagebrush and desert,” Kehmeier said.

This year, reduced snowpack atop Grand Mesa means he’ll produce less — 10,000 bales of hay compared with 15,000 bales last year. Kehmeier, too, is considering investments in high-efficiency irrigation technology as part of a project to improve water quality in the river. Yet the costs are huge.

“You see, my alfalfa plants are going to use the same amount of water no matter how I give it to them,” he said, emphasizing how unconsumed diverted water returns underground to the river.

“The only way to significantly decrease agricultural consumption of water is to decrease the amount that is grown. What does that mean? Either we irrigate less or plant fewer acres,” he said.

Some farmers must reduce irrigation just to survive due to scarcity, let alone profit from temporary leasing of surplus water to cities.

Barley and potato grower Brendon Rockey, who lives north of Center in the San Luis Valley, began changing his mix of crops eight years ago as state officials warned of crackdowns on overpumping from dwindling aquifers.

Rockey planted more grasses and broad-leaved legumes. He cut irrigation on his 500 acres from an average of 18-20 inches of water a year to 9 inches.

“We’ve got to be able to maintain our farms and maintain a living while also saving water,” he said.

The pressures of population growth amid prolonged drought in California and other Far Western states are shifting attention to agriculture’s 85 percent share.

It has gotten to the point that U.S. Department of Agriculture Secretary Tom Vilsack in a recent interview called for a cohesive national policy on water.

“We all have to be careful about pointing a finger (at farming),” Vilsack said.

“There must be creative ways to retain the water we have,” he said, noting that 30 percent of food produced in the U.S. — which requires a huge use of water — is wasted, ending up in landfills. “What’s the water vision, the water plan, the water strategy for this country?”

Southern California farmers have agreed to shift water to cities using the temporary lease deals that Colorado leaders favor — in return for payments from cities, without ceding ownership of rights.

Colorado’s water conservation board has directed $4 million toward pilot projects in the Arkansas River Valley, where farmers recently agreed to lease water to towns.

Water being saved

But out on his farm east of Keenesburg, Arnusch is focusing primarily on the new solar-powered sensors, which cost $3,000 each.

In June, when he assumed it made sense to flood fields, he trusted a sensor reading that showed roots already had plenty of water. He saved water. In July, when muddy soil suggested roots would be saturated, the sensor told him the opposite and he fired up his center-pivot sprinklers.

He also watched as a neighbor, who had been unable to obtain rights to sufficient water, laid coils of irrigation tape, burying the tubes 16 inches deep across a plowed 65-acre field.

Arnusch said he’s wary of even leasing any water back to cities.

Every year for more than a decade, Arnusch has had to leave about 250 of his 2,500 acres fallow for lack of water to irrigate. Farmers here since his grandfather began irrigating in 1952 have accepted limits of nature and, in dry years, planted less, Arnusch said.

The problem with cities is they build based only on market economics, disregarding water, he said.

“Buy-and-dry is happening, and it will continue to happen. But as our nonagriculture water needs increase, what is that going to mean?” Arnusch said. “The urban areas should be like farmers, only using exactly as much as they need. If I don’t have a sufficient water source, how am I supposed to produce?”

Bruce Finley: 303-954-1700, bfinley@denverpost.com or twitter.com/finleybruce

85 percent

of total water supplies that are used for agriculture across Colorado and the West

163 billion

in gallons, the projected annual shortfall of water, according to Colorado officials