As New Mexico continues to experience a year that could end up being its driest on record, a lawsuit over water rights in the state is heating up. And while New Mexico Attorney General Gary King says he's fighting to keep New Mexico's water, one critic says the case lacks legitimacy.

The lawsuit brings into question a decades-old agreement on how New Mexico, Colorado and Texas share Rio Grande water. Known as the Rio Grande Compact, the agreement was approved by the states involved, ratified by Congress and signed by President Franklin D Roosevelt in 1939.

Now, King is arguing that a 2008 change to the compact's operating agreement gives Texas a disproportionately large share of water, while shortchanging New Mexico. But some say King's lawsuit may actually do more to harm than good to New Mexico water users.

"The attorney general is coming down to southern New Mexico and telling us what he thinks is good for us," Steve Hernandez, a Las Cruces-based attorney for the Elephant Butte Irrigation District, tells SFR. "That's pretty typical of people from Santa Fe."

In dispute is the approximately 89-mile section of the Rio Grande that flows from the Elephant Butte Reservoir, near Truth or Consequences, to the El Paso County Water Improvement District No. 1 in Texas. Though EBID, which encompasses approximately 90,640 acres of southern New Mexico farmland located downstream of Elephant Butte Dam, is located within New Mexico, once water leaves the reservoir, it's technically considered Texas' water.

Before the change, EBID received 88,000 acre-feet of water use for irrigated land, while El Paso received 67,000 acre-feet, according to a federal survey cited in the lawsuit. That represented a roughly 57 percent to 43 percent split of water rights between New Mexico and Texas.

Today, that ratio has shifted to a 38 percent to 62 percent split, according to figures from the Office of the State Engineer. Amy Haas, general counsel for the OSE's Interstate Stream Commission, says the state appointed its own people to measure the numbers after the US Bureau of Reclamation refused to be transparent.

"They completely changed it around," Phil Sisneros, a spokesman for King, tells SFR. He adds that the change caused farmers to worry that "they might not have the amount of water to irrigate their crops."

In part, the case challenges the bureau's authority to change the compact's operating agreement without input from the state.

"The state was not invited to participate in the discussions or negotiations," Haas tells SFR. "Once the disparity became apparent after a year, we were able to see the percentages were not equitable."

The bureau, which hasn't formally responded to the case yet, wouldn't comment other than saying it was meeting its contractual obligations on the suit.

Jeff Wechsler, a lawyer who specializes in water rights at Montgomery & Andrews, says that, if the numbers are accurate, the attorney general's point is legitimate. The question, he underlines, is whether King's numbers are indeed right.

In Hernandez' view, they're skewed. He says New Mexico's numbers justify the case by double-counting water El Paso has saved from previous years. (King's office denies this.)

But Hernandez also notes that suing to keep water from being delivered to Texas will have an adverse effect on the roughly 8,000 New Mexicans who, as part of EBID, rely on that water for irrigation before it crosses the state line.

"The attorney general and the state engineer do not represent southern New Mexico for surface water," he says. "It puts us in a very complex situation in respect to the state."

Finally, Hernandez bemoans the amount of money the case will cost the state. A $1.5 million appropriation by the state Legislature for this fiscal year will kick off the lawsuit, and King admits it will be long and expensive.

But in King's view, this is a case about water conservation. Under the current agreement, EBID allows farmers to pump the allotted acre-feet of water they miss from the river in dry years. This, according to King, doesn't ensure southern New Mexico will have an adequate water supply down the line.

"If you pump four or five acre-feet of water per year, eventually you will do damage to the aquifer," King says. "It's important for me to protect long-term viability of aquifer and river, even if that means everybody has to do less irrigation this year to assure an adequate water supply 40 years from now."