“They’re going to acquire the land for their wall, whether you negotiate with them upfront or they end up filing a lawsuit and taking it by a declaration of taking,” said Roy Brandys, a lawyer specializing in eminent domain who represented Mr. Drawe.

Adding to the heartache is where the wall is actually going. The construction is not on the border, which runs along the Rio Grande. It is well within the American side.

Mr. Drawe will lose easy access to the land between the wall and the river — about 350 of his 525 acres. The government has agreed to pay him about $42,000 for the 12 acres that the wall will be built on and about $197,000 to compensate for depressing the value of his farm, Mr. Drawe said. Gates are supposed to provide access to his property south of the wall.

By Mr. Drawe’s reckoning, that might be of limited value. He has found packages of drugs on his farm before, he said, and is concerned that the cartel members that Mr. Trump cites as the reason for the construction will take control of all the land south of the wall.

“If the wall goes up,” Mr. Drawe said, “it will be the new border.”

Becky Jones is preparing for a fight. The Trump administration recently sent Ms. Jones, 69, and her family a letter saying that it was preparing to take them to court if they did not allow the government to survey their farmland for border wall construction.

For Ms. Jones, the construction undercuts language in Congress’s 2019 spending bill that said land within the Santa Ana Wildlife Refuge adjacent to her property would be exempt from the wall. She said the construction, which will run on the road alongside the refuge, will harm the wildlife she grew up admiring.