Christopher Allen Carlson, 45, also was ordered by a federal judge to serve one year of supervised release stemming from the two hikes made last August with the boys, who were 8, 9 and 12 years old at the time.

He was convicted in February of three lesser child abuse charges by a federal jury. He was indicted on six abuse charges in September.

In a rambling address at the sentencing hearing, Carlson said: "I would not hurt these children. I love my grandchildren." He ended with an apology to the court, saying "I'm sorry for this mess."

Prosecutors had sought 3.75 years in prison followed by a year of supervised release.

Carlson's attorney, Jeffrey Williams, told Reuters that he would appeal the sentence.

Authorities said Carlson led the three young boys on two hikes at the crimson-hued canyon as temperatures soared past the 100-degree-Fahrenheit (38-C) mark, severely limiting their access to food and water.

Prosecutors say he put the boys through the forced marches over treacherous terrain, at times kicking and hitting them along the way.

Carlson maintained he was not guilty of child abuse and told investigators that the hikes were an attempt to get the youths, who he considered out of shape, tougher and more physically fit, according to court documents.

During the trial, each of the boys took the stand against their grandfather and chronicled to their ordeal.

The boys said they were instructed to say they were fine when asked how they were by passing hikers, according to court documents. All three said they vomited during the hikes. Signs of physical abuse were present when they were examined.

The youngest of the boys had severe blisters on his feet and the eldest suffered from vision problems which experts said were a precursor to heat stroke, prosecutors said in a court filing.

"All of the boys ate and drank voraciously when provided with the ability to eat without hiding it from the defendant," according to the filing.

(Editing by Tim Gaynor and Eric Walsh)

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