There were 533 farms with 213,728 acres irrigated in North Dakota in 2013*, according to the 2013 Farm and Ranch Irrigation Survey results, published by USDA's National Agricultural Statistics Service. That is down 4,679 acres compared to the previous year, on 262 fewer farms.  

In MInnesota, 516,724 acres were irrigated in 2013 compared to 524,016 in 2012.  The number of farms irrigating in Minnesota dropped from 2,853 in 2012 to 2,162 in 2013.

In North Dakota, average water use per acre was 0.694 acre-feet while average depth to water was 29 feet.  In Minnesota, water use per acre was 0.625 acre-feet while average depth to water was 45 feet.

An index to this data, along many other detailed reports on irrigation in all 50 states can be accessed here.

*Note: Stats run one year behind, no stats are available yet for the 2014 crop.