Description: The Montana Statewide Irrigation Dataset (SID) is a GIS polygon vector representation of Montana's irrigation-equipped agricultural fields. It consists of over 50,000 agricultural fields that were aggregated from various existing data sources and manually digitized. The majority of the data is derived from Montana Department of Revenue's 'Final Land Unit' data, which was derived itself in large part from USDA Farm Service Agency 'Common Land Unit' parcel data. The data has been edited to meet three geometric and data specifications: 1) the fields do not overlap; 2) each field is represented by a single object; 3) each field is attributed with data describing the editor's judgement of the irrigation type from high- photography, and a confidence score (1 - 3) in the estimate of the likelihood of active irrigation and irrigation type. Field boundary delineation and irrigation type attribution was based on 0.6 m resolution USDA National Agricultural Imagery Program imagery captured in 2019 and 2020, and from Landsat and Sentinel satellite-derived Normalized Density Vegetation Index imagery from 2018-2021. The fields represent the an estimate of irrigated agriculture in 2020 in Montana. The data is not absolutely comprehensive; it covers about 2.15 million acres of Montana's irrigated agriculture. A previous estimate of total area by the 2015 Montana State Water Plan indicate about 2.5 million acres were irrigated, while estimates of irrigation on revenue-generating farms by the USDA National Agricultural Statistics Service in 2017 and 2022 placed the irrigated area at 2.06 million acres and 1.72 million acres, respectively. Careful inspection of the data overlain on high-resolution imagery reveal that numerous small fields of ambiguous irrigation status are excluded from the dataset and suggest this dataset is indeed comprehensive of large irrigated fields. DNRC hopes to examine omitted, potentially irrigated lands in future versions of the SID.
Copyright Text: Montana Department of Natural Resources and Conservation, University of Montana Climate Office