Abstract. Data on irrigation patterns and trends at field-level
detail across broad extents are vital for assessing and managing limited
water resources. Until recently, there has been a scarcity of comprehensive,
consistent, and frequent irrigation maps for the US. Here we present the
new Landsat-based Irrigation Dataset (LANID), which is comprised of 30 m
resolution annual irrigation maps covering the conterminous US (CONUS) for
the period of 1997–2017. The main dataset identifies the annual extent of
irrigated croplands, pastureland, and hay for each year in the study period.
Derivative maps include layers on maximum irrigated extent, irrigation
frequency and trends, and identification of formerly irrigated areas and
intermittently irrigated lands. Temporal analysis reveals that 38.5×106 ha of croplands and pasture–hay has been irrigated, among which the
yearly active area ranged from ∼22.6 to 24.7×106 ha. The LANID products provide several improvements over other
irrigation data including field-level details on irrigation change and
frequency, an annual time step, and a collection of ∼10 000
visually interpreted ground reference locations for the eastern US where
such data have been lacking. Our maps demonstrated overall accuracy above 90 % across all years and regions, including in the more humid and
challenging-to-map eastern US, marking a significant advancement over
other products, whose accuracies ranged from 50 % to 80 %. In terms of
change detection, our maps yield per-pixel transition accuracy of 81 %
and show good agreement with US Department of Agriculture reports at both
county and state levels. The described annual maps, derivative layers, and
ground reference data provide users with unique opportunities to study local
to nationwide trends, driving forces, and consequences of irrigation and
encourage the further development and assessment of new approaches for
improved mapping of irrigation, especially in challenging areas like the
eastern US. The annual LANID maps, derivative products, and ground
reference data are available through https://doi.org/10.5281/zenodo.5548555 (Xie and Lark, 2021a).