Exploring the Regional Dynamics of U.S. Irrigated Agriculture from 2002 to 2017

Abstract

The United States has a geographically mature and stable land use and land cover system including land used as irrigated cropland; however, changes in irrigation land use frequently occur related to various drivers. We applied a consistent methodology at a 250 m spatial resolution across the lower 48 states to map and estimate irrigation dynamics for four map eras (2002, 2007, 2012, and 2017) and over four 5-year mapping intervals. The resulting geospatial maps (called the Moderate Resolution Imaging Spectroradiometer (MODIS) Irrigated Agriculture Dataset or MIrAD-US) involved inputs from county-level irrigated statistics from the U.S. Department of Agriculture, National Agricultural Statistics Service, agricultural land cover from the U.S. Geological Survey National Land Cover Database, and an annual peak vegetation index derived from expedited MODIS satellite imagery. This study investigated regional and periodic patterns in the amount of change in irrigated agriculture and linked gains and losses to proximal causes and consequences. While there was a 7% overall increase in irrigated area from 2002 to 2017, we found surprising variability by region and by 5-year map interval. Irrigation land use dynamics affect the environment, water use, and crop yields. Regionally, we found that the watersheds with the largest irrigation gains (based on percent of area) included the Missouri, Upper Mississippi, and Lower Mississippi watersheds. Conversely, the California and the Texas–Gulf watersheds experienced fairly consistent irrigation losses during these mapping intervals. Various drivers for irrigation dynamics included regional climate fluctuations and drought events, demand for certain crops, government land or water policies, and economic incentives like crop pricing and land values. The MIrAD-US (Version 4) was assessed for accuracy using a variety of existing regionally based reference data. Accuracy ranged between 70% and 95%, depending on the region.

Mapping 20 years of irrigated croplands in China using MODIS and statistics and existing irrigation products

“…S1 ). The statistical data is the only reliable data covering the most irrigated areas in China and has been widely used to assist the mapping of irrigated croplands in existing studies 22 , 23 . Due to the varied integrities of statistics and adjustments of administrative division in different provinces in the last two decades, we adopted the following measures to produce a consistent statistical dataset.…”

“…Further, a couple of time-series irrigation maps at regional or continental scales were also developed by different institutes. For instance, the MIrAD-US 20 – 22 (MODIS Irrigated Agriculture Dataset for the US) which utilized a geospatial modelling framework that assimilates irrigation statistics with remote sensing vegetation index to identify the irrigated lands at a 250-m resolution every five years since 2002; the 500-m irrigated dryland map for the US in 2001 produced with remotely-sensed temporal and spectral signatures and a decision tree method 23 ; the yearly irrigated area maps in India for 2000–2015 using 250-m MODIS vegetation index, land use/cover data, and a decision tree irrigation model 24 . In addition, several time series 30-m irrigation datasets have been generated using Landsat imagery, environmental variables, and random forest model on the Google Earth Engine platform 25 – 30 .…”

Rain-fed to irrigation-fed transition of agriculture exacerbates meteorological drought in cropped regions but moderates elsewhere

“…The croplands included both rain-fed and irrigated lands. The irrigation-fed region was selected based on the Moderate Resolution Imaging Spectroradiometer Irrigated Agriculture Datasets for the Conterminous United States (MIrAD-US) Version 4 for 2007 at the 1 km spatial resolution (Shrestha et al 2021). We used the Pu-Xleim land surface model (Gilliam and Pleim 2010) that includes shallow (surface to 1 cm) and root-zone (1-99 cm) soil layers.…”

Greenhouse gas emissions from US irrigation pumping and implications for climate-smart irrigation policy

“…Expansion of irrigation is an increasingly valuable climate adaptation strategy as croplands experience increasing heat stress, precipitation variability, and, in many places, a decrease in total precipitation [10][11][12] . Irrigated area in the United States continues to expand nationally 13,14 despite regional variability associated with increasing water competition in many regions and ongoing aridification in the American Southwest 15 . In addition to its adaptive benefits, irrigation also produces GHG emissions through energy use and other sources, potentially conflicting with agricultural sector GHG mitigation goals.…”