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.

中文翻译：

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探索2002年至2017年美国灌溉农业的区域动态

美国拥有地理上成熟且稳定的土地利用和土地覆盖系统，其中包括用作灌溉农田的土地；但是，灌溉土地利用的变化经常与各种驱动因素有关。我们在较低的48个州采用了250 m空间分辨率的一致方法，对四个地图时代（2002年，2007年，2012年和2017年）和四个五年制图间隔的灌溉动态进行了地图绘制和估算。生成的地理空间图（称为中分辨率成像分光辐射计（MODIS）灌溉农业数据集或MIrAD-US）包含来自美国农业部，国家农业统计局的县级灌溉统计数据，来自美国地质调查局的农业土地覆盖量国家土地覆盖数据库 以及从MODIS卫星影像加速得出的年度峰值植被指数。这项研究调查了灌溉农业变化量的区域和周期性模式，并将得失与近因和后果联系起来。尽管从2002年到2017年，灌溉面积总体增加了7％，但我们发现按地区和按5年地图间隔的变化却令人惊讶。灌溉土地的使用动态会影响环境，用水和农作物产量。在区域上，我们发现灌溉收益最大的流域（基于面积百分比）包括密苏里州，密西西比州上流域和密西西比州下流域。相反，在这些制图间隔期间，加利福尼亚州和德克萨斯州-墨西哥湾流域遭受的灌溉损失相当稳定。灌溉动力的各种驱动因素包括区域气候波动和干旱事件，对某些农作物的需求，政府土地或水资源政策以及诸如作物价格和土地价值之类的经济激励措施。使用各种现有的基于地区的参考数据，对MIrAD-US（版本4）的准确性进行了评估。准确度在70％到95％之间，具体取决于区域。