*2.1. Study Region*

Eastern Arkansas is one of the largest irrigated regions in the USA that has seen a rapid increase in the number of OFRs during the last 40 years [35–37]. The region has a humid subtropical climate with an average annual precipitation of 1300 mm, mostly distributed between March and May and November and January [23]. Recent studies [35,36] mapped the spatial distribution of 340 OFRs with surface area <30 ha and distributed across three sub-watersheds in the study region (Figure 1). The OFR dataset was manually mapped using the high-resolution (1 m) National Agriculture Imagery Program archive in combination with 2015 Google Earth satellite imagery. The authors of the OFR dataset used Google Earth Explorer to sharpen the image details when zooming in and to provide a validation for features appearing indistinct or pixelated in the 1-m mosaic imagery [35]. We assigned the OFRs to three size classes (0.1–5 ha, 5–10 ha, and 10–30 ha) based on the surface area mapped in the OFR dataset. These classes were used to support the surface area monitoring analyses when accounting for different OFR sizes (Figure 1).

**Figure 1.** Study region in eastern Arkansas, USA, and the OFRs size distribution. The inset map represents the OFRs shapefile overlaid on SkySat satellite imagery.

We downloaded PlanetScope images and processed daily Basemap and Planet Fusion images between July 2020 and July 2021. This time frame was chosen based on the imagery availability to generate both analysis ready datasets. The images spatial resolution and band-wavelength ranges are presented in Table 1. In addition, the general workflow used to assess the OFRs' surface area time series is provided in Figure 2.

**Table 1.** PlanetScope, Basemap, and Planet Fusion image spatial resolutions and different wavelengths bands.


**Figure 2.** Workflow used to estimate the OFRs' surface area-time series from PlanetScope, Basemap, and Planet Fusion between July 2020 and July 2021.
