*2.4. Landsat Satellite Dataset and Processing*

Landsat 5 TM cloud-free images were selected for analysis, which were obtained through Earth Explorer (https://earthexplorer.usgs.gov/), with Paths 30 and 31 and Row 36 from 2001 to 2010. A total of 129 images were analyzed with a spatial resolution of 30 m and a temporal resolution of 16 days. The number of clear images vary from year to year based upon geographic location. For this study site, 2001 had the lowest number of annual clear images, with six images, and 2008 had the highest number of clear images with 16 images, as summarized in Table 1. Processed image date and day of the year (DOY) are summarized in Table 1.


**1.**Landsat image dates and corresponding day of year (DOY).

**Table**

#### *2.5. Landsat ET Gap Filling*

Linear interpolation methods were used to estimate the satellite-based ET during the gap period using the satellite-based daily evaporation fraction between consecutive images. The gap between consecutive images was split equally into two periods of eight days; the first eight days used the first image evaporation fraction value, and the second eight-day period used the next image evaporation fraction value.

To estimate the actual ET time series, the evaporation fraction (kc) for each day was multiplied by the reference ET [43]. The daily reference ET was estimated using the ASCE−2005 [44] standardized reference evapotranspiration equation. Hourly ET was calculated for the study period, and the daily ET was obtained by accumulating the hourly ET in a given day. The average frequency and the maximum gap periods (days) were calculated using Equations (1) and (2), respectively. The year of 2006 had the longest average frequency with 52 days, and 2008 had the shortest average frequency with 23 days. The longest and shortest maximum gap period was 184 days and 40 days for 2004 and 2008, respectively, as shown in Table 2. Areas of interest (AOIs) of 3 by 3 grids (30 m spatial resolution), with a total of 9 pixels and a surface area of 8100 m<sup>2</sup> each, were created, and each lysimeter was located at the center of each AOI. ArcGIS 10.2.2 model builder tool software was utilized to extract the average ET for each AOI.

$$Average\ frequency = \frac{\text{Number of days in the growing sensor (April to October)}}{\text{Number of clear images used in the analysis}}\tag{1}$$

$$Average\,frequency = \frac{\text{Number of days in the entire year (Inuary to December)}}{\text{Number of clear images used in the analysis}}\tag{2}$$


**Table 2.** Average frequency and maximum gap each year for the study site.

The years 2004 and 2007 were omitted from the analysis due to limited clear image availability. Day of the year (DOY).
