3.1.4. Irrigated Map

A global irrigated area map (GIAM) and global rainfed, irrigated, and paddy cropland (GRIPC) were also collected in this study for irrigated area validation. Based on the unsupervised classification method, GIAM provides irrigated area recognition results with a spatial resolution of 1 km in the year 2000 [34]. GRIPC is the result of the decision tree method for the classification of MODIS data and the spatial resolution is 500 m in year 2005 [17].

#### 3.1.5. In Situ SM Measurement Data and Irrigation Records

There are 135 SM stations in the study area, and SM data are provided every 10 days (1st, 11th and 21st). The SM data measurement (oven-drying method) depths include 10 cm, 20 cm and 40 cm, and the measurement time is concentrated at 8:00 AM Beijing time. These sites also provide information on precipitation and irrigation times between measurements. The recorded irrigation data include areas of agricultural irrigation, irrigation crops, timing and volume. Although the recorded irrigation information is relatively abundant, the spatial scale is the agricultural irrigation region. The data collected in this study are shown in Table 1. Since this study only collected information on irrigation records in 2018, only the SM changes in 2018 were plotted during sample training and validation.


#### **Table 1.** Datasets collected in this study.

PRE: precipitation.
