Study area and datasets
2.1 Study area
Tuha Basin is the abbreviation of Turpan and Hami Basin and located in
eastern Xinjiang of China (86⁰44′55″-96⁰25′0″E, 40⁰49′13″-45⁰3′21″N,
Figure 1), which comprises two districts (Gaochang and Yizhou) and four
counties (Tuokexun, Shanshan, Balikun, and Yiwu). With the average
elevation of 800 m and elevation drop beyond 5000 m, Tuha Basin shows
high mountain in the north and low basin in the south.
Tuha Basin has uneven distribution of precipitation and temperature.
Rainfall occurs primarily in the mountain areas between April and
September annually. Annual precipitation is usually less than 20 mm,
while evaporation can reach 3000 mm, causing typical arid climate, with
the water resource mostly relying on the snow meltwater from the
mountains. The annual average temperature is around 15 ⁰C. The maximum
temperature exceeds 50⁰C in plain areas, whereas in the mountain areas,
it only reaches 27 ⁰C.
In this study, we categorized oasis into natural and artificial oasis
according to the oasis features and function (Guo et al. , 2016;
Wang et al. , 2021). Natural oasis was defined as the basic
ecological environment, including forest, shrubland, grassland and
waterbody. Artificial oasis is formed by the combination of natural
disturbances and human interventions, and predominant by cropland and
built-up in Tuha Basin. Other land types (bare land, permanent ice and
snow) were classified into non-oasis type. Generally, oases are situated
in the plain area of Tuha Basin, with the elevation range of –50 to 300
m. There is a small percentage of oases embedded in river basins formed
by the meltwater from snow mountains.