The oasis transition during 1990 and 2020 was exhibited in Figure 6, which illustrated the distribution features of various oasis types in Tuha Basin. Totally, the area of oasis converted to non-oasis was 3940.70 km²; and 9570.38 km² of non-oasis converted to oasis, which demonstrated the oasis expansion in Figure 3. Specifically, as an almost transfer-in type, the converted area from non-oasis to artificial oasis was 1418.18 km², distributing in the southeast of Gaochang district, surrounding of Yizhou district and northern Balikun county. Natural oasis converted 3520.84 km² to non-oasis, mainly occurred in northern and eastern Balikun; as an important transfer-in oasis, non-oasis converted 8152.20 km² to natural oasis, mainly concentrating in northern part of Balikun county.