Analysis of Water Heat Flux and Drought based on Wetland Classification in the Yellow River Delta

Based on the wetlands classification map, the difference in water and heat flux was studied, as well as the drought conditions in different wetlands. The relationship between the retrieved land surface temperature (LST) and evapotranspiration (ET) was analyzed through two section profiles in different directions using Geographic Information System (GIS) tools. It shows that LST values are relatively higher in built-up or core urban areas than in other areas, and the ET is relatively lower accordingly. The LST is relatively lower and the ET is relatively higher in areas mostly covered by wetlands of bush swamp, water body, saltern, and waterlogged lowland. On the whole, the ET values increase from inland to coastal areas, and the corresponding drought index decreases. When analyzed according to a certain wetland type, ET and the regional water index (RWSI) showed a close negative correlation. The coefficients of the regression equations presented by different land use types such as swamps, built areas, bush swamps, dry farmland, cultural ponds, and other wetland types have slight differences. Generally, the non-wetland areas (including dry farmland and built areas) still show a large RWSI value, though the ET is relatively small. On the contrary, the artificial wetland is subjected to lower drought risk as indicated by its lower RWSI in spite of the high ET level. The RWSI of some natural wetland areas is larger than that of artificial ones, which indicates that proper development and utilization can reduce the drought risk to a certain extent in natural wetlands.