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

To provide scientific basis for utilizing wetland resources, the drought conditions of different wetland types were evaluated 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. 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. There is a close negative correlation between ET and the regional water index (RWSI). The coefficients of the regression equations presented by different land use types such as swamp, built area, bush swamp, dry farmland, cultural pond, and other wetland types have slight differences. Generally, the non-wetland 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 utilization can reduce the drought risk to a certain extent in natural wetlands. Results showed that reasonable development of wetland resources may alleviate regional drought conditions.