Sponge city ecological moisturizing system and application thereof in urban engineering

The invention relates to a sponge city ecological moisturizing system and application thereof in urban engineering, and belongs to the technical field of urban ecological construction. The sponge cityecological moisturizing system comprises greening land, and the greening land sequentially comprises a soil layer, a water retention layer, a gravel layer, a garbage layer and a garden waste layer from top to bottom; and the water retention layer comprises a water retention agent and loess in a volume ratio of (0.1-0.3): 100, wherein the water retention agent is prepared from the following components in parts by weight of 50-70 parts of degradable super absorbent resin, 20-30 parts of volcanic ash and 10-20 parts of artemis sphaerocephala krasch colloid. The application in urban engineering comprises the following steps that S1, deep trenches with the depth of 60-70cm are dug in a to-be-treated area; and S2, the deep trenches are sequentially filled with a garden waste layer with the thickness of 15-20 cm, a garb