Seepage and drainage system for sponge city

The sponge city seepage and drainage system comprises a first drainage unit, a drainage well, a water storage tank and a second drainage unit, the first drainage unit comprises a permeable pavement and a plurality of seepage pipes, the seepage pipes are located on the lower portion of the permeable pavement in the first direction, and the first direction is the gravity direction; the drainage wells are connected with a permeable pavement through water seepage pipes, the multiple drainage wells are communicated through a drainage main pipe, convection mechanisms are arranged in the drainage wells, and the convection mechanisms are configured to conduct convection on at least part of rainwater entering the drainage wells so as to reduce deposition of silt in the drainage wells. The water storage tank is communicated with the drainage well through a connecting pipe; the second drainage unit comprises a drainage groove and a sand discharge port, the drainage groove is provided with a water inlet end and a water o