A hollow drywell apparatus adapted to being positioned beneath the ground and to receive surface water for discharge over a subsurface area in the ground is provided. The drywell has a top with a large diameter top port, a side wall with a plurality of smaller diameter drain-type ports generally uniformly distributed about the drywell side wall surface, and an open bottom. The top port receives a collector assembly acting as a surface drain. Optional larger diameter inlet ports may be formed in the sidewall to provide interconnection between and ganging of adjacent drywells. A diverter is positioned over each drain-type port along either the drywell wall surface exterior, or optionally the wall surface interior. Each diverter laterally dispenses water from the drywell interior while blocking back fill from entering the drywell assembly interior.