My concern is i may not be building it large enough while 2000 gallons sounds like a lot it's only 3'x8'x11' and for the feature i have that could be used up pretty quick. Thats roughly only this is being generous adding about 8 " of water across the ponds and bog ,while we rarely have droughts they have become more and more these days . I have room to add more but i am not planning on leaving the entire space open on top but only open /rocked on one end where the negative edge / falls into the side of the block. The top of the system will be covered with epdm. so i keep some of my yard. after all it's 60 aquablocks for the main vault and another 6 for the negative edge collection area. I think i just answered my own question that's what i get for building a larger feature I guess if i want it to be a backup it will need some more storage area.