The cities here pull from the Edwards Aquifer, a massive limestone groundwater source that fits under most of the central state. The aquifer is porous, cracked, carved out, so water trickles in easy, especially at a huge, crescent-shaped exposed area called the recharge zone that runs roughly alongside the I-35 and then curves south and west. “It has a lot of crevice, fractures, caves. As rains happen, they flow over the limestone surface, and that rapidly recharges the water table directly,” rather than having to percolate through layers of soil and bedrock, says Larry French, the director of groundwater resources with the Texas Water Development Board. Though not as easy to monitor as the reservoirs, French says this aquifer rose about seven to eight feet over the past week. Which is a lot, considering the aquifer is over 1,250 square miles in area.