Wednesday, July 1, 2009

Blanco River flow approaching drought of record conditions

Flow in the Blanco River at Wimberley is approaching low levels not seen since the 1950s. Currently the river is flowing ~5 cfs (the lowest recorded is ~2 cfs in 1956).

The picture shows that only a trickle remains of the river as it enters the recharge zone of the Edwards Aquifer. Residents tell us that this portion of the river normally flows higher than this during drought periods, and is as bad as it was in the 1950s.

The exceptional drought conditions combined with increasing pumping from the Trinity aquifer in the Hill Country have produced these low flow conditions. Baseflow in the Blanco River is derived from springs and seeps that issue from the Trinity Aquifer. As those springs and seeps diminish, so does the river flow. In addition, the Blanco River is a source of recharge for the Edwards Aquifer. With less flow entering the recharge zone of the Edwards Aquifer, less recharge occurs.