Need help to understand soil behavior after a dry season (SP, Brasil)

[MarcioAB]

Hello. I'm from Sao Paulo, Brasil and we are facing an odd dry season down here that is producing a strange behavior in the water flow in one of the major city reservatory (Cantareira Water System). I'm looking for help to understand what is going on. I have data from the water company that I can send but to make it short I made a time based diagram (since 2003) showing cumulative rainflow (mm/day) and cumulative water flow (m3/s) entering in the reservatory. Up to recently both curves were quite similar and closely corresponding, but in the last months they are not closely corresponding anymore. The water flow now has a large distance from the rainflow (see image please). It is like a lot of water is gone.

Anyone can help me to understand this behavior ?

Thank you
Marcio