When cabarita river is the hydrographic basin what is the lowest groundwater discharge (million m 3)?
create table table_26609958_1 (groundwater_discharge__million_m_3__ integer, hydrographic_basin varchar, PRIMARY KEY (groundwater_discharge__million_m_3__))
select min(groundwater_discharge__million_m_3__) from table_26609958_1 where hydrographic_basin = "cabarita river"