The primary reason our rivers and creeks have been low: lack of precipitation. The table below shows monthly precipitation amounts since January of 2015. Most of the last 22 months have been significantly below the average – especially since March of this year.
Rainfall increases the natural runoff into streams and rivers. It also recharges groundwater that can come to the surface as a spring. The rains of early December will certainly help offset the deficit. It will take many months of steady precipitation (yes, that includes snow in the winter!) to help relieve the drought conditions.