Lake No. 4The St. Vrain and Left Hand Water Conservancy District and Boulder County purchased Lake No. 4 from Mobile Premix, Inc. in November  2001.  The District entered into a Tenancy-in-Common Agreement with Boulder County to facilitate the cooperative management of the reservoir.  In conjunction with Boulder County, the District applied for a 2001 water storage right for the reservoir.  Lake No. 4 is being used in the permanent augmentation plan.  The Conservancy District was able to store water in Lake No. 4 and this water is then leased for augmentation purposes.  During 2009, the District leased water for wintertime releases to meet augmentation for several gravel mining companies.  Approximately 37.5 acre feet of water was released from Lake No. 4.