The average rainfall for the years 2014-2016 is 40 in/yr, or 20% above the historical average. Lake elevation climbed nearly 4 ft in this 3-year period. However, lake elevation has climbed 11 ft during the 26-year period from 1990 to 2016. Although above-average rainfall in recent years have contributed to the flooding, lake levels have been rising since about 1990. Essentially, the wastewater is the equivalent of 20% above average annual precipitation falling on Twin Lakes.

Years Period Change in elevation (ft) Average annual elevation change (inches)
3 2013 to 2016 4 17
26 1990 to 2016 11 5
43 1974 to 2017 10 3

For the 43-year period from 1974-2016, over 1 billion gallons of wastewater has been pumped into Twin Lakes.  This is 3070 acre-ft or 15 ft of water for this 210-acre lake.  Twin Lakes has absorbed about 5 ft of wastewater.  The remaining wastewater has raised lake levels by approx 10 ft.  The capacity of the lakes to absorb and dissipate the effluent flow has been exceeded for many years, and continues to be exceeded, leading to current flooding conditions. The above average rainfall of 2014-2016 hastened the exceeding of the critical flood stage of Twin Lakes, but is not the root cause.