October 2009 - South Tahoe Public Utility District

MDG
Average Daily Effluent Flow (MGD)
6
5
4
3
2
y = -0.0918x + 188.12
R 2 = 0.6957
2.04 MGD
1
0
1995 2000 2005 2010 2015 2020 2025 2030
Figure 5.1.1 Recycled Water Flow versus Time, 1997-2028
5.1.1.2 Recycled Water Flow Estimate Method 2
The second method for estimating the recycled water flow quantity for the year 2028 uses
recycled water inflow and discharge from Harvey Place Reservoir data provided by the District;
reference Table 5.1 (page 5-31) and Figure 5.1.2 (page 5-31). The District data indicate a
decreasing trend in total yearly recycled water inflow and discharge from Harvey Place
Reservoir from 1997 to the beginning of 2007. Applying a trendline to the data results in a
projected 2028 inflow of 1838 acre-feet per year (AF/Yr) (R-squared value=0.7658) and a
discharge of 1,668 AF/Yr (R-squared value=0.4162). The R-squared value for the trendlines
was compared to determine which projected value was more reliable, with the projected inflow
of 1,838 AF/Yr determined to be the more reliable value. It is believed that the value for amount
of recycled water discharged from Harvey Place Reservoir is more variable than the inflow due
to climatic fluctuations resulting in varying evapotranspiration rates as well as other geologic
and environmental factors. The 2028 projected annual inflow of 1,838 AF/Yr equates to an
average daily inflow of 1.64 MGD. Using the peaking factor previously determined of 1.2, the
peak month in 2028 is projected to have a maximum flow of 1.97 MGD.
South Tahoe Public Utility District
Recycled Water Facilities Master Plan - October 2009 Page 5-30