Page 33 - Beaumont Basin Watermaster

Beaumont Basin Watermaster
2013 Reevaluation of the Beaumont Basin Safe Yield 3-Apr-15

It is noted that a portion of the low-density residential area (as with the other land use areas)
consists of roads which are assumed to be impermeable. Based on an analysis of air photos, the
percentage of area covered by roads was determined to be approximately 12 percent. Thus, the
return flow for the low-density residential area was reduced by 12 percent to account for the
roads.

4.1.5.3 Return Flow in High-Density Residential and Commercial Land Use Areas

For areas designated as high-density residential, 50 percent of water use was assumed to be
indoors and 50 percent outdoors. Unlike the low-density residential area, these areas are
connected to the City of Beaumont’s wastewater treatment plant. As such, none of the indoor
water use becomes groundwater return flow. As with low-density residential, 25 percent of the
outdoor water use is assumed to become return flow. For the high-density residential and
commercial areas, the final weighted average annual return flow was reduced by 24 percent to
account for the impervious surfaces represented by roads. The percentage reduction was based
on an analysis of air photos of the Beaumont area.

For commercial areas, indoor water use is assumed to be 95 percent of delivered water and all
water used is discharged to the wastewater treatment system (i.e. no return flow). Return flow
from the remaining outdoor water use is assumed to be 25 percent of water used. Return flow
was not applied to highway areas that were classified as commercial land use. This was due to
the very limited amount of landscaping along the highways.

4.1.5.4 Return Flow from Urban Landscape

Return flow associated with outdoor irrigation of golf courses and parks (i.e. urban landscape)
was assumed to be 25 percent of delivered water. Applied water rates (in acre-ft/yr/acre) for
urban landscapes was assumed to be equal to applied water rates for the Brookside Sports Park
based on delivered water records.

4.1.5.5 Changes in Return Flow Over Time
The amount of return flow that has historically occurred within the Study Area has increased
over time as land use has changed. Although the areas of irrigated agriculture have decreased
since 1970, residential, commercial and areas of urban landscape (i.e. golf courses and parks)
have increased significantly since that time. The total return flow for each land use category
(irrigated agriculture, low-density residential, high-density residential, commercial and urban
landscape) was estimated based on the land use area and the return flow rates described earlier.

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