A Study of the Safe Yield and Replenishment Conditions for the Yucaipa Basin Area, California
<p>A ground water inventory made for a basin area of about 51 square miles and situated 6 miles southeast from Redlands, California, disclosed that a mean annual recharge of 4322.5 acre-feet from rainfall on foothill and mountain areas plus a mean annual deep penetration volume of 1693 acr...
| Summary: | <p>A ground water inventory made for a basin area of about
51 square miles and situated 6 miles southeast from Redlands, California,
disclosed that a mean annual recharge of 4322.5 acre-feet from
rainfall on foothill and mountain areas plus a mean annual deep penetration
volume of 1693 acre-feet from water artificially applied (irrigation
and domestic uses) are exceeded by local consumptive uses plus exportation
losses. Detailed studies showed that no appreciable contribution from
rainfall in irrigated and non-irrigated valley lands occurs to the
sub-surface ground water body.</p>
<p>Elimination of the net basin drawdown loss caused by
exportation will still put the overdraft within the order of 3000
acre-feet per year. An inevitable increase of land cultivation brings
about no chance to mitigate that figure in the near future.</p>
<p>Increasing volumes of water extraction are shown by a mean
annual drop in water level of wells, from 1.67 feet for the period
1927-1942 to 7.5 feet for the period 1942-1954.</p>
<p>An estimated specific yield of 0.1085 for the ground water
reservoir places the time-life of Yucaipa basin within 35 years,
assuming the existence of a 250 feet thick aquifer under the 400 feet
deepest wells.</p>
<p>A depth of 650-750 feet in water wells is arbitrarily
established as a limit for the economic and profitable exploitation
of the basin.</p>
<p>A conservative figure of 5000 acre-feet plus minus 1000
acre-feet safe yield is based on the mean annual recharge to valley
lands from foothill and mountain areas. This quantity is likely to be
increased by additional yields from the aquifer, upon rebounding and
expansion.</p>
<p>The low porosity value and its close specific yield (0.12 and
0.1085 respectively) associated with a rather low specific retention
value, seem to indicate that the hydrological properties of the
Yucaipa aquifers reflect the existence of a type of rock near to a
sandy gravel, with locally abundant interstitial materials.
Plio-Pleistocene(?) San Timoteo bed can well appear in Yucaipa basin
at aquifer depths. Younger Quaternary fanglomerates, stream gravels,
weathered soils and modern alluvium occur widely distributed in the
surface area of Yucaipa. These sediments are bordered to the north,
east, and southeast by hills and mountains of basement complex rocks
which are probably pre-Cambrian, but most certainly pre-Cretaceous in
age.</p> |
|---|