Radiocarbon dating is used for estimating the ages of
When spring systems are in equilibrium, spring flow will generally remain constant.
Thus, for springs sourced primarily by local recharge, spring flows are temporally well-correlated with precipitation and evapotranspiration patterns.
The area covered in this study spans a substantial portion of the Mojave Desert, a region of isolated mountain ranges separated by expanses of desert plains.
Overall, the Mojave Desert forms a wedge-shaped area bounded by the Garlock Fault on the north, the San Andreas Fault (and the north slope of San Bernardino Mountains) on the south, and the Colorado River to the east.
These local springs are wholly dependent on flow within their respective watersheds.
There is no recognized planar, perched groundwater-table that extends across ridges and valleys in these desert ranges.
Rock types are variable, with some mountain ranges dominated by intrusive igneous rocks (e.g., Granite Mountains, Old Woman Mountains, Chemehuevi Mountains); and volcanic rocks (e.g., Clipper Mountains), while other ranges are variable in lithology (e.g., the Marble Mountains, which are primarily comprised of volcanic rocks on the north and carbonate sedimentary rocks on the south).
The principal surface water bodies throughout the region include scattered springs and the normally dry playas on the valley floors, which receive water during occasional summer and winter precipitation events that eventually evaporate.
The water in both groundwater and spring flow are controlled by a water balance simply shown by the following equation: For groundwater, when outflow exceeds inflow, groundwater in storage decreases and groundwater elevations decrease. When the system is in equilibrium, groundwater levels will generally remain constant.
This study focuses on a review of the past recharge estimates and associated uncertainties for the southeastern Mojave region, and it considers the results of the observed flow patterns of the springs and recent radiocarbon analyses on selected spring waters, to narrow the range of plausible estimates.
The implications of a narrowed set of plausible recharge rates is then discussed in the context of the sustainability of spring flow in this region.
This is evident in the southeastern Mojave Desert, where calculated recharge estimates by previous investigators that range over an order of magnitude (from ~2500 to ~37,000 acre feet per year) are reported.
To narrow down this large span of recharge estimates to narrower and more plausible values, this study evaluates the previous recharge estimates in this region, to examine the sources of variability in the reported results and to constrain the recharge estimates based on the hydrologic conditions and the radiocarbon age-dating of spring flows—even without knowledge of the precise subsurface hydrology.