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| Titel |
A basin-scale approach for assessing water resources in a semiarid environment: San Diego region, California and Mexico |
| VerfasserIn |
L. E. Flint, A. L. Flint, B. J. Stolp, W. R. Danskin |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1027-5606
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| Digitales Dokument |
URL |
| Erschienen |
In: Hydrology and Earth System Sciences ; 16, no. 10 ; Nr. 16, no. 10 (2012-10-26), S.3817-3833 |
| Datensatznummer |
250013531
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| Publikation (Nr.) |
 copernicus.org/hess-16-3817-2012.pdf |
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| Zusammenfassung |
Many basins throughout the world have sparse hydrologic and geologic data,
but have increasing demands for water and a commensurate need for integrated
understanding of surface and groundwater resources. This paper demonstrates
a methodology for using a distributed parameter water-balance model, gaged
surface-water flow, and a reconnaissance-level groundwater flow model to
develop a first-order water balance. Flow amounts are rounded to the nearest
5 million cubic meters per year.
The San Diego River basin is 1 of 5 major drainage basins that drain to the
San Diego coastal plain, the source of public water supply for the San Diego
area. The distributed parameter water-balance model (Basin Characterization
Model) was run at a monthly timestep for 1940–2009 to determine a
median annual total water inflow of 120 million cubic meters per year for
the San Diego region. The model was also run specifically for the San Diego
River basin for 1982–2009 to provide constraints to model calibration and to
evaluate the proportion of inflow that becomes groundwater discharge,
resulting in a median annual total water inflow of 50 million cubic meters
per year. On the basis of flow records for the San Diego River at Fashion
Valley (US Geological Survey gaging station 11023000), when corrected for
upper basin reservoir storage and imported water, the total is 30 million
cubic meters per year. The difference between these two flow quantities
defines the annual groundwater outflow from the San Diego River basin at 20
million cubic meters per year. These three flow components constitute a
first-order water budget estimate for the San Diego River basin. The ratio
of surface-water outflow and groundwater outflow to total water inflow are
0.6 and 0.4, respectively. Using total water inflow determined using the
Basin Characterization Model for the entire San Diego region and the 0.4
partitioning factor, groundwater outflow from the San Diego region, through
the coastal plain aquifer to the Pacific Ocean, is calculated to be
approximately 50 million cubic meters per year.
The area-scale assessment of water resources highlights several hydrologic
features of the San Diego region. Groundwater recharge is episodic; the
Basin Characterization Model output shows that 90 percent of simulated
recharge occurred during 3 percent of the 1982–2009 period. The groundwater
aquifer may also be quite permeable. A reconnaissance-level groundwater flow
model for the San Diego River basin was used to check the water budget
estimates, and the basic interaction of the surface-water and groundwater
system, and the flow values, were found to be reasonable. Horizontal
hydraulic conductivity values of the volcanic and metavolcanic bedrock in
San Diego region range from 1 to 10 m per day. Overall, results
establish an initial hydrologic assessment formulated on the basis of sparse
hydrologic data. The described flow variability, extrapolation, and unique
characteristics represent a realistic view of current (2012) hydrologic
understanding for the San Diego region. |
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