Ground Water - Coastal Santa Ana Basin Subunit

The Coastal Basin includes a relatively small unconfined recharge area and a relatively large confined area where ground-water pumping is the primary source of discharge. Land use is almost entirely urban.

Four studies were conducted in the Coastal Basin and Orange County vicinities.

(View the Hamlin et. al. Report)

COSUS:

The COSUS study provides an integrated, regional assessment of ground-water quality in the Coastal sub basin of the Santa Ana watershed. Wells were selected using a grid-based program to produce equal-area, random cells (Scott, 1990). The program was used to generate 20 cells in the Coastal Basin. An attempt was made to select one well per cell. Wells from adjacent cells were used to populate cells that either had no active wells or contained wells that did not meet NAWQA selection criteria, such as those lacking well-construction data.

COFPS:

The COFPS was designed to characterize variation in ground-water quality as water moves from recharge facilities located in the forebay of the Coastal Basin toward the natural discharge area at the coast. As a result of urbanization in the basin, pumpage from production wells is now the primary component of ground-water discharge. Sources of recharge include treated wastewater, imported water, runoff from urban, agricultural, and undeveloped areas. Ground-water flow in the deep aquifers becomes mostly confined a few miles from the recharge facilities and is generally insulated from overlying land uses. The COFPS is defined by data from 23 wells that are completed in the intermediate-depth aquifer zone; most depths are between 200 and 800 feet, and average depth is about 500 ft.

COLUS:

The Coastal Urban LUS (COLUS) was designed to assess the effect of recent urban development on shallow ground-water quality in the Coastal Basin. Areas of new urban development were delineated by comparing residential and urban land uses from mid-1960s topographic maps with those from 1993 GIS maps generated by the Southern California Association of Governments. The wells were constructed to sample the upper 10 to 15 ft of the unconfined aquifer (water-table) system and were generally less than 25 ft deep. Twenty-six wells were drilled and sampled as part of the COLUS assessment.

OCCAS:

In response to concern about potential degradation of ground-water quality, the California State Water Resources Control Board (SWRCB) implemented the California Aquifer Susceptibility (CAS) program with the objectives of assessing water quality and determining the susceptibility of ground water used for public supply to contamination resulting from anthropogenic activities. The OCCAS study encompassed wells in Orange County and includes an area slightly larger than the COSUS study.

Sampling started in April 1998

20' Teflon line from well head into camper window Detail of radon-collection fitting w/ Teflon outflow line disconnected. Willie Kinsey sets up pesticide filter.

YSI 610 and ground-water sampling manifold YSI multiparameter sonde and YSI flow-through chamber Willie Kinsey and chamber bag for isolation of samples during filtration

Reference:

Scott, J.C., 1990, Computerized stratified random site-selection approaches for design of a ground-water-quality sampling network, U.S. Geological Survey, Water Resources Investigations Report 90-4101(Photos by Scott Hamlin, USGS)