Hydrogeology

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Hydrogeology is the study of the occurrence, distribution and movement of water below the surface of the earth. Groundwater occupies the voids within geologic formations. OCWD’s hydrogeologists work to utilize groundwater resources while maintaining future supplies and protecting groundwater quality.

Contour Maps

Groundwater Basin Model
The basin-wide groundwater flow model is capable of simulating various basin management and project-specific scenarios. The two-dimensional (single-layer) model will be used to evaluate groundwater production versus drawdown of various locations within the groundwater basin. 

North Basin Groundwater Protection Project (NBGPP)
In the northern section of OCWD’s groundwater basin (under Fullerton and Anaheim), portions of the shallow aquifer are contaminated with volatile organic compounds, or VOCs. From the late 1950s through early 1980s, VOCs were used for industrial degreasing in metals and electronics manufacturing. VOCs were released into the environment and impacted the shallow aquifer, which is generally less than 200 feet deep. Although the shallow aquifer is not directly being used for drinking water supplies, groundwater in this aquifer eventually flows into the deeper principal aquifer, which is used for potable water supplies. To date, two City of Fullerton production wells have been removed from service and destroyed due to VOC contamination in that area. Fullerton's drinking water supplies are tested regularly and meet all state and federal drinking water standards.

In accordance with OCWD’s groundwater protection policy, OCWD implemented the North Basin Groundwater Protection Project (NBGPP) to protect drinking water supplies in the principal aquifer. OCWD is constructing five to seven wells specifically to remove and contain contaminated groundwater in the shallow aquifer. OCWD also will construct pipelines to bring the contaminated groundwater to afuture treatment facility where the contaminants will be removed. The purified water will then be re-injected back into the shallow aquifer. OCWD is suing the parties responsible for contamination to seek cost recovery so that the public does not have to pay for this project. An overview map of the VOC plumes and the NBGPP is linked here: NBGPP Overview Map or view the NBGPP 2005 Geologists and Engineers Report.

Water Resources Management System
OCWD has implemented a water resources management system to improve its ability to respond quickly to District and member agency needs. WRMS, as the system is known, is a computerized information storage and retrieval system that serves both technical and management staff by providing well location maps, geologic cross sections, water table contours, water quality concentration maps and tabular data summaries needed for reports and presentations. It comprises the data and graphics that support the ongoing development of the basin groundwater model.

WRMS is one of the preeminent geographic information and groundwater management systems in the world. Its custom applications were designed and programmed by both in-house staff and outside consultants over the last seven years. Most recently, the system has been upgraded from a DOS to Windows NT environment.

Currently, data for more than 3,500 wells have been entered into WRMS, including well construction details, lithologic descriptions, and water level information dating back more than 50 years. Data from the District's monitoring wells, as well as active production wells in the groundwater basin have been continuously collected and entered into the system.

In addition, WRMS has the ability to produce time-series hydrographs for nearly 30 key wells throughout the basin. These wells, monitored on a monthly basis, function as key indicators of seasonal fluctuations in the basin's groundwater levels. WRMS increases the efficiency of data management and presentation, thereby accelerating the decision-making process with regard to water resources issues. In addition, WRMS provides a standardized format for the centralized storage of data, and simple menus and procedures allow WRMS users to store and retrieve data quickly. WRMS is continually updated to enhance performance and to take advantage of new features in the component software. It is the goal of the Hydrogeology Department to eventually allow access to the WRMS system through the Internet.

Groundwater Tracer Study Using Isotopes
As part of the Santa Ana River Water Quality and Health Effects Study, a study evaluating the use of isotopes to determine groundwater age and travel time, delineate groundwater flow paths, estimate the percentage of water from various sources, and provide hydraulic data to refine OCWD's understanding of the groundwater basin is being performed by the Lawrence Livermore National Laboratory, an agent of the U.S. Department of Energy.