Progress in the fields of electronics and computers has produced data‐acquisition equipment beneficial to ground water field studies. This equipment controls data collection from sensing devices and saves the data for later processing. There are many types of sensors available for in situ use in water quality monitoring wells, observation wells and water supply wells. Sensors are separated into two groups, those used to measure water levels and those used to measure water quality parameters. There are three major types of sensors for measuring water levels. They are floats, transducers and acoustic devices. Most types have proven accuracy and can be successfully applied to short‐term monitoring (i.e., aquifer tests) and long‐term field studies (i.e., one month to multi‐year trend analyses). They are most cost‐effective when augmented with the programmability of computers. For example, water level measurements are made only when the water level has changed some predetermined amount. Sensors to measure water quality include those that measure temperature, pH, specific conductance, dissolved oxygen and specific ions. Unlike water level sensors the accuracy of water quality sensors, with the exception of temperature, is difficult to verify in field conditions. This is because measurement of water quality parameters is dependent on the water in contact with the sensor being representative of the ground water in the formation. In addition, the performance of the sensor over periods greater than a few hours is reduced either because of the naturally occurring constituents in the water that interfere with the sensor or because of loss of sensor calibration. A potential use of water quality sensors for in situ investigations is to aid in surveillance monitoring to indicate the arrival of contaminants at the earliest possible moment. This has a narrow limit of practicality at this time because of problems associated with sensor accuracy. Many water quality sensing devices are well‐suited for research purposes. This includes measuring the migration of thermal fronts and application in conducting tracer tests.

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Subsurface fluid flow (ground-water and vadose zone) modeling / Joseph D. Ritchey and James O. Rumbaugh, editors. Papers from a symposium held June 22-23, 1996, in Denver Colo. Includes bibliographical references (p.

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