Salinity Sensors for Hydrology Analysis and Control
Linda G. Bushnell†
Electrical Engineering Department
University of Washington
Seattle, WA 98195-2500
Abstract
This talk will first give an overview of the projects in our lab related to the control and analysis of
hydrology systems. The talk is in two parts. The first part is our work focuses on the hydrology in Willapa
Bay, WA, where our biologist colleagues conduct most of their field work. The core electronic
development here is our low-cost, data-logging salinity sensor. The development of this sensor was
motivated by many discussions with the environmental biologists at UW, who are seeking small, low-cost,
data-logging salinity sensors for their field work. Their dream is to have a “movie” of the change in salinity
on the estuary’s shores over various seasons and throughout the year. We present the complete design for
the sensor and a newly developed graphical user interface (GUI) using LabView™ that will aid in the
analysis of the sensor data back in the laboratory. The sensor is designed around two electromagnetic coils:
one for inductance and one for sensing the conductivity of the salt water. We will describe in detail the
testing done on the different magnetic coils’ orientations and experimental (lab and field) results. We will
also cover the experimental results of the integrated sensor and GUI system as a whole.
The second part of the work focuses on the hydrology in the Mekong Delta of southern Vietnam. We apply
automatic control techniques to the problem of coming up with an optimal schedule of opening and closing
the sluice gates that are sprinkled throughout the vast river system (in which the flow of the water goes both
directions). Currently the gates are adjusted with the tides, but this has caused acid build-up in the farms
(e.g., rice and shrimp farms). By framing this hydrological system as a controllable system, most control
techniques are applicable. Our goal is to deploy the above salinity sensors along with flow sensors and
depth sensors to modify the existing Vietnamese state river model (VRSAP - Vietnam River Systems and
Plains model) to achieve a simpler, more efficient model that we can build our control algorithms on.
Preliminary work in this direction will be presented.
Bio
Linda G. Bushnell received the B.S. degree in electrical engineering and the M.S. degree in electrical and
systems engineering from the University of Connecticut in 1985 and 1987, respectively. She received the
M.A. degree in mathematics and the Ph.D. degree in electrical engineering from the University of
California at Berkeley in 1989 and 1994, respectively. She was the Program Manager of the Systems &
Control Program at the U.S. Army Research Office and an Adjunct Assistant Professor of Electrical and
Computer Engineering at Duke University from 1994 to 2000. In September 2000, she joined the Electrical
Engineering Department at the University of Washington, where she is now a Research Assistant Professor.
Dr. Bushnell’s research interests include sensor design for environmental systems and networked control
systems.
† Joint work with students Thanh-Tung Pham, Thomas Green, Jonathan Chen, Phuong Truong and Aditya
Vaidya
“Irrigation Channels and Related Problems” Workshop, October 2 - 4, 2008, Maiori (Salerno, Italy)