This white paper describes the emerging technologies used in distributed sensing systems and the opportunities these systems present for environmental management, and in particular, water quality protection. A team of faculty, students, and staff at the Center for Embedded Networked Sensing (CENS) wrote the report. CENS is a National Science Foundation sponsored Science and Technology Center, headquartered at the University of California, Los Angeles (UCLA). In addition to UCLA, the California Institute of Technology, the Riverside and Merced campuses of the University of California, and the University of Southern California are partners in the center. CENS is developing embedded networked sensing systems and applying this technology to critical scientific and social applications. The Foresight and Governance Project at the Woodrow Wilson International Center for Scholars edited and finalized this document for the U.S. Environmental Protection Agency’s Office of Water.

This paper first briefly describes the potential applications of sensing systems to four common water quality management problems. This potential includes: (1) providing early warning for septic systems, (2) allowing for the trading of credits for non-point source runoff, (3) monitoring beach water quality, and (4) management of combined sewer overflows. Section 4 describes these scenarios in further detail.

Section 1 provides an overview of sensors (i.e., the devices that convert environmental phenomena into an electronic response) and actuators (i.e., the devices that convert electrical signals into mechanical responses). Sensors have the potential to detect physical, chemical, biological, and radiation properties in the environment. A variety of sensors is currently available for networked environmental sensing, while others are still in early research and development phases. Physical sensors for water quality monitoring are generally the most field-ready and scalable to distributed applications, followed by chemical and then biological sensors. The costs for these sensors depend on the physical, chemical, or biological parameter of interest. Indicator sensors and event-triggering sampling can be used when direct detection sensors are not ready for field deployment. To more extensively detect environmental properties, even more sophisticated sensors and sensing strategies are needed, including: (1) hardening novel sensors types (such as lab-on-a-chip technology) to withstand harsh conditions for extended periods, and (2) devising integrated sensing systems for higher order observations, such as quantifying materials fluxes in the environment.

Section 2 on Deployment Platforms discusses three new sensing system classes: static, mobile robotic, and mobile handheld. These sensing systems differ from traditional measurement systems in that sensors are attached to wireless radios that enable real-time communication of the data collected. For any particular situation, the best system class to use depends on the environment’s spatial and temporal variation. Among the three classes of sensing systems, mobile handheld systems are best used when the environmental phenomena of interest cover a broad area and do not require great spatial resolution. Static sensing systems are best used over smaller areas when high spatial resolution is not required, and mobile robotic systems are appropriate for intensive measurement of very small areas. To improve overall sensing efficiency (e.g., time or cost), adaptive sampling allows the system to dynamically adjust its measurement location or frequency to meet spatial or temporal variation in the environment. Sensing platforms can also be combined such that different platforms can provide information at different scales. This type of multi-scale system can also often help improve the efficiency of a monitoring effort. Despite the opportunities these sensing systems present, the ability to deploy them in the field can be limited by power availability and faults that interfere with communication or sensing hardware.

To help address some of the challenges facing the effective implementation of sensing systems and the interpretation of the acquired data, section 3 discusses the usefulness of considering the entire “life cycle” of data in a sensing system. This life cycle consists of three distinct phases: design and deployment of the observing system; operation and monitoring; and analysis, modeling and data sharing.

The final section of the report offers recommendations for future research. In spite of the substantial success in research and development activities that has given rise to existing sensing systems, relatively few have been deployed in real-world applications. The time is ripe to expand the range of applications where embedded sensing systems are used. Some of the key recommendations outlined in section 5 for novel uses of embedded sensing systems include:

Sensors and Actuators
• (1) Long-term research and development for sensors where new or improved detection methods are needed and (2) short-term market incentives targeted at moving already well-developed sensing technology from research prototypes (e.g., biological and chemical sensors) to commercially available products.
• Long-term research to develop detection methods for carbonaceous compounds, heavy metals, large molecular mass molecules such as dissolved organic compounds and dissolved organic nitrogen compounds, pathogenic organisms, biologically-active compounds, biomarkers, and lab-on-achip sensors.
• Research on methods to minimize sensor maintenance in the field.
• Investments to bring prototype technologies, such as small robust nitrate sensors that can be deployed for long periods, to market in forms suitable for environmental sensing.

Deployment Platforms
• Investments in a range of pilot studies to determine specific deployment and analysis methodologies for target systems (e.g., septic system or sewage discharge monitoring).
• Definition of requirements of large scale uses of the technology to encourage the production of user-friendly systems.

The Data Life Cycle
• The encouragement of pilot deployments to test and refine data management tasks for specific applications.
• Continued research and testing of tools to improve system robustness and ensure high-quality data.
• Additional focus on the integration of sensing systems with external data sources and third-party applications, especially map-based visualization with tools for both rigorous GIS techniques and more public friendly web applications.

Training
• Training at multiple levels (school systems and professional development) to ensure that a ready workforce exists that is prepared to use these new sensing technologies.

Embedded networked sensing systems will form a critical infrastructure resource for society—they will monitor and collect information on such diverse subjects as plankton colonies, endangered species, soil and air contaminants, medical patients, and buildings, bridges and other manmade structures. Investments in further research to help bring the sensing technologies discussed in this report into practice will transform the way we monitor and manage the health of our natural resources and predict and respond to crises.

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Jeff Goldman, Nithya Ramanathan, Richard F. Ambrose, David Caron, D Estrin, Jason Fisher, Robert Gilbert, Mark Hansen, T C. Harmon, J A. Jay, W J. Kaiser, Gaurav Sukhatme, and Yu-Chong Tai, "Distrbuted Sensing Systems for Water Quality Assesment and Management" (2007). Center for Embedded Network Sensing. Artice 1005.