Expert Report

Each report is produced by a committee of experts selected by the Academy to address a particular statement of task and is subject to a rigorous, independent peer review; while the reports represent views of the committee, they also are endorsed by the Academy. Learn more on our expert consensus reports.

Water is essential to life for humans and their food crops, and for ecosystems. Effective water management requires tracking the inflow, outflow, quantity and quality of ground-water and surface water, much like balancing a bank account. Currently, networks of ground-based instruments measure these in individual locations, while airborne and satellite sensors measure them over larger areas. Recent technological innovations offer unprecedented possibilities to integrate space, air, and land observations to advance water science and guide management decisions. This report concludes that in order to realize the potential of integrated data, agencies, universities, and the private sector must work together to develop new kinds of sensors, test them in field studies, and help users to apply this information to real problems.

Key Messages

  • Addressing the Fractured Federal Responsibility for Hydrologic Measurement, Monitoring, and Modeling. The overarching barrier to the development and implementation of integrated hydrologic measurement systems is the lack of a single federal agency with primary responsibility for measuring, monitoring, and modeling the environmental factors and processes that control the hydrologic cycle.
  • Airborne Sensors. Airborne measurements operate at a spatial scale that fills the gap between the in-situ plot-scale observations and the larger satellite-scale observations.
  • Bridging the Gap between Sensor Demonstration and Integrated Field Demonstration. Closing this gap would involve integrating the sensor networks and webs within hydrologic observatories and experimental demonstration sites, and interfacing the sensor networks with the broader development of cyber infrastructure.
  • Development and Field Deployment of Land-Based Chemical and Biological Sensors. Physical sensors, such as those that measure air and water temperature and pressure, radiation, and wind speed and direction, are now mass produced and routinely packaged together in small instruments along with power and communication devices.
  • Funding Highly Interdisciplinary Science. Interdisciplinary science is increasingly common, but the design and use of integrated hydrologic measurement systems in specific research applications adds complexity to the challenge. These new kinds of projects will require unprecedented interdisciplinary cooperation among electrical engineers, computer scientists, modelers, and the physical, chemical, and biological scientists who apply technology to hydrologic research.
  • Spaceborne Sensors. In satellite-based remote sensing, NASA has made good progress in developing and deploying sensors used primarily for research.
  • Two chalenges are relevant to this report: (1) a resolution of the research-to-operations transition from NASA-developed experimental satellite observations to the broad variety of operational agencies and users that need routine (i.e., operational) observations, and (2) the lack of a corresponding monitoring strategy by entities such as EPA, USDA, NOAA, and state water and natural resources agencies that would incorporate airborne and/or satellite remote sensing measurements, where appropriate.
  • Water Resources Applications. In the United States, large water resources problems involve multiple stakeholders, including government agencies, business interests, and the public. Management is typically diffuse, and standard measurement and modeling techniques and rules for water management are entrenched and often legally mandated.
  • observations would offer improved predictions.