perhaps, these are problems of complex aggregation that are confounding our attempts to quantify predictions of large-scale hydrologic processes. The physics of a nonlinear process is well known under idealized, one-dimensional laboratory conditions, and we wish to quantify the process under the three-dimensional heterogeneity of natural systems, which are orders of magnitude larger in scale. Solving these problems will require well-conceived field data collection programs in concert with analysis directed toward “renormalization” of the underlying dynamics. Success will bring to hydrologic science the power of generalization, with its dividends of insight and economy of effort.

Opportunities in the Hydrologic Sciences (NRC, 1991)

Innovative Engineering Approaches for Improving Water Quantity and Quality Management: The research should aim to improve our capabilities in hydrologic forecasting for water resource managers to evaluate and make decisions. Networks of sensors, robotic water quality monitoring sites, realtime data collection, and communication links can be developed into an intelligent environmental control system that will enhance the protection of urban ecosystems and the health and safety of its inhabitants. Such a system can be used as an early warning system and to identify emerging problems such as flooding, lack of water, riparian habitat degradation, and the presence of toxic compounds.

CLEANER and NSF’s Environmental Observatories (NRC, 2006)

Land Surface-Atmosphere Interactions: Understanding the reciprocal influences between land surface processes and weather and climate is more than an interesting basic research question; it has become especially urgent because of accelerating human-induced changes in land surface characteristics in the United States and globally. The issues are important from the mesoscale upward to continental scales. Our knowledge of the time and space distributions of rainfall, soil moisture, ground water recharge, and evapotranspiration are remarkably inadequate, in part because historical data bases are point measurements from which we have attempted extrapolation to large-scale fields. Our knowledge of their variability, and of the sensitivity of local and regional climates to alterations in land surface properties, is especially poor. The opportunity now exists for great progress on these issues.

Opportunities in the Hydrologic Sciences (NRC, 1991)

Find solutions to existing and emerging problems involving contaminants in the environment that affect ecosystems and human health. Some environmental problems that affect water resources are of such a magnitude that they are of