The full dimensions of the challenges and opportunities associated with data collection and management for the hydrologic sciences have become evident in recent years. These issues are especially important for federal agencies because these agencies are instrumental in developing new monitoring approaches, in validating their efficacy through field studies, and in managing nationwide monitoring networks over long periods.

This chapter is not a comprehensive assessment of water resources data collection activities. Rather, it is intended to highlight the importance of data collection and its role in stimulating and facilitating water resources research. Thus, it relies upon a few specific examples from certain federal agencies. As a consequence, not all data collection activities relevant to water resources research are included (e.g., active disease surveillance and monitoring of land use are not discussed), nor are all federal and state agencies that support or actively conduct monitoring mentioned.

CHALLENGES IN MONITORING

There are important challenges facing federal agencies that collect and manage hydrologic data. One of these challenges is related intrinsically to the types of problems for which hydrologic data are being used. For example, the analysis of problems related to floods and droughts requires specific information about extreme events, which can be developed only after conducting decades or even centuries of precipitation and streamflow monitoring across a variety of different climatic and hydrologic settings. Similarly, an assessment of the impact of global climate change on groundwater and surface water resources will require basic monitoring systems capable of providing data for time periods of centuries. With other problems, like nonpoint source contamination of streams resulting from runoff laden with nitrate, pesticides, and sediment, hourly data may be required because of the close association of stream contamination with the timing of storms and resulting runoff processes. In this case, the greater challenge is encompassing all relevant spatial scales, because the local variability in contaminant loading is related to changes in land use and farming practices. In general, the broad spectrum of present and future scientific water problems nationwide requires monitoring systems that function reliably over both large and small time and space scales.

Unfortunately, as described in detail in later sections, observational networks to measure various water characteristics have been in decline during the last 30 years because of political and fiscal instabilities (e.g., NRC, 1991; Entekhabi et al., 1999). The following sections provide a detailed discussion of how several national monitoring networks have fared over time. The funding situation for monitoring networks is remarkably similar to that for research on improving data collection activities (Category VII), which Chapter 4 showed as having declined to a level that is only a fourth of its value in the mid 1970s. These facts point to



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