Applying Geographic Information Techniques to Study Water Resources for the Next 20 Years

摘要

For the next twenty years, water availability, water quality, and, thus, water conservation are arguably among the primary challenges that every country in the world will face. Monitoring water quality and identifying the location and magnitude of existing and potential pollution sources and impacts will continue to be the important activities to ensure an adequate supply of earth's most precious natural resource. Geographic information techniques, such as remote sensing and Geographic Information Systems (GIS), will continue to be some of the effective tools for collecting and analyzing the data for water quality and quantity.Documented water-related attributes that can be remotely measured include surface area, water quality, bathymetry, surface temperature, snow and ice mapping, snow and ice to water calculation, cloud cover, precipitation and water vapor (Jensen 2007). In measuring these parameters, remote sensing will continue to be one of most appealing fields of study and instrumentation to resource managers because it provides the simultaneous overview for a large region, which is unmatched by in situ measurement. The spatial component is always inherent in remote sensing processes. In addition, the pace and ease of data collection through remote sensing has become nearly a prerequisite to compiling the multitemporal datasets required for multi-scale and multidimensional biophysical change detection.Remote sensing will continue to be useful in monitoring water quality. While the optically active water constituents are measurable with remote sensing, other water parameters may still be indirectly detected. Chlorophyll a, due to its unique absorption characteristics in the visible spectrum, will be the prime test constraint. Inorganic suspended sediment concentration is another water quality indicator where remote sensing technology can be applied.Several satellite sensing systems were specifically designed for monitoring water quality chlorophyll a in ocean water, such as Coastal Zone Color Scanner (1978-1986) and the Sea-viewing Wide Field of View Sensor (SeaWiFS). They are mostly useful for Case I waters (deep ocean). Although the spectral resolution is not ideal, Landsat TM/ETM+ data have proven to be adequately useful for assessing estuarine systems because they are economical, routinely available, and archived. For example, chlorophyll a concentration, an indicator of the abundance of algae in water was mapped over Pensacola Bay, Florida using Landsat 7 ETM+ imagery (Figure 1).Figure1. Open FigureDownload Powerpoint slideChlorophyll a concentration map of Pensa-cola Bay, FL (May 2002) (after Han and Jordan 2005)