Remote Sensing and Freshwater
This post was written as a guest post for the MyWonderfulWorld blog for Geography Awareness Week. Be sure to head over and check out more of the MWW blog-a-thon for GAW.
Continuing Geography Awareness Week, we would like to talk about a topic that brings together geospatial technologies (it is GIS Day after all) with this year’s Geography Awareness Week theme of Freshwater. Water quality assessment is a crucial issue in many parts of the world due to causes such as pollution in manufacturing countries, scarcity in arid regions, and issues of access in urban areas. While Earth Observation Day is still a few months away (April 8, 2011), we wanted to take a look at geographic information gathered from remote sensing technologies to understand how this imagery can be used in studying water quality and other water-related issues.
There are a number of remote sensing studies that have taken advantage of spectral responses of specific phenomena to look at how light of different wavelengths can capture various water quality issues including sediments suspended in water, algae blooms, aquatic plants, and water temperature. Additional studies of these spectral responses have also been used to derive information on salinity (pdf) , water clarity, and other water topics. The United States and the European Union, for instance, both have water quality mandates that have been supported through the use of remote sensing imagery, and they are not alone in the use of such imagery to address this need.
In addition to studies that look at water quality, remotely sensed data has also been used to support a wide range of studies that deal with other water issues, such as identifying spatial changes in water bodies, by providing researchers with detailed views of an area. For example, remotely sensed data has been crucial in monitoring the contraction of the Aral Sea in central Asia, as well as other important bodies of water throughout the world. Other examples include mapping oil spills such as the spill this past summer in the Gulf of Mexico oil spill or change detection to track snow pack or glacial melt.
While information derived from aerial or satellite images can support the large area assessment of surface water sources, it is often supported through the use of other location information/technologies. In-situ sensors are used by agencies such as the USGS. A network of fixed location sensors is maintained that can be used to ground truth certain aspects of water quality. In the case of studies that look at locations other than those with static location sensors, GPS receivers are used to record locations, such as in the case of randomly sampled ground truth test sites.
Of course, the information that is captured and classified using remote sensing can be fused with other types geographic information to provide users and consumers with a contextual, and often richer, understanding of water quality issues. An article from the Summer 2009 issue of Imaging Notes, for example, talks about some of the GIS tools that are used in water quality modeling. The wealth of tools that can be brought to bear to assess water quality issues are growing and now include a number of geospatial technologies. So remember, even though we only celebrate Geography Awareness Week and GIS Day once a year, there are many amazing resources and research projects out there that utilize remotely-sensed information to help us understand and try to solve many of today’s pressing environmental issues, including water quality and availability.