Water Quality characterization and Aquatic, Sub-aquatic and Benthic mapping are key applications for environmental monitoring. Among the many aquatic applications are: Eutrophication monitoring, sub-aquatic vegetation mapping, turbidity, and coral reef and littoral mapping.
Eutrophication and Chlorophyll-A Mapping
Hyperspectral imagery can be used to characterize the known absorption features of chlorophyll-a found in phytoplankton and algae. Increases in measured chlorophyll-a content within a water body represent the biological response to nutrient availability and indicator of its trophic state. Such spatially mapped information can be used for point-source and non-point source pollution detection and monitoring. The imagery itself can be used to generate a relative map of the chlorophyll-a but when coupled with in-situ measurements, true quantitative concentrations (µg/L) can be modeled such as in the above example for Hood Canal, Oregon.
Hyperspectral imaging can be used characterize the water turbidity levels. Turbidity is a measure of suspended solids in the water column on the transmission of light. While mapped turbidity levels are useful for identifying sources of runoff and sediment, it also is an important measure of ecosystem health. Increases in turbidity levels decrease the photic zone depth, the depth at which enough light penetrates to allow the support of photosynthetic organisms like coral reefs or submerged aquatic vegetation.
Sub-Aquatic Vegetation Mapping
Far better than the human eye or standard photography, the narrow bands associated with hyperspectral imagery provide better water penetration and therefore improved mapping capability for submerged aquatic vegetation. Whether for outlining protection areas for eel grass (Zostera) or for aiding eradication programs for invasive species like Elodia or Hydrilla, airborne hyperspectral imagery can be an important tool.