Novel approach to define the morphology of shallow lakes

Background/Question/Methods

The National Ecological Observatory Network (NEON) will detect and enable forecasting of ecological change from regional to continental scales over multiple decades, through the collection of data on the impacts of climate change, land use change and invasive species on natural resources and biodiversity. In order to enable comparative data analysis across the US at multiple temporal and spatial scales, the NEON infrastructure will be standardized both at the sensor and the field sampling level.  Following stringent quality-control checks the data will be posted on the open-access NEON web portal.

This poster presents technological capabilities to quantify lake bathymetry and morphology. Over the next year, NEON will census potential users of these data (e.g. lake ecologists, hydrologists) to determine the utility of various data products. Lake bathymetry and morphology are crucial data products used to drive both biological and chemical sampling strategies as well as informing the design, location and data products of long term continuous water quality sampling buoys. In addition, the data products defined by lake morphology will aid in identifying, at higher resolution, the current status and long term ecological changes incurred in the lakes. Researchers can combine these data with NEON data on riparian and watershed characteristics to evaluate the influence of landscape features on long-term lake morphology, water quality, and diversity.

Results/Conclusions

NEON is in the process of defining morphological data products that are of high utility to the research community. Using a novel approach of side-scan and down-looking sonar images processed in GIS, morphological maps can be produced with high accuracy. Using a Dual Beam (50 kHz and 200 kHz) High Definition Side Imaging (455 kHz and 800 kHz) instrument, depth is measured at 1 second intervals (average of 30 pings). Side scan images can be pre-processed using various software programs and then imported into GIS to create a sonar file for the whole lake. Morphological parameters that can be identified and recorded include biological (e.g. macrophyte distribution, large woody debris), physical (e.g. sediment hardness, shoals, rocks, depressions ect.) and other non-natural features (e.g. buoys, docks ect.). Using Image Classification in GIS, the features in the collated sonar images can be identified and assigned a class that will convert an image to a thematic map.