Mapping Aquatic Vegetation on Lake Victoria

Moderate Resolution Imaging Spectroradiometer (MODIS)  imagery depicting Lake Victoria normalized difference vegetation index (NDVI) extraction before (left) and after (right). The left shows an unprocessed satellite image, while the NDVI image is shown on the right, depicting aquatic vegetation in green. Bright green areas indicate dense aquatic vegetation. Source: USGS.

Moderate Resolution Imaging Spectroradiometer (MODIS) imagery depicting Lake Victoria normalized difference vegetation index (NDVI) extraction before (left) and after (right). The left shows an unprocessed satellite image, while the NDVI image is shown on the right, depicting aquatic vegetation in green. Bright green areas indicate dense aquatic vegetation. Source: USGS.

Team Location: Mobile County Health Department

Authors: Hunter Winstanley, Tharini Jeyaprakash, Moara Martins, Naresh Aligeti, Josh Stodghill

Advisors/Science Mentors: Dr. Bert Eichold, Dr. George Crozier, Joe Spruce

Abstract: Lake Victoria in Africa is the second largest freshwater lake in the world and is known for its abundance of aquatic wildlife, in particular more than 200 different fish species that are caught and sold by local fishermen. The lake is a major contributor to the local economy as a corridor of transportation, a source of drinking water, and a source of hydroelectric power. However, the invasion of aquatic vegetation such as water hyacinth (Eichhornia crassipes) in the lake has disrupted each of these markets. Aquatic vegetation now covers a substantial area of the coastline, blocking waterways, disrupting hydroelectric power, hindering the collection of drinking water, and decreasing the profitability of fishing. It serves as a habitat for disease-carrying mosquitoes, as well as snakes and snails that spread the parasitic disease bilharzia. The current control measures of invasive aquatic vegetation rely on biological, chemical and mechanical methods. Our results were used to assess the effectiveness of each control measure. The objective of this study was to use remote sensing to map the aquatic vegetation growth from 2000- 2011 within Lake Victoria. ASTER, MODIS and Landsat 4-5TM and 7-ETM imagery was employed to perform change detections in vegetation and identify the dispersion of water hyacinth throughout time. The feasibility of using the Advanced Land Observing Satellite Phased Array type L-band Synthetic Aperture Radar for such studies also was assessed. The efficiency of containment efforts was evaluated and an ideal timeline for the application of such efforts were suggested. A methodology for aquatic vegetation surveillance also was created. The results of this project were presented as a workshop to the Lake Victoria Fisheries Organization, SERVIR, and other partner organizations. The workshop provided instruction into the use of NASA and other satellite-derived products. A written report of this study’s findings was provided to organizations involved in aquatic vegetation removal efforts. Time-series animations of the spatial extent of aquatic vegetation within the lake were created. SERVIR will subsequently use the methodologies and mapping results of this study to develop operational aquatic vegetation surveillance for Lake Victoria.

Video transcript available here.