Monitoring the Spread of Water Hyacinth Using Satellite Imagery a Case Study of Lake Victoria
Abstract
Water hyacinth is aquatic vegetation that is believed to have been introduced to Lake Victoria in
1988. Using satellite images from 1988 to 2016, this research identifies the trend in the spread
and how human activities have contributed to the trend of spread of the water weed.
Landsat satellite images were obtained from internet open sources. Mosaicking and classification
were done to the images. During classification, six classes comprising of water, water hyacinth,
built up area, bare ground, other vegetation and unclassified were obtained. Built up area is
captured in the study because a 10 km buffer along the shores of the lake was included. This was
used to monitor the growth of urban centers around the lake. Growth in urban centers is due to
population pressure resulting from rural urban migration, and this resulted in increase in
pollutants draining into the lake.
From the satellite images used, it is observed that water hyacinth occupied very small area of
Lake Victoria in 1988. In this year, the area of the lake covered by water hyacinth was 2,846 m2,
this is approximately 3.4% of the total area of the lake. The weed spread over the years and in
the year 2000, it was occupying an area of 19,122 m2, which is approximately 23% of the whole
lake. This shows a tremendous spread of the weed. After the year 2000, the government took
some steps to counter the spread. And in the years 2004, 2008, 2012 and 2016, there was a
continuous reduction in the spread of the weed, whereby in the year 2016, it occupied an area of
4.9% of the whole lake. The weed is observed to be occupying mostly along the shores of the
lake where the water is shallow. This has greatly affected the fishing industry since navigation is
not possible in the areas occupied by the water weed. Where the fishermen find small entry or
navigation, overfishing is done due to small area available for fishing and the demand is high.
The results show that growth in urban areas is proportional to the amount of spread in water
hyacinth. Several efforts to curb the spread have been employed by different countries but none
has been totally successful. Human activities have been clearly demonstrated in this study to be
the major cause of the spread. NDVI maps were used to demonstrate where the water hyacinths
were healthy as compared to other regions.
This study recommends that human activities around the lake should be monitored and
controlled so as to reduce the pollutants entering the Lake. The study further recommends on
further study to discover other possible propellers of the spread of water hyacinth in the Lake.
Publisher
University of Nairobi
Subject
Monitoring the Spread of Water Hyacinth Using Satellite Imagery a Case Study of Lake VictoriaRights
Attribution-NonCommercial-NoDerivs 3.0 United StatesUsage Rights
http://creativecommons.org/licenses/by-nc-nd/3.0/us/Collections
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