Remote and Proximal Sensing for the Study of Anthropogenic Stress on lake Abijata

ABSTRACT

Lake Abijata is an endorheic lake with a centripetal drainage alimented by R.Bulbula, Horakelo and Gogesa. The Lake is bounded and surrounded by gently sloping bold watersheds with a number of rills and miner streams descending to the lake basin. The adjacent land is being used as animal feedlot and tillage which in turn supply rich nutrients for algal crops. Before the introduction of soda ash, the lake was rich in fish population, especially Tilapia which is the main species in the lake. Due to its fertility, it has been a feeding area for planktivorous birds. Because of this, the lake basin and the adjacent land is part of the 'Abijata-Shalla National park', especially for harboring birds of the Ethiopian and Palearctic biogeographic realms. The water has a sodic phase, which is also a favorable medium for algal growth. With the introduction of agro-industrial Ziway and Abijata, especially pumping lakes water for irrigation and soda-ash extraction have been imparting serious ecological problems. However, Lake Abijata offers an idea site for the algal culture.

The principal aim of the proposal is to introduce algal culture at Lake Abijata to supplement the ailing food shortage in the country.

To estimate the eutrophic state of Lake Abijata, two new approaches were proposed, namely imaging and non-imaging systems. The former dealt with remote while the latter was based on proximal sensing. The Remote Sensing technique employed is a new approach. The idea stemmed from the difference which exists between higher forms and Phytoplankton in the utilization of the Photosynthetic Active Radiation (PAR). Most algal species, especially Chl-a exhibit a maximum reflectance in the green and medium in the infrared regions of the EMR.

The parametric analysis done using proximal sensing showed peak reflectance in the green region of the spectrum. This shows that Lake Abijata is a productive lake. For algal eutrophication and hypereutrophication study, a new PS SPECROSCOPY is suggested at the annex, please.

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