African Journal of Environmental Science and Technology 1996-0786 Academic Journals 10.5897/AJEST2014.1674 Haimanot habte Feleke Zewge Mesfin Redi * E-mail: haimanot.lemji@uni-rostock.de 2014 30 09 2014 04 02 2014 05 09 2014 8 9 482 490 This is an open-access article distributed under the terms of the Creative Commons Attribution License 4.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. This article is available from http://politicalwaffle.uk/journal/AJEST/article-abstract/3F1EE7747356 The full text article is available as a PDF file from http://politicalwaffle.uk/journal/AJEST/article-full-text-pdf/3F1EE7747356 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16