An investigation of the nature, causes and effects of long term environmental degradation on watershed natural resources : a case of Belbela-Wadecha watershed ecosystem, Central Ethiopia

Abstract

Land degradation is a process in which the value of the biophysical environment is affected by a combination of nature and human-induced processes acting upon the land. It is viewed as any change or disturbance to the land perceived to be undesirable. Soil degradation is one aspect of land degradation and others are vegetation or water resource degradation. The Belbela-Wadecha watershed ecosystem in its current state is practically a degraded phenomenon, and thus the previous benefits it could provide would have been affected, as a result. As can be perceived from physical observation, vegetation has vanished, soils are eroded, gullies have formed, reservoirs are filled up with sediments, canals are blocked / clogged, dam water storages have declined, and flooding have caused major damages. Reportedly, malarial incidents have become high because of formation of damp soils due to the stagnation of water. As a result, existing economic, social, and environmental benefits have been affected in a way imposing hard and unusual way of experience of pattern of life. Since 1985, different LandSat satellites have been used to observe Earth from space and provide data that help the public and scientific community to understand the state and condition of Earth’s surface through time. In order to assess the land change, remote sensing (RS) imageries from the LandSat satellites have been used. Satellite remote sensing can help to enhance largely the capabilities of monitoring the actual state of land uses in a comprehensive and timely manner. It fulfills the requirements for monitoring and mapping the status of agricultural land use and land change, because satellites deliver objective and timely (every 5-6 days) information regularly. The high spatial detail of satellite images (10-meter pixels) enhances tracing these activities at different scales: from the single field level (study area) and even up to country level. In this study, the methodologies that were deployed to assess land degradation (land cover changes) of the study area relied on the processes of remotely sensed imageries using different satellites of LandSats 4-5 Thematic Mapper (TM), and LandSats 7 and 8. The main dominant bands were bands 1, 2, 3, 4, 5, 6 and band 7 based on the types of LandSats. In general, Green, Red and Blue (RGB) colors and reflectance of vegetation in Near Infrared (NIR) bands were used in the analysis. In addition, qualitative primary data was sought through focus group discussions, questionnaire survey and secondary information from document analyses to explore the causes and effects of environmental degradation in Belbela-Wadecha watershed ecosystem in Central Ethiopia. The participating communities were also involved from the beginning through Participatory Action Research (PAR), in identifying causes of degradation in the watershed responding to them through a pilot trial project. The combination of data collected from satellite remote sensing, Participatory Action Research process, physical ground observation, questionnaire survey, focus groups discussions and the secondary data was analyzed qualitatively and quantitatively and the results interpreted to help in designing future directions in watershed resource management. Furthermore, the integration of the results of both qualitative and quantitative research analyses helped in making conclusions and recommendations towards improving the natural setting of the ecosystem. The main findings and conclusions hinged on ensuring parallel and harmonious operation of both environmental management and agricultural irrigation systems with a view to achieve sustainable environmental, social and economic well-being. Because of ecosystem restoration and sustainable downstream irrigation agriculture, it was hoped that this would lead to the improvement of livelihood sustenance through economic, social and environmental benefits.