A QUALITATIVE INDEX OF SOIL EROSION FOR THE TEKEZE RIVER WATERSHED IN ETHIOPIA

Jared Heath and Johannes Beeby

    From its different cultures, tribes, wildlife, and landscapes, Ethiopia has long been known as a country of great diversity. Despite all of its beauty, Ethiopia might be better known for its harsh lands and starving people. It is this harsh reality that has begun to change the land of Ethiopia in ways that are not sustainable.

    For our project, we are looking at the Tekeze River watershed in Northern Ethiopia. The Tekeze watershed is just one of many areas within Ethiopia that are experiencing negative changes due to harsh lands that cannot provide for an ever growing population. Many local people within the Tekeze lowlands have found the soil too poor to grow crops and have resorted in keeping livestock, resulting in increased erosion near the river’s banks. Others have left the lowlands of the Tekeze and have moved to the highlands where mountains reach over 4000 meters. Here the soils are more fertile, however, the available land for producing crops is not enough to sustain the local communities.This in turn has forced the local people to try and cultivate crops on the steepest of lands to feed their families. All of this has led to increased soil erosion within the Tekeze watershed. This increased sediment is important as the Tekeze River is one of the Nile’s tributaries, which is the lifeline to many neighboring countries. Also the many dams already in place within the Tekeze watershed could be compromised by sediment deposition in the reservoirs. Not to mention the on going construction of the highest double curve arch dam in Africa being put in place on the Tekeze River. It may be a long time before sediment could possibly fill the enormous reservoir, however, soil erosion within the Tekeze watershed will have a huge negative impact on the surrounding lands and the people who are trying to live off of those lands.

    Therefore, we found it important to come up with a qualitative erosion index for the Tekeze River watershed. A qualitative index was chosen over quantitative because having never stepped foot in Ethiopia, neither of us felt comfortable with calculating actual numbers of soil erosion, but opted with finding areas within the Tekeze watershed that would be at higher risk to erosion. This qualitative analysis was performed by applying the Universal Soil Loss Equation (USLE) within GIS to the Tekeze watershed. Actual methods of applying USLE within GIS can be found on the GIS Analyses page.