Shrinking Water Sources: Lake Chad.

Lake Chad is a classic example of the impacts of environmental change on the hydrological system in Africa and therefore an excellent place for us to begin our exploration of this topic. Lake Chad is located in the centre of the semi-arid Sahel region of West Africa, spanning areas in Niger, Nigeria, Chad, and Cameroon.  In the 1960’s it was ranked as the world’s 6^th largest inland water body, covering an area of 25,000 km². By 2004, its area was just 532 km², a reduction of approximately 90%. The scale of the change can be visualised in Figure 1. The lake has huge economic importance for the area, namely for the fishing industry but also for agriculture and pastoralism. Therefore measuring the changes to the lake and identifying the parameters that influence them is vital to adaptation.

Figure 1- A map of Lake Chad and its surrounding area, showing the character of the lake in 1960 and 2002.

The rainfall patterns over the Lake Chad basin have a latitudinal gradient, with the south of the basin experiencing more rainfall than the north due to the differences in their climatic zone and there are existing seasonal variabilities in rainfall. There are a number of rivers and streams that supply water to Lake Chad, including the Komadugu Yobe and the Yedseram. The most important of its tributaries is the Logone-Chari river system which provides >90% of the total water discharged into the lake every year. Both of the inputs defined above are balanced by evaporation and groundwater seepage. Since the 1960s, the basin has experienced an overall decline in rainfall, amplified by a series of droughts throughout the 1970s and 1980s and therefore reducing the water inputs to Lake Chad. Equally, discharge from the Logone-Chari has decreased by approximately 75% between 1960 and 2000, decreasing the water levels and extent of the lake further. The shallowness of Lake Chad (>7m) means it responds rapidly to these changes in inputs and is another factor in the lake’s dramatic reduction over the past few decades.

The Lake Chad case study also showcases how climatic factors and human influence so often go hand in hand in instigating environmental degradation. After 1983, precipitation remained low but irrigation withdrawals from the lake increased up to four times the rate of the previous two decades. The increase in irrigation was directly spurred by the dry climate conditions and the water insecurity ambient at this time. In this way, it’s difficult to untangle climatic and human influences but it makes clear the necessity for effective water management, especially under the circumstance of environmental change.

In my next post, I’ll discuss some of the measures in place to aid in the protection of Lake Chad and how they can be improved to ensure Lake Chad continues to be a valuable and sustainable resource.