Lower Niger Basin to lose more soil with increasing rainfall in next 50 years

The Lower Niger Basin is expected to see an increase in soil loss in the coming decades with higher precipitation amounts, a new study by Chinese scientists found.

All Global Circulation Models scenarios applied in the study showed steady increases of rainfall-runoff erosivity by about 14.1%, 19%, and 24.2% from the baseline climate for the 2030s, 2050s, and 2070s respectively. Soil loss in this area gains by 12.2%, 19.3% and 20.6% from the baseline during the same period.

Erosivity is a measure of the potential ability of soil, regolith, or other weathered material to be eroded by rain, wind, or surface runoff.

The study, carried out by scientists from the Xinjiang Institute of Ecology and Geography (XIEG) of the Chinese Academy of Sciences, evaluated the long-term variations in the annual rainfall-runoff erosivity in the Lower Niger Basin with observation climate data from 1970 to 2013 from 20 meteorological stations in the Basin area.

Lower Niger Basin, located in western Africa, covers an area of 528,000 km2 and has a tropical climate with high rainfall intensity and highest mean erosivity.

“Climate change is expected to impact erosivity in Lower Niger Basin and other parts of the world. Temporal and spatial prediction of future rainfall-runoff erosivity under a changing climate has not been well documented, at the same time,” said LI Lanhai, scientist from XIEG who led the study.

As a sensitive basin responding to environmental change by climate, the Lower Niger Basin has experienced a recurrence of heavy precipitation events, more so in recent decades.

Higher precipitation amounts were the major drivers of the increase in the spatial and temporal rainfall-runoff erosivity. Rainfall-runoff erosivity has a significant contribution to the increase in soil erosion, LI and his team found in their study.

“The evaluation of rainfall erosivity and its implications can help practitioners and scientists to formulate better soil conservation practices and improve dam construction and agricultural management,” LI said.

More studies should be performed to include other important factors that encourage future increases in erosivity, especially future changes in land use, according to LI.

Results of the study were published in the recent issue of CATENA, entitled “Spatio-temporal variation in rainfall-runoff erosivity due to climate change in the Lower Niger Basin, West Africa”.