Week 3 - Weathering and Erosion in the Nyabarongo River, Rwanda

Nyabarongo River, Rwanda

The Nyabarongo River is at the center of Rwanda’s hydrological system. Long of 297 km (184 miles), it is the longest river in the country. Its waters are a good indicator of much of the state of Rwanda’s environment. It takes its source in the high altitude rainforest of Rwanda’s South-West, perched at 2,600 to 2,750 meters (8,530 to 9,020 ft) above sea level. Although contested, some assert that here, in the Nyungwe Forest, a tributary of this river is the most distant source of the mighty Nile River. From this source, it flows in the North-West direction with a dendritic drainage pattern. It then pours through the Centre in the South-East direction in remarkable meanders, where it joins its main tributary, the Akagera River. It ends its course in the Lake Victoria, the largest lake on the continent and a reservoir for the Nile.

Its drainage basin is divided into two systems that present very different features.

The Upper Nyabarongo drainage basin is the largest with 3,348 Sq. km, representing 12.7 % of the total surface area of Rwanda.

Upper Drainage Basin (IWRM)

And the Lower Nyabarongo drainage basin is the smallest in surface area, with 3,304 Sq. km, but contains an important drainage sub-basin of streams and a lake.

Lower Drainage Basin (IWRM)

But a worrisome development in the Upper basin picked my interest following this week’s reading. It is considered one of the water towers of Rwanda. However, it is situated in a densely populated region of the country with approximately 1.4 million people living within its drainage divides, including urban settings. The land is mostly used for rain-fed agriculture and irrigated agriculture in wetlands. However, most problematic of all, an increase in illegal mining and quarry activities have been registered in the area.

Nyabarongo River meanders with muddy appearance (Kwizera)

The erosion of soil in the area has become an issue of great public concern following these persistent trends of unsustainable land use practices. The river appears very muddy which is indicative of a considerable amount of sediments beings washed away from arable land upstream. It has necessitated grand scale public programs of promoting sustainable mining, terraces, agro-forestry, and afforestation. I hope these measures will yield the expected results for prosperous communities living in harmony with their environment.

Source:

The Rwanda Water Resource Portal: https://waterportal.rwfa.rw/data/surface_water

IWRM Programme Rwanda:
http://www.water.rw/