Complex sentence: The Sankarani River is a tributary of the Niger River flowing northward from the Fouta Djallon highlands of Guinea, it crosses into southern Mali, where it joins the Niger approximately 40 km upstream of Bamako.
Split into simpler sentences: The Sankarani River is a tributary of the Niger River. Flowing northward from the Fouta Djallon highlands of Guinea, it crosses into southern Mali, where it joins the Niger approximately 40 km upstream of Bamako.