Referred to as ‘Scotland with lions’ the Aberdare ranges (Kenya) not only forms a section of the Great Rift Valley but it also gives rise to the longest river in Kenya. Flowing over 900km and through the snow-capped Mount Kenya, the Tana River marks the western boundary of the hirola’s geographic range and brings life to our semi-arid region.
With an average annual flow of 5000 cubic meters, the Tana river flows throughout the year and it is the only permanent river within the hirola’s range and a vital resource to locals, wildlife and vegetation. When the river discharge water over its banks and onto the floodplain, a large amount of sediment rich in nutrients is deposited. This periodic inflow (recharge) of water and nutrients makes these floodplains productive and have played a critical role in providing seasonal “fall-back” forage for a portion of the hirola population for centuries.
However, with a series of hydroelectric dams constructed along the river since the 1960s, the regeneration potential of these floodplains have been reduced and subsequently altering the frequency of the forage available for hirola during critical periods. These floodplains can be up to to 6 km wide over parts of hirola’s range. The natural hydrological regime of the Tana river typically consists of biannual floods, with peaks in May and November. Historically, flood extent (heights) and periods varied considerably along the Tana. These are now partly controlled by the five dams constructed along the Tana in the last five decades. Further, these critical areas are also threatened by overgrazing, farming and bush encroachment from invasive introduced species such as the Prosopis spp.
Within the hirola’s range, the river is flanked by two main tribes; the Pokomos (western bank) and the Somalis (eastern bank). Though neighbors for centuries, they have contrasting backgrounds and cultures. The Pokomos are ethnically Bantus who mostly depend on farming. These groups rely on the Tana river to irrigate their farms and provides water for their domestic use. They also carry out small scale fishing around the banks of Tana. Within the length of the Tana, you will find the Pokomos in their homemade canoes fishing, despite the presence of vicious predators under the waters. Somalis on the other hand are Cushite who predominantly practice pastoralism. They mostly depend on their livestock for livelihood and traverse the vast hirola’s range for pasture and water. Like the hirola, they mostly move closer to the Tana during the dry seasons and drought spells. These movements usually trigger a lot of conflicts as livestock invade the farms of their neighbors. Despite these differences, a common factor is that they are the unofficial custodians of the flora and fauna around the Tana river including the hirola antelope.
This river is not only a lifeline of the people, livestock and hirola but also plays host to wildlife including the Nile croc and the dreaded giant hippopotamus. The Nile croc, the largest fresh water predator in Africa, is perhaps the most successful predator the world has ever seen. They have a cerebral cortex that makes them extremely intelligent and helps them learn behavior, patterns and timings. This makes them very dangerous more so to the local folks who follow routines such as early morning fishing, fetching of water by females, bathing of children by the banks and evening quench of thirst by livestock.
On the other hand, the hippos usually mind their own business during the day but turn disastrous in the cover of darkness. They come out of the river at night and destroy farms within their vicinity. They are dreaded and most locals fear encountering them. Their attacks are usually vicious and almost always end up in death.
Despite the lurking dangers around the flow of the Tana, the locals cannot do without it. They depend on it for their livelihood and survival and have adopted ways of living with these dangers. As intelligent as the crocs might be, the locals are usually a step ahead. Unfortunately, once in a while these predators win as death of a local occurs.