FLOOD AND DROUGHT CYCLES IN THE TANA RIVER BASIN

ABSTRACT
There are five major river basins in Kenya namely, Lake Victoria, Rift Valley, Athi River,
Ewaso Ngiro and the Tana River Basin which is one of the biggest river basins in the country.
This project will focus on the lower parts of Tana River basin that are prone to recurrent
floods and droughts. The Tana River Basin gives rise to the Tana River drainage network, the
longest river in Kenya, stretching about 1,014 km, which drains the excess water from the
basin and discharges its silt-rich, muddy waters into the Indian Ocean near Kipini on
Ungwana Bay. The Tana Delta is a vast seasonal wetland complex which experiences
extreme seasonal climatic variations, ranging from drought to flood. Water availability
fluctuates from year to year. In a wet year, for example, water is added to the storage whereas
water losses from evaporation and evapotranspiration are less. However, in a dry year the
converse is true; there is great abstraction from the basin without sufficient recharge and
evaporation and evapotranspiration cause great water losses.
In this dissertation, I sought to do a detailed investigation of the hydrological conditions of
the Tana River basin and delta focusing mainly on the flood and drought cycles that occur

along the length of the Tana River. As the project is theoretical it required gathering and
analyzing large amounts of data. To this end the relevant authorities and experts were
approached and consulted. After the compilation of data was complete, analysis was done on
it and the results presented in chapter 5. I consulted the Water Resources Management
Authority (WRMA) and the Ministry of Water and Irrigation (MWI) for their data. WRMA
provided me with the flow data for the Tana River over the period of consideration, around
50 years, while the Ministry had the data pertaining to water availability and use in the basin.
In order to ascertain the causes of the perennial drought and flooding in the Tana basin
required an in depth look into the information already held by government institutions and by
private firms which have conducted similar surveys in the area. Annual rainfall analyses
indicated that the amounts of rainfall in the areas alone may not be enough to cause such
flood and drought cycles. Instead, massive water inflows emanating from the bursting of
River Tana’s banks are the main cause of floods. The drought situation is further aggravated
by deforestation, rapid urbanization and weak enforcement of the government’s policies.

Finally, recommendations were made on how best to address the issues plaguing the Tana
delta and how to avoid the same problems occurring in the future.

 

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