TITLE:
Influence of Tea Plantations, Forest and Mixed Farming on Stream Flow and Sediment Loads, Case of Sondu Miriu River Basin, Kenya
AUTHORS:
Nancy C. Koech, Johnson U. Kitheka, Hesbon Otieno
KEYWORDS:
Sediment Loads, Stream Flows, Tea Plantation, Forest, Mixed Farming and Sondu Miriu
JOURNAL NAME:
Open Journal of Modern Hydrology,
Vol.12 No.4,
October
9,
2022
ABSTRACT: The changing patterns of land cover and land use in
the tropical river basin over time are critical. The hydrological phenomena at
basin and sub basin scale are affected positively or negatively by dynamics of
the land cover and land use patterns. Hence identifying causes and driving
factors aid in taking appropriate measures to avert the impacts. This study
determined the influences of sub basins dominated by tea plantations, forests
and agricultural land uses in terms of streamflow and sediment flux variability
in Sondu Miriu River Basin in Kenya, East Africa. Field-based investigations
were conducted through sampling of flow velocities, turbidity and TSSC obtained
from existing River Gauging Stations established within the three sub basins.
The sub basin dominated by mixed farming
land cover exhibits high turbidity approximately 620 NTU and high levels
of total suspended sediment concentration (TSSC) of the order of 630 mg/l in
wet seasons. The turbidity levels and TSSC were low in sub basins dominated by
forest and tea plantations with approximately mean value of 17 - 29 NTU and
0.019 g/l. The sediment loads in sub basin dominated by mixed farming in the
pre planting season in January to February were about 900 tonnes/day higher than
that in crop growing season. In sub basins dominated by forest cover and tea
plantations, sediment loads were low ranging between 2 - 7 tonnes/day. The
relationship between stream flows and area under tea plantations, forests and
mixed farming ranged between R2 of 0.025 and 0.16. Tea plantations and forests influence the stream flows and
sediment yields in long term duration while in mixed farming variations were
observed seasonally. The strong relationships between rainfall and stream flows
at the sub basins ranging between R2 of 0.84 and 0.97 revealed the
significance of rainfall in hydrologic response of the Sondu Miriu River Basin.