| dc.description.abstract | Sand storage dams have been observed to be able to meet the integrated water requirements in
the arid Kitui district. This has been through various studies that have reported increased water
availability in the catchments developed with the sand dams.
This study looks at the causes of this increased amount of water in the stream channel. Among
the major study parameters include the storage capabilities of sand storage dams. This includes
the channel storage, bank storage capabilities, and the fluctuation in water levels both in time and
in different section of the stream channel in relation to position of the sand dam. This is in
relation to precipitation episodes in the catchment. The distribution of the sand dams in the
catchment was also mapped to show the convenience of water points. This showed great
reduction to the distribution of water points in terms of distances.
The volume of sand column in the river mapped using a dipping rode to show the storage
capacity in the stream channel. There was a large volume of sand which resulted from the
installation of the dam wall. This acted as an aquifer that stored water abstracted by the dam. In
the banks, remarkable raise in water levels observed from installation of piezometers. Monitoring
of the fluctuations with time was also observed with water levels raising and falling with
subsequent precipitation episodes. This was both in the stream channel and in the banks of the
river. Measurements were carried out in both the wet and the dry season.
Rainfall was measured with piezometers placed in strategic places in the catchment. This was to
compare the rainfall events with the fluctuation of the water levels. Discharge of the stream was
also determined at the study dam in relation to rainfall intensity measured by a tipping bucket
placed on the upstream section of the dam.
Surface evaporation was compared from subsurface. evaporation from the sand. There was a
great reduction in the amount of water losses due to-evaporative processes .
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Electrical conductivities were measured along the stream channel using a hand held electrical
conductivity meter. There was a remarkable variation in these both in space and time over the
periods of the study and in different sections of the study profile.
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The general conclusion of the study is that the sand dams greatly increased the storage capacity
of the stream channel, big volumes of water was also stored in the banks. It is also observed that
the river recharged the banks during the rainy season and the vise versa happened in the dry
season when the water levels in the channel are lowered, the flow is reversed. Hence the banks
act as buffers for the stream in the dry season.
Evaporative losses were greatly reduced by storing the water below the surface. This was
determined by comparing the surface evaporation with evaporation from the subsurface below
the sand. | en |
