Effects of Water Abstraction on the Riparian Vegetation along Kiladeda River in Pangani River Basin, Tanzania
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Date
2013-09-25
Authors
Mromba, Clement
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Abstract
Water and vegetation are vital for sustaining life. However, they are becoming more
stressed following population growth and associated demands for water. As a result, most
continent discharges. are classified as "moderate" to "highly threatened" by human
activities, partly through water abstraction. Kiladeda river of Pangani river basin in
Tanzania is no exception. The river is experiencing over abstraction driven by a number
of forces, including increased human population and irrigation farming. The latter is by
far the biggest user of water from the river, especially in upstream. Consequently,
downstream discharges have now reduced to zero during dry season. The main aim of
this study was to investigate the effects of water abstraction on the riparian vegetation
along Kiladeda river. Specifically, this study analyzed discharge and abstraction trends
from Kiladeda river, between the years 2000 and 2011, indicators of over abstraction and
water stress which were then related to the status of riparian vegetation in terms of
vegetation percentage cover and species diversity. Finally the study assessed measures
being taken to mitigate the effects of water abstraction on the riparian vegetation along
Kiladeda river. Data collection methods included; in-depth interview, participatory
observation and transect walk, vegetation survey, river discharge and abstraction
measurements and secondary sources such as review of available literature. Analytical
tools used were water withdrawal ratio (WWR) , percentage flow reduction (PFR),
Daubenmire forms, Simpson diversity index (SDI), and Microsoft office Excel 2003 and
2007. The seven furrows found in the study area were investigated. The long-term
average river discharge decreased and water abstraction by open furrows from Kiladeda
river portrayed increasing trend over time with a slight decreasing trend during wet
season. There was a strong relationship R2=0.8 between increasing water abstraction to a
declining river discharge. Water stress indicators showed that, dry season had high PFR
(54.01 %) compared to wet season PFR (34.93%). Water abstraction at the upstream and
middle stream was very high compared to downstream, to the extent of exceeding the
amount of water spelt out in water use permit (0.3m
3
/s). WWR during dry season was
very high (0.73) compared with wet season (0.17). The totals of 26 large (15M2) SQPs
were established, within which other small quadrats (2M2) SQPs were established. From
these quadrats, 26 different plant species were identified. Riparian vegetation results
indicated absolute decline in percentage cover ground (PCG), increase in percentage bare
ground (PBG), decrease in species richness, abundance as well as diversity D=0.05. More
than 15 plant species had disappeared while 11 new species were identified. To control
the effects of water abstraction, water and vegetation management practices were
identified. These included; periodic cleaning and maintenance of furrows, introduction of
water users association (WUA) called UKAKIWI, water use permit, penalties and fines
that ranged from 5,000Tsh to 500,000Tsh. Though mitigation measures taken in the study
area showed signs of success, they were extremely fragmented. They were not taking into
account increased human populations which was escalating demand on freshwater
resources and riparian vegetation. The study puts forward the following
recommendations; sustainable management of the buffer zones along all rivers, effective
multi-sector participation in planning, design and management of river water and riparian
vegetation and construction of boreholes and wells in downstream areas to cater for
domestic water requirements during dry season.
Description
A Thesis Submitted in Partial Fulfilment of the Requirements for the Award of the Degree of Master of Science in Integrated Watershed Management in the School of Pure and Applied Sciences of Kenyatta University; September, 2012. Call Number: The TD 429 .K4M7 2012
Keywords
Water reuse --Kenya