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| Titel |
Drivers of spatial and temporal variability of streamflow in the Incomati River basin |
| VerfasserIn |
A. M. L. Saraiva Okello, I. Masih, S. Uhlenbrook, G. P. W. Jewitt, P. Van der Zaag, E. Riddell |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1027-5606
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| Digitales Dokument |
URL |
| Erschienen |
In: Hydrology and Earth System Sciences ; 19, no. 2 ; Nr. 19, no. 2 (2015-02-02), S.657-673 |
| Datensatznummer |
250120615
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| Publikation (Nr.) |
 copernicus.org/hess-19-657-2015.pdf |
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| Zusammenfassung |
The Incomati is a semi-arid trans-boundary river basin in southern Africa,
with a high variability of streamflow and competing water demands from
irrigated agriculture, energy, forestry and industries. These sectors compete
with environmental flows and basic human water needs, resulting in a
"stressed" water resource system. The impacts of these demands, relative to
the natural flow regime, appear significant. However, despite being a
relatively well-gauged basin in South Africa, the natural flow regime and its
spatial and temporal variability are poorly understood and remain poorly
described, resulting in a limited knowledge base for water resource planning
and management decisions. Thus, there is an opportunity to improve water
management, if it can be underpinned by a better scientific understanding of
the drivers of streamflow availability and variability in the catchment.
In this study, long-term rainfall and streamflow records were analysed.
Statistical analysis, using annual anomalies, was conducted on 20 rainfall
stations, for the period 1950–2011. The Spearman test was used to identify
trends in the records on annual and monthly timescales. The variability of
rainfall across the basin was confirmed to be high, both intra- and
inter-annually. The statistical analysis of rainfall data revealed no
significant trend of increase or decrease. Observed flow data from 33 gauges
were screened and analysed, using the Indicators of Hydrologic Alteration
(IHA) approach. Temporal variability was high, with the coefficient of
variation of annual flows in the range of 1 to 3.6. Significant declining
trends in October flows, and low flow indicators, were also identified at
most gauging stations of the Komati and Crocodile sub-catchments; however, no
trends were evident in the other parameters, including high flows. The trends
were mapped using GIS and were compared with historical and current land use.
These results suggest that land use and flow regulation are larger drivers of
temporal changes in streamflow than climatic forces. Indeed, over the past 40
years, the areas under commercial forestry and irrigated agriculture have
increased over 4 times. |
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