A three month stream flow forecast for water management in the upper Olifants catchment

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Date
2007-11
Authors
Phahlane, Mmotong Obed
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Publisher
University of the Free State
Abstract
English: A Climate Predictability Tool was used to evaluate the relationship between sea-surface temperatures and stream flow at different lead-times in the upper Olifants catchment in Mpumalanga, South Africa. Four stream flow stations were selected from each of the subcatchments of the upper Olifants, namely the Groot Olifants on the eastern side and the Wilger on the western side of the catchment. Canonical correlation analyses were used to make three month stream flow forecasts for October-November-December (OND) and January-February-March (JFM) seasons. Monthly global-scale SSTs were used to evaluate the effect of lead-times on correlations between global Sea-Surface Temperatures (SSTs) and stream flow. Then the lead-times with Pearson’s correlation values greater than 0.50 were selected to be used for evaluating possible origins of stream flow forecasting skill in the Equatorial Atlantic, Southern Atlantic, Equatorial Indian and Pacific Oceans. Although local climatic and hydrological characteristics were not considered in this study good hit score skill from the Southern Atlantic Ocean was found at a short lead-time of two months for both OND and JFM seasons. The equatorial Atlantic Ocean gave a good hit skill score at longer lead-times of seven and eight months. The equatorial Indian Ocean gave a higher Heidke score at a short lead-time of two months during OND and JFM seasons in the Groot Olifants sub-catchment. The oceanic domains adjacent to the southern African subcontinent gave a good Heidke score at a shorter lead-time as compared to the equatorial Pacific Ocean. These forecasts could be used for planning water storage and releases in dams that are down stream of these stream flow monitoring points.
Afrikaans: ʼn Klimaatvoorspellingshulpmiddel is gebruik om die verwantskap te evalueer tussen see- oppervlaktemperature en str oomvloei by verskillende aa nlooptye in die bo-Olifants opvanggebied in Mpumalanga, Suid-Afrika. Vier stroomvloeistasies is gekies vir elk van die sub-opvanggebiede van die bo-Olifants, nl. die Groot-Olifants aan die oostekant en die Wilger aan die westekant van die opvanggebied. Kanoniese korrelasie analise is gebruik om ʼn drie maande stroomvloei voorspelling vir die Oktober-November-Desember (OND) en Januarie-Februarie-Maart (JFM) seisoene te genereer. Maandelikse globale -skaal see-oppervlaktemperature is ingespan om die uitwerking van voorgeetye op ko rrelasies tussen globale s ee-oppervlaktemperature en stroomvloei te bestudeer. Die aanlooptye met Pearson se ko rrelasiewaardes van meer as 0.50 is dan gekies om die moontlike oorspronge van stroomvloei voorspellingsvaardigheid in die Ekwatoriale en Suidelike Atlantiese, Ekwatoriale Indiese en Ekwatoriale Stille Oseane vas te pen. Alhoewel die plaaslike klimaat en hidrologiese eienskappe nie oorweeg is in hierdie studie nie, is ʼn goeie treftelling waargeneem vir die Suidelike Atlantiese Oseaan vir ʼn kort aanlooptyd van twee maande vir beide OND en JF M seisoene. Die Ekwatoriale Atlantiese Oseaan het ʼn goeie treftelling gebied by langer aanlooptye van sewe en agt maande. Die Ekwatoriale Indiese Oseaan het ʼn hoër Heidke treftelling ve rskaf by die kort voorgeetyd van twee maande gedurende OND en JFM seisoene in die Groot-Olifants sub- opvanggebied. Die oseaanstreke aangrensend aa n die Suider-Afrikaanse subkontinent het ʼn goeie Heidke treftelling vir korter aanlooptye gebied as di é van die Ekwatoriale Stille Oseaan. Hierdie voorspellings kan gebruik word om waterstoring en–vrylating in damme te beplan wat stroomaf van hierdie stroomvloeimoniteringspunte geleë is.
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Keywords
Dissertation (M.Sc.Agric. (Agrometeorology))--University of the Free State, 2007, Rivers -- Regulation -- Environmental aspects -- South Africa, Streamflow -- South Africa -- Olifants River watershed, Stream measurements -- South Africa -- Olifants River watershed, Probability forecasts (Meteorology), Long-range weather forecasting, Olifants River, Sea-surface temperature, Climate predictability tool
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