The impactof climate change on hydrological predictions, with specificreference to 24-hour rainfall intensities in the Western Cape

[摘要] The climate of the world varies from one decade to another, and a changing climate isnatural and expected. However there is a well-founded concern that theunprecedented human industrial development activities of the past two centuries (andmainly the last century) have caused changes over and above natural variation.Climate change is the natural cycle through which the earth and its atmosphere aregoing to accommodate the change in the amount of energy received from the sun.There are various indicators that can be monitored to measure and verify possibleclimatic changes. This thesis will firstly emphasize what the possible effects ofclimate change could be on amongst others, the coastal zone, biodiversity and waterresources. If the impact of climate change on the above mentioned processes aremonitored, and changing trends can be identified, these processes could in fact beseen as climate change indicators. This is of major importance to us, to be able toaccurately identify whether climatic changes are experienced in any given area and toattempt to quantify it.Engineering hydrologists are, amongst other duties, responsible for the determinationof peak discharges to be able to size conduits to safely convey the stormwater forgiven recurrence interval events. All hydrological predictions are indirectly or directlybased on historical data. Empirical formulas and deterministic methods weredeveloped and calibrated from known historical data. Statistical predictions aredirectly based on actual data. The question that arises is whether the historical datastill provides an accurate basis from which possible future events can be predicted?This thesis strives to find an answer to this question and will also try to advisehydrologists on how they should interpret historical data in the future, taking climatechange into consideration. The methodology that will be followed will be to comparethe percentage of occurrence of 24-hour rainfall events of different magnitudes, forhistorical- as well as predicted rainfall, for five different rainfall stations in theWestern Cape. A detailed analysis of measured data at a rainfall station, with 42years of useable data, will also be performed, to verify whether any measurable trendshave already been experienced. Conclusions shall be drawn as to possible trends, andrecommendations will be made as to how hydrologists could allow for the possiblechanging rainfall patterns.

[发布机构] Stellenbosch University