Variability and trends of rainfall, precipitation and discharges over zambezi river basin, southern africa: review

Abstract

Variability and trends of rainfall, precipitation and discharges over zambezi river basin, southern africa: review Submit Manuscript | http://medcraveonline.com IntroductionHuman influence on the climate system is clear, and recent anthropogenic emissions of greenhouse gases are the highest in history. Their effects, together with those of other anthropogenic drivers, have been detected throughout the climate system and are extremely likely to have been the dominant cause of the observed warming since the mid-20th century. Recent climate changes have had widespread impacts on human and natural systems. Warming of the climate system is unequivocal, and since the 1950s, many of the observed changes are unprecedented over decades to millennia. 1 according to Res & Trenberth,2 there is a direct influence of global warming on precipitation. Increased heating leads to greater evaporation and thus surface drying, thereby increasing the intensity and duration of drought. The African continent has been identified as particularly vulnerable to the changing climate due to its envisaged low adaptive capacity and vulnerability and the southern African region is regarded as one of the most vulnerable regions in Africa.3 This affects the water resource in terms of quality and quantity of water.4 Africa is highly vulnerable to the impacts of climate change and numerous climate change models predict that the continent's weather patterns will become more variable, and extreme weather events are expected to be more frequent and severe, with increasing risk to health and life. 1,4,5 The droughts and floods will increase in their frequency leading to more water stress. Alterations in agricultural, livestock and fisheries productivity will occur and Africa will face further food insecurity as well as possibly the spread of water-related diseases.According to Swain et al.,6 Zambezi basin is already experiencing drastic changes to its climate. In recent years the annual rainfall in the region decreased considerably and affected the annual flow levels. Over 128 million inhabitants that are part of the Zambezi River Basin are dependent on this river directly or indirectly as a source of food and water. In total the countries along the Zambezi Basin have 2.17 million km 2 of agricultural land, of which just 202,900 km 2 is arable. But as a consequence of increased agricultural land, there is also an increased need for irrigation. The Intergovernmental Panel on Climate Change (IPCC) has categorized the Zambezi as the river basin exhibiting the "worst" potential effects of climate change among 11 major African basins. Over the next century, climate change is expected to increase this variability, and the vulnerability of the basin and its hydropower dams. 5 The Zambezi River Basin has one of the most variable climates of any major river basin in the world and the runoff is highly sensitive to variations in climate, as small changes in rainfall pattern produce large changes in runoff. The hydrology of the basin is very important for hydropo...

Evaluation of Streamflow under Climate Change in the Zambezi River Basin of Southern Africa

“…The results for the RCP 4.5 scenario may also be comparable to a previous study on median change in rainfall that projected to be close to no change in the ZRB for both RCP 4.5 and RCP 8.5 climate scenarios [17]. Further previous studies in the ZRB generally predicted rising temperatures and precipitation decrease and that season may become shorter and more variable, predicting more extended drought periods and more severe floods [43]. The results under RCP 4.5 also agree with previous climate change impact studies that used five GCM (CGCM3.1, CSIRO3.0, ECHAM5, CCSM3.0 and HACDM3), and concluded that the ZRB will have increased temperatures and decreased precipitation leading to reduced streamflow according to a special report on emission scenario A1B (SRES A1B) [18].…”

“…The GCM, Access1-0 under RCP 8.5 had simulated higher magnitudes of streamflow compared to the other five GCMs, indicating uncertainties, and a conclusion was made based on strong consensus and high uncertainty. The streamflow results for RCP 8.5 showed uncertainty in magnitude, which was also observed by other researchers who stated that there is uncertainty in magnitude and direction of change in the Zambezi River basin response to future GCM projections [43,44]. It was pointed out that GCM runs performed under RCP 8.5 result in more uncertainty than under RCP 4.5 because of climate distribution [17].…”

“…The streamflow results for RCP 8.5 showed uncertainty in magnitude, which was observed by other researchers who stated that there is uncertainty in magnitude and direction of change in the Zambezi River basin response to future GCM projections [43,44]. It was pointed out that GCM runs performed under RCP 8.5 result in more uncertainty than under RCP 4.5 because of climate distribution [17].…”

Trend analysis of selected hydro-meteorological variables for the Rietspruit sub-basin, South Africa

“…Using data from 138 South African stations between 1910 and 2004, Kruger (2006) detected no significant changes in rainfall in a majority of the stations. Banze et al (2018), from a review of rainfall trends in southern Africa, concluded that rainfall will both increase and decrease in the different parts of the region; however, there is still no total agreement among researchers on the magnitude of the anticipated rainfall change in the region. In contrast, Murungweni et al (2020), from a local-scale study in Limpopo (South Africa), established that there is a non-significant decrease in the annual rainfall.…”

“…Climate change has a significant impact on society primarily through water-related effects, for instance, by affecting sectors such as energy, agriculture, infrastructure, and transport (IPCC 2014a). Hence, besides being an important environmental concern climate change is equally a development limitation particularly in underdeveloped nations (Banze et al 2018;MacAlister & Subramanyam 2018). Meanwhile, the key determinants of current and future climate change impacts on freshwater supplies are rising temperatures, local rainfall variability, and shifts in the magnitude of these variables (IPCC 2014a).…”