Predicting the Impact of Future Land Use and Climate Change on Potential Soil Erosion Risk in an Urban District of the Harare Metropolitan Province, Zimbabwe

Monitoring urban area expansion through multispectral remotely sensed data and other geomatics techniques is fundamental for sustainable urban planning. Forecasting of future land use land cover (LULC) change for the years 2034 and 2050 was performed using the Cellular Automata Markov model for the current fast-growing Epworth district of the Harare Metropolitan Province, Zimbabwe. The stochastic CA–Markov modelling procedure validation yielded kappa statistics above 80%, ascertaining good agreement. The spatial distribution of the LULC classes CBD/Industrial area, water and irrigated croplands as projected for 2034 and 2050 show slight notable changes. For projected scenarios in 2034 and 2050, low–medium-density residential areas are predicted to increase from 11.1 km2 to 12.3 km2 between 2018 and 2050. Similarly, high-density residential areas are predicted to increase from 18.6 km2 to 22.4 km2 between 2018 and 2050. Assessment of the effects of future climate change on potential soil erosion risk for Epworth district were undertaken by applying the representative concentration pathways (RCP4.5 and RCP8.5) climate scenarios, and model ensemble averages from multiple general circulation models (GCMs) were used to derive the rainfall erosivity factor for the RUSLE model. Average soil loss rates for both climate scenarios, RCP4.5 and RCP8.5, were predicted to be high in 2034 due to the large spatial area extent of croplands and disturbed green spaces exposed to soil erosion processes, therefore increasing potential soil erosion risk, with RCP4.5 having more impact than RCP8.5 due to a higher applied rainfall erosivity. For 2050, the predicted wide area average soil loss rates declined for both climate scenarios RCP4.5 and RCP8.5, following the predicted decline in rainfall erosivity and vulnerable areas that are erodible. Overall, high potential soil erosion risk was predicted along the flanks of the drainage network for both RCP4.5 and RCP8.5 climate scenarios in 2050

An assessment of the impacts of climate and land use/cover changes on wetland extent within Mzingwane catchment, Zimbabwe

A thesis submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Doctor of Philosophy(Geography and Environmental Science). Johannesburg, June 2018.Wetlands ecosystems are amongst the most diverse and valuable environments which provide a number of goods and services pertinent to human and natural systems functioning yet they are increasingly threatened by anthropogenic and climatic changes. This thesis, examines the impact of climatic trends and variations, and land use/land (LU/LC) cover changes on wetland extent within Mzingwane catchment, south-western of Zimbabwe. An attempt is made to establish how the two stressors (climate and LU/LC changes) modify areal extents of wetlands over time, grounded on the hypothesis that, climate and LU/LC related changes impact on wetland ecosystems resulting in their degradation, shrinking in size and in some cases overall loss. To achieve the broader objective of the study, a number of parametric and non-parametric statistical analyses were employed to quantify and ascertain climate variability and change in Mzingwane catchment through the use of historic and current climatic trends in rainfall and temperature (T). Remote sensing data was used for wetland change analysis for the period between 1984 and 2015as well as future land cover predictions based on CA-Markov Chain model. LU/LC changes on nested wetlands were modelled at catchment level. In addition the study simulated future rainfall and extreme events and their implications on wetland dynamics using Regional Climate Models derived from CORDEX data. Trends in annual Tmax significantly increased (p=1mm) has decreased by 34%, thus suggesting much more concentrated and increased rainfall intensity. A notable shift in both the onset and cessation dates of the rainy season is recorded, particularly during the 21st century, which has resulted in a significant reduction (p<0.05) in the length of the rainy season. Land change analysis results show a decline in woodland and wetland cover which could be resulting from both human and natural factors. Major conversions are from wetland cover to crop field, suggesting agricultural encroachment onto wetland areas. Wetland area thus significantly decreased by 60.16% (236, 52 ha) in the last 30 years (p < 0.05). CA-Markov model results for the years 2025, 2035 and 2045 predicted an overall increase in the crop field areas at the expense of woodland and wetland areas. LU/LC modelling results suggest that LU/LC changes modify wetland hydrology which consequently influences wetland areal extent. Trend results for projected rainfall suggest a significant decreasing trend in future rainfall (2016-2100) at p<0.05. In addition, a general decreasing trend in the number of rainy days is projected for the future climate although the significance and magnitude varied with station location. Regional Climate Models projections suggest an increased occurrence of future extreme events particularly towards the end of this century. The findings are important for developing appropriate sustainable and adaptive strategies given climate changes as well as designing catchment level wetland management approaches aimed at sustaining wetland ecosystems for the current and future generations. Any future efforts towards protection of the remaining wetlands should be combined with developing a sustainable relationship between social and ecological systems which will enable communities to adapt to the effects of changing climates.LG201

Ecological Changes in the Zambezi River Basin

This research article was published in Council for the Development of Social Science Research in Africa, 2021.Africa faces a plethora of challenges and chief among these is a change in the climate (Zakaria and Maharjan 2014) which is one of the key factors affecting the ecology and hydrology of its river basins (Kusangaya et al. 2014). Beilfuss (2012) proposed that Africa’s arid regions are highly vulnerable to climate change with the Zambezi River Basin (ZRB) being particularly at risk (Kling et al. 2014). After the Nile and Niger rivers, the ZRB is the next most trans-boundary river basin in Africa as it serves eight African countries. Consequently, water resource development planning is crucial, since any changes in climate will impact the hydrological cycle and the amount of water retained in hydrological systems (Beilfuss 2012) of which only up to 3 per cent is readily available as usable and shared freshwater. Like some Sub-Saharan countries, which have experienced up to 0.5 C increases in temperature (Hendrix and Glaser 2007), the Zambezi River Basin is also facing changes in climate (Ndhlovu 2013). A recent study by Kling et al.(2014) reported rises in temperature and more variable precipitation in the basin since the 1980s. Such historical climatic changes, and those projected towards the mid-century (2050), are of concern with serious social and economic implications to local communities (Mubaya et al. 2012). The Intergovernmental Panel on Climate Change (IPCC) projected a global decadal temperature rise of 0.2 C (IPCC 2007). However, regional climat

City to city learning and knowledge exchange for climate resilience in southern Africa

This paper argues that learning is essential for cities to become resilient to challenges. The Future Resilience for African CiTies And Lands (FRACTAL) project is profiled. Following FRACTAL’s city-to-city learning approach of sharing good practices, knowledge and experiences framed around transdisciplinary research, the study cities of Harare, Lusaka, Windhoek and Durban conducted city learning exchange visits between 2017 and 2018. FRACTAL contributes towards climate resilient development by providing relevant climate information for decision-making at the city regional scale in southern Africa. Transferable lessons and practices included effective water conservation and waste management and the use of public-private partnerships.UK’s Department for International Development (DFID)Natural Environment Research Council (NERC) (2015-2019)START International’s Global Environmental Change (GEC) grants (2016-2017

Establishing the link between urban land cover change and the proliferation of aquatic hyacinth (Eichhornia crassipes) in Harare Metropolitan, Zimbabwe

Urbangrowthisakeyprocessaffectingthefunctioningofnaturalecosystems,andconsequentlythegloballand-surface process. This work aimed at establishing the link between land cover changes around HarareMetropolitancityandtheproliferationofaquatichyacinth(Eichhornia crassipes)inLakeChivero.RemotelysensedLandsatseriesacquiredintheyear1973,1981,1994,1998,2008,2009and2014wasused.Imageclassificationwasimplementedtomaptheassociatedchangesovertimeusingdiscriminantanalysisalgorithm.Derivedthematiclandcovermapsshowedthatagriculturallandincreasedfrom2%in1973toa5%in1981reachingupto30%in2014,whereasthecity'slandareasignificantly(p<0.05)increasedbetween1973and1994.However,waterhyacinthconstantlyincreasedovertime.ThespatialandtemporalresolutionofLandsatimagesdetectedlandcoverchangesandtheproliferationofaquatichyacinth(Eichhorniacrassipes)intheLakeChiveroovertime

A Risky Climate for Southern African Hydro

This in-depth study of the hydrological risks to hydropower dams on the Zambezi River gives an early warning about what Southern Africa could be facing as it contemplates plans for more large hydropower dams in a time of climate change.Currently, 13,000 megawatts of new large-dam hydro is proposed for the Zambezi and its tributaries. The report finds that existing and proposed hydropower dams are not being properly evaluated for the risks from natural hydrological variability (which is extremely high in the Zambezi), much less the risks posed by climate change.Overall, Africa's fourth-largest river will experience worse droughts and more extreme floods. Dams being proposed and built now will be negatively affected, yet energy planning in the basin is not taking serious steps to address these huge hydrological uncertainties. The result could be dams that are uneconomic, disruptive to the energy sector, and possibly even dangerous.The report recommends a series of steps to address the coming storm of hydrological changes, including changes to how dams are planned and operated

The physic-chemical assessment of urban river basin using macroinvertebrate indices for the environmental monitoring of urban streams

BACKGROUND AND OBJECTIVES: The major sources of pollution along the Mukuvisi River are industrial effluents from Msasa, Graniteside, and Southerton industrial sites, sewage effluent from Firle sewage works, pesticide and fertilizer runoff from Pension and surrounding farms, and domestic and diffuse pollution from residential areas. The primary objective of this study was to assess the impact of point and non-point pollution sources on macroinvertebrates variability and investigate the seasonal water quality deterioration along the Mukuvisi River. To evaluate macroinvertebrate community diversity using South African Scoring System 5 protocol for rapid bioassessment of water quality. The combined application of benthic macroinvertebrates and physic-chemical parameters was the focus of this research to validate the water quality status of the urban River systems concerning emerging pollutants in urban areas.METHODS: According to the Harare municipality pollution control strategy and surveillance, only twelve accessible sampling points were chosen along the river. Macroinvertebrate samples and physic-chemical measurements were collected once or twice a month, according to the city of Harare’s sampling schedule. The ancillary information, temperature, pH, and conductivity were measured on-site with a mercury bulb thermometer, a pH meter, and a conductivity meter, respectively. The standard South African Scoring System 5 sampling protocol was used for the sampling and identification of the macroinvertebrates community.FINDINGS: The early assessments showed that water pollution was, in the 1st place and as a primary issue, a biological matter, and its primary effects could have been traced to living organisms. Eutrophication in Manyame catchment, Harare, Zimbabwe is subjected to prolonged and cumulative ecosystem stress because of human activities, sewage disposal, and industrial discharges, among other pollution sources. The Phosphorus-P, Biological Oxygen Demand, Chemical Oxygen Demand, and Ammonia-NH3 (from 0, 6.9, 118, and 0 to 3.8, 81.9, 840, and 31 mg/L respectively) concentration increases downstream in both seasons. The Dissolved Oxygen saturation was 75% and 67% upstream in the dry-and-wet season and was reduced to 0% downstream in both seasons. The evaluation of macroinvertebrate diversity provided evidence that Mukuvisi River water was polluted based on the South African Scoring System, especially in the dry season.CONCLUSIONS: The physic-chemical parameters were significantly related to macroinvertebrates diversity. In the assessment of river water quality, both macroinvertebrate indices and physio-chemical parameters can be sampled together to avoid bias. The results indicated that human activities from the upstream were inducing water pollution. Industries need to adhere to the wastewater discharge guidelines