GIS-based modelling of climate variability impacts on groundwater quality: Cape Flats aquifer, Cape Town, South Africa

Tesfaye Tessema Gintamo,Haile Mengistu,Thokozani Kanyerere

doi:10.1016/j.gsd.2021.100663

Tesfaye Tessema Gintamo, Haile Mengistu + Show 1 more

Open Access

https://doi.org/10.1016/j.gsd.2021.100663

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Abstract

The need to improve groundwater security remains critical, especially in urban areas where demand for groundwater as an alternative source of water supply is increasing following unprecedented population growth. Climate change continues to threaten groundwater resources in such areas. This study assessed and analysed data from a variety of sources that required holistic analytical tools to demonstrate the impacts of climate change on groundwater quality at the local level. We evaluated how climate conditions affect groundwater quality using a hydrological model (WaterWorld model) in a GIS context. The Cape Flats Aquifer in the city of Cape Town in South Africa was chosen as a case study. The WaterWorld model was used to calculate hydrologic scenarios based on climate change factors and groundwater quality parameters for the period 1950–2000. Mean annual precipitation and temperature were simulated using the multi-model mean and Representative Concentration Pathway 8.5 for the years 2041–2060. Simulation results showed that annual precipitation will increase until 2041 and then decrease until 2060. A significant temperature increase of 1.9 °C–2.3 °C was predicted. Water balance simulations showed a decrease of about 8.6% per year under the future dry climate. ArcGIS 10.3 was used to combine geospatial data and develop a groundwater vulnerability map. Modelling analysis based on GIS showed that the southern and central suburbs of the study area are more susceptible to groundwater contamination and have high surface runoff and higher average temperatures. The groundwater vulnerability index and electrical conductivity concentrations showed a strong positive correlation when the model was validated using linear regression analysis (R2 = 0.99, P < 0.05). In this article, we recommend the use of the WaterWorld model in a GIS environment to simulate hydrologic scenarios on climate change and groundwater quality parameters to provide practical and feasible insights for actions to improve groundwater management.

Highlights

Fabaceae represents the second largest plant family in the Cape Floristic Core Cape Region (CCR), approaching 800 species (Manning and Goldblatt 2012)
Unlike the three main tropical clades that have members dispersed across multiple continents, the Cape Clade is endemic to South Africa and especially within the winter-rainfall area (Schrire et al 2009; Schrire in Manning and Goldblatt 2012)
Members of Indigofera Section Brachypodae, the I. brachystachya group (I. brachystachya (DC.) E.Mey. and I. hamulosa Schltr.), are especially diverse in this region, with several putative undescribed taxa related to I. brachystachya, noted from recent field studies (Schrire and du Preez, unpublished data)

Summary

Introduction

Fabaceae represents the second largest plant family in the Cape Floristic Core Cape Region (CCR), approaching 800 species (Manning and Goldblatt 2012). Indigofera species in the CCR are largely part of a monophyletic clade referred to as the Cape Clade by Schrire et al (2009).

Results

Conclusion