Fig 1.
Schematic of the Buffalo River catchment with local municipalities (red circle nodes) and the main reservoirs (blue triangle nodes).
The vector shapefiles were retrieved from the South African Department of Water and Sanitation (https://www.dws.gov.za/iwqs/gis_data) and Standford University’s online library (https://earthworks.stanford.edu). The map was created using ESRI’s ArcGIS Software Version 10.6.0.8321.
Fig 2.
Diagram showing the data flow and expected results using the CLEWS approach adapted from [20].
Table 1.
Summary of Water Evaluation and Planning (WEAP) model input parameters [27].
Table 2.
Summary of current practice approach results [27].
Fig 3.
Global agro-ecological zones (gAEZ) assessment’s data extraction flow chart.
Table 3.
Global agro-ecological zone (gAEZ) assessment’s suitability class description [40].
Fig 4.
Long-range Energy Alternatives Planning (LEAP) model flow chart for modelling household and irrigation energy demands.
Fig 5.
Eskom’s energy rates (R/kWh) for rural and farming activities [51] and total sprinkler energy rates (R/year/ha) derived using the Ruraflex electricity tariff.
Table 4.
Optimal investment and electricity costs for operating a small and large centre pivot using Eskom’s Ruraflex electricity tariff [52].
Table 5.
Household statistics of local municipalities within the Buffalo River catchment.
Fig 6.
Household incomes per annum of the (a) Newcastle local municipality [59], (b) Utrecht local municipality [60], (c) Nquthu local municipality [62] and (d) Dannhauser local municipality [61].
Table 6.
WEAP model calibration and validation statistics performed by Dlamini et al. [27] for observed streamflow retrieved from DWS [67] and simulated streamflow using the CHIRPS historical dataset and global circulation model’s average precipitation’s ensemble for the period 01/01/1990 to 31/12/2018.
Table 7.
Historical, near-, mid-, and far-future projections of surface runoff in the Buffalo River catchment (Mm3/annum).
Fig 7.
Historical and projected (near-, mid- and far future) irrigated areas and irrigation water requirements of ryegrass, soybean, oats and maize in the Buffalo River catchment, derived using the food and agriculture organization’s global agro-ecological zones assessment (https://gaez.fao.org/) under (a) RCP4.5 and (b) RCP8.5 climate change scenarios.
Fig 8.
Historical and projected energy demands (MWh/annum) and energy generation water requirements (Mm3/annum) under the RCP4.5 and RCP8.5 climate change scenarios in the Buffalo River catchment throughout the study period (01/01/1990-31/12/2099).
Table 8.
Total water supply requirements (Mm3/annum) in the Buffalo River catchment under all scenarios from period 01/01/1990–31/12/2099.
Fig 9.
Simulated and projected annual reservoir storage (Mm3/annum) and unmet demands (Mm/annum) in the Buffalo River catchment using the CPA and CLEWS approach for the period 01/01/1990 to 31/12/2099.
Fig 10.
Annual demand site coverage (%) of the following local municipalities in the Buffalo River catchment: (a) Newcastle (range = 67% to 100%), (b) Dannhauser (range = 80% to 100%), (c) Nquthu (range = 8% to 11%) and (d) Utrecht (range = 9.5% to 12.5%), under the RCP4.5 and RCP8.5 climate scenarios, established using the CPA and CLEWS approaches, for the period 01/01/1990–31/12/2099.
Table 9.
Shapiro-Wilk normality test results of local municipalities’ projected demand coverage under the RCP4.5 and RCP8.5 climate change scenarios, derived using the CLEWS approach.
Table 10.
Inferential statistics comparing the significant differences in projected demand site coverage results per local municipality in the Buffalo River catchment, obtained under the RCP4.5 and RCP8.5 scenarios.
Fig 11.
Water system supply reliability (%) for the Buffalo River catchment’s water treatment plants (WTP), local municipalities and the Majuba power station’s water provisions throughout the study period (01/01/1990-31/12/2099).