Integrated hydrological model of the Central Kalahari Basin – optimal tool for assessment of sustainability of groundwater resources: powerpoint

M. Lekula, M.W. Lubczynski

Research output: Contribution to conferenceOtherOther research output

Abstract

Groundwater resources replenishment dynamics evaluation is critical for management purposes, especially in arid and semi-arid regions where it accounts for the majority of potable water demand. That evaluation, nowadays is done using distributed, integrated hydrological models(IHMs). Such models, inherently account for surface-groundwater interactions, relying on realistic hydrogeological conceptual models(HCMs)and reliable input data involving also surface hydrological fluxes like rainfall and potential evapotranspiration. In this study, the productive Central Kalahari Basin (CKB, ~200000km2) transboundary(Botswana and Namibia)Karoo Aquifer System IHM, was developed, to define its groundwater resources replenishment dynamics. An efficient data integration method for developing HCM of the CKB, was undertaken, applying 3-D geological modelling based on RockWorks code, in iterative combination with ArcGIS. Six hydrostratigraphic units(Kalahari Sand Unit, Stormberg Basalt Aquitard, Lebung Aquifer, Inter-Karoo Aquitard, Ecca Aquifer and Ghanzi Aquifer)were identified, their heads and related flow system interdependencies evaluated and hydraulic properties defined. The daily spatio-temporally variable IHM driving forces(rainfall and potential evapotranspiration)were defined using remote sensing technique. A fully 3-D, six-layer CKB IHM was developed using MODFLOW-NWTwithUZF1 package, accounting for variably saturated flow. The transient CKB IHM was calibrated throughout 13.5 years, using borehole hydraulic heads as state variables. Results of the model showed dominant water balance role of subsurface evapotranspiration restricting gross recharge to only few mm/year and typically negative, yearly net recharge (median -1.5mmy-1), varying from -3.6 (2013) to +3.0 (2006) mmy-1with respective rainfalls 287 and 664 mmy-1, explaining water table decline within the simulated period. Primary determinants of spatio-temporal distribution of net recharge in the CKB were amount and temporal distribution of rain, unsaturated zone thickness and vegetation type/density. The calibrated CKBIHM represents optimal tool for further assessment of impact of climate change upon the replenishment dynamics of groundwater resources of the CKB.
Original languageEnglish
Number of pages18
Publication statusPublished - 2018
Event1st SADC-GMI/IWMI-SA Groundwater Conference: Adapting to Climate Change in the SADC Region through
Water Security – A Focus on Groundwater
- Johannesburg, South Africa
Duration: 26 Sep 201828 Sep 2018
Conference number: 1st

Conference

Conference1st SADC-GMI/IWMI-SA Groundwater Conference: Adapting to Climate Change in the SADC Region through
Water Security – A Focus on Groundwater
CountrySouth Africa
CityJohannesburg
Period26/09/1828/09/18

Fingerprint

groundwater resource
sustainability
basin
aquifer
recharge
aquitard
potential evapotranspiration
temporal distribution
rainfall
hydraulic head
hydraulic property
water demand
semiarid region
vadose zone
vegetation type
evapotranspiration
water table
water budget
borehole
basalt

Cite this

Lekula, M., & Lubczynski, M. W. (2018). Integrated hydrological model of the Central Kalahari Basin – optimal tool for assessment of sustainability of groundwater resources: powerpoint. 1st SADC-GMI/IWMI-SA Groundwater Conference: Adapting to Climate Change in the SADC Region through
Water Security – A Focus on Groundwater, Johannesburg, South Africa.
Lekula, M. ; Lubczynski, M.W. / Integrated hydrological model of the Central Kalahari Basin – optimal tool for assessment of sustainability of groundwater resources : powerpoint. 1st SADC-GMI/IWMI-SA Groundwater Conference: Adapting to Climate Change in the SADC Region through
Water Security – A Focus on Groundwater, Johannesburg, South Africa.18 p.
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Lekula, M & Lubczynski, MW 2018, 'Integrated hydrological model of the Central Kalahari Basin – optimal tool for assessment of sustainability of groundwater resources: powerpoint' 1st SADC-GMI/IWMI-SA Groundwater Conference: Adapting to Climate Change in the SADC Region through
Water Security – A Focus on Groundwater, Johannesburg, South Africa, 26/09/18 - 28/09/18, .

Integrated hydrological model of the Central Kalahari Basin – optimal tool for assessment of sustainability of groundwater resources : powerpoint. / Lekula, M.; Lubczynski, M.W.

2018. 1st SADC-GMI/IWMI-SA Groundwater Conference: Adapting to Climate Change in the SADC Region through
Water Security – A Focus on Groundwater, Johannesburg, South Africa.

Research output: Contribution to conferenceOtherOther research output

TY - CONF

T1 - Integrated hydrological model of the Central Kalahari Basin – optimal tool for assessment of sustainability of groundwater resources

T2 - powerpoint

AU - Lekula, M.

AU - Lubczynski, M.W.

PY - 2018

Y1 - 2018

N2 - Groundwater resources replenishment dynamics evaluation is critical for management purposes, especially in arid and semi-arid regions where it accounts for the majority of potable water demand. That evaluation, nowadays is done using distributed, integrated hydrological models(IHMs). Such models, inherently account for surface-groundwater interactions, relying on realistic hydrogeological conceptual models(HCMs)and reliable input data involving also surface hydrological fluxes like rainfall and potential evapotranspiration. In this study, the productive Central Kalahari Basin (CKB, ~200000km2) transboundary(Botswana and Namibia)Karoo Aquifer System IHM, was developed, to define its groundwater resources replenishment dynamics. An efficient data integration method for developing HCM of the CKB, was undertaken, applying 3-D geological modelling based on RockWorks code, in iterative combination with ArcGIS. Six hydrostratigraphic units(Kalahari Sand Unit, Stormberg Basalt Aquitard, Lebung Aquifer, Inter-Karoo Aquitard, Ecca Aquifer and Ghanzi Aquifer)were identified, their heads and related flow system interdependencies evaluated and hydraulic properties defined. The daily spatio-temporally variable IHM driving forces(rainfall and potential evapotranspiration)were defined using remote sensing technique. A fully 3-D, six-layer CKB IHM was developed using MODFLOW-NWTwithUZF1 package, accounting for variably saturated flow. The transient CKB IHM was calibrated throughout 13.5 years, using borehole hydraulic heads as state variables. Results of the model showed dominant water balance role of subsurface evapotranspiration restricting gross recharge to only few mm/year and typically negative, yearly net recharge (median -1.5mmy-1), varying from -3.6 (2013) to +3.0 (2006) mmy-1with respective rainfalls 287 and 664 mmy-1, explaining water table decline within the simulated period. Primary determinants of spatio-temporal distribution of net recharge in the CKB were amount and temporal distribution of rain, unsaturated zone thickness and vegetation type/density. The calibrated CKBIHM represents optimal tool for further assessment of impact of climate change upon the replenishment dynamics of groundwater resources of the CKB.

AB - Groundwater resources replenishment dynamics evaluation is critical for management purposes, especially in arid and semi-arid regions where it accounts for the majority of potable water demand. That evaluation, nowadays is done using distributed, integrated hydrological models(IHMs). Such models, inherently account for surface-groundwater interactions, relying on realistic hydrogeological conceptual models(HCMs)and reliable input data involving also surface hydrological fluxes like rainfall and potential evapotranspiration. In this study, the productive Central Kalahari Basin (CKB, ~200000km2) transboundary(Botswana and Namibia)Karoo Aquifer System IHM, was developed, to define its groundwater resources replenishment dynamics. An efficient data integration method for developing HCM of the CKB, was undertaken, applying 3-D geological modelling based on RockWorks code, in iterative combination with ArcGIS. Six hydrostratigraphic units(Kalahari Sand Unit, Stormberg Basalt Aquitard, Lebung Aquifer, Inter-Karoo Aquitard, Ecca Aquifer and Ghanzi Aquifer)were identified, their heads and related flow system interdependencies evaluated and hydraulic properties defined. The daily spatio-temporally variable IHM driving forces(rainfall and potential evapotranspiration)were defined using remote sensing technique. A fully 3-D, six-layer CKB IHM was developed using MODFLOW-NWTwithUZF1 package, accounting for variably saturated flow. The transient CKB IHM was calibrated throughout 13.5 years, using borehole hydraulic heads as state variables. Results of the model showed dominant water balance role of subsurface evapotranspiration restricting gross recharge to only few mm/year and typically negative, yearly net recharge (median -1.5mmy-1), varying from -3.6 (2013) to +3.0 (2006) mmy-1with respective rainfalls 287 and 664 mmy-1, explaining water table decline within the simulated period. Primary determinants of spatio-temporal distribution of net recharge in the CKB were amount and temporal distribution of rain, unsaturated zone thickness and vegetation type/density. The calibrated CKBIHM represents optimal tool for further assessment of impact of climate change upon the replenishment dynamics of groundwater resources of the CKB.

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Lekula M, Lubczynski MW. Integrated hydrological model of the Central Kalahari Basin – optimal tool for assessment of sustainability of groundwater resources: powerpoint. 2018. 1st SADC-GMI/IWMI-SA Groundwater Conference: Adapting to Climate Change in the SADC Region through
Water Security – A Focus on Groundwater, Johannesburg, South Africa.