Abstract:
The main issue associated with groundwater supply in Botswana are the rate of its
replenishment relative to its extraction rate and quality. This study aims to identify the
possible causes and effects of groundwater decline at the Dukwi Wellfield. Specifically, it
aims to investigate the contributing variables for groundwater decline at the wellfield area;
the trend and significance of groundwater level decline using the linear trend model; the
influence of groundwater decline on water quality and chemistry change; the water quality
and chemistry compliance based on the Botswana Bureau of Standard natural water
specifications (BOS 262:2011) and to simulate and predict land subsidence using
MODFLOW SUB and ModelMuse 4. The Pearson’s correlation method was used to
determine an association between various variables such as recharge and rainfall with the
drop of water levels. The recharge rates were estimated using the hydrogeological model
and were compared with abstraction rates. A piper plot was used for the geochemical
characterization of groundwater at the wellfield area. The results from the hydrogeological
model showed mean annual recharge rate of 1 149 691 m3/year which is less than the mean annual total abstraction rate of 1 253 546 m3/year. This influenced the decline of
groundwater levels and a higher concentration of parameters such as Total Dissolved Solids and Electrical Conductivity. The simulated land subsidence of the study area from 2013 to 2019 ranged from 0.008 m to 0.022 m while the projected land subsidence from 2019 to 2031 will range from 0.015 m to 0.031 m. Overall, this study revealed that higher
transmissivity estimates of 8.171 m2/min, hydraulic conductivities of 0.0413 m/min and
storativities of 0.0003299 were experienced at the study area, which influenced more
extraction of groundwater resources and mean abstraction rates as high as 355 392 m3
/year.
The statistical trends showed a declining water table with the coefficient of determination
of 80% and above for most of the results from the trend model. The Electrical Conductivity
and Total Dissolved Solids concentrations can be measured and monitored by implementing less energy consuming methods such as the Electromagnetic method
Abijah, D (2024). Groundwater depletion at the Dukwi wellfield: causes and effects. Afribary. Retrieved from https://afribary.com/works/groundwater-depletion-at-the-dukwi-wellfield-causes-and-effects
Abijah, Diphofu "Groundwater depletion at the Dukwi wellfield: causes and effects" Afribary. Afribary, 12 Apr. 2024, https://afribary.com/works/groundwater-depletion-at-the-dukwi-wellfield-causes-and-effects. Accessed 07 Sep. 2024.
Abijah, Diphofu . "Groundwater depletion at the Dukwi wellfield: causes and effects". Afribary, Afribary, 12 Apr. 2024. Web. 07 Sep. 2024. < https://afribary.com/works/groundwater-depletion-at-the-dukwi-wellfield-causes-and-effects >.
Abijah, Diphofu . "Groundwater depletion at the Dukwi wellfield: causes and effects" Afribary (2024). Accessed September 07, 2024. https://afribary.com/works/groundwater-depletion-at-the-dukwi-wellfield-causes-and-effects