The monitor-model-manage approach forms the basis for wellfield management practiced at Umvoto. The approach involves the collection, analysis and interpretation of relevant hydroclimatological, geological, hydrogeological data and information, which is used to develop a conceptual and numerical model of a study area. The model is used to run various predictive scenarios with the model results informing decision making and best management practices/strategy to support sustainable implementation and wise water use.
How this is used at Umvoto
Umvoto’s monitor-model-manage approach is demonstrated through the City of Cape Town’s New Water Programme which aims to develop and optimise wellfields in the Atlantis, Cape Flats and Table Mountain Group Aquifers. All of Umvoto’s projects rely on thorough application of science including accurate data collection, analysis and interpretation.
Examples of data required for developing a numerical model include 1) physiographic details of hydroclimate, topography, land cover, and hydrology; 2) geological data from maps, field mapping, borehole and geophysical logs; and 3) hydrogeological data such as water level measurements, hydrochemistry, abstraction rates, aquifer parameters, and ecological health. The data is used to develop a conceptual understanding of the hydrogeological system (aquifer geometry, boundary conditions, aquifer parameters, water levels, flow directions and influencing features, recharge, discharge, etc.). The correctness of the conceptual model is then evaluated through the development of a numerical groundwater model. The numerical model is developed in specialised software’s such as ESI’s Groundwater Vistas using the MODLFOW code or MIKE powered by DHI’s FeFlow.
Once the model is constructed and calibrated with observed field measurements, various scenarios are used to evaluate an unknown or question. Examples of scenarios include likelihood of seawater intrusion from groundwater abstraction with and comparatively without managed aquifer recharge; or the inflow of groundwater to a mine or shaft under different mine and dewatering designs; or possibly the travel path and time of a contaminant during different remediation stages. Scenarios undergo uncertainty analyses, whereby the various model runs are conducted with varying parameters to provide a range of potential outcomes. The range of parameter variance to each outcome allows identified risks to be evaluated and quantified. For example if the outcome of the model run is a water balance, the yield of a wellfield or borehole can be evaluated under different recharge and abstraction scenarios, each with a range of uncertainty applicable to sensitive parameters (e.g., recharge, hydraulic conductivity, or hydraulic head variation).
Numerical models are also useful to evaluate contaminant transport and inform the protection of groundwater from potential contamination by anthropogenic activity. Groundwater protection zones are established by contaminant fate and transport modelling where the time and pathway of potential contaminants informs decision makers of areas over the aquifer where specific types of land use activities should be limited or prohibited.
Ongoing monitoring is necessary to inform if field observations differ from simulated predictions. Should this occur, the source of the difference is investigated, and the incorporation of monitoring data allows for updates of the conceptual and numerical models. Modelling is thus an iterative approach, growing and evolving as more data and understanding of the system is gained.
3D animation of the finite element mesh used to construct the Cape Flats Aquifer numerical model.
Why Umvoto are leaders in the field of groundwater modelling
Umvoto has extensive experience in all aspects required in the application of the monitor-model-manage approach. Groundwater development, implementation and ongoing monitoring is practised with great success across a variety of our projects, including the Overstrand Local Municipality’s Groundwater Management and City of Cape Town’s New Water Programme. The approach has allowed successful and sustainable development and implementation of innovative wellfield designs that are cognisant of existing groundwater users, engineering requirements, relevant legislation, and ecological needs.
Do not hesitate to contact us to assist with any of your groundwater modelling needs.