services - hydrological modelling

We have experience in the application and use of several different types of hydrological models. The models range from simplified conceptual lumped models, through to complex fully distributed, physically based models.

Ekosource has been involved in numerous rainfall-runoff hydrological assessments. Application of rainfall-runoff hydrological assessments include the following:

  • Real time forecasting systems

  • Mine dewatering

  • Landuse change scenarios

  • EIA’s (Environmental Impact Assessments)

  • Climate change

  • Basin planning

  • Basin management

  • Low flow assessments

  • Flood studies

There are various methods used for hydrological assessments, depending on the purpose thereof. The software packages used to perform these assessments include MIKE SHE, NAM, SWAT and ACRU. These are explained in more detail below.

Hydrological Studies

MIKE SHE

MIKE SHE (Système Hydrologique Européen) is an advanced, integrated surface water-groundwater, flexible framework for hydrologic catchment modelling. It includes a full suite of pre- and post-processing tools, plus a flexible mix of advanced and simple solution techniques for each of the hydrologic processes.

MIKE SHE covers the major processes in the hydrologic cycle and includes process models for evapotranspiration, overland flow, unsaturated flow, groundwater flow and channel flow and their interactions. Each of these processes can be represented at different levels of spatial distribution and complexity, according to the goals of the modelling study, the availability of field data and the modeller’s choices.

SWAT

SWAT (Soil and Water Assessment Tool) is a small watershed to river basin-scale model to simulate the quality and quantity of surface water and groundwater and predict the environmental impact of land use, land management practices, and climate change. SWAT is widely used in assessing soil erosion prevention and control, non-point source pollution control and regional management in watersheds (SWAT, 2017).

NAM

The NAM (“Nedbør-Afstrømnings-Model”) rainfall-runoff model is the Danish abbreviation which translates into English as “Rainfall-Runoff Model”. NAM simulates the terrestrial phase of the hydrological cycle. The NAM model can be applied independently or it can be used to generate boundary contributions to a river network model. In this way, it is possible to model an individual catchment as well as a group of sub-catchments contributing a larger basin with a more complex river network.

Parameters are required for each catchment included in the model. Initial model parameters are estimated based on soil and land use characteristics of the catchment. The parameters are then further refined during a manual calibration process (depending on the availability of time series data for gauges within the catchment). The NAM rainfall-runoff model has hot-start capability that is a fundamental requirement for near real-time systems. Hot-start is the ability of the model to save the state variables from previous simulations to be used in simulations in the near future.

ACRU

The ACRU model is a physical conceptual agrohydrological model that has been developed since the early 1970s. The ACRU model operates at a daily time step, which is a multi-purpose model which can be applied in design hydrology, crop yield modelling, reservoir yield simulation and irrigation water demand and supply, and assessment of climate change, land use and management impacts. The ACRU model has been applied extensively in South Africa, but also in other countries (Thornton-Dibb et al, 2012).

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