Water Overlay

A Water Overlay is an overlay for which results are calculated by the Water Module. The Basic theory of the Water Module in the Tygron Platform is an implementation of a 2D grid based shallow water model based on the 2D Saint Venant equations. The module is further enhanced with infiltration, evaporation, groundwater flow and hydraulic structures. Its calculations form a simulation of an arbitrary amount of time, during which water is allowed to move. The theory section describes in detail how calculations are performed.

To perform the calculations, the project area is divided into a grid of cells. Each cell has a specific quantity of water and specific hydrological parameters based on the data in the project. The total time which should be simulated is divided into discrete timesteps. Per timestep, each cell communicates with its adjacent cells to exchange water, based on its water level, surface height, current flow direction and other factors. Accuracy and reliability is obtained by dividing the project area and simulation time into sufficiently small cells and steps, at the cost of more computation time.

The final results of the calculation can be inspected, as well as intermediate snapshots of the hydrological situation during the simulation, known as timeframes.

Variants

The Water Module can be called upon by adding one of the following Overlays to a project. Each variant has a number of parameters tuned to best fit specific use-cases. This means that each of these overlays is based on the same theory and calculation method, however they are customized to conveniently provide insight in different aspects of the Water Module.

	Rainfall Overlay	provides insight into the water stress and impact caused by (excessive) rainfall
	Flooding Overlay	provides insight into water stress and impact caused by breaches in levees or other sources causing excessive water inflow
	Groundwater Overlay	provides insight into long-term processes of water flow both on the surface and underground