Canyon exchange option

The Canyon exchange option is only available in the steady state PCG solver. It can be used to describe the exchange between a groundwater aqui­fer and a river when the river cuts deeply into the aquifer (e.g. through a nar­row valley). If the river water level is below the bottom of the adjacent computational groundwater layer, the potential head gradient is reduced. In this case, the head difference in layers above the river level is limited by the bottom elevation of the layer. Thus,

(30.19)   

where h_i is the head in the adjacent groundwater node, h_riv is the head in the river, and z_i is the bottom of the current layer.

Without the ‘Canyon’ option, MIKE SHE effectively assumes that the river is hydraulically connected to the upper most model layer, since MIKE SHE cal­culates the exchange flow with all layers that intersect the river based on the difference between the river level and the water table.

Figure 30.6        Water table elevation versus the head difference.