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## Runoff from Glaciers and Snow-Capped Surfaces

The article discusses the treatment of runoff from glaciers and snow-capped surfaces in the model. Key points:

- All surfaces are constrained to have a maximum snow water equivalent of 10,000 kg/m^2.
- For snow-capped columns, any addition of mass at the top is balanced by an equally large mass flux at the bottom, partitioned into solid (q_snwcp,ice) and liquid (q_snwcp,liq) runoff.
- The q_snwcp,ice runoff is sent to the River Transport Model where it is routed to the ocean as an ice stream.
- For non-glacier/lake surfaces, the q_snwcp,liq runoff is assigned to the glaciers and lakes runoff term q_rgwl.
- For glacier surfaces, q_rgwl is calculated from the residual of the water balance, accounting for ground ice/liquid, evaporation, and changes in snow/soil water.
- Glaciers are assumed to be non-vegetated, so canopy evaporation is zero.
- The q_rgwl term may be negative for glaciers and lakes, reducing the total runoff available to the river routing model.