# Tunnels

Tunnels are direct couplings between hydraulic nodes. The tunnel pathways have a maximum transfer, but no other special functionality.

$$ \\{i \in reservoirs ,t \in tunnels,\ k \in \\{0, 1, ..., timesteps - 1\\}\\}$$

$$ RESBAL(1,k): res(1,k) - res(1,k-1) = Inflow(1,k) + tun(2,k) - Outflow(1,k) - tun(1,k) $$

![](./resources/Case3.svg)