Reservoir

This element is treated in subroutine reservoir.f. In forward mode the value of hup can be negative or positive. If it is negative no frontwater curve was calculated and a backwater curve has to be determined (hdo is set to -1). If it is positive a backwater curve was calculated and hdo is calculated as the height after a jump using subroutine hns.f.

The further calculation depends on the value of hdo:

• If hdo exceeds the depth of the reservoir hr the backwater curve leads to a fall in the reservoir or a jump in the reservoir and the downstream depth is set to hr.
• If hdo is less than or equal to hr the critical hk and normal depth he are calculated. If hk $<$ he a backwater curve is calculated starting at hk in ndo (nstack is incremented and istack(1,nstack) is set to nelem and istack(2,istack) is set to ndo). If hk $\ge$ he a backwater curve is not plausible and no solution is found.