Not being a nuclear physicist I can't begin to guess if the bomb could do it or not, but lets assume it could.
Well, Tartesh sees a lot of its people devastated by the floods and will certainly be hurt, but since few of their people and none of their major cities were in the inhospitable depression, IIRC, they're not devastated population-wise. Hiowever, 80% of their power (to quote wiki) was from bottomlands hydro plants, sothey'll have a major power crisis. They are also sure to want bloody revenge against the nuclear attack. "Starbombs" may fly.
Krepalgan gets an *Atlantic coast. Morgaf maybe succeeds in getting the two nations at war while their own hands are kept clean.
Otherwise, too little information to go into too much detail.