There are no major rivers in the country. Of the small rivers and streams, the only one that is navigable is the -long Karun, which shallow-draft boats can negotiate from Khorramshahr to Ahvaz, a distance of about . Other major rivers include the Karkheh, spanning and joining the Tigris; and the Zayandeh River, which is long. Several other permanent rivers and streams also drain into the Persian Gulf, while a number of small rivers that originate in the northwestern Zagros or Alborz drain into the Caspian Sea.