The general slope of the southern part is southward to the river Balsas, or Mescala, which forms its boundary-line with Guerrero.
The Lerma, on the northern frontier, and the Balsas on the southern, are the only rivers of importance of the state, their tributaries within its boundaries being small and swift-flowing.
It receives only one important tributary from Maranhao - the Rio das Balsas, 447 m.
It is drained by the Amacusac river, a northern tributary of the Mescala, or Balsas.
A southern extension of the Mexican Central, via Cuernavaca, has reached the Balsas river and will be extended to Acapulco, once the chief Pacific port of Mexico and the depot for the rich Philippine trade.
