step 1: go to sierrarios.org
step 2: click on “links” in the top navigation bar
step 3: click on "topo maps"
step 4: open a directory or two and take a look
step 5: shit in pants! topos of pretty much everything, with areas drained, gradient, and kilometers marked out on all of them!
step 6: click on “join” in the top navigation bar
step 7: follow directions and send some money to SierraRios, because progress is afoot in Mexico–many proposed dams in paradise
step 8: look at the rest of the site, lose sleep for weeks on end, daydream constantly, plan a trip