While still part of Haleakala National Park, Ohe'o Gulch is accessed via the Hana Highway (about a half hour drive past Hana town).  If you plan to visit Haleakala Crater save your park pass as it is good for 3 day's throughout Haleakala National Park.  There are at least 7 pools with water flowing into and out of each one. The pools can be closed to swimming for either excessive water flow or stagnant water depending on the rainfall in the forest.  If you happen to be in the pools, and the water starts to rise, get to higher ground immediately.  It's rare, but rains in the mountains above can cause a flash flood in the pools.  Also, be careful not to drink the water untreated from any pool or stream.  Unfortunate bathroom habits of the wildlife can contaminate the waters with bugs that will behave unpleasantly in your digestive tract.  

The Pipiwai Trail begins from the park entrance at Ohe`o Gulch and is a 1.8 mile hike from there to Waimoku Falls.  The hike can be slippery, and muddy in parts, but it is well worth the 800' climb.  Several waterfalls can be seen along the trail, and the bamboo forest is a site to behold all on it's own.  There is a gate along the trail.  Please close it as you pass.  The fence system is there to keep wild pigs and goats from destroying the natural habitat in the park.