Mountain Streams of Hawaii

We usually do archaeological projects for our annual excursions, but in 2001 we decided to go to Hawaii.  Earthwatch was sponsoring a biological survey on Maui and we signed up.
The Hawaiian Islands experience the rain shadow climate effect.  The prevailing wind blows the air up over the central mountains and the moisture laden air cools as it rises.  Clouds form and it begins to rain.  The air is usually dry by the time it descends on the leeward side of the island.  The result is a wet side and a dry side.  
     During the colonial period, sugar plantations were set up on the dry side of the islands and elaborate irrigation systems were built to carry water diverted from the streams on the wet side of the islands to the plantations on the dry side.  The water from many of these diverted streams never reaches the ocean.  This has likely drastically affected several aquatic species that hatch in the head waters of the streams, follow the stream flow to the ocean and then return to headwaters to spawn at the end of their life cycle.  These unique species not only manage against strong downstream flows but can actually climb 100-foot waterfalls! 

Working with Dr. Eric Benbow and field supervisor Mollie McIntosh, our task was to survey and sample several diverted and non-diverted streams to collect data to quantify the effect on stream life and the ecology of the stream system.  In the process we visited numerous isolated and exotic locations like Hanawi Falls pictured here.

The survey team at Hanawi Falls
     We stayed in a condo in Kihei on the dry side and traveled each day in the team van to the various wet-side stream locations to work.  We also processed filed data data in a lab set up in condo.  Click the image links below for more on each location.

Honomanu Stream

Hanawi Stream Waihee Stream Iao Stream Gary in the lab


Hanawi Waihee Iao Lab work
A diversion grate collects most of the stream flow.

The sugar mills are going but the stream diversions will still be needed as tourism expands and new resorts are built on the dry side of the islands.

 An old mill and a cane field.

The photo above of a diversion grating shows how diversion works in the Hawaiian streams.  Under normal flow nearly all the water runs into the grating as in the photo.  Gary's feet are completely dry.  During flooding excess water flows right over the grate and on to the sea, or to another diversion lower in the stream.
     Water resource diversion is not a problem only in the islands, but the limited scale of an island's ecological system makes the effects easier to measure, as well as exacerbating the problem.

You can do this!

Hawaiian Streams is not currently active, but you can join a similar Earthwatch project in the coming season.  Use this link for information

Click to visit Earthwatch (new window)

Site Map


Return to Nature


  This page and its contents Copyright 2003 Michael & Karen Crisafulli. All rights reserved.