Introduction - Hawaiÿi. ISLAND OF HAWAIÿI

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ISLAND OF HAWAIÿI The Island of Hawaiÿi is the southernmost and largest of the oceanic islands that comprise the southeastern part of the Hawaiian Archipelago. It is also the youngest.

1 ISLAND OF HAWAIÿI The Island of Hawaiÿi is the southernmost and largest of the oceanic islands that comprise the southeastern part of the Hawaiian Archipelago. It is also the youngest. The entire chain extends from the Big Island (Hawaiÿi) northwestwardly some 1,600 miles to Kure and Midway atolls. Among the five major islands, the Big Island has a land mass (4,038 square miles) greater than all the other islands combined, and it sits over the hot spot where magma extrusion from the ocean floor has created each of the islands in turn as the Pacific Plate moves slowly toward the northwest. The Big Island boasts the only drive-up volcanoes in the world where persistent volcanism continues to create some of the newest and therefore youngest land anywhere on the planet. All the Hawaiian high islands depend on trade winds to generate orographic rain at elevations between about two and three thousand feet on windward slopes, but perhaps the Big Island, with a maximum elevation of nearly 14,000 feet, is unmatched in having such a sharp delineation between wet and dry sides of the island. Most of the island s perennial streams, i.e., those that flow year round, are thus located on the windward sides of the island. However, during weather fronts approaching from the west, rainfall on the usually dry side of the island causes formerly dry stream beds to conduct water to the sea. At this time, the larvae and postlarvae of stream organisms (fishes, prawns, shrimp, and xliii

2 Introduction - Hawaiÿi mollusks) leave the ocean and move upstream where they become isolated in spring-fed pools as the stream dries. When such rain events recur, the animals continue to hopscotch their way up the side of the mountain. All five major species of stream fishes ( oÿopu) and all four major species of larger invertebrates (hīhīwai, hapawai, and two species of ōpae,) are well represented year round in species-typical habitats among the perennial streams on the windward side of the Big Island. With persistent trade winds and resulting orographic rain, the Big Island is noted for its abundance of clear-running perennial streams. However, continuing development, the need to meet dry-side requirements, and weather (often associated with El Niño) that halts the normal flow of trades may produce drought conditions on the usually rainy side of the island. At this time, stream mouths can become blocked by sand, gravel, and rubble pushed inland by ocean waves. Stream pools become deoxygenated and incapable of sustaining aquatic organisms, and the path of amphidromous animals migrating to and from the ocean is blocked. Fortunately, such events occur for a few days or perhaps even for two or three weeks but usually not for months. xliv

3 The Island of Hawaiÿi has five regions (outlined in yellow) and 290 watersheds. The Atlas includes 146 watersheds. Of the 290 watersheds only 130 of them are considered to have a perennial stream by the USGS Digital Line Graphs, About 37.9 percent of the island s watersheds (highlighted in red) and 66.2 percent of the island s perennial streams have been surveyed by the Division of Aquatic Resources, by the former Division of Fish and Game, by the United States Geological Survey (USGS), and during other non-governmental surveys.. In addition to surveys of aquatic macrofauna (fishes, crustaceans, and mollusks), damselfly surveys and museum insect collections are a significant source of information for the island s streams. Because it is the youngest of the Hawaiian Islands, the effects of erosion are often less conspicuous than on the other islands. All stream types described by Parham (2002) occur on the Big Island, but relatively short, high gradient streams, sometimes ending in a waterfall that drops onto the beach or directly into the sea, are more common than elsewhere among the islands. The formation of true estuaries, i.e., a long reach where fresh water mixes with the ocean, is relatively uncommon. Waipiÿo Stream in North Hāmākua and Wailoa River in Hilo are notable exceptions The Island of Hawaiÿi is remarkably similar in percentages of categories of land management to those that occur statewide. Most of the island is unprotected, but a small fraction receives permanent biodiversity protection. Categories of protected but unmanaged and management for multiple uses are similar to average percentages recorded for the other Hawaiian islands. xlv

4 Patterns of land use and land cover on the Big Island also approximate statewide configurations. Scrub/shrub, evergreen forest, grassland, and bare land cover 97 percent of the island. Cultivated land and high and low intensity development capture small percentages but do reflect conditions statewide. Land use districts on the Island of Hawaiÿi have similar distributions for the averages noted for all the high islands. Conservation and agriculture are the predominant categories while urban environs are a small fraction. xlvi

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6 Stewardship for Big Island rests mostly with private owners (about half the land) and with the State of Hawaiÿi (about one third). Military, federal, and Hawaiian Homestead lands approximate the percentages recorded statewide. References: Juvik, S. P. & J. O. Juvik, Atlas of Hawaiÿi, 3 rd edition, University of Hawaii Press, Honolulu. 333 pp. Parham, J. E Spatial models of Hawaiian streams and stream fish habitats. Ph.D. Dissertation, Louisiana State University, 149 pp. xlviii

Wailua River, Kauaÿi. Wailua River, Kauaÿi WATERSHED FEATURES

Wailua River, Kauaÿi. Wailua River, Kauaÿi WATERSHED FEATURES Wailua River, Kauaÿi DAR Watershed Code: 22008 Wailua River, Kauaÿi WATERSHED FEATURES Wailua River watershed occurs on the island of Kauaÿi. The Hawaiian meaning of the name is two waters. The area of