Final Comprehensive Conservation Plan - U.S. Fish and Wildlife ...

Hakalau Forest National Wildlife Refuge
Comprehensive Conservation Plan
to drier conditions and changes in the microclimate. One natural pond, known as Frog Pond, occurs
between the Honohina and Hakalau Tracts at about 5,600 ft (Tomonari-Tuggle 1996).
A baseline water resource assessment and stream fauna assessment has not been conducted at the
HFU (USFWS 2007). However, numerous surveys have been conducted at the lower elevations of
streams that pass through the Refuge. The lower reaches of these streams support native fishes and
invertebrates (Tate 1996, Nishimoto and Kuamo‘o 1997). Although unstudied, stream fauna at higher
elevations within the HFU are believed to be exclusively invertebrate.
According to the Water Resources Protection Plan (USFWS 2005), the HFU is located in the
Pa‘auilo, Hakalau, and Onomea hydrological units. These aquifers have a sustainable yield of 60,
150, and 147 mgd, respectively. The size of these systems shows that a large amount of potable basal
groundwater can be developed in the area (Yuen and Associates 1990).
3.3.2 Kona Forest Unit Hydrology
Due to the extremely permeable lava and well-drained soils, there are no perennial surface waters or
drainages on the KFU. As a result, no standard water resource assessments have been performed
(USFWS 2007). The closest permanent surface water is the Lumiawai waterhole, located about
0.5 mi south of the southeast corner (Rayond and Valentine 2007). Ki‘ilae Stream, which is south of
Hōnaunau, is the closest stream (Yuen and Associates 1990).
The Water Resources Protection Plan (USFWS 2005) depicts the KFU within the Ka‘apuna
hydrological unit. Groundwater in this region is primarily composed of a thin basal lens that is not
protected by caprock. The aquifer in the Ka‘apuna hydrological unit has a sustainable yield of
50 mgd (Yuen and Associates 1990). The Refuge area functions as an important groundwater
recharge area for Kona as a result of the porous substrate and high moisture conditions (USFWS
2008a).
South Kona is vulnerable to flooding due to the combination of intense storms, lack of drainages,
steep terrain, permeable soils, and urban land uses (County of Hawai‘i 2006, TMA 2007). No records
of flooding on the unit have been found.
3.4 Topography
The Island of Hawai‘i is considered the highest oceanic island in the world. However, similar to
other volcanic islands, summit heights are constantly changing due to erosion, lava deposition, and
isostatic compensation (Jordan et al. 2003). Hawai‘i Island is characterized by high elevation areas
and gentle slopes. The majority of Hawai‘i Island (88 percent) is above 500 ft (HDBEDT 2007).
Furthermore, almost 70 percent is above 2,000 ft (Mitchell et al. 2005, HDBEDT 2007). The highest
point on the island, Mauna Kea, reaches 13,796 ft. Although Hawai‘i Island has some of the highest
peaks in the State, the inclines are relatively mild. Approximately 70 percent of Hawai‘i Island has a
slope of less than 10 percent (HDBEDT 2007).
Chapter 3. Physical Environment 3-11