Glossary Terms
"E mālama i ka wai" is a Hawaiian saying meaning to cherish and care for the water. The tremendous value of streams in Hawai‘i extends to their critical role in the traditional practice and cultural knowledge of taro cultivation, their use for modern agricultural irrigation, and the important ecological habitats they provide for native aquatic species.
Surface water erosion and mass wasting have etched the dramatic ravines of the Wai‘anae range.
Source: U.S. Geological SurveyThe powerful effect that streams can have on the terrestrial environment can be seen in the dramatic contours of the mountains and cliffs of the Wai‘anae range. The steep ravines of Wai‘anae’s mountains were caused by water-precipitated erosion in combination with massive landslides (Oki 2003).
The major valleys of the Wai‘anae moku have well-articulated systems of intermittent streams: Nānākuli, Ulehawa, and Mā‘ili‘ili Streams in Lualualei Valley; Kaopuni and ‘Āwiwi Streams in Wai‘anae Valley; and Mākaha Stream and Mākua Stream in their respective valleys. Surface water has been diverted in Mākaha Valley and in Wai‘anae Valley at Kaopuni and Kūmaipō Streams.
Streams in the Wai‘anae moku.
Source: CZM Hawai‘iThe term "stream flow" refers to the rate at which water flows through the natural stream channel. Stream flow directly reflects climatic variation, such as rainfall, and is very important to virtually all environmental monitoring of surface water. Stream systems play a key role in the regulation and maintenance of biodiversity. Stream flow can be described as a combination of several factors (Oki 2003):
Components of stream flow include (A) direct runoff of rainfall (overland flow and subsurface storm flow), (B) ground-water discharge (base flow), and (C, D) flow related to bank storage.
Source: Oki 2003.Human intervention such as diversions, dams, channelization, and changes in land use can have a significant effect on stream flow. Recently, the makai portions of many streams are being "modernized" with the construction of concrete drainage channels. This removes the ability of the stream to interact naturally with the land. Unlike a natural stream bed, which traps debris and sediment and filters out contaminants, concrete channels create impervious surfaces that increase the stream flow of surface water, conveying sediments and other potential contaminants to the sea. Other human impacts on stream flow include the effects of road and house lot construction, which sometimes includes moving natural stream channels; siltation from agricultural and suburban development; and the dumping and accumulation of trash and debris in streams.
Concrete drainage channel at Kaupuni Stream.
Source: CZM Hawai‘iThe majority of Wai‘anae’s perennial streams flow consistently only in the upper elevations. The absence of perennial streams in the lower elevations is a reflection of the Wai‘anae region’s arid climate and alluvial soils. Because of the general sandy qualities of these soils, surface water percolates down into them, creating "underflow" that either flows through the subsurface to the ocean, or enters the water table.
Streams in Hawai‘i react quickly to storms, often reaching their maximum flow rates in just hours. These high stream flows can transport large amounts of sediment, nutrients, trash, and other debris to the ocean and have a severe impact on coastal areas. Corals and intertidal fish nurseries are prone to injury from sedimentation and chemical contaminants. Because healthy, natural streams slow the flow of water to the ocean, they play a critical part in maintaining the quality of downstream waters.
Streams and springs in the upper Wai‘anae Valley that were diverted for agricultural use during the plantation era were once part of a vibrant agricultural-based Hawaiian community (see the Ka Po‘e: Land Management, Agriculture section). The Wai‘anae moku’s historic kalo lo‘i is just under 3,000 acres in size, and a cooperative effort to restore it by the Ka‘ala Cultural Learning Center, the State Department of Land and Natural Resources, and Wai‘anae High School is under way. Other groups and families have also entered into partnerships to preserve the water resources of the moku. Protecting the streams and springs throughout the moku is crucial to the kalo lo‘i restoration and other stewardship efforts in the watershed.
Not too long ago, over 200 acres of upper Wai’anae Valley, known as Wai’anae Kai, was under cultivation of taro. In the foothills of Mount Ka’ala, are many acres of overgrown lo’i terraces, evidencing an extensive taro production area, as well as, cultivation of banana, ti and other food and medicinal plants of the Po’e Hawai’i (Indigenous People of Hawai’i).
– Excerpt from Kalo
Streams provide for more than 50 percent of the irrigation supply for agriculture in the state of Hawai‘i (Oki 2003), with about 38 million gallons per day of surface water diverted for irrigation on O‘ahu alone (Juvik and Juvik 1998). About 23 percent of the land area in Wai‘anae is designated for agricultural use, and the district is considered the largest and most commercially important center for livestock production in the state (City and County of Honolulu, Department of Planning and Permitting 2000). Maintenance and restoration of streams in the Wai‘anae moku would help ensure its continued viability as an agricultural center and help Wai‘anae maintain the rural character that is an important part of the community’s identity, as well as its economy.
City and County of Honolulu, Department of Planning and Permitting. 2000. Waianae Sustainable Communities Plan. http://www.honoluludpp.org/Planning/DevSust_Waianae.asp
Juvik, S.P. and J.O. Juvik. 1998. Atlas of Hawaii. University of Hawaii Press.
Oki, D.S. 2003. Surface Water in Hawaii: U.S. Geological Survey Fact Sheet 045-03. USGS.
Burgess, P., and E. Enos. 1999. From Then To Now, A Manual For Doing Things Hawaiian Style. Members of the Opelu Project Ohana, Kaala Farm. Waianae, HI.
Lau, C. 2002. Hydrogeology of the Watersheds of Makaha Valley and Waianae Valley. Honolulu Board of Water Supply.
