COM 1470.000 2006-2008 - Laserfiche WebLink

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The primary source of data for the following section on water resources is from the DRAFT Hawaii County Water Use and Development Plan Update: Hawaii Water Plan completed in December 2006. Another information source was a report prepared by Waimea Water Services Inc. for the County Department of Water Supply entitled "Hydrolgeologic study of the Waimea High Level Ground Water," dated Februazy 2001. The Kohala Aquifer Sector Area (ASEA) has two Aquifer System Areas that cover portions of South Kohala, the Waimanu ASYA and the Mahukona Aquifer System Area (ASYA). The West Mauna Kea ASEA only has one ASYA, the Waimea ASYA and the North West Mauna Loa ASEA only has one ASYA, the Anaehoomalu ASYA. An aquifer's `Sustainable Yield' refers to the estimated maximum amount of water that the aquifer can safely produce. Extracting amounts of water greater than the sustainable yield may irreparably damage the aquifer. It should be emphasized that sustainable yield numbers are only estimates. These estimates should not be considered as the exact amount of groundwater that can be safely utilized. In many regions with high sustainable yield numbers, groundwater cannot be utilized because it would not be economically feasible to install water systems to deliver water to users. Current water usage in Table 2.12 (page 21) includes water use from County Department of Water Supply (DWS) systems, private water systems, agricultural use, and irrigation use, including use of reclaimed waste water and water use from domestic rain catchments. Table 2.12 distinguishes between current water use that includes agricultural water use and current water use that does not include agricultural water use. As can be seen in the table, agricultural water use accounts for a significant percentage of current water use inmost ASYA. It is also important to note that current use for the ASYA's of Waimanu, Mahukona, and Anaehoomalu, includes users from outside the district of South Kohala as well. The Waimea ASYA is the only ASYA that exclusively serves South Kohala. Water demand estimates aze based upon current County Zoning and County Population Projection C for the year 2025 (please reference section 2.4.1 of the SKCDP in regards to population projection C). Estimates for the County Zoning and population projections take into account future water demand that includes and does not include agricultural water use. There is a tremendous difference in water projections if agricultural lands are not taken into account when looking at the County Zoning designations. The future estimates of water use that include agricultural use in the County zoning assume irrigation of all lands zoned as agriculture by the County. This includes lands that are currently zoned as agriculture by the County but are not in active agricultural production, including the areas in the district that aze very dry, rocky, and have topography that would make viable agriculture extremely difficult without substantial investments in improving the land such as extending irrigation systems, removing rocks, and massive grading. The estimates that include agricultural use assume that all of these lands will be watered at a rate of 3,400 gallons of water per acre per day, hence the significantly higher estimates. The estimate that takes into account no agricultural use makes the assumption that those lands that are currently designated as agriculture by County zoning and are not being currently used will remain OPEN, unused, and un-watered. Future realistic 16