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Instream Flow Standard Assessment Report Island of Oahu Hydrologic Units 3082 Kiikii June 2021 DRAFT PR-2021-03

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Instream Flow Standard Assessment Report Island of Oahu Hydrologic Units 3082 Kiikii June 2021 DRAFT PR-2021-03 Instream Flow Standard Assessment Report Island of Oahu Hydrologic Units 3082 Kiikii June 2021 DRAFT PR-2021-03 State of Hawaii Department of Land and Natural Resources Commission on Water Resource Management COVER Satallite image of Kiikii hydrologic units with the Kaukonahua and Poamoho streams flowing into Kaiaka Bay, Oahu [Google Earth, 2015]. Note: This report is intended for both print and electronic dissemination and does not include diacritical marks in spelling of Hawaiian words, names, and place names due to problems associated with its use electronically. However, Commission staff has made attempts to include diacritical marks in direct quotations to preserve accuracy. Table of Contents 1.0 Introduction ......................................................................................................... 1 General Overview ................................................................................................................................... 1 Current Instream Flow Standard ........................................................................................................... 1 Instream Flow Standards ....................................................................................................................... 2 Interim Instream Flow Standard Process ............................................................................................. 2 Instream Flow Standard Assessment Report ...................................................................................... 3 Surface Water Hydrologic Units ............................................................................................................ 5 Surface Water Definitions ...................................................................................................................... 5 2.0 Unit Characteristics .......................................................................................... 11 Geology .................................................................................................................................................. 11 Soils ....................................................................................................................................................... 13 Rainfall ................................................................................................................................................... 13 Solar Radiation...................................................................................................................................... 18 Evaporation ........................................................................................................................................... 19 Evaporation from Wahiawa Reservoir ................................................................................................ 22 Land Use ................................................................................................................................................ 24 Land Cover ............................................................................................................................................ 24 Flood ...................................................................................................................................................... 24 Drought .................................................................................................................................................. 30 3.0 Hydrology .......................................................................................................... 33 Streams in Hawaii ................................................................................................................................. 33 Groundwater.......................................................................................................................................... 34 Wells in the Kiikii Hydrologic Unit ...................................................................................................... 36 Groundwater Pumping and Salinity Levels ....................................................................................... 44 Streamflow Characteristics ................................................................................................................. 45 Seepage Gains and Losses ................................................................................................................. 46 Long-term trends in flow ...................................................................................................................... 50 4.0 Maintenance of Fish and Wildlife Habitat ....................................................... 53 Hawaii Stream Assessment ................................................................................................................. 54 DAR Atlas of Hawaiian Watersheds .................................................................................................... 54 Recent Biota Surveys ........................................................................................................................... 55 5.0 Outdoor Recreational Activities ...................................................................... 57 6.0 Maintenance of Ecosystems............................................................................ 59 7.0 Aesthetic Values ............................................................................................... 68 8.0 Navigation ......................................................................................................... 69 9.0 Instream Hydropower Generation ................................................................... 69 10.0 Maintenance of Water Quality ......................................................................... 70 11.0 Conveyance of Irrigation and Domestic Water Supplies .............................. 78 12.0 Protection of Traditional and Customary Hawaiian Rights ........................... 79 Appurtenant Water Rights ................................................................................................................... 81 Taro Production .................................................................................................................................... 88 i Archaeological Evidence for Hawaiian Agriculture .......................................................................... 91 Fishponds .............................................................................................................................................. 91 13.0 Public Trust Uses of Water .............................................................................. 96 Public Water Supply ............................................................................................................................. 96 Hawaiian Home Lands .......................................................................................................................... 96 14.0 Noninstream Uses ............................................................................................ 98 Historic Agricultural Demands ............................................................................................................ 98 Registered Diversions .......................................................................................................................... 99 Utilization of Important Agricultural Lands ...................................................................................... 108 Current and Future Agricultural Demands ....................................................................................... 108 Wahiawa Reservoir ............................................................................................................................. 110 15.0 Bibliography .................................................................................................... 115 16.0 Appendices ..................................................................................................... 124 ii List of Figures Figure 1-1. Information to consider in setting measurable instream flow standards. ..................................................... 3 Figure 1-2. Simplified representation of the interim instream flow standard and permanent instream flow standard processes. Keys steps of the adopted interim IFS process are depicted in the left column by the boxes drawn with dotted lines. ...................................................................................... 4 Figure 1-3. World View 2 satellite imagery of the Kiikii hydrologic unit and streams on Oahu, Hawaii. (Source: State of Hawaii, Planning Department, 2004; State of Hawaii, Commission on Water Resource Management, 2015c)................................................................................... 7 Figure 1-4. Elevation range and contours of the Kiikii hydrologic unit, Oahu. (Source: State of Hawaii, Office of Planning, 2004e; U.S. Geological Survey, 2001) .................................................................. 8 Figure 1-5. USGS topographic map of Kiikii hydrologic unit, Oahu. (Source: U.S. Geological Survey, 1996) .................................................................................................................................................. 9 Figure 1-6. Major and minor roads for the Kiikii hydrologic unit, Oahu. (Source: State of Hawaii, Office of Planning 2020) ...............................................................................................................................
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