Instream Flow Standard Assessment Report Island of Kauai Hydrologic Unit 2018 Waioli January 2021 DRAFT PR-2021-01 State of Hawaii Department of Land and Natural Resources Commission on Water Resource Management COVER Satellite image of Waioli hydrologic unit with the Waioli Stream flowing into the Pacific Ocean, northern Kauai [Google Earth, 2008]. 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. Introduction ......................................................................................................... 9 General Overview ................................................................................................................................... 9 Current Instream Flow Standard ........................................................................................................... 9 Instream Flow Standards ..................................................................................................................... 10 Interim Instream Flow Standard Process ........................................................................................... 11 Instream Flow Standard Assessment Report .................................................................................... 12 Surface Water Hydrologic Units .......................................................................................................... 12 Surface Water Definitions .................................................................................................................... 13 2. Watershed Characteristics .............................................................................. 19 Geology .................................................................................................................................................. 19 Soils ....................................................................................................................................................... 19 Rainfall ................................................................................................................................................... 19 Solar Radiation...................................................................................................................................... 23 Evaporation ........................................................................................................................................... 23 Land Use ................................................................................................................................................ 25 Land Cover ............................................................................................................................................ 29 Flood ...................................................................................................................................................... 32 Drought .................................................................................................................................................. 33 3. Hydrology .......................................................................................................... 36 Streams in Hawaii ................................................................................................................................. 36 Groundwater.......................................................................................................................................... 36 Streamflow Characteristics ................................................................................................................. 38 Long-term trends in rainfall and streamflow ..................................................................................... 40 4. Maintenance of Fish and Wildlife Habitat ....................................................... 44 Hawaii Stream Assessment ................................................................................................................. 45 DAR Atlas of Hawaiian Watersheds .................................................................................................... 45 5. Outdoor Recreational Activities ...................................................................... 47 6. Maintenance of Ecosystems............................................................................ 49 Wetland Habitat ..................................................................................................................................... 51 Economic Value of Ecosystem Services ............................................................................................ 52 7. Aesthetic Values ............................................................................................... 58 8. Maintenance of Water Quality ......................................................................... 59 9. Conveyance of Irrigation and Domestic Water Supplies .............................. 66 10. Protection of Traditional and Customary Hawaiian Rights ........................... 67 Appurtenant Water Rights ................................................................................................................... 67 Information relating to Pre-Contact Practices ................................................................................... 70 Land Commission Awards ................................................................................................................... 71 Ahupuaa and Aha Moku Systems ....................................................................................................... 74 Traditional and Customary Practices ................................................................................................. 78 i 11. Other Public Trust Uses of Water ................................................................... 84 IMPACT TO HAWAIIAN HOME LANDS ............................................................................................... 84 IMPACT TO MUNICIPAL WATER SUPPLY ......................................................................................... 84 12. Noninstream uses ............................................................................................ 85 Water Leaving the Waioli Hydrologic Unit in Ditch Systems ........................................................... 87 Current Agricultural Demands ............................................................................................................ 90 Modifications of Ditch Systems and Groundwater Recharge .......................................................... 93 Utilization of Important Agricultural Lands ........................................................................................ 93 13. Bibliography ...................................................................................................... 96 14. Appendices ..................................................................................................... 101 ii List of Figures Figure 1-1. Information to consider in setting measurable instream flow standards. ................................................... 10 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. .................................................................................... 11 Figure 1-3. World View 2 satellite imagery of the Waioli hydrologic unit and streams in northern Kauai, Hawaii. (Source: State of Hawaii, Planning Department, 2004; State of Hawaii, Commission on Water Resource Management, 2015c; State of Hawaii, Office of Planning - Division of Aquatic Resources, 2005) .......................................................................................................... 15 Figure 1-4. Elevation range of the Waioli hydrologic unit. (Source: State of Hawaii, Office of Planning, 2004e; U.S. Geological Survey, 2001) ........................................................................................... 16 Figure 1-5. USGS topographic map of Waioli hydrologic unit. (Source: U.S. Geological Survey, 1996).............................................................................................................................................................. 17 Figure 1-6. Major and minor roads for the Waioli hydrologic unit. (Source: State of Hawaii, Office of Planning 2015) ........................................................................................................................................... 18 Figure 2-1. Orographic precipitation in the presence of mountains higher than 6,000 feet. ......................................... 20 Figure 2-2. Generalized geology of the Waioli hydrologic unit, Kauai. (Source: Sherrod et al., 2007).............................................................................................................................................................. 21 Figure 2-3. Soil classification of the Waioli hydrologic unit, Kauai. (Source: State of Hawaii, Office of Planning, 2015m) ....................................................................................................................................... 22 Figure