Hydrology of Three Loko Iʻa, Hawaiian Fishponds
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Hydrology of three Loko Iʻa, Hawaiian fishponds, on windward Hawaiʻi Island, Hawaiʻi Presented to the Faculty of the Tropical Conservation Biology and Environmental Science Graduate Program University of Hawaiʻi at Hilo In partial fulfillment of the requirement for the degree of Master of Science In Tropical Conservation Biology and Environmental Science August 2018 By Cherie Kauahi Approved By: Steven Colbert Jene Michaud Noelani Puniwai Kehau Springer Acknowledgements Mahalo nui loa to my advisor, Steven Colbert, and committee members, Noelani Puniwai, Kehau Springer and Jene Michaud. Their support and guidance through this program has helped my growth as not only a scientist but as a member of my community. Mahalo to my many friends and family who have supported me over the past two years. Mahalo to Hui Hooleimaluō, especially Kamala Anthony, and the kiaʻi at Hale o Lono and Waiāhole/Kapalaho for your guidance and expertise in working along side me through this collaborative project. Mahalo to the Keaukaha, Waiuli, Leleiwi and Honohononui communites for allowing me to grow within these places that I hold dear to my heart. Mahalo to the funding agency that made this project possible: the U.S. Department of the Interior Pacific Islands Climate Adaptation Science Center managed by the United States Geological Survey National Climate Adaptation Science Center through Cooperative Agreements G12AC00003 and G14AP00176. I would also like to mahalo all the interns, undergraduate, graduate students and other University of Hawaiʻi at Hilo faculty that contributed to this project; Kainalu Steward, Uʻi Miner-Ching, Mary Metchnek, Jowell Guerreiro, Uakoko Chong, Kailey Pascoe, Leilani Abaya, John Burns and Tracy Wiegner. Also mahalo to the University of Hawaiʻi at Hilo Analytical Laboratory for this projects sample analyses. There are too many people to thank so I would like to mahalo everyone else who has helped me through this journey, you know who you are. ii Table of Contents Abstract ........................................................................................................................................... vi Preface............................................................................................................................................ vii Introduction ..................................................................................................................................... 1 Methods........................................................................................................................................... 3 Site Description ......................................................................................................................................... 3 Freshwater Distribution Surveys ............................................................................................................... 4 Relative Groundwater Flow Data Collection ............................................................................................ 4 Calculating Relative Depth ....................................................................................................................... 5 Adjusting to Mean Lower Low Water Datum........................................................................................... 6 Calculating Relative Groundwater Flow ................................................................................................... 6 Calculating Tidal Day and Daily Relative Groundwater Flow ................................................................. 8 Chemical Analysis of Water Samples ....................................................................................................... 8 Sea Level Rise Scenarios .......................................................................................................................... 9 Statistical Analyses.................................................................................................................................. 10 Results ........................................................................................................................................... 11 Temperature............................................................................................................................................. 11 Salinity..................................................................................................................................................... 11 Relative Groundwater Flow .................................................................................................................... 12 Relative Groundwater Flow and Rain ..................................................................................................... 13 Groundwater Chemistry .......................................................................................................................... 13 Sea Level Rise ......................................................................................................................................... 14 Discussion ..................................................................................................................................... 15 Relative Groundwater Flow .................................................................................................................... 15 Groundwater Chemistry .......................................................................................................................... 16 Salinity..................................................................................................................................................... 17 Climate Change ....................................................................................................................................... 18 Conclusion .................................................................................................................................... 19 Epilogue ........................................................................................................................................ 20 List of Tables ................................................................................................................................ 21 List of Figures ............................................................................................................................... 33 Literature Cited ............................................................................................................................. 49 iii List of Tables Table 1. Description of three loko iʻa in Keaukaha, Hawaiʻi ..................................................................... 21 Table 2. Average SD of temperature, salinity, daily relative groundwater flow and depth .................... 22 Table 3. Average ± SD of temperature (C) in groundwater and brackish water ...................................... 23 Table 4 Factors associated with high daily maximum practical salinity ..................................................... 24 Table 5. Statistics table for correlations between relative groundwater flow and rainfall scenarios .......... 25 Table 6. Average ± SD of relative groundwater flow under varying rain conditions ................................. 26 Table 7. Average ± SD of Ca2+, K+, Mg2+ and Na+ concentrations ............................................................. 27 - Table 8. Average ± SD of Cl , SO4 and alkalinity concentrations ............................................................... 28 - - 3- + Table 9. Geometric means ± SD of NO2 + NO3 , PO4 , H4SiO4 and NH4 ................................................ 29 Table 10. Statistics table for regressions between Cl- and nutrients ............................................................ 30 Table 11. Average ± SD of mean rainfall recharge elevation ..................................................................... 31 Table 12. Latitude and longitude of groundwater spring locations .................................................32 iv List of Figures Figure 1. Map of study sites in Keaukaha, Hawaiʻi ................................................................................... 33 Figure 2. Map of Honokea loko iʻa at Waiuli ............................................................................................ 34 Figure 3. Map of Hale o Lono and Waiāhole loko iʻa in the ahupuaʻa of Honohononui ............................ 35 Figure 4. Keaukaha, HI shoreline map highlighting the spring locations along the coast .......................... 36 Figure 5. Simplified representation of the mass balance equation for water applied to loko iʻa ................ 37 Figure 6. Average SD of relative groundwater flow at Honokea loko iʻa................................................ 38 Figure 7. Average SD of relative groundwater flow at Hale o Lono loko iʻa .......................................... 39 Figure 8. Average SD of relative groundwater flow at Waiāhole loko iʻa ............................................... 40 Figure 9. Correlation between 3-day sums of averaged rainfall and relative groundwater flow ................ 41 Figure 10. Correlation between 3-day sums of high elevation rainfall and relative groundwater flow ...... 42 Figure 11. Correlation between 3-day sums of low elevation rainfall relative groundwater flow .............. 43 Figure 12. Comparisons between mean sea level and projected sea level rise scenarios ............................ 44 Figure 13. Average SD of rain in the Hilo