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— NOAA / USGS Cooperative Program — Simulation of Coastal Wastewater Injection in Hawaii using SUTRA … and the Value of Compelling Visualizations in Conveying Results to the Non-Specialist Public. Chip Hunt U.S. Geological Survey, Honolulu, HI cdhunt@usgs.gov.
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— NOAA / USGS Cooperative Program —Simulation of Coastal Wastewater Injection in Hawaii using SUTRA… and the Value of Compelling Visualizations in Conveying Results to the Non-Specialist Public Chip Hunt U.S. Geological Survey, Honolulu, HI cdhunt@usgs.gov
Maui Municipal Wastewater Injection Sites Kahului Lahaina 3000 m 1500 m
Photo: Jennifer Smith Nuisance algal blooms …… are land-derived nutrients a contributing factor ? Funding by NOAA ECOHAB (Ecology and Oceanography of Harmful Algae Blooms) Hypnea musciformis
Objectives • Estimate ground-water nutrient loads • Identify useful wastewater tracers • Answer injection-plume questions: • Where does it go? • “We inject this stuff, and if it gets to the coast …” - Plume width at coast?
Sugar cane (fertilizers) Resort / urban coastal strip Dryland forest, low-intensity ranching Some small farms on upper road 3000 m 1500 m
Sugar cane Condominiums Photo: Univ. of Hawaii Coastal Geology Group
Dryland scrub-forest in uplands Suburban residential Resorts / condos Photo: Univ. of Hawaii Coastal Geology Group
Approximate plume extent Kalama Park Shallow fringing reef +/-1m Basalt promontory Photo: NOAA Coastal Habitat Atlas No fringing reef
Sand beach; no fringing reef Basalt promontory Basalt promontory Photo: NOAA Coastal Habitat Atlas
N=7.3 mg/L=6xBackground conc P=1.7 mg/L=26xBackground conc 13 km coast 11,400 m3/d injected effluent Ambient GW flow 6,600 m3/d per km coast Plume 1.5 km wide
3-D Ground-Water Model • Code: SUTRA(Voss & Provost, 2002, USGS) • Variable-density flow & solute transport • Solute = Salt (freshwater-saltwater flow) • DID NOT simulate nutrient transport • Post-processing to visualize plume, GW age • Kh= 3000 m/dKh:Kv anisotropy=200:1 • aL= 76 m aT= .022 m
Model Mesh 74,592 elements 63 32 x 37 vertical
Freshwater Lens (Natural flow) Recharge nodes v Freshwater Mixing zone Saltwater Brackish water Saltwater circulation < Constant pressure nodes Visualizations via Model Viewer(Hsieh and Winston, 2002, USGS)
Injection Plume is Buoyant 3% ledge Salinity Visualization (fluid fresher than 3% removed) - looking northwest Upstream shoulder 3% ledge Percent seawater Shoreline 3% Effluent = 1% salinity (buoyant) 20% 40% 60% 80% Injection interval -14 to -58 m within mixing zone and saltwater) 100%
Salinity Visualization Salinity 100% Upstream shoulder 0% 3% ledge
Effluent-Tracer Visualization Percent effluent 100% fluid more than 90% effluent removed 20%
Plume internal structure, 20% shells Percent effluent 100% 80% 60% 40% 20% 0%
Plume width1.5 km at shore Percent effluent 100% 5% 60% effluent at shore (yellow)
Lipoa St Lipoa St algae site Superimpose over tax map and landmarks Welekahao Rd Halama St algae site Kalama Park Cove Park
Ground-Water Ageat Water Table Years fluid younger than 1 year removed
Downgradient well in plume was anoxic, with wastewater tracers, denitrification, and heavy d15N Percent effluent 100% 0%
Hypnea Ulva Algal tissued15N highest near plume C. Smith, J. Smith, Univ. of Hawaii
Nutrient loadper kilometer coast(kg / day – km coast) Upland background N=7.8P=.44 13 km 1.5km Injected N= 55 ( 7xB)P= 13 (30xB)
Attenuated*wastewater nutrient load(kg / day – km coast) 13 km Attenuated N=27=3.5xBwas 7x…. P=1.5=3.4xBwas 30x…. 1.5km * very speculative, based on just 1 well in plume
UrbanNutrient Load? Don’t know. Fertilizers Background Injection Houses on cess- pools ?
Enough modeling, let’s go look Wading survey for wastewater tracers … rough work but somebody’s gotta do it Water-quality meter and GPS Funding: Hawaii Dept. of Health, USEPA Photo: Joshua Marvit, Hawaii Dept. of Health
Smaller platform: coolers strapped together GPS unit Multiparameter water-quality meter
Wading Salinity(red=freshest) Injection wells Approximate plume extent
Fabric-Brightener Fluorescence(water-column samples) • Also: • - Caffeine • Carbamazepine • NO3= 2-4 mg/L • Algal 15N= 18 * • (* Meghan Dailer) Injection wells Approximate plume extent
Funding by NOAA ECOHAB (Ecology and Oceanography of Harmful Algae Blooms) Online report: