NOAA USGS Cooperative Program Simulation of Coastal Wastewater

— 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

Nuisance algal blooms … … are land-derived nutrients a contributing factor ? Funding by NOAA ECOHAB (Ecology and Oceanography of Harmful Algae Blooms) Hypnea musciformis Photo: Jennifer Smith

Objectives l Estimate ground-water nutrient loads l Identify useful wastewater tracers l 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) Dryland forest, low-intensity ranching So fa m ro rm e s ad s o ma n ll up pe r Resort / urban coastal strip 1500 m 3000 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 Shallow fringing reef +/ -1 m Kalama Park Basalt promo ntory Photo: NOAA No frin ging r Coastal eef Habitat Atlas

Sand beach; no fringing reef Basalt promontory Photo: NOAA Coastal Habitat Atlas

N=7. 3 mg/L= 6 x Background conc P=1. 7 mg/L= 26 x Background conc km t 13 as co Plume 1. 5 km wide 11, 400 m 3/d injected Ambient GW flow effluent 6, 600 m 3/d per km coast

3 -D Ground-Water Model l Code: SUTRA (Voss & Provost, 2002, USGS) l Variable-density flow & solute transport l Solute = Salt (freshwater-saltwater flow) l DID NOT simulate nutrient transport l Post-processing to visualize plume, GW age l l Kh= 3000 m/d Kh: Kv anisotropy=200: 1 a. L = 76 m a. T =. 022 m

Model Mesh 74, 592 elements 32 63 x 37 vertical

Freshwater Lens ar h c (Natural flow) Re es d o ge n Brackish water <C ons tant pre ssu nod re es v er t a hw s e r F e on z r e g t n i a w t Mix al er t a w Salt lation u circ S Visualizations via Model Viewer (Hsieh and Winston, 2002, USGS)

ed ge 3% - looking northwest le 3 d% ge l Injection Plume is Buoyant e n i l re o h S (fluid fresher than 3% Salinity Visualization U pstr removed) e shou am lder Percent seawater 3% Effluent = 1% salinity (buoyant) 20% Injection interval -14 to -58 m within mixing zone and saltwater) 40% 60% 80% 100%

Velocity vectors show regional flow diverging around plume

Salinity Visualization Up str sho eam uld er 3% ledge Salinity 100% 0%

Effluent-Tracer Visualization Percent effluent 100% flu mo id 90 re t ha eff % n l rem uen ov t ed 20%

Percent effluent 100% 80% 60% 40% 20% Plume internal structure, 20% shells 0%

Plume width 1. 5 km at shore Percent effluent 100% 5% 60% effluent at shore (yellow)

Lipoa St algae site t Halama S algae site o Rd a h a k e l e W Kalama Park k r a P e v Co Superimpose over tax map and landmarks

Ground-Water Age at Water Table Years flu id youn ger than 1 ye ar remo ved

Downgradient well in plume was anoxic, with wastewater tracers, denitrification, and heavy d 15 N Percent effluent 100% 0%

Algal tissue d 15 N highest near plume Hypnea Ulva C. Smith, J. Smith, Univ. of Hawaii

Nutrient load per kilometer coast (kg / day – km coast) m 13 k m 1. 5 k Upland background N=7. 8 P=. 44 Injected N= 55 ( 7 x. B) P= 13 (30 x. B)

Attenuated* wastewater nutrient load (kg / day – km coast) m 13 k m 1. 5 k Attenuated N= 27=3. 5 x. B * very speculative, based on just 1 well in plume was 7 x…. P=1. 5=3. 4 x. B was 30 x….

Fe rti liz er Urban Nutrient Load? s Don’t know. Background Injection ? Houses on cesspools

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 Multiparameter water-quality meter GPS unit

Even better:

Wading Salinity (red=freshest) Injection wells Approximate plume extent

Also: - Caffeine - Carbamazepine - NO 3= 2 -4 mg/L - Algal 15 N= 18 * (* Meghan Dailer) Fabric-Brightener Fluorescence (water-column samples) Injection wells Approximate plume extent

Online report: Funding by NOAA ECOHAB (Ecology and Oceanography of Harmful Algae Blooms)