Water Resource Sustainability Issues on Tropical Islands December, - PowerPoint PPT Presentation

…innovation through engineering and scientific excellence…since 1985 Robert Bourke, Natalie Waters, and Jordon Moniuszko Water Resource Sustainability Issues on Tropical Islands December, 2015

Estuary Rehabilitation Stream Flow Restoration to Kaelepulu Estuary

1,000 BC 1 Km Kailua Bay

1928 1 Km Kailua Bay Kawai Nui Swamp Kaelepulu Pond

1928 Kailua Bay Kawai Nui Kawai Nui Swamp Swamp Kaelepulu Kaelepulu Pond Pond

1952 New 1 Km Channel

1952 1 Km 1966

1952 1966

1952 1966 1990

1958

ESTUARY CHALLENGES • EXCISED FROM HEADWATER FLOWS • DECREASED STREAM MOUTH EXCHANGE • BATHYMETRY CHANGES • URBAN STORM WATER FLOWS • INVASIVE SPECIES

ESTUARY CHALLENGES • EXCISED FROM HEADWATER FLOWS • DECREASED STREAM MOUTH EXCHANGE • BATHYMETRY CHANGES • URBAN STORM WATER FLOWS • INVASIVE SPECIES

ESTUARY IS ONLY EXPOSED TO TIDAL FLOW ON A PERIODIC BASIS MANUAL OPENING OF STREAM MOUTH ON ~MONTHLY SCHEDULE BY C&C HONOLULU

Total Tidal Inflow 0.23 M cuft

Timing of Stream Mouth Opening to Maximize Initial Outflow Results in an Increase of Total Exchange Total Tidal Inflow 0.23 M cu ft Total Tidal Inflow 0.75 M cu ft Total Tidal Inflow 21x10 3 m3

ESTUARY CHALLENGES • EXCISED FROM HEADWATER FLOWS • DECREASED STREAM MOUTH EXCHANGE • BATHYMETRY CHANGES • URBAN STORM WATER FLOWS • INVASIVE SPECIES

SHOALING OF STREAM CHANNEL AT POND OUTFLOW INHIBITS TIDAL FLOW OF SALT WATER TO THE POND

Being addressed through ESTUARY State TMDL CHALLENGES City NPDES • EXCISED FROM HEADWATER FLOWS • DECREASED STREAM MOUTH EXCHANGE • BATHYMETRY CHANGES • URBAN STORM WATER FLOWS • INVASIVE SPECIES

A 2004 ELRA $24K – 319 Grant ESTUARY B 2009 KCC $29K – Hi. Comn. Foundation & Castle Foundation CHALLENGES C 2016 (?) C&C $750K State funded • EXCISED FROM HEADWATER C FLOWS • DECREASED STREAM MOUTH B EXCHANGE • BATHYMETRY CHANGES • URBAN STORM WATER FLOWS A • INVASIVE SPECIES

Of the principle problems confronting the estuary: • Pollutant flows from urban storm drains • Poor salt wedge penetration into pond • Poor exchange at stream mouth • Invasive Species (mangrove) • Lack of sufficient water flow Improving water flow was deemed likely to provide the greatest benefit with the least effort.

526,300m 2 135 acres Estuary Area – Volume – 750,000m 3 = 26.5 Mft 3 Volume of 8-inch (0.2m) tidal inflow – 106,000m 3 = 3.7 Mft 3 2.0 1.0 1.0 22.5 NOTE: All volumes given in millions of cubic feet

CLASSICAL SALT WEDGE AND EXCHANGE CURRENTS IN AN ESTUARY

Lanikai Bridge (Kbay Tide) Water Height Ft. MLLW 3 6 M cu ft DEPTH 2 Feet MLLW 1 0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Lanikai Bridge Water Turbidity 50 40 Turbidity NTU 30 20 10 0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 TURBIDITY Lanikai Bridge Water Salinity 50 40 Salinity PPT 30 20 10 0 SALINITY 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 1.4 1.2 Kaelepulu Rain per Hr 1 Rain Inch/Hr. 0.8 0.6 RAIN 0.4 0.2 0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Days, Beginning Dec. 18, 2010 D A B C

PHYSICAL WATER QUALITY TRANSECTS OF ESTUARY CONDUCTED BEFORE AND AFTER EACH STREAM MOUTH OPENING EVENT T, Salinity, pH, NTU, Chl-a, PC, DO% @ 15 cm 30 cm 60 cm 120 cm 180 cm

Beach Channel Pond

Shallows Beach Channel Pond

9/15/13 Salinity Kawainui Pre Opening 9/15/13 Salinity Kaelepulu

9/26/13 Salinity Kawainui Post opening 9/26/13 Salinity Kaelepulu

11/16/13 Salinity Kawainui – Pre opening 11/16/13 Salinity Kaelepulu

9/15/13 Oxygen Kaelepulu 9/15/13 Oxygen Kawainui Pre Opening

9/26/13 Oxygen Kawainui Post opening 9/26/13 Oxygen Kaelepulu

11/16/13 Dissolved Oxygen Kawainui – Pre opening 11/16/13 Dissolved Oxygen Kaelepulu

Salinity for 10 Sampling Events Other Parameters Tracked: • Temperature • Dissolved Oxygen • pH • Turbidity • PC • CHL-A • Volume Exchange

% Exchange = (S F -S I ) / (35-S I )

% Exchange = (S F -S I ) / (35-S I )

PROPOSAL TO TEST FLOW RESTORATION BY INSTALING TEMPORARY SIPHON OVER LEVEE ~ 6 L/s

2 ft 3 /sec  5.2 M ft 3 /Month  ~1 ft Rise (- Evaporation)

2 ft 3 /sec  5.2 M ft 3 /Month  0.9 ft Rise (- Evaporation)

Construction of Four 6-inch PVC Siphons over Levee

TEST TRIAL IS HYPOTHESIZED TO DEMONSTRATE THAT THE FLOW RESTORATION WILL • Increase monthly water exchange in the Kawainui Stream Channel thereby improving water quality • Increase volume and period of exchange with the ocean by enhanced opening head and flow dynamics

WATER SURFACE ELEVATION OF KAWAINUI MARSH SOURCE WATER Control Portion of Experiment Experiment Duration Marsh Water Surface Rate of Fall = 0.20 inch/da Marsh Water Surface Rate of Fall = 0.2 to 0.34 inch/da

WATER SURFACE ELEVATION OF KAWAINUI STREAM SHOWING STREAM MOUTH OPENING PERIODS Kaelepulu Water Surface Elevation, 2015 Feet MLLW 3 Water Surface Elevation, Feet MLLW 2.5 Syphons ON 2 1.5 1 0.5 J F M A M J J A S O Months, 2015

WATER SURFACE ELEVATION OF KAWAINUI STREAM WAS ABOVE FLOOD THREAT LEVEL ON THREE OCCASIONS Kaelepulu Water Surface Elevation, 2015 Feet MLLW 3 Stream Mouth Openings Water Surface Elevation, Feet MLLW Periodsof Increased Flood Threat 2.5 due to High Water Surface Elevation Syphons ON 2 1.5 1 0.5 J F M A M J J A S O Months, 2015

WATER SURFACE ELEVATION OF KAWAINUI MARSH SOURCE WATER

WATER SURFACE ELEVATION OF KAWAINUI MARSH SOURCE WATER ~ 3M cu ft Water Transferred Each Month

3M cu ft

FRESH WATER INFLOW SPREADS RAPIDLY ALONG THE SURFACE OF KAWAINUI STREAM AND DOWNSTREAM TOWARDS THE BEACH. VERTICAL MIXING OCCURS MORE SLOWLY MAINTAINING STRATIFICATION THROUGHOUT THE MONTH.

FRESH WATER INFLOW APPEARS TO FLOW RAPIDLY ALONG THE SURFACE AND EITHER EVAPORATE OR SLOWLY MIX WITH LOWER WATER LAYERS AND MAINTAINING STRATIFICATION

SYPHON INFLOW RESULTED IN GREATER STRATIFICATION OF THE ENTIRE STREAM

DISSOLVED OXYGEN REMAINED WELL BELOW 20% SATURATION IN THE KAWAINUI STREAM THROUGHOUT THE PERIOD OF INFLOW. D.O. WAS NOT DISTINGUISHABLE FROM CONTROL (NO SYPHON FLOW) CONDITIONS ABUNDANT MANGROVE ALONG THIS STREAM REACH ARE LIKELY RESPONSIBLE FOR THE LOW D.O.

MANGROVE STANDS LINE THE CHANNEL WHERE DISSOLVED OXYGEN LEVELS ARE LOW ABUNDANT MANGROVE ALONG THIS STREAM REACH ARE LIKELY RESPONSIBLE FOR THE LOW D.O.

3 1

Kawainui Kawainui Marsh Dr Drain pipe through levee ain from Kawainui Marsh to Level Control Drain pipe Kawainui Stream through levee from Kawainui Stream to Oneawa Canal Level Control High Tide 2.0 ft Overflow Weir 2.0 ft Low Tide 0.0 ft 12” Pipe through Levee Kawainui Stream Oneawa Canal

QUESTIONS ?

TRACE- CONTAMINANT STUDY BY USGS 41 SAMPLE SITES WITHIN ESTUARY 71 POLLUTANT TRACERS CAFFEINE FOUND AT 3 SITES

TRACE- CONTAMINANT STUDY BY USGS 41 SAMPLE SITES WITHIN ESTUARY 71 POLLUTANT TRACERS CAFFEINE FOUND AT 3 SITES

TRACE- CONTAMINANT STUDY BY USGS 41 SAMPLE SITES WITHIN ESTUARY 71 POLLUTANT TRACERS CAFFEINE FOUND AT 3 SITES