Inflow, water quality, and flushing of Lake Worth Lagoon Christopher Buzzelli, Cassondra Thomas, Peter Doering* Coastal Ecosystems Section South Florida Water Management District Photo by C. Buzzelli
OBJECTIVES FOR PRESENTATION Lake Worth Lagoon watershed & estuary attributes Summary of inflow & water quality patterns 2007-2015 Effects of estuary flushing on water quality
LAKE WORTH LAGOON ATTRIBUTES Atlantic Ocean Lake Okeechobee West Palm Beach Palm Beach Inlet Lake Worth Lagoon LWL Watershed North (C-17) Central (C-51) South (C-16) Boynton Beach Inlet 3 Watershed = 305,710 acres Estuary = 7363 acres Ratio = 41.5:1
LAKE WORTH LAGOON ATTRIBUTES NORTH Distance = 8.6 miles Depth = 3.4+2.6 m Area = 8.2 km 2 (2018 acres) Volume = 34.5 x 10 6 m 3 S-44 (C-17) WQ Stations 1,2,4,5,6 CENTRAL Distance = 7.1 miles Depth = 2.6+1.6 m Area = 8.8 km 2 (2168 acres) Volume = 17.7 x 10 6 m 3 S-155 (C-51) WQ Stations 7,8,10,11 SOUTH Distance = 6.0 miles Depth = 2.3 + 1.1 m Area = 12.9 km 2 (3184 acres) Volume = 17.9 x 10 6 m 3 S-41 (C-16) WQ Stations 12,13,15,16,18 4
LWL INFLOW & WATER QUALITY C-17 Cooperative agreement PBC-DERM and SFWMD 13 stations monitored monthly 2007-2015 Salinity (S), chlorophyll a (CHL), total N & P (TN & TP), turbidity, (NTU), total suspended solids (TSS) C-51 Analytical objectives (2016) Spatial patterns Temporal trends Relationships between inflow and variables C-16 5
LWL INFLOW & WATER QUALITY (freshwater inflow 2007-2015) S-44 (C17) S-155 (C51) S-41 (C16) cfs Wet Seasons 2013-2015 Reduced 2010-2012 dry wet dry wet dry wet dry wet dry wet dry wet dry wet dry wet dry wet dry 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 6
C-17 C-51 SOUTH FLORIDA WATER MANAGEMENT DISTRICT LWL INFLOW & WATER QUALITY (trends from 2007-2015 by station) Segment Stations Salinity CHL TN TP NTU TSS 1 (-) 2 North 4 (-) 5 (-) 6 (-) 7 (+) 8 (+) Central 10 (+) (+) (+) 11 (+) 13 (+) (-) 15 (-) South 16 (-) 17 (-) 18 (-) TSS decreased (-) in North and South segment stations CHL increased (+) in stations 7-13 CHL, TP, and turbidity (NTU) increased (+) at station 10 C-16 7
C-17 C-51 SOUTH FLORIDA WATER MANAGEMENT DISTRICT CHL (µg L -1 ) TN (mg L -1 ) TP (mg L -1 ) Turbidity LWL INFLOW & WATER QUALITY (relationships with water quality) 15 12 9 6 3 0 1.0 0.8 0.6 0.4 0.2 0.0 0.08 0.06 0.04 0.02 0.00 10 8 6 4 2 0 Central Segment 0 200 400 600 800 1000 1200 0 200 400 600 800 1000 1200 0 200 400 600 800 1000 1200 0 200 400 600 800 1000 1200 Inflow from C-51 (cfs) wet dry C-16 C-51 inflow correlated to average seasonal CHL, TN, & TP C-51 inflow not correlated to turbidity in either season 8
S O U T H F L O R I D A W A T E R M A N A G E M E N T D I S T R I C T C-17 CHL (µg L-1) LWL INFLOW & WATER QUALITY 07 C-51 C-16 Station 10 35 30 25 20 15 10 5 0 15000 12000 9000 6000 3000 0 08 09 10 11 12 13 14 15 Avg + SD N [CHL]ref* n > [CHL]ref 2014-2015 5.5+4.1 µg L-1 143 6.1 µg L-1 32 of 143 (22%) 14 of 32 elevated samples [CHL]US1 [CHL]CES06 [CHL]FL** 8.8+8.0 µg L-1 9.1+11.5 µg L-1 11.0 µg L-1 *The CHL reference concentration estimated as the value of the 75% percentile **Florida DEP water quality reference for most estuaries 16 9
ESTUARY FLUSHING If physical flushing is greater than the rate of phytoplankton growth: If physical flushing is less than the rate of phytoplankton growth: 10
FLUSHING OF LAKE WORTH LAGOON Q FW Coastal Ocean Q C17 Q C51 Q C16 V e estuary volume (m 3 ) S e estuary salinity S o = salinity of coastal ocean τ flush CHL (mg m -3 ) ( days) 25 20 15 10 5 0 Ve = Q FW Tflush (d) ( S LWL 2007-2015 t flush = 5.5 + 3.5 days o S S 0 2 4 6 8 10 12 14 o e ) 11
FLUSHING OF LAKE WORTH LAGOON LWL = faster flushing Potential for water quality problems reduced with faster flushing Reduces potential for phytoplankton blooms Moderate eutrophication could affect benthic habitats (e.g. seagrass) 12
C-17 SOUTH FLORIDA WATER MANAGEMENT DISTRICT LWL INFLOW & WATER QUALITY (2007-2015) Decrease in TSS in North & South; Increase in CHL in Central Q FW NOT correlated to turbidity and TSS Q FW correlated to CHL, TN, & TP in Central segment [CHL] increase, but less than estimated reference 78% of time C-51 Flushing time (τ flush ) of LWL Average of 5.5 days to flush entire LWL Flushing time ~1-2 days with increased inflow (Q FW ) τ SLE = 2-20 days; τ CRE = 5-60 days Severe water quality problems less likely due to fast flushing, but could affect benthic habitats such as seagrasses C-16 13
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