The State of the Severn RiverJune, 2015

Andrew C. Muller, PhD.Associate Professor

Oceanography DepartmentUnited States Naval Academy

Introduction

• In order to understand the current state of the Severn River and where it may be headed in the near future, we must understand the physical processes that govern the river and past conditions

Tides in the Chesapeake Bay• Chesapeake Bay is a partially

mixed estuary. Density stratification will vary with Spring-Neap cycle and river discharge.

• The tide in the Bay is mixed, mainly semidiurnal, and it loses energy through turbulent mixing in the bottom boundary layer as it propagates northward

• Range of tide is approx. 3 feet at mouth of Bay,

• 1 foot at AnnapolisAvg Depth: 21 ftMax Depth: 174 ft

Salinity and Tidal Currents

Chesapeake Bay Hypoxia

Spatial Variability vs. Temporal Variability

• In any monitoring program or research endeavor to understand the bio-physical processes that dominate ecological systems we face the spatio-temporal dilemma, we can be

• Spatial intensive – lower temporal resolution– or

• Temporal intensive – lower spatial resolution• May loose vertical dimension

• But, water quality parameters exist in the spatiotemporal domain

Resolving the Spatio-Temporal dilemma

• HydroLab DS 5• REMUS 100

• NOAA Annapolis Buoy

Monitoring Locations

Severn River D.O. 2010

Severn River 2011

REMUS 100Remote Autonomous Environmental Unit sPhysical Specs:Manufacturer: HydroidBody Type: Torpedo Size (LxWxH): 1.60m x 0.19m x 0.19m Body Size (LxWxH): 1.60m x 0.19m x 0.19m Hull Material: Aluminum Weight: 37.00kg Maximum Depth: 100.00 m Self-Righting: Yes Obstacle Avoidance: No Endurance (nominal load): 22 hours -

Mission: Round Bay, Severn River hypoxia

Mission: Round Bay, Severn River hypoxia (Aug 13, 2010)

Mission: Round Bay, Severn River hypoxia (Aug. 13, 2010)

Mission: Severn RiverJune,15 2011- Round Bay to College Creek

RBNUSNA

WT 7.1

REMUS (6-8 AM) SRK weekly monitoring (8 AM – 2 PM)

Hypoxic Squeezing

𝐻𝑆𝐼=Δ𝐷𝑜

depth avg . Do

Hypoxic Squeeze Index

Percent below 2 mg/l

0 20 40 60 80

HV

I

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

Rsqrd=.72

Station

HS

I

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

Severn River Hypoxic Squeezing

• CS

SRO ASQ SR7CHS SR5WMS SLTBRW

Route 50 bridgeBottom Do, mg/l

WT 7.1

Feb Mar Apr MayJun Jly AugSep Oct NovDec0

2

4

6

8

10

12

14

Mean2014

Increasing the importance and relevance of buoy data and AUVs, building the network

• Hindcasting water quality parameters

What if you could extract buoy information and cat it throughout the rest of a small tributary.

Theoretical Approach: Slice up the tributary into 1 meter sections.Consider well mixed within a section; stratification occurs between sections.As a result conservative properties may be modeled as Gaussian distribution.

24.5

25

25.5

26

26.5

27

27.5

28

28.5

29

29.5

Severn River Temp Gaussian

.3 Meters1 Meter2 Meter3 Meter4 Meter5 Meter6 Meter7 Meter8 Meter9 Meter10 Meter11 Meter12 Meter13 Meter

SR0 SR1 SR2 SR3 RBS SR5 RBN SR6 SR7Station

Tem

pera

ture

(C )

9

9.5

10

10.5

11

11.5

12

12.5

13

13.5

Severn River Salinity Gaussian

1 Meter2 Meter3 Meter4 Meter5 Meter6 Meter7 Meter8 Meter9 Meter10 Meter11 Meter12 Meter13 Meter

SR0 SR1 SR2 SR3 RBS SR5 RBN SR6 SR7Station

Salin

ity

9

9.5

10

10.5

11

11.5

12

12.5

13

13.5

Severn River Salinity Gaussian

1 Meter2 Meter3 Meter4 Meter5 Meter6 Meter7 Meter8 Meter9 Meter10 Meter11 Meter12 Meter13 Meter

SR0 SR1 SR2 SR3 RBS SR5 RBN SR6 SR7Station

Salin

ity

25

25.5

26

26.5

27

27.5

28

28.5

29

29.5

30

1 August 2012Predicted vs. Actual Temperature

Surface Predicted2 Meter Predicted4 Meter Predicted6 Meter PredictedSurface Actual2 Meter Actual4 Meter Actual6 Meter Actual

SR0 SR1 SR2 SR3 RBS SR5 RBN SR6 SR7 Station

Temperature (C)

8.5

9.5

10.5

11.5

12.5

13.5

1 August 2012Predicted vs. Actual Salinity

Surface Predicted2 Meter Predicted4 Meter Predicted6 Meter PredictedSurface Actual2 Meter Actual4 Meter Actual6 Meter Actual

SR0 SR1 SR2 SR3 RBS SR5 RBN SR6 SR7 Station

Salinity

2012 Severn River Forecasts

Tem

p

40

50

60

70

80

90

The Future

USNA-NECOS ConceptSecure, Adhoc, Semi-Mobile, Environmental Monitoring Network

REMUS-100

Autonomous Underwater

Vehicles (AUVs)*

Drifting Buoys*

Moored Buoys*

Buoy Array

Fixed Meteorological

Stations*

Benthic Chambers

Coastal Kayaks w/ Handheld In Situ Probes*

Central Hub (Hendrix)

Santee Basin Severn River

* Existing USNA asset

Naval Estuarine and Coastal Ocean Observation System

Conclusion• It is important to understand the complete system when attempting to

make important policy decisions regarding restoration.• Physics dominates and controls the system, no coriolis and no sloshing of

water in and out by tides,• Hypoxia and anoxia are locally controlled (it’s the creeks!!!)• Susquehanna River is NOT the main polluter to Severn and South Rivers.• Severn is not getting worse, but its not getting better either.• Need more studies on restoration effectiveness, including BAAs, long-term

studies and downstream measurements

• Use of technology like REMUS, CONMONS, and a more complete observing system will allow for better modeling, and therefore better policy decisions. Initial hindcasting results promising