Department of Physical and Environmental Science, Harte Research Institute for Gulf of Mexico Studies, Texas A&M University-Corpus Christi, TX 78412.
Ecosystem Response to Freshwater Inflow: Determining a Link Between Freshwater Pumping Regimes and Ecological Benefit Elizabeth A. Del Rosario*, Paul A. Montagna Department of Physical and Environmental Science, Harte Research Institute for Gulf of Mexico Studies, Texas A&M University-Corpus Christi, TX 78412
INTRODUCTION Inflow into the Nueces Estuary has been reduced by impoundments in the Nueces River Basin:
METHODS
WATER RESOURCE ALLOCATIONS
• Wesley E. Seale Dam (Lake Corpus Christi) • Built on the Nueces River in 1958 • Reduced inflow by 99% • Choke Canyon Reservoir • Built on the Frio River in 1982 • Reduced remaining inflow by an additional 55%
Choke Canyon Dam. Image (Water.weather.gov)
Data was obtained from the listed sources and analyzed using SAS 9.3 software and Microsoft Excel 2010.
Station C
Salinity, Depth, Temperature
Interval
Date Range
Agency
1. Analyses of Hydrology Data
Website
Continuous Sept. 2009 - Montagna Stations Discrete Dec. 2015 HRI TAMUCC (psu, m, °C)
Not available online
Salinity gradient: * Width of bar indicates duration of pumping event
Rincon Bayou Daily total Sept. 2009 Pumped Inflow Pipeline (Acre-ft/day) Dec. 2015 USGS Rincon Natural Inflow Channel Gage and Discharge NUDE2 SALT03
Salinity
NUDEWX
Mean daily rate (f3 /sec)
Nueces River Authority (NRA)
http://www.nueces-ra.org/CP/CITY/rincon/
United States Sept. 2009 Geological Survey Dec. 2015 (USGS)
Every 15 May 2009 minitues (psu) Dec. 2015
Computed Daily total at Jan. 2014 Cumulative Rain midnight (cm) Dec. 2015 Fall (ccrf)
http://nwis.waterdata.usgs.gov
Conrad Blucher Institute for Surveying and Science (CBI)
http://www.cbi.tamucc.edu/dnr/station
Depiction of links between estuaries and catchments (from Yoskowitz and Montagna 2009)
Benthic macrofauna biomass, abundance and community structure was measured: • Sediment cores covering an area of 35.4 cm2 • Animals extracted using a 0.5mm mesh sieve • Animals enumerated and dried at 50 ̊C for 24 hours then weighed for biomass • Mollusk shells were removed by an acidic vaporization technique
DATA ANALYSIS
Texas Law Requires Environmental Flows for Estuaries: • 1990 Agreed Order: The City of Corpus Christi must provide 185 million cubic meters of water per year to the Nueces Estuary by a combination of releases (stored water that is let out) and spills (overflows). • 2001 Agree Order: The City of Corpus Christi must “pass-through” freshwater to the Nueces Estuary based on seasonal requirements of estuarine organisms and inflows into the Reservoir System, up to a monthly target amount, if sufficient flows enter the reservoir. To meet the requirement the City of Corpus Christi agreed to: • Construct a pipeline to convey up to 3.7 x 106 m3 (3,000 acre-feet) directly to the Nueces Delta at Rincon Bayou per month. • Implement an ongoing monitoring and assessment program to facilitate adaptive management for freshwater flow into the Nueces Estuary.
Study Site:
Why Rincon Bayou? The primary source of inflow is from pumping.
http://sanpatwater.com/
www.cbbep.org
Thus, salinity and depth regimes are directly controlled through management release actions. www.mysoutex.com
OBJECTIVES www.cbbep.org www.cbbep.org
Hydrological Parameter
Percent occurrence:
Prolonged periods of increased salinities Reverse estuary conditions (higher salinities upstream) Disturbed hydrology Loss of species biodiversity and critical habitat
www.nueces-ra.org
Station Name
Benthic Sampling
Decreased freshwater inflow into the Nueces Estuary has resulted in: • • • •
Data Sources
RESULTS
1. Analyze hydrology data to see what has happened: • Salinity in upper delta vs. Nueces Bay • Salinity and depth at Station C • Pumped inflow (Rincon Bayou Pipeline (RBP)) • Natural inflow (USGS Rincon Gage) 2. Analyze benthic macrofauna data (Stations C, F, and G) • Correlate to hydrology data using indicator species 3. Create prediction graphs: • Salinity from inflow; depth from inflow
REFERENCES Montagna, P.A., L. Adams, C. Chaloupka, E. DelRosario, A. Gordon, M. Herdener, R.D. Kalke, T.A. Palmer, and E.L. Turner. 2015. Effects of Pumped Flows into Rincon Bayou on Water Quality and Benthic Macrofauna. Final Report to the Coastal Bend Bays & Estuaries Program for Project # 1417. Harte Research Institute, Texas A&M University-Corpus Christi, Corpus Christi, Texas, 46 pp. Full report available online: http://www.cbbep.org/manager/wp-content/uploads/CBBEP-1417-Final-Report.pdf Turner, E.L., P.A. Montagna. Forthcoming 2016. Quantifying responses of ecological indicators to environmental variables using a maximum bin method. Ecological Indicators.
ACKNOWLEDGMENTS
Pumped inflow, natural inflow, salinity at Station C:
Salinity gradient: • Downstream salinity - Upstream salinity • SALT03 (Nueces Bay) - NUDE2 (Upper Delta) • Estuary condition: • Negative = salinity at NUDE2 > SALT03 • Positive = salinity at NUDE2 < SALT03
2. Analyses of Benthic Macrofauna Data
Percent occurrence:
Max Bin Method for benthic bioindicators:
• How often the event has occurred in a time period. • Derived form histogram frequencies and converted to %.
Percent exceedance: P = 100 ∗ [ M / (n + 1) ] • • •
P - probability that a given flow will be equaled or exceeded (% of time) M - ranked position of the flow amount n - number of flow events
http://nas.er.usgs.gov/queries/FactSheet.aspx?speciesID=1188
Streblospio benedicti
Chironomidae larvae
Max Bin Method for benthic bioindicators (Turner and Montagna 2016): • Determines optimal conditions for biological response (biomass/abundance). • Montagna Stations C, F, and G sampled bi-weekly with a YSI 6600 sonde. • Numerically dominant species were considered bioindicators: • Streblospio benedicti (disturbance indicator species) • Chironomidae larvae (freshwater indicator species) • Macrofauna data were joined to the respective hydrographic data. • Histograms were produced for indicator species (biomass or abundance). • A curve was fitted using a log normal model: 𝑏𝑖𝑛 𝑐 𝐵𝑖𝑜𝑖𝑛𝑑𝑖𝑐𝑎𝑡𝑜𝑟 = 𝑎 × exp −0.5 × log 𝑏 • • • •
Relationship between hydrographical variables (salinity and depth) with biomass and abundance for Strebiospio benedicti (left) and Chironomidae larvae (right).
3. Prediction Graphs
2
a is the peak value for biological response b is the skewness / rate of change of the response as a function of salinity c the location of the peak response value on the salinity axis Bin is the bin size number used to group the data into segments
CONCLUSION Management Release Recommendations:
Predicted salinity and depth from pumped inflow:
I would like to thank the HRI Ecosystems and Modeling Group for their work in sample collection, sorting, species identification, etc. which made this research possible. This study was partially supported by the National Oceanic and Atmospheric Administration (NOAA) under Grant – Educational Partnership Program (EPP) Environmental Cooperative Science Center (ECSC) Grant # NA11SEC4810001. The statements contained within the manuscript/research article are not the opinions of the funding agency or the U.S. government, but reflect the author’s opinions. The study was partially supported by Coastal Bend Bays & Estuaries Program grant numbers 1417 and 1617, and Texas Water Development Board Interagency Agreement number 1548311787 to Montagna. Partial support was also provided by the Harte Research Institute for Gulf of Mexico Studies (HRI).
Percent exceedance:
𝐼𝑛𝑓𝑙𝑜𝑤 = 𝑎 ∗ •
𝑒 −𝑏∗𝑠𝑎𝑙𝑖𝑛𝑖𝑡𝑦
𝐼𝑛𝑓𝑙𝑜𝑤 =
𝑚𝑎𝑥
1 + 𝑒 −𝑏(𝑑𝑒𝑝𝑡ℎ−𝑎)
a, b, and max are the negative regression parameters
Inflows should be a trickle not a flood.
To maintain ecological benefit: • Salinity: 1 to 14 psu • Depth: 0.05 to 0.5 m Required to achieve salinity and depth target: • Continuous maximum inflows of 0.0013 m3/s
