Nutrient Fluxes in Rivers of the Mobile – Alabama River System Using WRTDS Alex Maestre Amy Ward Derek Williamson

Agenda ● Nutrient contributions by the MARS watershed into the Gulf of Mexico ● MARS watershed ● Discharge and Water Quality Data ● Flux Estimates Calculations in Kg/Km²/y ● WRTDS: Weighted Regression on Time, Discharge, and Season

Nutrient Fluxes into Coastal Areas ● During the period 1976 – 2000, global ocean oxygen concentrations were declining faster in the coastal ocean than in the open ocean for depths between 0 – 300 meters (Gilbert et al, 2010). ● Nutrient is the main driver behind the expansion of coastal hypoxic conditions (Rabalais et al, 2010).

Source: Dynamics and distribution of natural and human-caused hypoxia, Rabalais et al 2010

Nutrient Fluxes and MARS ● The Mobile – Alabama River System (MARS) is the second largest basin that discharges into the Gulf of Mexico (TMDL, Nutrient Criteria). ● Previous studies conducted at the University of Alabama indicated that MARS is Nitrogen retentive. ● What are the nutrient fluxes by each of the major basins of the MARS? ● We are exploring the use and improvement of WRTDS for the estimation of nutrient fluxes

Source: Mobile – Alabama River Basin

Coosa – Tallapoosa - Cahaba Coosa River (Jordan Dam) Tallapoosa River (Near Montgomery) Cahaba River (Marion Junction)

Alabama River (at Claiborne)

Black Warrior River Black Warrior (Near Eutaw) Locust Fork Mulberry Fork

Tombigbee and Sipsey River Sipsey River (Near El Rod) Upper Tombigbee (Near Pickensville) Lower Tombigbee (at Coffeeville )

Sources of Information Flow data: Downloaded from the National Water Information System (NWIS) Current rating curves were not found on-line Stations located in dams with locks Some stations out of service Water quality data: Downloaded using storage and retrieval data warehouse (STORET) and NWIS. Gaps in water quality time series. Changes in analytical methods, detection limits, etc.

Water Quality Samples Used in the Analysis River Period USGSADEMn Alabama CLAM Lower Tombigbee COFC Tallapoosa TARE Coosa COSE-177 Upper Tombigbee ALIP Black Warrior WARG Cahaba DANW Sipsey SPYG AmmoniaTKNNitrite + Nitrate PhosphateOrthophosphate

Estimation of Concentrations and Fluxes Using WRTDS ● Estimation by weighted regression on time, discharge, and season ● R ● Uses a weight function

WRTDS - Requirements ● At least 200 samples ● Samples collected for 20 years ● Complete record of daily discharge ● Decide how to use censored observations ● Samples should be representative of the cross section ● Not appropriate for small streams

WRTDS - Example Concentration (Discrete Samples) Discharge (Continuous Series)

WRTDS

Unusual Extreme Event Upper Tombigbee Limitations

Flux Estimates

Conclusions ● The weighted regression method appears to generate a more credible concentration estimates than the traditional linear regression methods because it is adjusting the parameters of the model with time ● The existing datasets of the Alabama, Tombigbee, Black Warrior, and Sipsey rivers appear to be appropriate for the use of WRTDS ● More samples are needed in the Cahaba, Coosa, and Tallapoosa rivers to take full advantage of the capabilities of the model. However, preliminary analysis show promising results even with small datasets

Conclusions ● Sampling efforts in major rivers of the MARS need to be distributed throughout the whole year and involving the collection of samples during extreme events ● The measurement and/or estimation of daily discharges are critical for WRTDS. There is a need to generate and make available rating curves to complete gaps and missing records of active streamflow-gaging stations

Acknowledgements All the agencies that collect, analyze, and distribute information about the quantity and quality of the water in rivers and streams of the U.S. Acknowledgement of support from NSF EPSCoR EPS , in collaboration with the Northern Gulf Coastal Hazards Collaboratory.

Questions?