Estimation of Groundwater and Nutrient Fluxes to the Neuse River Estuary, North Carolina

Abstract

A study was conducted between April 2004 and September 2005 to estimate groundwater and nutrient discharge to the Neuse River estuary in North Carolina. The largest groundwater fluxes were observed to occur generally within 20 m of the shoreline. Groundwater flux estimates based on seepage meter measurements ranged from 2.86×10 8 to 4.33×10 8 m 3 annually and are comparable to estimates made using radon, a simple water-budget method, and estimates derived by using Darcy's Law and previously published general aquifer characteristics of the area. The lower groundwater flux estimate (equal to about 9 m 3 s −1 ), which assumed the narrowest groundwater discharge zone (20 m) of three zone widths selected for an area west of New Bern, North Carolina, most closely agrees with groundwater flux estimates made using radon (3-9 m 3 s −1 ) and Darcy's Law (about 9 m 3 s −1 ). A groundwater flux of 9 m 3 s −1 is about 40% of the surface-water flow to the Neuse River estuary between Streets Ferry and the mouth of the estuary and about 7% of the surface-water inflow from areas upstream. Estimates of annual nitrogen (333 tonnes) and phosphorus (66 tonnes) fluxes from groundwater to the estuary, based on this analysis, are less than 6% of the nitrogen and phosphorus inputs derived from all sources (excluding oceanic inputs), and approximately 8% of the nitrogen and 17% of the phosphorus annual inputs from surface-water inflow to the Neuse River estuary assuming a mean annual precipitation of 1.27 m. We provide quantitative evidence, derived from three methods, that the contribution of water and nutrients from groundwater discharge to the Neuse River estuary is relatively minor, particularly compared with upstream sources of water and nutrients and with bottom sediment sources of nutrients. Locally high groundwater discharges do occur, however, and could help explain the occurrence of localized phytoplankton blooms, submerged aquatic vegetation, or fish kills.

Simulating algal dynamics within a Bayesian framework to evaluate controls on estuary productivity

“…Note that 18.75 ºC is the mean NRE water temperature, and θd and θp are the associated temperature correction factors. While other types of nutrient fluxes (e.g., microbial N2 fixation) may also occur in the estuary, they are not expected to be large enough to substantially influence model calibration and prediction (Affourtit et al, 2001;Spruill and Bratton, 2008;Whitall et al, 2003).…”

Application of SPARROW Modeling to Understanding Contaminant Fate and Transport from Uplands to Streams

“…Remaining surplus nitrogen may be volatilized to the atmosphere as ammonia (Van Breemen et al, 2002), stored in soils, or carried to surface waters in overland runoff, but is commonly converted to nitrate and transported with infiltration to groundwater (Vitousek et al, 1997;Nolan and Stoner, 2000;B€ ohlke, 2002). Nitrate is persistent and effectively transported through aquifers in which dissolved oxygen is sufficient to preclude denitrification (B€ ohlke and Denver, 1995;Reichard and Brown, 2009;Tesoriero et al, 2009;Denver et al, 2010Denver et al, , 2014Ator and Denver, 2012), and groundwater is an important vector for nitrogen transport from uplands to surface waters in many areas (Staver and Brinsfield, 1996;B€ ohlke, 2002;Phillips and Lindsey, 2003;Nolan and Hitt, 2006;Spruill and Bratton, 2008;Hirsch et al, 2010). Ator and Denver (2012) estimated that 70% of the nitrogen flux to Chesapeake Bay tributaries on the Delmarva Peninsula moves through groundwater as nitrate, and best-management practices designed to limit nitrogen losses to surface waters in the area are increasingly focusing on limiting nitrate in groundwater (Staver and Brinsfield, 1998;Hively et al, 2009;Ator and Denver, 2015).…”

Spatial relationship of groundwater–phosphorus interaction in the Kissimmee river basin, South Florida

“…Over the karst aquifers of SF, the effectiveness of wetlands for nutrient removal would be constrained by high transmissivity of such aquifers reaching values of up to 28 000 m 2 /day (Dausman and Langevin, ). At that high transmissivity, nutrients are drained from aquifers to waterbodies at a faster rate through percolation and seepage (Balla et al ., ; Spruill and Bratton, ). Although the dissolution of calcium carbonate can precipitate nutrients such as P, the precipitated nutrients could also be transported with water because of the porous nature of the aquifer layer (Zhou and Li, ; Janardhanan and Daroub, ).…”