Control of nitrogen and phosphorus transport by reservoirs in agricultural landscapes
- 698 Downloads
Reservoirs often receive excess nitrogen (N) and phosphorus (P) lost from agricultural land, and may subsequently influence N and P delivery to inland and coastal waters through internal processes such as nutrient burial, denitrification, and nutrient turnover. Currently there is a need to better understand how reservoirs affect nutrient transport in agricultural landscapes, where few prior studies have provided joint views on the variation in net retention/loss among reservoirs, the role of reservoirs apart from natural lakes, and differences in effects on N versus P, especially over time frames >1 year. To address these needs, we compiled water quality data from many rivers in intermediate-to-large drainages of the Midwestern US, including tributaries to the Upper Mississippi River, Great Lakes, and Ohio River Basins, where cropland often covers >50 % of the contributing area. Incorporating 18 years of data (1990–2007), effects of reservoirs on river nutrient transport were examined using comparisons between reservoir outflow sites and unimpeded river sites (N = 869, including 100 reservoir outflow sites) supported by mass balance analysis of individual reservoirs (n = 17). Reservoir outflows sites commonly had 20 % lower annual yields (mass per catchment area per year) of total N and total P (TP) than unimpeded rivers after accounting for cropland coverage. Reservoir outflow sites also had lower interannual variability in TP yields. The mass balance approach confirmed net N losses in reservoirs, suggesting denitrification of agricultural N, or N burial in sediments. Net retention of P ranged more widely, and multiple systems showed net P export, providing new evidence that legacy P within reservoir systems may mobilize over the long-term. Our results indicate that reservoirs broadly influence the downstream transport of N and P through agricultural river networks, including networks where natural lakes and wetlands are relatively scarce. This calls for a more complete understanding of agricultural reservoirs as open, connected features of river networks where biogeochemical processes are often influential to downstream water quality, but potentially sensitive to changes associated with sedimentation, eutrophication, infrastructure aging, and reservoir management.
KeywordsReservoirs and dams Agriculture Nitrogen and phosphorus River Lake Water quality
We gratefully acknowledge financial support from the Notre Dame Environmental Change Initiative (ND-ECI). We also thank the numerous personnel of the U.S. Geological Survey and partner State agencies who have helped collect and compile discharge and water quality records over the years.
Conflict of interest
The authors declare that they have no conflict of interest. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government.
- Brett MT, Benjamin MM (2008) A review and reassessment of lake phosphorus retention and the nutrient loading concept. Freshw Biol 53:194–211Google Scholar
- Bruesewitz DA, Tank JL, Hamilton SK (2012) Incorporating spatial variation of nitrification and denitrification rates into whole-lake nitrogen dynamics. J Geophys Res Biogeosci 117:1–12Google Scholar
- Dendy FE (1968) Sedimentation in the nation’s reservoirs. J Soil Water Conserv 23:135–137Google Scholar
- Dodds WK, Lopez AJ, Bowden WB, Gregory S, Grimm NB, Hamilton SK, Hershey AE, Martí E, McDowell WH, Meyer JL, Morrall D, Mulholland PJ, Peterson BJ, Tank JL, Valett HM, Webster JR, Wollheim W (2002) N uptake as a function of concentration in streams. J N Am Benthol Soc 21:206–220CrossRefGoogle Scholar
- Graf WL, Wohl E, Sinha T, Sabo JL (2010) Sedimentation and sustainability of western American reservoirs. Water Resour Res 46:W12535Google Scholar
- Hedin LO, von Fischer JC, Ostrom NE, Kennedy BP, Brown MG, Robertson GP (1998) Thermodynamic constraints on nitrogen transformations and other biogeochemical processes at soil–stream interfaces. Ecology 79:684–703Google Scholar
- Homer C, Dewitz J, Fry J, Coan M, Hossain N, Larson C, Herold N, McKerrow A, VanDriel JN, Wickham J (2007) Completion of the 2001 national land cover database for the conterminous United States. Photogramm Eng Remote Sens 73:337–341Google Scholar
- Howarth RW, Billen G, Swaney D, Townsend A, Jaworski N, Lajtha K, Downing JA, Elmgren R, Caraco N, Jordan T, Berendse F, Freney J, Kudeyarov V, Murdoch P, Zhu ZL (1996) Regional nitrogen budgets and riverine N&P fluxes for the drainages to the North Atlantic Ocean: natural and human influences. Biogeochemistry 35:75–139CrossRefGoogle Scholar
- Kadlec RH, Wallace SD (2009) Treatment wetlands. CRC Press, Boca RatonGoogle Scholar
- Mulholland PJ, Helton AM, Poole GC, Hall RO, Hamilton SK, Peterson BJ, Tank JL, Ashkenas LR, Cooper LW, Dahm CN, Dodds WK, Findlay SEG, Gregory SV, Grimm NB, Johnson SL, McDowell WH, Meyer JL, Valett HM, Webster JR, Arango CP, Beaulieu JJ, Bernot MJ, Burgin AJ, Crenshaw CL, Johnson LT, Niederlehner BR, O’Brien JM, Potter JD, Sheibley RW, Sobota DJ, Thomas SM (2008) Stream denitrification across biomes and its response to anthropogenic nitrate loading. Nature 452:202–246CrossRefGoogle Scholar
- Schwarz GE, Hoos AB, Alexander RB, Smith RA (2006) The SPARROW surface water-quality model: theory, application, and user documentation. U.S. Geological Survey Techniques and Methods Report, 6-B3Google Scholar
- Stenback GA, Crumpton WG, Schilling KE, Helmers MJ (2011) Rating curve estimation of nutrient loads in Iowa rivers. J Hydrol 396:158–169Google Scholar
- Thornton KW, Kimmel BL, Payne FE (1990) Reservoir limnology: ecological perspectives. Wiley, New YorkGoogle Scholar
- USACE (2013) In: Engineers USACo (ed) National inventory of dams. U.S. Army Corps of EngineersGoogle Scholar
- Wetzel RG (2001) Limnology: lake and river ecosystems. Academic, San DiegoGoogle Scholar
- Wurtsbaugh WA, Baker MA, Gross HP, Brown PD (2005) Lakes as nutrient “sources” for watersheds: a landscape analysis of the temporal flux of nitrogen through subalpine lakes and streams. Verh Int Ver Limnol 29:645–649Google Scholar