Influence of shifting flow paths on nitrogen concentrations during monsoon floods, San Pedro River, Arizona

T. Meixner, A. K. Huth, Paul D. Brooks, M. H. Conklin, Nancy Grimm, R. C. Bales, P. A. Haas, J. R. Petti

Research output: Contribution to journalArticle

23 Citations (Scopus)

Abstract

Hydrologic flow paths control transport, and therefore are a major constraint on the cycling and availability of nutrients within stream ecosystems. This control is particularly evident in semiarid streams, where hydrologic connectivity between stream, riparian, and upland systems increases greatly during storms in the rainy season, We measured chloride concentrations in base flow, precipitation, soil water, and stream water to quantify the hydrologic connectivity and solute flux between soil water, groundwater, and the stream channel during six summer floods in 2001 (a wet year; 25 cm winter rain) and 2002 (a dry year; 5 cm winter rain) in the San Pedro River, southeastern Arizona. This hydrologic information was used to evaluate observed patterns in nitrate, dissolved organic nitrogen (DON) and dissolved organic carbon (DOC) concentrations in floods. The first floods of each year showed increased stream nitrate concentration that was approximately two orders of magnitude higher than base flow concentration. DOC consistently doubled to tripled during storm events, while DON in 2001 showed no response and showed a marked increase in 2002. A chloride mixing model indicated that soil and groundwater contributions to storm water discharge were related to antecedent conditions and to flood magnitude. Soil and groundwater contributions were the highest early in the 2001 monsoon season following the wet winter, much lower early in 2002 following a dry winter, and lowest during the largest floods of the 2002 monsoon season when flows were derived primarily from precipitation and overland flow. Stream water nitrate-N concentrations during floods were consistently 0.2-0.5 mg/L higher in 2002 than during 2001, suggesting greater over-winter accumulation of soil nitrate during the drier year. This result is consistent with higher mean nitrate-N concentrations in soil water of the riparian zone in 2002 (3.1 mg/L) than in 2001 (0.56 mg/ L). These data highlight the importance of seasonal and interannual variability of hydrology in semiarid regions, and the role of water availability in driving patterns of soil nutrient accumulation and their transport to the stream.

Original languageEnglish (US)
Article numberG03S03
JournalJournal of Geophysical Research: Biogeosciences
Volume112
Issue number3
DOIs
StatePublished - Sep 28 2007

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monsoons
rivers
monsoon
Nitrogen
Rivers
soils
Nitrates
Soils
nitrogen
Water
winter
nitrates
nitrate
river
water
ground water
base flow
Groundwater
dissolved organic nitrogen
monsoon season

ASJC Scopus subject areas

  • Soil Science
  • Forestry
  • Water Science and Technology
  • Palaeontology
  • Atmospheric Science
  • Aquatic Science
  • Ecology

Cite this

Influence of shifting flow paths on nitrogen concentrations during monsoon floods, San Pedro River, Arizona. / Meixner, T.; Huth, A. K.; Brooks, Paul D.; Conklin, M. H.; Grimm, Nancy; Bales, R. C.; Haas, P. A.; Petti, J. R.

In: Journal of Geophysical Research: Biogeosciences, Vol. 112, No. 3, G03S03, 28.09.2007.

Research output: Contribution to journalArticle

Meixner, T. ; Huth, A. K. ; Brooks, Paul D. ; Conklin, M. H. ; Grimm, Nancy ; Bales, R. C. ; Haas, P. A. ; Petti, J. R. / Influence of shifting flow paths on nitrogen concentrations during monsoon floods, San Pedro River, Arizona. In: Journal of Geophysical Research: Biogeosciences. 2007 ; Vol. 112, No. 3.
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