Journal article
Total Phosphorus Concentration Trends in 40 Iowa Rivers, 1999 to 2013
Journal of environmental quality, Vol.45(4), pp.1351-1358
07/2016
DOI: 10.2134/jeq2015.07.0365
PMID: 27380084
Abstract
Excessive phosphorus (P) in rivers is prompting states to develop strategies to reduce P concentrations and export. The goal of this study was to assess the current condition by analyzing trends in total P (TP) concentrations at 40 river monitoring sites in Iowa for the period 1998 to 2013. We used monthly river monitoring data collected by the State of Iowa at ambient sites located beyond the influence of point sources or cities. Study objectives were to assess the presence of any linear trends in the TP concentration data using a time-series method that accounted for temporal correlation in the data and discharge and to combine the trend information from individual sites into an assessment of the statewide rate of change in river TP concentrations. Results indicated that annual TP concentrations were significantly decreasing at 12 sites (p < 0.05), with concentrations ranging from 7.5% (Maple River) to 2.6% (Boyer River) and averaging 4.1% for the 12 sites. No statistically significant change was measured at 28 sites (p > 0.05), although all but four of these sites had decreasing concentrations. As a population of sampled rivers across Iowa, TP concentrations were declining at an annual rate of approximately 2.6%. The decreasing trends are consistent with reported reductions in sediment concentrations measured in the Raccoon River and with decreasing trends detected in other midwestern rivers. We attribute the decreasing TP trends primarily to improvements in conservation and land management. Although reducing nonpoint source TP concentrations in Iowa rivers will be a tremendous challenge for the agricultural community, progress is being made toward meeting this goal with existing programs.
Details
- Title: Subtitle
- Total Phosphorus Concentration Trends in 40 Iowa Rivers, 1999 to 2013
- Creators
- Chao Wang - University of IowaKung-Sik Chan - University of IowaKeith E. Schilling - Iowa Geological Survey; Univ. of Iowa; Iowa City IA 52242
- Resource Type
- Journal article
- Publication Details
- Journal of environmental quality, Vol.45(4), pp.1351-1358
- Publisher
- Amer Soc Agronomy
- DOI
- 10.2134/jeq2015.07.0365
- PMID
- 27380084
- ISSN
- 0047-2425
- eISSN
- 1537-2537
- Number of pages
- 8
- Language
- English
- Date published
- 07/2016
- Academic Unit
- Statistics and Actuarial Science; Radiology; Earth and Environmental Sciences; IIHR--Hydroscience and Engineering
- Record Identifier
- 9984383925202771
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