Approaches to stream solute load estimation for solutes with varying dynamics from five diverse small watersheds

Ecosphere

卷:7

Dong Yi¹  Yang Yang¹  Ruth D. Yanai¹  Kikang Bae¹  Adam D. Wild¹  James B. Shanley²  Douglas A. Burns³  Brent T. Aulenbach⁴ 

[1] State University of New York College of Environmental Science and Forestry Syracuse New York 13210 USA;

[2] U.S. Geological Survey New England Water Science Center Montpelier Vermont 05601 USA;

[3] U.S. Geological Survey New York Water Science Center Troy New York 12180 USA;

[4] U.S. Geological Survey South Atlantic Water Science Center Norcross Georgia 30093 USA;

关键词: load methodology;    sample design;    Special Feature: Uncertainty Analysis;    streamwater fluxes;    streamwater loads;    water quality;   

DOI  :  10.1002/ecs2.1298

来源: DOAJ

【 摘 要 】

Abstract Estimating streamwater solute loads is a central objective of many water‐quality monitoring and research studies, as loads are used to compare with atmospheric inputs, to infer biogeochemical processes, and to assess whether water quality is improving or degrading. In this study, we evaluate loads and associated errors to determine the best load estimation technique among three methods (a period‐weighted approach, the regression‐model method, and the composite method) based on a solute's concentration dynamics and sampling frequency. We evaluated a broad range of varying concentration dynamics with stream flow and season using four dissolved solutes (sulfate, silica, nitrate, and dissolved organic carbon) at five diverse small watersheds (Sleepers River Research Watershed, VT; Hubbard Brook Experimental Forest, NH; Biscuit Brook Watershed, NY; Panola Mountain Research Watershed, GA; and Río Mameyes Watershed, PR) with fairly high‐frequency sampling during a 10‐ to 11‐yr period. Data sets with three different sampling frequencies were derived from the full data set at each site (weekly plus storm/snowmelt events, weekly, and monthly) and errors in loads were assessed for the study period, annually, and monthly. For solutes that had a moderate to strong concentration–discharge relation, the composite method performed best, unless the autocorrelation of the model residuals was <0.2, in which case the regression‐model method was most appropriate. For solutes that had a nonexistent or weak concentration–discharge relation (model R2 < about 0.3), the period‐weighted approach was most appropriate. The lowest errors in loads were achieved for solutes with the strongest concentration–discharge relations. Sample and regression model diagnostics could be used to approximate overall accuracies and annual precisions. For the period‐weighed approach, errors were lower when the variance in concentrations was lower, the degree of autocorrelation in the concentrations was higher, and sampling frequency was higher. The period‐weighted approach was most sensitive to sampling frequency. For the regression‐model and composite methods, errors were lower when the variance in model residuals was lower. For the composite method, errors were lower when the autocorrelation in the residuals was higher. Guidelines to determine the best load estimation method based on solute concentration–discharge dynamics and diagnostics are presented, and should be applicable to other studies.

【 授权许可】

Unknown