Dissolved oxygen concentrations of Flat Lake and East Grand Lake Water Management Units of the Atchafalaya River Basin

Data were retrieved from a long-term data set for analyses of the relationship between residence time of flood waters with dissolved oxygen concentration collected as part of a long-term water quality monitoring program from 1 January 2000 through 31 December 2010 in East Grand Lake/Flat Lake Water Management Unit in the Atchafalaya River Floodway System. Dissolved oxygen data were collected biweekly by Louisiana State University, Renewable Natural Resources Dept (by personnel of Bill Kelso and Michael Kaller) at permanently flooded and floodplain locations as accessible during the annual flood cycle. We limited our analyses to the latter stages of the annual flood pulse, based on results of previous research indicating widespread floodplain inundation at 3.7 m at Butte La Rose (USGS gage 07381515), and a strong association of low dissolved oxygen levels with water temperatures ≥ 20?C (Kaller et al., 2011; Pasco et al., 2015). For all flood years, mean floodplain DO levels across sites per day (when water temperatures were ≥ 20?C) were plotted against the days at Butte La Rose stage heights of 3.7, 4.0, and 4.7 m, and were analyzed with generalized linear mixed models (DATA RELEASE) (GLMs; identity link with normal distribution, log link with lognormal distribution, log link with exponential distribution, log link with Poisson distribution, and inverse link with Gamma distribution). Candidate models were evaluated for model fit by Pearson Χ2/degree of freedom fit statistic, Root Mean Square Error (RSME), and Mean Absolute Error (MAE), and the best fitting version was selected for analyses. Each GLM included calculated days at the three river stages of interest as fixed explanatory variables, flood year as a first-order autoregressive random variable, and dissolved oxygen concentration as the response variable (PROC GLIMMIX, SAS vers.9.4, SAS Institute, Inc., Cary, NC). relationship between dissolved oxygen with residence time.