water quality, rivers and streams, Arkansas
The Arkansas Water Resources Center monitored water quality at the Illinois River at the Arkansas Highway 59 Bridge, just upstream from the Arkansas-Oklahoma state border during base flow and storm events from July 1, 2008 through June 30, 2009. Water samples were collected manually or with an auto-sampler and analyzed for nitrate-nitrogen, ammonia-nitrogen, total nitrogen, total phosphorus, soluble reactive phosphorus, sulfate, chloride and total suspended solids. The U.S. Geological Survey recorded instantaneous stage and discharge at the site, total annual discharge was 1,010,000,000 m³ , with 37% attributed to base flow and 63% attributed to storm flow. Loads were estimated using the mid-interval integration approach using continuous discharge (i.e., 30 min intervals) and measured concentration as applied to sampling intervals; the incremental loads were then summed to get annual loads for the 2008 calendar year. The constituent loads and annual flow-weighted concentrations for the 2008 calendar year are summarized in the table below, using data collected through this study (July through December 2008) plus data from the prior study year (January through June 2008).
Massey, L.B.; Cash, L.W.; and Haggard, B.E.. 2009. Water Quality Sampling, Analysis and Annual Load Determinations for the Illinois River at Arkansas Highway 59 Bridge, 2008. Arkansas Water Resource Center, Fayetteville, AR. MSC352. 10