Water Quality of Potential Reference Lakes in Two Level-Three Ecoregions of Arkansas

Science Center Objects

Short Title: Reference Lakes

Project Chief: Billy Justus

Cooperators: Arkansas Department of Environmental Quality and U. S. Environmental Protection Agency

Project Time Frame: 2007 - 2008

The Arkansas Department of Environmental Quality has classified all lakes within Arkansas into five classifications called lake "Types" (A-E); however, reference water quality characteristics of these lake types has not been determined. This study addresses reference water quality in Type C and D lakes located in the Mississippi Alluvial Plain (Delta) and South Central Plains level-three ecoregions within Arkansas.

The Arkansas Department of Environmental Quality has classified all lakes within Arkansas into five classifications called lake "Types" (A-E); however, reference water quality characteristics of these lake types has not been determined. This study addresses reference water quality in Type C and D lakes located in the Mississippi Alluvial Plain (Delta) and South Central Plains level-three ecoregions within Arkansas.

Type C lakes include reservoirs generally less than 1,000 acres in the upland regions of the two ecoregions that were constructed for fishing, most of which have a fishery managed by the Arkansas Game and Fish Commission (AGFC). Type D lakes are impoundments that are less than 1,000 acres within the delta floodplain in areas of both ecoregions., These are either oxbows that are now disconnected from the large rivers that once flowed through them, or are reservoirs that were constructed by public (such as the AGFC) or private entities. Within the lake Types C and D and, based primarily on differences in soil types and topography, four distinct lake groups can be identified- 1) oxbow lakes that are disconnected from the main stem of what are usually large rivers (the Ouachita, Arkansas, White, Red, and Mississippi Rivers), 2) lowland reservoirs, 3) upland reservoirs constructed in the southern coastal plain, and 4) upland reservoirs constructed on Crowleys Ridge.

This study is focusing on identifying criteria for reference lake selection, and identifying reference lakes for each of the four lake groups. Aspects of the study include: a) selecting appropriate criteria for reference lake determination; b) selecting up to six candidate reference lakes for each of the four lake types; c) a reconnaissance effort that includes a preliminary water-quality sampling at all of the 24 candidate reference lakes; d) using data collected in the reconnaissance effort, and pre-existing historical data, selecting two candidate reference lakes for each of the four lake classifications out of the six lakes that were sampled during the reconnaissance effort; e) intensively sample the eight selected reference lakes; and f) providing an interpretive report that will focus on comparing data collected at the two lakes representing each of the four respective lake types (but also will contain all data collected in the study).