Water as a resource has become increasingly important due to increased use and demand. Thus there is a need to define the current condition of this resource and to document changing conditions due to natural and human influences.

OBJECTIVES:

To describe the status and trends in surface- and ground-water quality of the Iowa, Cedar, Wapsipinicon, and Skunk River watersheds. Study the primary natural and human factors that affect the quality of water in the study area.

PROGRESS:

NAWQA personnel have been collecting water samples as part of several multi-agency efforts to understand the occurrence of selected pesticides in rain, air, drinking-water supplies, and stream discharge. The pesticides included several common herbicides and their degradation products. Water-quality data collected previously by State and Federal agencies have been compiled and are being used to prepare a retrospective reports documenting the occurrence and distribution of nutrients and pesticides in the study unit. Sites on six watersheds ranging in size from about 120 to 400 square miles were selected to study the effect of different combinations of physical and land use factors (environmental settings) on stream quality. Five additional sites that integrate a number of environmental settings were selected to document the quality of water leaving the study unit. Water samples are collected on a monthly basis at these 11 fixed sites for major dissolved ions, nutrients, selected herbicides, herbicide degradation products, suspended sediment, and bacteria.

Ground-water is assessed in two sub-unit surveys and a land-use survey. A random selection method was used to select 30 existing domestic wells for collection of water-samples for the sub-unit surveys of the Silurian-Devonian and the Alluvial aquifers. Geographic Information Systems (GIS) datasets were developed for the study unit that show the location and extent of alluvial deposits, agricultural landuse, and urban landuse. Sites where water samples will be collected from the alluvial aquifer in agricultural and urban areas were identified from the GIS datasets. Thirty monitoring wells in agricultural and 30 in urban areas were constructed and sampled for the land-use survey. A special ground-water study was conducted in a 20 mile stretch of the Iowa River Alluvial aquifer from Marengo to Belle Plaine to define water-quality in an area where agricultural land is being converted to grassland and wetlands. Samples were collected in 1996 and 1998 from 23 monitoring wells. All ground-water samples were analyzed for major dissolved ions, nutrients, selected herbicides, herbicide degradation products, volatile organic compounds, radon, selected stable isotopes, and tritium.

Ecological data have been collected at the basic surface-water sites to assist in understanding the physical, chemical, and biological characteristics of the streams. The biological community (fish, algal, and macroinvertebrate), and habitat conditions are described and documented. Variability in the biological community was defined at three sites (intensive ecological sites) by sampling multiple reaches of the stream. Samples were collected for three years at the three intensive sites to document year-to-year variability. An ecological synoptic study was conducted in August 1997 to provide an understanding of the spatial variability of algal and macroinvertebrate populations. Algal, macroinvertebrate, and samples for analysis of selected water-quality constituents were collected at 25 sites. Bottom sediment and fish (primarily carp) were collected from 16 stream and river sites to understand the occurrence of trace elements and hydrophobic organic compounds in the hydrologic system.

Detailed information on the Eastern Iowa Basins NAWQA project including a map of the study area showing sampling sites, the list of publications resulting from the study, and plots showing selected water-quality constituents at the basic fixed sites is available on the EIWA NAWQA homepage.