Study design and data collection

Study design and data collection (see http://water.usgs.gov/pubs/circ/circ1112/)

More details are avaialble on each of the 20 study units that began in 1991 at: http://water.usgs.gov/pubs/nawqasum/

Study component	What data were collected and why (see table of chemical parameters)	Types of sites sampled	Number of sites	Sampling frequency and period
Stream Chemistry
Basic sites-- general water chemistry	Concentrations, seasonal variation, and annual loads. Data included streamflow, nutrients, major ions, organic carbon, suspended sediment, water temperature, specific conductance, alkalinity, pH, and dissolved oxygen.	Basic Fixed Sites: representative of common land uses, as well as basin outflow sites	about 10 per study unit	Monthly plus storms:
Intensive sites-- pesticides	Concentrations and seasonal variations in pesticides.	Subset of basic sites: where land use was most homogeneous and some mixed outflow sites in some study units	about 2 per study unit	Weekly to monthly: Feb. 1993-Mar. 1994
Synoptic sites-- water chemistry	Spatial distribution of pesticides and nutrients. Data included 85 dissolved pesticides plus same constituents as basic sites.	Basic sites Other sites plus reference sites	10-30 per SU	1-4 times in a season
Contaminants in bed sediments	Occurrence and distribution of contaminants in bed sediment. Data included total PCBs, 32 organochlorine pesticides, 63 semivolatile organic compounds, and 44 trace elements.	Depositional zones of most stream sites sampled in other components of study	about 20 per study unit	Once
Contaminants in fish and benthic invertebrates	Occurrence and distribution of contaminants in biota. Data included total PCBs, 30 organochlorine pesticides and 24 trace elements in targeted bottom fish or other aquatic life.	Most stream sites sampled in other components of study where tissue could be collected	about 20 per study unit	Once
Ground-Water Chemistry
Aquifer survey--domestic, public supply, or monitoring wells	Occurrence and distribution of chemicals in randomly selected wells in an area. Data included major ions, nutrients, 85 pesticides, 60 volatile organic compounds, dissolved organic carbon, and radon.	Varied depth wells across a Study Unit or a homogeneous part of the study unit	30 per area: 1 or 2 areas per study unit	Once
Land-use effects-- shallow wells	Describe the effects of a particular pattern of agricultural land use on shallow ground water. Data included major ions, nutrients, 85 pesticides, 60 volatile organic compounds, dissolved organic carbon, and radon.	Shallow domestic or monitoring wells	about 30 wells for each of 1-4 land users in a study unit	Once