Well data, surface-water discharges, and nitrate concentrations, February 1986 - September 1987, in parts of the Pasco Basin, Washington

The U.S. Geological Survey, in cooperation with the State of Washington Department of Ecology, initiated a study in 1986 of parts of the Pasco basin, Washington, to determine: (1) the effects of dams, irrigation, canal seepage, and ground-water pumping on ground-water levels; (2) the quality of ground water, with emphasis on probable sources of large concentrations of nitrate;(3) whether pesticides are present in the ground-water system; (4) directions and general rates of movement of undesirable chemicals and (or) chemical concentrations in the ground-water system; and (5) the possible results of various management alternatives for dealing with high ground-water levels and large concentrations of nitrate in ground water.This report contains selected basic data collected from the start of the project (February 1986) through September 1987.The ground-water-level network consisted of about 500 wells that were measured in February 1986, September 1986, and February 1987.Water levels were measured monthly in about 70 wells, and 5 wells were monitored with continuous recorders during the same period.A surface-water-flow gaging network was operated from February 1986 through July 1987.All major flows into and out of the project area were gaged for at least one full year.Miscellaneous measurements were taken at additional locations.Ground-and surface-water samples were collected and analyzed for nitrate concentrations and specific conductance.Most of the water-level network wells and selected surface-water sites were sampled in September 1986.Selected wells were sampled periodically from September 1986 through September 1987. Well-Numbering SystemThe well numbers used in this report give the location of wells according to the official rectangular public-land survey.For example, in well number 08N/30E-14M01, the part preceding the hyphen indicates successively the township and range (T.08 N. , R.30 E.) north and east of the Willamette base line and meridian, respectively.The number following the hyphen indicates the section (sec.14), and the letter (M) indicates the 40-acre subdivision of the section as shown in the sketch below.Last is a sequence number used to distinguish wells in the same 40-acre tract.Thus, well 08N/30E-14M01 is in the NWk of the SWH of sec.14, T.08 N. , R.30 E. A "D" following the sequence number indicates a well which has undergone changes in construction (generally deepening).The number following the "D" is a sequence number to distinguish multiple construction changes in the same well.R.