Water supplies are limited in much of northwestern Missouri, and water-resources data also are limited. This report presents a summary of hydrologic data and an evaluation of areas where additional hydrologic data are needed to provide a data base suitable for use in making decisions regarding future water development.

The largest and most dependable surface-water supplies that can be obtained without storage from tributary streams, as indicated by the 30-day low flow with recurrence interval of 10 years, potentially are available from the lower Grand River (15 to 30 million gallons per day) and the Nodaway and Chariton Rivers (5 to 10 million gallons per day). Flow of the Missouri River is greater than 1,300 million gallons per day at all points in Missouri. Surface water is primarily a calcium bicarbonate
type with dissolved-solids concentration less than 400 milligrams per liter.

Sources of water in surficial deposits are the Missouri River alluvium (well yields as much as 2,000 gallons per minute), glacial drift (well yields of 30 to 500 gallons per minute), and alluvium of tributary streams (well yields exceed 50 gallons per minute in large basins). The Pennsylvanian bedrock yields only a few gallons per minute to wells. The Cambrian and Ordovician formations are not evaluated because data are few, and there are no water wells open to these units. Water from the alluvium is a hard, calcium bicarbonate type that commonly has relatively large iron concentrations and typically has dissolved-solids concentrations of less than 500 milligrams per liter. Water from the glacial-drift and bedrock generally is a mixed calcium bicarbonate sodium sulfate type, is hard, has relatively large iron concentrations, and some of it is classified as saline.

Areas where additional hydrologic data are needed to provide a data base suitable for use in making decisions regarding future water development include the lower Grand and Thompson River basins, the Missouri River alluvial aquifer, the Nodaway-Tarkio-One Hundred and Two River basins, the Chariton River basin, and the 19 counties where surface-mineable coal reserves make coal-related industrial expansion possible.