Abundant groundwater is available for domestic, irrigation, and industrial uses from depths of a few feet down to 600 feet. In general, the quality of the water is good, but water from some aquifers contains objectionable amounts of iron and manganese. Water from the thick Mississippi River alluvium is generally hard to very hard. Water from the nonalluvium aquifers is soft and slightly acidic, with low dissolved solids. Generally, depths to groundwater are under 100 feet, except in the uplands, where sufficient water is obtained only at depths greater than 100 feet. Yields in some of the deeper wells are greater than 1,000 gallons per minute, enough for a community or industrial supply. Water quality generally is good, except in areas where percolation of surface water and fluids from domestic sewage-disposal systems and other sources of domestic or industrial pollution have contaminated the aquifer. Groundwater sometimes contains naturally occurring iron in objectionable amounts from the deeper zones. In some formations with slightly acidic groundwater, a chemical reaction between the acidic groundwater and steel well casing and pump equipment will produce a high iron content in the water.