Abundant quantities of groundwater are available for domestic, irrigation, and industrial uses, from depths of a few feet to below 700 feet; most wells are set at the 100-foot range. A few wells obtain shallow perched water from gravel or alluvial deposits, but these zones often will not yield enough water for a domestic supply during periods of low rainfall in late summer and fall. In general, the chemical quality of the water is good, but water from some aquifers contains objectionable amounts of iron and manganese. Water from alluvium is generally hard to very hard with moderate to high levels of dissolved solids. Water from the sand or gravel, nonalluvium aquifers is considered soft and slightly acidic, with low dissolved solids. Yields in some of the deeper wells (250 to 1,500 feet) are greater than 1,000 gallons per minute, which is sufficient 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. In a few wells, harmful amounts of nitrate have been detected. 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.