CAP delivers raw, untreated water to cities and water utilities, agricultural users and Native American communities. CAP does not own or operate any water treatment plants, though some of CAP's customers, cities and utilities, treat and deliver CAP water to residents. CAP's customers which deliver drinking water must comply with standards established by the Environmental Protection Agency (EPA). With passage of the Safe Drinking Water Act in 1974, the EPA established mandatory and voluntary drinking water standards and listed primary and secondary maximum contaminant levels for drinking water. CAP is not subject to the Safe Drinking Water Act because it does not deliver water directly to residents' homes.

As a service to municipal and industrial customers and the thousands of people who will ultimately drink the water, CAP has developed a comprehensive water quality testing program. The canal water quality is sampled on a monthly and quarterly basis and consists of more than 150 constituents. Lake Pleasant is sampled on a quarterly basis.

CAP has determined that Colorado River water displays many of the usual characteristics of river water. It typically has higher total dissolved solids (TDS) levels than some sources of groundwater. TDS are measured by the amounts of calcium, magnesium, bicarbonate, sodium and sulfate in the water. Because CAP water is composed of water from the Colorado and Agua Fria rivers and the system stretches 336 miles, levels of TDS vary throughout the canal. The water quality tests show that the TDS not only vary due to the mixture of the two water sources, but also change by season and other natural conditions, decreasing during floods and increasing during drought periods.

VARIABILITY OF CAP WATER

CAP water comes from two basic sources: the Colorado River and Lake Pleasant. Lake Pleasant water is both from the Colorado River via CAP and the Agua Fria River. CAP fills the lake during the winter and releases water during high demand period in the summer. The quality of the water from these sources can vary significantly. Water quality of the CAP is, to a large degree, dependent upon regional weather patterns. Total dissolved solid concentrations of CAP water behave in a cyclical nature related to natural flood and drought periods, with TDS dropping during wetter times and increasing during extended dry periods.

The CAP water intake at Havasu is located in a bay-like feature that is the mouth of the Bill Williams River. The Bill Williams River together with its head waters, Alamo Lake, form the majority of the drainage of west-central Arizona. During periods of heavy rains in this region, water flows from the Bill Williams River dominate this bay-like feature which serves as the intake for the CAP at Havasu. Water from these storm flows is lower in TDS than normal Colorado River water. Likewise, water entering Lake Pleasant from the Agua Fria River is also of lower TDS. The reason for this difference in TDS is basically related to the time and distance the water has traveled. Because waters from the Bill Williams River and Lake Pleasant are subject to less evaporation and use than those of the Colorado River, they are lower in total dissolved solid concentrations of minerals.