b'WaterDRINKING WATER SOURCES of irrigated agriculture and the rapid growth of Idaho encompasses approximately 1,960 publicthe industrialized dairy industry have resulted in water systems. Water customers pay the costs tosignicant levels of nutrient pollution (primarily maintain and improve water system infrastructure,nitrogen and phosphorus) being introduced to the which includes water treatment plants, wells, pumps,landscape, which has steadily inltrated the ground and pipes. Recent population growth has helpedwater, resulting in contamination problems. Degraded encourage investment in new drinking water systems,ground water quality has been shown to lead to a yet Idahos water-related infrastructure this centuryhost of health problems and presents a serious threat has proportionally diminished due to a rapidlyto one of Idahos most important aquifers.3 Best growing population, along with the increased costsmanagement practices for remediating contaminated associated with permitting, design, and construction.ground water and protecting ground water include Over the next 20 years, the Environmental Protectionproper disposal of hazardous materials, careful use Agency estimates Idaho will need $961.8 million toof pesticides and fertilizers, and maintaining maintain, repair, and replace its existing drinkingseptic systems.2water infrastructure.1 DRINKING WATER TREATMENT95 percent of Idahoans rely on groundwater as theirDrinking water sources may be contaminated and drinking water source. Surface water (streams, springs,require treatment to remove potential pathogens. rivers, and reservoirs) supply the remaining 5 percent.Public drinking water systems use a variety of Fortunately, Idaho has abundant groundwatertreatment methods to provide safe drinking water supplies thanks to a robust array of aquifersto their customers.The most common steps in throughout the state (see Figure 1). Groundwater alsowater treatment are coagulation and occulation, costs less to treat than surface water, is more reliablesedimentation, ltration, and disinfection. First, during droughts, and can be tapped where it isduring the coagulation and occulation process, needed. Though, the surface water provides a exiblechemicals with a positive charge are added to the safety net during spikes in demand.1 water. This action neutralizes the negative charge of dirt and other dissolved particles in the water, causing Idaho ground water is protected by federal andthe particles to bind with the chemicals and form state laws regulating activities that either directlylarger particles, called oc. Next, the oc settles to the or indirectly aect ground water quality. Lawsbottom of the water supply during the sedimentation are enforced by state and local governments toprocess due to its weight. After the sedimentation protect Idahos ground water resources and quality.2 process, the clear water on top passes through However, ground water quality in the Easternvarious lter types (i.e. sand, gravel, and charcoal) Snake Plain Aquifer (ESPA), southern Idahos mostand pore sizes to remove dissolved particles, such important source of drinking water, is decliningas dust, bacteria, parasites, viruses, and chemicals. because of contamination from the overapplicationLastly, during the disinfection stage, a disinfectant of fertilizers and animal waste across the Snake Riversuch as clorine or chloramine may be added to kill Plain.3 Although the aquifer is often treated as outany remaining parasites, bacteria, and viruses and to of sight out of mind by many, it supplies drinkingprotect the water from contamination as it is piped water to over 300,000 Idahoans and helps supportto homes and businesses.4 See Figure 2 for a visual a large swath of irrigated agriculture in what wouldoverview of a typical potable water system that otherwise be arid, high desert conditions. Proliferationutilizes both groundwater and surface water.Water 129'