Water quality plays a critical role in protecting public health, agriculture, and ecosystems, particularly as climate change, drought, and wildfire place increasing pressure on water systems. Both surface water and groundwater quality are shaped by natural conditions, land use, and water management practices.
Surface water (rivers, streams, lakes, and reservoirs) responds quickly to storms, seasonal changes, and disturbances. Common concerns include sediment, nutrients, pathogens, temperature, and dissolved oxygen, all of which can affect drinking-water treatment, irrigation, and aquatic habitat.
Groundwater is a primary drinking-water source for many rural communities and domestic well owners. Because groundwater moves slowly, water quality changes tend to occur over longer timeframes. Key concerns include naturally occurring constituents (such as arsenic, iron, manganese, boron, and salinity), nitrate, and contaminants mobilized by drought or wildfire.
Surface water and groundwater are physically connected, meaning changes in one can directly affect the other. Reduced flows, increased pumping, and limited recharge during drought can concentrate contaminants in both systems.
This page compiles technical notes, factsheets, and guidance to support water-quality monitoring, interpretation of results, and management decisions for domestic wells, agriculture, small water systems, and climate resilience planning.