Skip to main content

Oregon State Flag An official website of the State of Oregon »

Nitrate Contamination: Lower Umatilla Basin

Northern Morrow and Umatilla Counties

The Lower Umatilla Basin Groundwater Management Area includes parts of northern Morrow and Umatilla counties. DEQ designated it a groundwater management area in 1990 because of high levels of nitrate in the groundwater. It's one of three groundwater management areas in Oregon.

Map: Lower Umatilla Basin Groundwater Management Area


The Lower Umatilla Basin Groundwater Management Area Committee is tasked with developing long-term plans to reduce nitrate levels in the area. The committee includes local residents, businesses and government agencies. 

There are many sources of nitrate contamination in the area. The primary estimated source of contamination (about 70%) is from irrigated farmland. Additional contributors are large dairy and cattle farms known as CAFOs (about 13%), animal pastures (about 8%), food processing facilities that reuse wastewater to irrigate fields (about 5%), and residential septic systems and other sources (about 5%). Additional information about sources of contamination and plans for reducing those sources are in the LUBGMWA Action Plan.

Estimated sources of nitrate contamination in the Lower Umatilla Basin, LUBGWMA Second Action Plan


Drinking water safety

High levels of nitrate in drinking water can cause health problems. This includes respiratory and reproductive diseases, as well as kidney, spleen and thyroid problems. Nitrate is most harmful to infants and people who are pregnant. High levels of nitrate can increase the risk of methemoglobinemia, or blue baby syndrome, especially for infants who drink baby formula mixed with water containing nitrate above the safe level.

If your water is from a private well: The Oregon Health Authority recommends you test your water regularly for nitrate, bacteria and arsenic. These are common drinking water contaminants in Oregon. Water in private wells must be tested during real estate transactions, but otherwise private wells are not regulated in Oregon and water quality is the responsibility of the well user. Find additional information from OHA on well testing and maintenance.

If your water is from a city or community water system: Your water is safe to drink. You don't have to test your water. Public water systems are required to regularly test the quality of their water and ensure it is safe to drink. 

Get a free well water quality test: the Oregon Health Authority is offering residents with private wells in the Lower Umatilla Basin free vouchers to cover testing for nitrate, arsenic, bacteria, lead, iron, manganese and hardness.


Antony Vorobyov
Public Affairs, Eastern Region