Water Quality Improvement Project
Dissolved Oxygen & pH
As part of a larger effort to address all water quality impairments in the
Palouse River watershed, Ecology began a project to address low
dissolved oxygen and high pH in Palouse River in 2007. This project only
addresses the portion of river known locally as the North Fork Palouse
River (from the state line with Idaho to the confluence with the South
Fork Palouse River in Colfax). The mouths of major tributaries through
this section of river are also included.
Dissolved oxygen and pH impairments along the rest of the Palouse River
will be addressed in the future. Dissolved oxygen and pH impairments in
the South Fork Palouse River watershed are being addressed as a separate
project. Please see the
South Fork Palouse River Project page for more information on
studies in this sub-watershed.
Why this matters
The levels of dissolved oxygen and the pH of the water are vital to
the health of the fish, animals, and insects that live there. When a
river is outside of healthy conditions fishery populations decline, which
diminishes the resource for recreational and subsistence fishing.
Additionally, the pollutant that causes low dissolved oxygen levels and
wide pH swings in the North Fork Palouse River is nitrogen, a nutrient
that supports plant growth. When this nutrient is in excess, algae and
other plants grow at elevated rates in the water, leading to unsightly
algal blooms and surface scum. These conditions lessen the aesthetic
value of the river. The summer of 2014 saw both significant algal blooms
and fish kills, which may in part be attributed to these impairments.
Status of the project
Data for this study was collected in conjunction with the
bacteria study in
2007, and intensive surveys were conducted in the summers of 2007 and 2012. The
study found that the periphyton (bottom algae), which drive dissolved oxygen and
pH in the North Fork Palouse River, are extremely sensitive to inputs of
dissolved inorganic nitrogen (DIN). DIN is the combination of nitrate,
nitrite, and ammonia. Background levels of DIN in the river are near zero,
and even small DIN inputs can have large impacts on dissolved oxygen and pH.
This means that to restore natural dissolved oxygen and pH levels in the
watershed, DIN needs to be reduced to near-zero levels during May-October.
The primary form of nitrogen in this system is nitrate.
Ecology developed a report detailing the findings of the study, including the
amount of pollutant that can be allowed in the river without causing an
impairment. This report is required by the Clean Water Act for streams violating
water quality standards and is called a total maximum daily load (TMDL).
Ecology worked with several organizations in the watershed to draft an
implementation plan describing methods to address issues contributing to
elevated nitrogen. Some of these methods include reducing dissolved inorganic
nitrogen in wastewater effluent, elimination of effluent from failing septic
systems, prevention of soil erosion flowing to waterways, and the reduction of
human and livestock impacts to stream corridors and stream banks.
The study findings and implementation plan are combined into a single report
outlining how dissolved inorganic nitrogen will be reduced to achieve water
quality standards for dissolved oxygen and pH. The
TMDL study and
implementation plan underwent a public review and comment during
the summer of 2015. The report was submitted to the Environmental Protection
Agency (EPA) for their review and approval on November 2015. EPA approved it in
North Fork Palouse River Dissolved Oxygen and pH Total Maximum
Daily Load : Water Quality Improvement Report and Implementation
Presentation on the Dissolved Oxygen and pH TMDL Study and Implementation Plan given at the August 3, 2015 Public Meeting in Palouse, WA
Palouse River Dissolved Oxygen and pH Total Maximum Daily Load
Study-Water Quality Study Design (Quality Assurance Project Plan)
Addendum 2 to Quality Assurance Project Plan: Palouse River Dissolved Oxygen
and pH Total Maximum Daily Load Water Quality Study Design
WRIA 34: Palouse
Watershed Information (Environmental Assessment
Program web site)
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