Moses Lake Invasive Aquatic &
Riparian Vegetation Control Projects


Moses Lake is a 6,800 acre (surface area) water body with approximately 120 miles of shoreline, and is located in Grant County, Washington. At a water surface elevation of 1,047 feet, the depth ranges from 2 to 35 feet deep. Moses Lake’s water shed is inclusive of portions of Lincoln, Adams, Grant, and Spokane Counties and receives perennial flow from Crab Creek and Rocky Ford Creek. Rocky Ford Creek contributes substantial flow but is a spring-fed stream with a very small surface drainage area.

The Moses Lake Irrigation and Rehabilitation District (MLIRD) has the responsibility to maintain and enhance the water quality and usability of this fresh water reservoir. In 2008, the MLIRD conducted a lake-wide survey to map the characteristics of the lake including vegetation diversity and density, sediment types, and depths. In 2009, the MLIRD created an Integrated Aquatic Vegetation Management Plan in order to define the survey data and discuss current and proposed management techniques, including chemical control.

In 2010, the decision was made to implement a three (3) year aquatic herbicide control project, the first year of which consisted of approximately 330 acres.

During a multi-agency meeting with the MLIRD, Grant County Noxious Weed Control Board, and the Washington Department of Natural Resources, it was agreed that a separate herbicide control project for the shoreline plants would be implemented immediately after the aquatic treatment.

Project Goals – Aquatic Project

The goals of this three (3) year project are to:


  1. Substantially reduce the Eurasian Watermilfoil infestations in Moses Lake.
  2. Reduce nuisance aquatic plants in Moses Lake to levels that would better facilitate aquatic recreation, fishing, and overall use of the lake.
  3. Reduce the amount of time required to harvest aquatic plants using aquatic harvesting equipment. This would reduce the equipment wear and tear and the necessary man hours required to operate the harvesting equipment, allowing MLIRD staff to focus on other projects beneficial to the goals of the MLIRD.
  4. Prepare for dredging operations to further improve the quality of Moses Lake.

Want to learn more about invasive plants?  Click here to visit our FAQ!

Project Goals – Riparian (Shoreline) Project

The goals of the project for the first year were to:

  1. Create a current inventory of all invasive shoreline plants.
  2. Elimate invasive trees along the shoreline.
  3. Stop the spread of Phragmites around Moses Lake, and spray plants as far up the shore as possible (from an airboat) as to retard movement of the plant along the water’s edge.
  4. Contain the spread of Yellow Flag Iris along the water’s edge. Due to public concern, it was decided not to spray in the Laguna area due to the fact that most of the infestations were located in landscaped areas.
  5. Leave plants located in or near landscapes untreated.

2014 Treatment Plan

Alternative text – include a link to the PDF!

2014 Treatment Map

Alternative text – include a link to the PDF!

Bulletin Board

The Moses Lake Aquatic
treatment started
on June 23rd
and was completed
on June 25th.
Water restrictions
will be lifted
on Saturday, June 28th

*Algaecide treatments will occur on an as needed basis.


2014 Treatment Map

2014 Proposed Treatment Map

Treatment Letter

MLIRD Treatment Letter

Entry Posting

Shoreline Posting

Algae Posting

Business & Residential Notice 

call (877) 273-6674

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