Public Comment Opportunity
Nez Perce County Lower River Tributaries Watershed Assessment Project
The Nez Perce Soil and Water Conservation District (NPSWCD), completed a watershed assessment through the USDA Natural Resources Conservation Service’s National Water Quality Incentive Program (NWQI) to complete watershed assessments on 49,438 acres of land within five small streams within Nez Perce County, Idaho. These streams include Tammany Creek (22,225 acres), Ten-Mile Creek (8,867 acres), Hidden Creek (4,131 acres), Lindsay Creek (14,215 acres), and a small unnamed tributary (299 acres).
The NPSWCD is located at the confluence of the Snake and Clearwater River basins, which are important surface and ground water source areas. In addition, these streams provide critical Endangered Species Act (ESA) habitat for Snake River Steelhead and Spring Chinook. Because the major land use within the region is agricultural production (75%), proper farming practices are critical in protecting the area’s source waters.
The study area selected for this proposal includes streams that are not meeting water quality standards. Two of the streams have Total Maximum Daily Load (TMDL) allocations developed for the identified pollutants (Tammany and Lindsay Creeks).
A TMDL assessment for Tammany Creek was completed by Idaho DEQ in 2001 and amended in 2010. The pollutants of concern are sediment, total phosphorus, nitrite plus nitrate, and E. coli. A TMDL assessment for Lindsay Creek was developed by Idaho DEQ in 2007 and named bacteria, excess nutrients and sediment as the pollutants of concern. The TMDLs have been approved by USEPA. The proposed NWQI assessment will likely find that agricultural best management practices can reduce degradation of water quality by these pollutants. Idaho DEQ delineated 14,060 acres of source water protection area in the Lindsay Creek, Tammany Creek and Hidden Creek watersheds. Idaho DEQ also delineated 50,300 acres of Nitrate Priority Area in the Lindsay Creek and Tammany Creek watersheds where nitrates in groundwater are elevated and of concern. Implementation of agricultural BMPs will help protect sources of drinking water.
The proposed project area is also within the Lewiston Sole Source Aquifer and water supply is limited from groundwater resources. The Lewiston Orchards Irrigation District promotes water conservation activities to reduce water use in the Lewiston Orchards area. Irrigation occurs on pastures and hay fields within the project zone. The project area is within a 10 to 15 inch rainfall zone, which leads to limited moisture for crop production.
The TMDL assessment for Tammany Creek was completed by Idaho DEQ in 2001 and amended in 2010 and the TMDL assessment for Lindsay Creek was developed by Idaho DEQ in 2007. Hydrology, hydrologic condition, and erosion assessments for these watersheds are outdated and are not based on the methods now considered the standard-of-practice. High-resolution LiDAR elevation data (2016) cover the project watersheds. The impact of climate change has not been considered in previous assessments. The NPSWCD has completed substantially similar hydrologic assessments of the nearby watersheds including Bedrock Creek, Hatwai Creek, and Catholic Creek. PWS Source Water Assessments have also been completed for the City of Lewiston and Lewiston Orchards.
The purpose of NWQI is to work with producers and landowners to accelerate adoption of voluntary conservation practices that improve water quality in high-priority watersheds while maintaining agricultural productivity (USEPA 2021). This has been the primary mission of the Nez Perce Soil and Water Conservation District for over 80 years. The NPSWCD has many cooperative BMP implementation projects in these and neighboring watersheds. The NWQI program would help further the work of the NPSWCD and has the full support of the NPSWCD elected Board of Supervisors.
Portions of the study area were designated as a Ground Water Management Area (GWMA) by Idaho Department of Water Resources. A GWMA is all or part of a groundwater basin that may be approaching the conditions of a Critical Groundwater Area (CGWA). A CGWA is all or part of a groundwater basin that does not have sufficient groundwater to provide a reasonably-safe supply for irrigation or other uses at the current or projected rates of withdrawal.
After the planning phase, the NPSWCD will request USDA Natural Resources Conservation Service funding to assist land owners in the implementation of conservation practices to address the identified resource concerns.
The assessment is drafted and available for public comment. Please provide comments by:
July 27, 2023.
Comments should be addressed to:
Nez Perce Soil and Water Conservation District
PO Box 131
Culdesac, Idaho 83524
Or via email at npswcd@co.nezperce.id.us
Attention: Lynn Rasmussen
Several documents were created during the assessment process. Each document is listed below.