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Idaho’s Experience with Random Design using NHD

Explore Idaho Department of Environmental Quality's experience with sampling design on intermittent streams and other considerations using NHD data. Learn about survey design, site selection criteria, monitoring efforts, and the challenges faced in achieving the required sites per year. Understand the breakdown of land ownership, land use patterns, GIS site analysis, and conclusions drawn from the study. Discover efforts to improve NHD coverage for addressing intermittent and ephemeral waters, including ongoing collaboration with USGS on a low-flow model.

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Idaho’s Experience with Random Design using NHD

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  1. Idaho’s Experience with Random Design using NHD Mary Anne Nelson, Michael McIntyre, Michael Edmondson, Glen Pettit Idaho Department of Environmental Quality Intermittent streams and other considerations

  2. Sampling Design • Sample Population • All perennial, wadeable streams • 1:100,000 scale • Sampling Frame • NHD supplied to ORD (Corvallis, OR) • Strahler order (1-5) • DEQ Region • Survey Design • Generalized random tessellation stratified survey design for a linear network

  3. Sampling Design • Multi-Density Categories • DEQ Regions (6) • Strahler Order • 1&2 (50%) • 3 (30%) • 4&5 (20%) • Panels: 5 panels of 50 sites statewide, 1 panel monitored each year • 500% Oversample

  4. Site Selection Where rubber meets the road • Wadeable vs. Non-Wadeable • 4th order or less • Less than 15 m average wetted width • Less than 0.4 m average depth at base flow • Inaccessible • Minimum 2 hour hike to access • Safety issues • Dry • Wetland/No Flow • Denied Access • Impoundments • Beaver dams • Map Error

  5. Accessibility

  6. Flow

  7. Monitoring Effort in 2004 Total Sites 659 42.79% Effort in Random Sites 57.21 % Effort in Targeted Sites • 56 Random Sites (8.5%) • 220 Rejected Random Sites (33.38%) • 238 Target Sites (36.12%) • 104 Rejected Target Sites (15.78%) • 6 Random Repeat (0.91%) • 35 Reference Trend (5.31%)

  8. 2004 Site Selection Results 50 Primary Sites 250 Secondary Sites 56 Monitored Random Sites Of the 50 Primary Sites 11 Monitored 32 Rejected 7 unknown

  9. 2004 Rejected Random Sites 220 Rejected Sites in 2004

  10. Monitoring Effort in 2005 Total Sites 403 60.05 % Effort in Random Sites 39.95 % Effort in Targeted Sites • 49 Random Sites (12.16%) • 187 Rejected Random Sites (46.40%) • 109 Target Sites (27.05%) • 22 Rejected Target Sites (5.46%) • 6 Random Repeat (1.49%) • 30 Reference Trend (7.44%)

  11. 2005 Rejected Random Sites 187 Rejected Sites in 2005

  12. Dry Sites in Idaho

  13. Monitored Sites in Idaho

  14. Precipitation 77 Sites Rejected in 2004 as Dry 84 Sites Rejected in 2005 as Dry

  15. Public Lands

  16. Breakdown of Land Ownership

  17. Landuse Patterns

  18. GIS Site Analysis • GIS coverages • Precipitation • Land Use • Satellite imagery • NAIP imagery • Vegetative Cover • Catchment area • ArcGIS Spatial Analyst • USGS StreamStats

  19. Conclusions • To achieve the required 50 sites/year, roughly 200 sites were rejected • 31 % of sites are dry • 23 % of sites are inaccessible • Need to improve NHD coverage to address intermittent and ephemeral waters • Working on low-flow model with USGS • Assessment of these sites to be carried out in May 06 for inclusion in the 06 integrated report

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