Watershed Management Plan - Mason County

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Chapter 2 WRIA 16 – State of the Watershed In addition, please note that for the purposes of this document, WRIA 16 consists of six sub-basins. Five sub-basins are officially part of WRIA 16, and the sixth, the South Shore sub-basin, is officially part of WRIA 14. The South Shore sub-basin is considered here, under agreement with the WRIA 14 Planning Unit, to consolidate planning for Hood Canal and the nearshore environment. The six sub-basins are: • Dosewallips River sub-basin; • Duckabush River sub-basin; • Hamma Hamma River sub-basin; • Finch/Lilliwaup Creeks sub-basin; • Skokomish River sub-basin (including the North Fork, South Fork, and mainstem); and the • South Shore sub-basin. Key findings from particular sub-basins or creeks will be identified in this chapter as appropriate, but for a more detailed look at findings for each sub-basin, please see Appendix A. Competing demands and uncertainty about future water supplies indicate that careful planning is needed to avoid future conflict over WRIA 16’s water resources 2.1. Water Quantity In a watershed, water is present both as surface water (streams) and as groundwater. Although they may appear to be separate water sources, surface water and groundwater are often closely connected – a concept called hydraulic continuity. Groundwater can feed streams and, in turn, streams can recharge groundwater. A visible example of the interaction of groundwater and surface water is a wetland, as many wetlands are sites where groundwater is discharged to the surface. Wetlands serve many important functions in WRIA 16, including wildlife habitat, improvement of water quality, and moderation of streamflow (PSCRBT, 1995). All surface water and groundwater originates when rain, snow, or other forms of precipitation fall in the watershed. Some precipitation is intercepted by trees and plants, and some is stored as snow and glaciers, but a large portion either percolates into the ground or flows directly into streams or Hood Canal. The process by which water enters, travels through, and exits a watershed is termed the hydrologic cycle. page 10 Final Plan for County Adoption – May 11, 2006
Chapter WRIA 16 – State of the Watershed 2 Figure 2. The Hydrologic Cycle (Golder Associates, 2003) In WRIA 16, the majority of precipitation falls during the winter months, as moisture-laden clouds coming off the Pacific Ocean drop up to 250 inches of precipitation per year on the Olympic Mountains. By the time these clouds travel east to reach the lower portions of WRIA 16 and Hood Canal, most of their precipitation has already fallen. Consequently, precipitation along Hood Canal is about 60 inches per year. The highest, peak stream flows in many streams closely follow precipitation patterns; peak flows occur in winter when most rain falls. Streams that are fed significantly by snowpack, however, may not have their maximum flows in winter. Such streams often experience peak flows in late fall (before precipitation turns to snow) and again in late spring (when warming air temperatures melt the snow) (Golder Associates, 2003). The precipitation that falls in WRIA 16 feeds both the surface water and groundwater of the basin. In WRIA 16, snowmelt from the Olympic mountain is critical to spring and summer streamflow in the Dosewallips, Duckabush, and Hamma Hamma Rivers, as well as in the North Fork of the Skokomish River SURFACE AND GROUNDWATER QUANTITIES The Level 1 Technical Assessment estimated that the total annual volume of precipitation in WRIA 16 averages approximately 3.4 million acre-feet per year (AF/yr). An acre-foot is a volume of water equivalent to one foot of precipitation over an acre of land and is a common unit used by Final Plan for County Adoption – May 11, 2006 page 11
Page 1 and 2: Watershed Management Plan Skokomish
Page 3 and 4: WRIA 16 Summary of Watershed Manage
Page 5 and 6: WRIA 16 Summary of Watershed Manage
Page 7 and 8: WRIA 16 Watershed Management Plan T
Page 9 and 10: Chapter Introduction and Background
Page 15: Chapter WRIA 16 - State of the Wate
Page 19 and 20: Chapter WRIA 16 - State of the Wate
Page 41 and 42: Chapter Recommendations: Water Quan
Page 43 and 44: Chapter Recommendations: Water Qual
Page 45 and 46: 4.2. On-site Septic Systems 4.2.1.
Page 47 and 48: Chapter Recommendations: Water Qual
Page 49 and 50: Chapter Recommendations: Habitat 5
Page 51 and 52: Chapter Other Recommendations 6 ent
Page 53 and 54: Chapter Other Recommendations 6 6.1
Page 55 and 56: Chapter Other Recommendations 6 lan
Page 57 and 58: Chapter Other Recommendations 6 Pla
Page 59 and 60: Chapter Implementing the Plan 7 7.
Page 61 and 62: Chapter Works Cited 8 Hood Canal Co
Page 63 and 64: Chapter Works Cited 8 Puget Sound A
Page 65 and 66: Chapter Works Cited 8 Washington St
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Chapter Glossary 9 9. Glossary 303(
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Chapter Glossary 9 pH - A measure o
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Sub-basin Summaries Appendix A Appe
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Sub-basin Summaries Appendix A The
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Sub-basin Summaries Appendix A Duck
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Figure 7. Duckabush Sub-basin
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Sub-basin Summaries Appendix A Esti
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Figure 8. Map of the Hamma Hamma Su
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Sub-basin Summaries Appendix A perm
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Sub-basin Summaries Appendix A Figu
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Sub-basin Summaries Appendix A Spri
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Sub-basin Summaries Appendix A ISSU
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Sub-basin Summaries Appendix A Sout
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Sub-basin Summaries Appendix A Cree
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Figure 11. Map of the South Shore S
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Sub-basin Summaries Appendix A Depa
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Key Issues and Options - Water Quan
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Key Issues and Options - Water Qual
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Addressing Cumulative or Cross-Cutt
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Addressing Cumulative or Cross-Cutt
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Options for Funding New Efforts App
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Supporting Documents Appendix G App
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Watershed Management Plan - Mason County

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