1. Interaction Between Rivers and Aquifer Michael Barber Director, State of Washington Water Research Center Washington State University May 8, 2007 Spokane Valley – Rathdrum Prairie Aquifer Study

2. Surface/Groundwater Interaction Options Dingman, S. Lawrence. 2002. Physical Hydrology 2nd Edition.

3. Quantifying Aquifer/River Interaction This concepts explains why the total volume of the SVRP is not as important as the active portion –the part above the river bottom To determine gaining, losing and neutral reaches of surface/groundwater exchanges, additional Seepage Runs were conducted.

4. QDQD QCQC QBQB QAQA Losing reach Q B < Q A Transitional reach Q C ≈ Q B Gaining reach Q D > Q C river aquifer Nearly simultaneous measurement of river discharge (Q) at different locations (A, B, C, D) to determine streamflow gains and losses between sites. ABCD What are Seepage Runs?

6. Seepage Runs In addition to previous data, 2 seepage runs were conducted as part of this project –August 30, 2005 –August 8, 2006 The August 30 th run was the most comprehensive

7. near Post Falls near Coeur d’Alene Lake near Otis Orchards Greenacres Flora Rd Centennial Trail Bridge below Greene St below Upriver Dam Spokane below Meenach Bridge Rifle Club Rd below Nine Mile Dam at Dartford Waikiki Road near Dartford near confluence Sullivan Rd Seepage Run Measurement Sites Spokane & Little Spokane Rivers

8. near Coeur d’Alene Lake near Post Falls near Otis Orchards Green acres Flora Road Centennial Trail Bridge Spokane below Greene Street Rifle Club Road below Nine Mile Dam Seepage Run, August 26-31, 2005

9. Little Spokane River at Dartford Waikiki Rd near Dartford near confluence

10. Centennial Trail Bridge Spokane below Greene Street Limited Seepage Run, August 8, 2006 below Upriver Dam

11. Spokane at Dartford near Dartford near Post Falls near Otis Orchards Monthly average gains and losses (next 3 slides)

12. Monthly average streamflow gain (+) or loss (-) Spokane River: near Post Falls – near Otis Orchards This stream segment is: always losing loss is typically greater during winter and spring than summer and fall 200020022003200420052001

13. Monthly average streamflow gain (+) or loss (-) Spokane River: near Post Falls – Spokane This stream segment typically is: gaining during period of lower streamflow (summer and fall) and losing during periods of higher streamflow (winter and spring) 200020022003200420052001

14. Monthly average streamflow gain (+) or loss (-) Little Spokane River: at Dartford – near Dartford 200020022003200420052001 This stream segment is: always gaining gain is relatively constant over time

15. Surface/Groundwater in MODFLOW Streamflow Routing Package –Segment to segment flow is determined –Spokane River River Package –Define stage, bottom elevation, & conductance –Little Spokane River

16. Controlling Parameters Where: K = Hydraulic conductivity of bed material [ft/day] W = River width [ft] L = Length of river segment [ft] m = Thickness of bed deposits [ft] h r = Elevation of river surface [ft] h a = Groundwater elevation in cell adjacent to river [ft]

17. 11 Spokane River Zones

18. Description of Zones FromTo KVSR-1:Coeur d’Alene LakePost Falls KVSR-2:Post FallsOtis Orchards KVSR-3:Otis OrchardsGreenacres KVSR-4:GreenacresSullivan Road KVSR-5:Sullivan RoadMyrtle Point KVSR-6:Myrtle PointUpriver Dam KVSR-7:Upriver DamDowntown Spokane (E) KVSR-8:Downtown Spokane (W)Above Meenach Bridge KVSR-9:Above Meenach BridgeRifle Club Road KVSR-10:Rifle Club RoadNine Mile Dam KVSR-11:Nine Mile DamLong Lake

19. Little Spokane River Connection LSR Inflow Reach

20. USGS gaging station on the Little Spokane River near Dartford

21. Little Spokane River Inflow

22. Any Questions?