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Estimation of areal recharge for the Spokane Valley-Rathdrum Prairie Aquifer

Estimation of areal recharge for the Spokane Valley-Rathdrum Prairie Aquifer. J.R. Bartolino U.S. Geological Survey Idaho Water Science Center SVRP Aquifer Summit May 8, 2007—Spokane, WA. Magnitude of areal recharge. 1,471 ft 3 /s inflow.

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Estimation of areal recharge for the Spokane Valley-Rathdrum Prairie Aquifer

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  1. Estimation of areal recharge for the Spokane Valley-Rathdrum Prairie Aquifer J.R. Bartolino U.S. Geological Survey Idaho Water Science Center SVRP Aquifer Summit May 8, 2007—Spokane, WA

  2. Magnitude of areal recharge 1,471 ft3/s inflow • Areal recharge is second-largest single inflow component • 233 ft3/s: 16% of total • Includes permeable and impermeable surfaces • Permeable surface assumes no overland runoff • Impermeable surface excludes impervious cover that drains directly to the Spokane River or other water body 1,468 ft3/s outflow

  3. Runoff based: assumes Runoff = Recharge Langbein (1961): Raft River, ID Annual only Precipitation and PET ESPAM (Contor, 2004) Based on Rich (1951, 1952) and calibrated to previous GW flow model. Three soil types: thin and thick soils, lava rock Precipitation ET based: assumes Precipitation - ETc = Recharge USDA (1970) Effective rainfall calculated Precipitation, PET, and temperature FAO Penman-Monteith (Allen and others,1998) Reference ET (ETo) calculated—requires many meteorological data; most can be approximated Single coefficient approach: Four methods identified Pa / La vs Ra / La curve re = 0.70917 rt0.82416-0.11556(10)0.02426u(f) Precipitation vs Runoff curve ETc = Kc ETo

  4. Bayview Model Basin Coeur D’Alene 1E Newport Sandpoint Exp. Station Priest River Exp. Station Spokane WSO Airport Mean annual precipitation 16.1 in—Spokane 32.0 in—Sandpoint Mean annual temperature 50.3°F—Bayview 53.4°F—Coeur d’Alene Active NWS stations within 20 miles • Closest AgriMet station is Seven Bays Marina, Washington, (SBMW) 50 mi west of Spokane

  5. Mean monthly recharge • Langbein: • Annual only • ESPAM: • Recharge 1-57% of monthly precipitation • Lava rock > Thin > Thick • USDA: • Recharge 53-73% of monthly precipitation • FAO Penman-Monteith single coefficient (Spokane only): • Recharge 0-93% of monthly precipitation Mean monthly precipitation

  6. Mean annual recharge • Langbein: • Recharge 0-11% of annual precipitation • ESPAM: • Recharge 2-52% of annual precipitation • Lava rock > Thin > Thick • USDA: • Recharge 64-69% of annual precipitation • FAO Penman-Monteith single coefficient (Spokane only): • Recharge 30% of annual precipitation All problematic conceptually or in water budget

  7. Single coefficient FAO: no recharge for summer months—unlikely Monthly time steps assume that there is always sufficient soil moisture to satisfy ET, but: Daily soil moisture will occasionally be insufficient to meet ETc demand, thus actual ET will be less than the calculated ETc For recharge to occur soil moisture has to be replenished: Depends on the amount and timing of individual precipitation events The FAO Penman-Monteith dual-coefficient approach with daily time steps addresses this temporal variation Mass-balance to determine soil drainage/deep percolation/recharge Spreadsheet based Used wind speed from Spokane WSO Airport for all stations What’s wrong with these estimates? ETcd = (Kcb + Ke) ETo

  8. Recharge with 1990-2005 daily values • Daily calculations show timing of precipitation can be more important than the amount • Is this important? It depends on the model and purpose…

  9. Comparison and application • Realistic and defensible • Calculations are for points: • Triangular network-linear interpolation

  10. Recharge from impermeable surfaces • Precipitation on an impermeable surface that runs off to: • a recharge well • an infiltration basin • adjacent permeable surfaces • Assumed that 85% recharges and 15% lost to ET

  11. Reports and links • Report available from the USGS Publications Warehouse at URL: http://pubs.usgs.gov/sir/2007/ 5038/ • Rick Allen’s site: • Includes spreadsheets and links to the FAO report http://www.kimberly.uidaho.edu/ water/fao56/index.html

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