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Home My WebLink AboutOASIS_Overview_-_HydrologicsOverview of OASIS Overview of OASIS Brian J. McCrodden, P.E. November 27, 2012 Brian J. McCrodden, P.E. November 27, 2012 Ecological Flows Science Advisory Board Topics •What is OASIS? •Inflow development/verification •Strengths •Weaknesses 2 What is OASIS? •A patented, mass balance, water resources simulation/optimization model •Runs on a daily timestep with a 75+ year period of hydrologic record •Runs in two modes •Simulation •Position Analysis •Purposes: –Alternatives evaluation (planning/finding balance) –Real-time operations (following the plan) –Gaming Nodes and Arcs 4 Model Input •Time series data –Unregulated inflows –Evaporation –Precipitation •Static data –Physical data • Reservoir SAE, turbine characteristics, channel capacities, etc. –Withdrawals, discharges, demands •Operating Data, e.g. –Rule curves –Minimum releases/environmental flows –Drought and flood management policies –Energy requirements Model Output •Tables and Graphs of –Flow –Elevation, and –Derived attributes, e.g.habitat availability, energy, revenue, water supply shortages, recreation days for every time step at every point in the system Inflow Development •Unimpaired (unregulated, unaltered) inflows necessary for evaluating alternative facilities, operating policies and demand levels •Impairments include water withdrawals/discharges and reservoir regulation (including net evaporation) •Methodology: Force inflows to match monthly unimpaired gage flows; disaggregate to daily based on a proximate unimpaired gage 7 Gages Used USGS Number Description Period of Record Drain. Area 02081500 TAR RIVER NEAR TAR RIVER, NC 10/1939-present 167 02081747 TAR R AT US 401 AT LOUISBURG, NC 10/1973-present 427 02081800 CEDAR CREEK NEAR LOUISBURG, NC 10/1956-09/1975 47.8 02082000 TAR RIVER NEAR NASHVILLE, NC 10/1928-01/1971 701 02082506 TAR R BL TAR R RESERVOIR NR ROCKY MOUNT, NC 08/1972-present 777 02082770 SWIFT CREEK AT HILLIARDSTON, NC 08/1963-present 166 02082950 LITTLE FISHING CREEK NEAR WHITE OAK, NC 10/1959-present 177 02083000 FISHING CREEK NEAR ENFIELD, NC 10/1926-present 526 02083500 TAR RIVER AT TARBORO, NC 10/1931-present 2,183 02083800 CONETOE CREEK NEAR BETHEL, NC 12/1956-06/2002 78.1 02084000 TAR RIVER AT GREENVILLE, NC 04/1997-present 2,660 8 Gage Map Gage has significant impairment (2007 average flow and monthly minimum flow) Gage has little or no impairment Tar R. nr Tar R. (72 cfs, 0 cfs) Gage has moderate impairment Cedar Ck. Tar R. Louisburg (215 cfs, 4 cfs) Tar R. Nashville Tar R. Reservoir (399 cfs, 10 cfs) Tar R. Tarboro (1,164 cfs, 38 cfs) Tar R. Greenville (1,297 cfs, 31 cfs) Swift Ck. (93 cfs, 3 cfs) Fishing Ck. (245 cfs, 3 cfs) Conetoe Ck. 9 Gage Timeline 0 1 2 3 4 5 6 7 8 9 10 11 19301935194019451950195519601965197019751980198519901995200020052010 Ga g e R e f e r e n c e N u m b e r Timeline for Gage Data Greenville Conetoe Tarboro Fishing Little Fishing Swift Reservoir Nashville Cedar Louisburg Tar River 10 Unimpairing Inflows •Instream nodes (e.g., stream gaging sites) –Adjust inflows for upstream withdrawals and returns •Reservoirs –Use drainage-area adjusted, unimpaired stream gages immediately upstream –Otherwise, back-calculate from reservoir outflows and change in storage, adjust for upstream impairments 11 Developing Inflows (cont’d.) •Inflow records modified to eliminate negatives caused by time of travel issues and errors in impairments •Fill in missing inflow records by correlating with unimpaired inflows at other nodes –USGS Fillin program computes correlations on a monthly basis –Filled-in records must be scaled to ensure that actual unimpaired flow at downstream points is preserved •Monthly flows/gains disaggregated to daily flows using local unimpaired gage to preserve natural variation –Impairment data is often only available on a monthly average, and can cause noise on a daily basis –Tidal influence at Greenville can impact daily readings –Goal: to build daily flows whose variation is representative of history while preserving monthly gage flows as ground truth 12 Spreadsheet Showing Gage Unimpairment 13 Verification -Tarboro Flow, Monthly Unimpaired Gage = daily gage flow adjusted for impairments upstream Naturalized Inflow = monthly unimpaired gage flow disaggregated to daily to preserve natural variation 14 0 50 100 150 200 250 300 350 400 450 500 550 600 650 700 750 800 850 900 950 1000 1/1/2001 2/1/2001 3/1/2001 4/1/2001 5/1/2001 6/1/2001 7/1/2001 8/1/2001 9/1/2001 10/1/2001 11/1/2001 12/1/2001 cf s Unimp. Gage Naturalized Inflow Gage Flow Verification - Tarboro Flow, Daily Unimpaired Gage = daily gage flow adjusted for impairments upstream Naturalized Inflow = monthly unimpaired gage flow disaggregated to daily to preserve natural variation 0 50 100 150 200 250 300 350 400 450 500 550 600 650 700 750 800 850 900 950 1000 1/1/2001 2/1/2001 3/1/2001 4/1/2001 5/1/2001 6/1/2001 7/1/2001 8/1/2001 9/1/2001 10/1/2001 11/1/2001 12/1/2001 cf s Unimp. Gage Naturalized Inflow Gage Flow 15 Verification – Tar River Reservoir 16 Strengths •A systems approach –All management aspects captured, including WSRP –Allows for investigation of creative solutions •It’s fast •It’s easy to use •Can be linked to other models •Nodes and arcs can be added after the model is “done” 17 Weaknesses •No output between inflow nodes •Not appropriate for flood routing •Stationarity ? 18 19 Questions?