ponds and dams in the pedernales river basin n.
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Ponds and Dams in the Pedernales River Basin

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  1. Ponds and Damsin thePedernales River Basin John Middleton CE 394K.2 May 2005

  2. Project Goal Develop a simple water balance model to predict water levels in various storage structures. • Simple to use • Data readily available • Works Challenges • How to calibrate

  3. Motivation • Ponds and dams on family property • Roy Bedichek’s idea of “little waters” as habitats

  4. Analyze a progression of storage systems Cistern Tank Dam on intermittent creek Dam on river Approach

  5. Pedernales Watershed You Are Here Pedernales River Basin: 1294 mi²

  6. Upper Fall Creek

  7. Tools ArcGIS Watershed areas Landcover estimates Mathcad Infiltration model Excel Water balance calculations Data Precipitation NCDC, TWDB Evaporation TWDB Wells TWDB Flow USGS Miscellaneous – LCRA pubs, textbooks, Dad Tools and Data

  8. Plan A • Develop a monthly water balance in Excel • Infiltration – Mathcad Green-Ampt 2-layer model • Runoff estimates using SCS curve • Estimate demand based on published livestock consumption numbers • Assume storage volumes have uniform depth and vertical sides

  9. Cistern P - E - D Earthen Tank P - E - I - D + R Dam on Creek P - E - I - D + R + B P = Precipitation E = Evaporation D = Demand I = Infiltration R = Runoff B = Base Flow In Water Balance

  10. Plan B • Use daily rain data 1st Approach used mean monthly data • Problems with SCS model – single rain value not representative of the rain distribution

  11. Tank Catchment • Drainage: 235 acres • Tank depth: 8ft • Tank area: 1000 ft2

  12. Google Maps is Cool

  13. Spreadsheet Model

  14. Cistern/Tank Model Drainage: 235 acres Depth: 8ft Area: 1000 ft2 Start Depth: 8ft

  15. Cistern/Tank Model Drainage: 235 acres Depth: 8ft Area: 1000 ft2 Start Depth: 0ft

  16. Cistern/Tank Model Drainage: 235 acres Depth: 8ft Area: 1000 ft2 Start Depth: 0ft

  17. Upper Fall Creek Dam Catchment • Drainage: 3852 acres • Depth: 6ft • Tank area: 23,774 ft2

  18. Dam Model Drainage: 3582 acres Depth: 6ft Area: 23,774 ft2 Start Depth: 6ft

  19. Conclusions • Cistern/Tank model appears reasonable • Dam model • Difficult to calibrate • Creek baseflow not known • Runoff/infiltration model may be overly simplistic • Excel is good, but I’m tired of it

  20. Model Improvements • Infiltration model – convert to VB routine • SCS method needs daily data • Spring flow estimates • Shape of storage structure • NARR for evaporation • Doppler for rainfall • Improved runoff method

  21. Questions?

  22. Pedernales Basin

  23. Cistern/Tank Model Drainage: 235 acres Depth: 8ft Area: 1000 ft2 Start Depth: 0ft