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Calculation of Abstractions Using GIS

Calculation of Abstractions Using GIS. Gaurav Garg CVEN 689 Dept Of Civil Engg. Presentation Objectives. Definition of Abstractions. Methodology Data Gathering Data Processing using GIS Analysis using MS-Excel Interpretation with GIS Results. Abstractions.

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Calculation of Abstractions Using GIS

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  1. Calculation of Abstractions Using GIS Gaurav Garg CVEN 689 Dept Of Civil Engg

  2. Presentation Objectives • Definition of Abstractions. • Methodology • Data Gathering • Data Processing using GIS • Analysis using MS-Excel • Interpretation with GIS • Results

  3. Abstractions The part of the precipitation that does not contribute to the runoff. It includes- • Infiltration • Depression Storage • Interception • Evapo-Transpiration

  4. Infiltration Techniques • Richard’s Equation • Horton’s Method • Green and Ampt Method • SCS Curve Number Method • Initial loss plus Constant loss Method

  5. Data Collection • DEM for delineating watersheds • STATSGO – Soils Data Polygons • NWS – Weather Stations Points • Green-Ampt parameters ( Clapp and Hornberger 1978) • Assumed Uniform Precipitation

  6. Delineating Watersheds Using CRWR-Prepro Main steps involved: - • Flow Direction • Flow Accumulation • Stream Network • Delineate Watersheds

  7. Guadalupe Watershed Texas STATSGO Intersection

  8. Watershed-STATSGO Soils Intersection

  9. Procedure of Calculating Infiltration • Green-Ampt Model Assumptions: • Soil is homogeneous with depth. • Infiltration wetting front is perfectly sharp and is same everywhere in horizontal. For this project a constant precipitation of 6cms for 2 hrs has been assumed.

  10. Green-Ampt Equation • f(t) = Kh [1+( |Ψf|*(Φ-θ0)] F(t) f(t) = infiltration at time t F(t) = cumulative infiltration Kh = Hydraulic conductivity |Ψf|= Suction Head (Φ-θ0)= Change in moisture content

  11. Infiltration Results

  12. Infiltration Results

  13. Movement of Wetting Front

  14. Questions

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