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# Calculation of Abstractions Using GIS - PowerPoint PPT Presentation

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

Gaurav Garg

CVEN 689

Dept Of Civil Engg

• Definition of Abstractions.

• Methodology

• Data Gathering

• Data Processing using GIS

• Analysis using MS-Excel

• Interpretation with GIS

• Results

The part of the precipitation that does not contribute

to the runoff.

It includes-

• Infiltration

• Depression Storage

• Interception

• Evapo-Transpiration

• Richard’s Equation

• Horton’s Method

• Green and Ampt Method

• SCS Curve Number Method

• Initial loss plus Constant loss Method

• DEM for delineating watersheds

• STATSGO – Soils Data Polygons

• NWS – Weather Stations Points

• Green-Ampt parameters ( Clapp and Hornberger 1978)

• Assumed Uniform Precipitation

Using CRWR-Prepro

Main steps involved: -

• Flow Direction

• Flow Accumulation

• Stream Network

• Delineate Watersheds

Texas STATSGO

Intersection

• 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.

• f(t) = Kh [1+( |Ψf|*(Φ-θ0)]

F(t)

f(t) = infiltration at time t

F(t) = cumulative infiltration

Kh = Hydraulic conductivity