Calculation of abstractions using gis
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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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Calculation of abstractions using gis

Calculation of Abstractions Using GIS

Gaurav Garg

CVEN 689

Dept Of Civil Engg


Presentation objectives

Presentation Objectives

  • Definition of Abstractions.

  • Methodology

    • Data Gathering

    • Data Processing using GIS

    • Analysis using MS-Excel

    • Interpretation with GIS

  • Results


Abstractions

Abstractions

The part of the precipitation that does not contribute

to the runoff.

It includes-

  • Infiltration

  • Depression Storage

  • Interception

  • Evapo-Transpiration


Infiltration techniques

Infiltration Techniques

  • Richard’s Equation

  • Horton’s Method

  • Green and Ampt Method

  • SCS Curve Number Method

  • Initial loss plus Constant loss Method


Data collection

Data Collection

  • DEM for delineating watersheds

  • STATSGO – Soils Data Polygons

  • NWS – Weather Stations Points

  • Green-Ampt parameters ( Clapp and Hornberger 1978)

  • Assumed Uniform Precipitation


Delineating watersheds

Delineating Watersheds

Using CRWR-Prepro

Main steps involved: -

  • Flow Direction

  • Flow Accumulation

  • Stream Network

  • Delineate Watersheds


Calculation of abstractions using gis

Guadalupe Watershed

Texas STATSGO

Intersection


Watershed statsgo soils intersection

Watershed-STATSGO Soils Intersection


Procedure of calculating infiltration

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.


Green ampt equation

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


Calculation of abstractions using gis

Infiltration Results


Calculation of abstractions using gis

Infiltration Results


Calculation of abstractions using gis

Movement of Wetting Front


Calculation of abstractions using gis

Questions


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