Hydrologic Analysis - Advanced Hydrology - Lecture Slides, Slides of Aeronautical Engineering

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Hydrologic Analysis

Module 3

6 Lectures

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Module 3

Objective of this module is to introduce the watershed

concepts, rainfall-runoff, hydrograph analysis and unit

hydrograph theory.

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Topics to be covered

 Unit hydrograph theory

 Derivation of UH : Gauged watershed

 S-curve method

 Discrete convolution equation

 Synthetic unit hydrograph

 Snyder’s method

 SCS method

Module 3

(contd..)

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Lecture 1: Watershed and rainfall-runoff

relationship

Module 3

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Watershed concepts Contd…

 Watersheds are characterized in

general, by one main channel and

by tributaries that drain into main

channel at one or more confluence

points

 A “divide” or “drainage divide” is the

line drawn through the highest

elevated points within a watershed

 Divide forms the limits of a single

watershed and the boundary

between two or more watersheds

River

stream

Divide

Sub-catchment or Sub-basin

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• A water divide is categorized into:-
  1. Surface water divide –highest elevation line between basins (watersheds) that defines the perimeter and sheds water into adjacent basins, and,
  2. Subsurface water divide –which refers to faults, folds, tilted geologic strata (rock layers), etc., that cause sub-surface flow to move in one direction or the other.

Surface water divide Subsurface water divide

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Watershed concepts Contd…

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 Land use and land cover: It can affect the overland flow of the

rainwater with the improve in urbanization and increased pavements.

 Main channel and tributary characteristics: It can effect the stream

flow response in various ways such as slope, cross-sectional area, Manning’s roughness coefficient, presence of obstructions and channel condition

 Physiography: Lands altitude and physical disposition

 Socio-economics: Depends on the standard of living of the people and

it is important in managing water

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Characteristics of watershed Contd…

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 A watershed management approach is one that considers the watershed as a whole, rather than separate parts of the watershed in isolation

 Managing the water and other natural resources is an effective and efficient way to sustain the local economy and environmental health

 Watershed management helps reduce flood damage, decrease the loss of green space, reduce soil erosion and improve water quality

 Watershed planning brings together the people within the watershed, regardless of political boundaries, to address a wide array of resource management issues

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Watershed Management

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 Provide for ecosystem governance at appropriate ecological and institutional scales

 Use adaptive management as the mechanism for achieving both desired outcomes and new understandings regarding ecosystem conditions

 Integrate the best science available into the decision-making process, while continuing scientific research to reduce uncertainties

 Implement ecosystem management principles through coordinated government and non-government plans and activities

 Develop a shared vision of desired human and environmental conditions

Module 3

Principles for Watershed Management Contd…

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