Grady HillhouseM. Eng. Water Resources EngineeringTexas A&M University

Hydraulic Modeling of Water Distribution Systems

IntroductionA large percentage of EWB

projects involve water.Many of these project include a

transmission or distribution component.

A basic understanding of pressure conduit hydraulics is essential when designing water infrastructure.

In situations where solving pipe networks is too complex, modeling becomes necessary.

OutlineIntroduction to pressure conduit hydraulicsIntroduction to EPA NETBasics of Modeling

Only an introductionIf you have questions, ask!

Pressure Conduit HydraulicsSummed up in two equations:

zg

vP

2

2

constant

21 QQ

Head Loss

Lhzg

vPz

g

vP 2

222

1

211

22 Darcy-Weisbach head loss equation

g

v

D

LfhL 2

2

Head Loss (cont.)

vD

Re

Pipe Networks

Demand

Solving Pipe Networks

outin QQ

Continuity at nodes

Solving Pipe NetworksFixed grade node paths

Solving Pipe NetworksLoop Equations

Hydraulic Grade LineTotal energy less velocity head

EPANET

Public domain (free!)

Relatively simple

Uses the gradient method to solve pipe networks for flows and pressures.

Components in ModelsNode – junction between other model elements.

Can have external demands.Pipe – convey water between nodes.Reservoir – infinite source of water with a

constant or periodically changing water surface elevation.

Tank – stores water . Water surface is at atmospheric pressure.

Pumps – impart energy to waterValves – various methods of controlling flow or

pressure

SkeletonizationDepending on the complexity of the system

you’re modeling, in may benefit you to simplify the model.

What you provide the model

Layout and parameters of infrastructure

DemandsInitial conditions

What the model provides for you

Flow rates in pipes and tanks

Pressures at nodes

Examples

Final NotesA model is only as good as the input data you

provide.Reference the user’s manual!Never ask the model to do something you

don’t understand.Always verify results by checking with hand

calculations.Questions?