Chapter 20: WATER AND BASIC DESIGN
Summary
This chapter begins with the quote: “The next great world crisis will be water supply.” This sets the stage
for a review of the many roles water plays in our buildings—under the context of increasing population
and water usage. Historically, designers have had to deal with keeping water out of buildings; more
recently they have also had to deal with making it available within buildings. Water can provide
nourishment, be used for general cleaning and personal hygiene, play a ceremonial role, be used to
remove wastes, assist in the cooling of buildings and people, be used ornamentally, and extinguish fires.
Water also is used extensively in the construction of buildings and manufacture of building materials.
The hydrologic cycle describes the continuous process of evaporation, rainfall, runoff, and evaporation
that replenishes the world’s supply of fresh water. Precipitation is a resource (like solar energy, and
climate-dependent) that is generally extensive but diffuse. Runoff can concentrate rainfall and make it
more readily available for human use (although less pristine). Rainwater that penetrates the soil is known
as soil moisture, when it reaches a level where the soil is saturated it becomes groundwater. The upper
surface of the groundwater layer is called the water table.
Planning for water usage involves matching needs with resources. The extent of needs can vary greatly
with philosophy of use—ranging from conventional practice usage patterns to less demanding
conservation practices. Preliminary estimates of water supply requirements can be made on a per capita
basis. Plumbing codes specify fixture requirements for different building types; these are always
minimum acceptable requirements. Water can be supplied by public systems (distribution mains) or
private systems (wells). Rainwater collection may be used as a water source. Cistern sizes and rainwater
capabilities can be estimated for preliminary design purposes.
Sewage may be handled either by private systems (septic tanks, etc.) or by public systems (collection
mains). Sewage flow rates can be estimated on a per capita basis for different occupancy types. Private
sewage disposal methods include septic tanks and drainfields, leaching mounds, and sewage lagoons—
all of which must be properly considered very early in the design process.
Rainwater and its control can influence site design and building design. Gutters, downspouts, and leaders
may be provided to direct rainfall from roof areas. Historically, rainwater was quickly directed off site.
There is a trend, however, for communities to ask or require that runoff problems be solved on site rather
than downstream. Retention of rainwater on roofs for later discharge to the site is one such approach.
The use of pervious surfaces on site, such as porous pavement materials, is another. Water recharge
typically involves holding water on site long enough for it to percolate into the soil; this may involve
trenches, dry wells, basins, or ponds. Site conservation of water resources may lead to the use of
hydrozone or xeriscape landscaping practices.
Chapter Outline
20.1 Water in Architecture
(a) Nourishment
(b) Cleansing and hygiene
(c) Ceremonial uses
(d) Transportation uses
(e) Cooling
(f) Ornamental uses
(g) Protective uses
20.2 The Hydrologic Cycle
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20.3 Basic Planning
(a) Water supply
(b) Cisterns
(c) Required facilities
(d) Sewage
20.4 Rainwater
20.5 Collection and Storage
20.6 Rainwater and Site Planning
(a) Roof retention
(b) Porous pavement
(c) Site design for recharging
20.7 Components
References
Key Concepts
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hydrologic cycle (as a driving force behind water resources)
water characteristics (reflectivity, liquidity, life-sustaining)
potable water (suitable for human consumption)
sewage (sewer; liquid-borne waste)
current and conservation practices (as they differentially affect water demands)
plumbing fixture (as a user of water and supplier of wastes)
cistern (for rainwater storage)
catchment area (the collector size for rainfall resources)
plumbing code (for minimum acceptable practices)
septic tank (a means of private disposal of sewage)
drainfield (an adjunct to the septic tank)
groundwater recharge (as a philosophy for runoff control or good water management)
roof retention ( as a means of reducing runoff)
hydrozone (as a landscape planning concept)
xeriscape (as a landscaping approach)
Terminology and Metrics
Important Terminology
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potable
storm sewer
combined sewer
sanitary drainage (or sewer)
precipitation
runoff
soil moisture
groundwater
water table
cistern
low-flush toilet
porous concrete
incremental paving
open-celled paver
gutter
leader
downspout
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Important Metrics
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g/cd (gallons per capita per day)
[also see Table 20.1 for typical water-related units]
Links to Resources
U.S. Geological Survey, Water Resources of the United States:
http://water.usgs.gov/
A Sourcebook for Green and Sustainable Building (xeriscape):
http://www.greenbuilder.com/sourcebook/xeriscape.html
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