Urban Regions : Ecology and Planning Beyond the City

Water in urbanregions 161

Lake

Distant

(>50-100)

Nearby

(>15-50)

Adjacent

(0-15)

Reservoir River Stream Groundwater

Ber+

Can•

Atl• Abe•

Te g•

Eas•

Kag•

Ott•

Chi+

Bra+

Bra+

Sto+ Sdt+

Bar+

Edm•

Ban*

Bam+

Phi+

Por•

Iqu•

Nai+

Bei*

Mos*

Te h*

San*

Lon*

Seo*

Primary water-supply source for city

Distance to water-supply source (km)

Figure 6.15Distance from city center to water-supply source relative to type of

watersupply. Brasilia is listed twice because water pollution in an adjacent large

reservoir has effectively caused the construction of distant small reservoirs.

10 km = 6.2 mi. See Figure 6.2 for city information.

Since cities typically grow in population and spread outward, alternatives for
watersupply are important for stability. Two suitable sources are much better
than one, and three are somewhat better than two. Large reservoirs for large
cities are hard to locate and create, so their protection is especially important.
Medium cities typically have more options, but probably should plan for when
theymay be large cities. Small cities normally have still more options, but may
have limited resources to locate and create water supplies for a future medium-
sized city. Providing adequate alternatives to supply a future larger city popula-
tion with clean water is apriority.Some cities doubtless benefit from a nearby
large aquifer which must be protected with vegetation cover.

[W13]On average, reservoirs have the best drainage-area protection by natural vegetation,
while drainage-area protection for lakes and rivers varies widely(Figure6.16).

Reservoirs usually have an upstream drainage basin and headwater stream
network that should be protected. Without adequate land protection, rapid
stream erosion, reservoir sedimentation, and loss of reservoir water capacity is