Environmental Engineering Reference
In-Depth Information
Disturbance:
Any relatively discrete event in time that disrupts ecosystem, commu-
nity, or population structure and changes resources, substrate availability,
or the physical environment.
Diversity exchange:
An exchange of capacity or energy, or both, between systems
whose peak loads occur at different times.
Divestiture:
The stripping off of one utility function from the others by selling
(spinning-off) or in some other way changing the ownership of the assets
related to that function. Stripping off is most commonly associated with
spinning-off generation assets so they are no longer owned by the share-
holders that own the transmission and distribution assets.
Downwind turbine:
A turbine that does not face into the wind and whose direction
is controlled directly by the wind.
Drag bit:
Drilling bit that drills by scraping or shearing the rock with fixed hard
surfaces, or
cutters
.
Drainage basin:
The land drained by a river system.
Drawdown:
The lowering of the water level of a reservoir as a result of withdrawing
water.
Drilling:
Boring into the Earth to access geothermal resources, usually with oil
and gas drilling equipment that has been modified to meet geothermal
requirements.
Dry natural gas:
Natural gas that remains after (1) the liquefiable hydrocarbon por-
tion has been removed from the gas stream (i.e., gas after lease, field, and/or
plant separation), and (2) any volumes of non-hydrocarbon gases have been
removed where they occur in sufficient quantity to render the gas unmarket-
able.
Note:
Dry natural gas is also known as consumer-grade natural gas.
The parameters for measurement are cubic feet at 60°F and 14.73 pounds
per square inch absolute.
Dry steam:
Very hot steam that does not occur with liquid.
Dump load:
A device that allows excess energy to be safely disposed of.
E
E-10:
A mixture of 10% ethanol and 90% gasoline based on volume.
E-85:
A mixture of 85% ethanol and 15% gasoline based on volume.
E-95:
A fuel containing a mixture of 95% ethanol and 5% gasoline.
Ecological integrity:
Refers to native species populations in their historic variety
and numbers naturally interacting in naturally structured biotic commu-
nities. For communities, integrity is governed by demographics of com-
ponent species, intactness of landscape-level ecological processes (e.g.,
natural fire regime), and intactness of internal community processes (e.g.,
pollination).
Ecological system:
Dynamic assemblages of communities that occur together on
the landscape at some spatial scale of resolution, are tied together by simi-
lar ecological processes, and form a cohesive, distinguishable unit on the
ground. Examples are a spruce-fir forest, a Great Lakes dune and swale
complex, and Mojave desert riparian shrublands.
