Igneous rockA crystalline rock formed by the cooling and solidification of molten or partly molten material (magma).
ImpactThe effect, influence, alteration, or imprint caused by an action.
ImpermeableRefers to a rock matrix that water cannot infiltrate.
ImpingementThe entrapment of aquatic organisms on the outer part of an intake structure or against a screening device during periods of intake water withdrawal.
IMPLANInput-output economic model based on economic accounts showing the flow of commodities to industries from producers and institutional consumers.
Impoundment (surface)A body of water or sludge confined by a dam, dike, floodgate, or other barrier.
Impulsive noiseNoise from impacts or explosions (e.g., from a pile driver, forging hammer, punch press, or gunshot), which is brief and abrupt, and its startling effects…
In attainmentIn compliance with air-quality standards. Areas that are in attainment have air quality that is as good as or better than specified in the National…
In situ(in si'too) the natural or normal place; confined to the site of origin without invasion or spread to neighboring tissues.
Incidental take permitA permit issued under Section 10 of the Federal Endangered Species Act to private parties undertaking otherwise lawful projects that might result in the…
Indian trust assetsLands, natural resources, or other assets held in trust or restricted against alienation by the United States for Native American tribes or individual…
Indian trust resourcesThose natural resources, either on or off Indian lands, retained by or reserved by or for Indian tribes through treaties, statutes, judicial decisions…
Indirect effectsSecondary effects that occur in locations other than that of the initial action or significantly later in time.
Indirect impactsImpacts that occur away from the place of origin. Effects that are related to, but removed from, a proposed action by an intermediate step or process.
IndurationThe hardening of a rock, usually sedimentary, by drying, pressure, or cementation.
Industrial wasteMaterials discarded from industrial operations or derived from manufacturing processes.
InfiltrationLeakage of ground water into a sewage collection system.
Infiltration pondA shallow impoundment designed to infiltrate stormwater into the soil. Also referred to as an infiltration basin.
InflowWater (and pollutants) that enter sewage systems through street inlets, roof drains, and similar sources.
Inset fansAn alluvial fan that occurs on top of an older alluvial fan.
InsolationThe solar power density incident on a surface of stated area and orientation, usually expressed as Watts per square meter or Btu per square foot per hour.
IntaglioAn impression, design, or figure created on the ground by man through the placement of rocks or mounding of earth.
Interbasin flowSurface water or groundwater flow between two hydrologic basins.
Interbasin transfer of waterA transfer of water rights and/or a diversion of water (either groundwater or surface water) from one drainage or hydrographic basin to another.
Interdune flatThe area between dunes, generally flat and often erosion-resistant.
Intermittent StreamA stream that flows for a portion of the year but occasionally is dry or reduced to a pool stage when losses from evaporation or seepage exceed the…
Intermontane basinAn alluvium-filled valley between mountain ranges, often formed over a graben.
Interpretive siteInformation communicated via plaques, markers, and other methods, about the natural and/or cultural resources, their history and values, that are found at…
IntrusiveAn igneous rock that forms under the Earth's surface. Examples include granite, diorite, and gabbro.
Invasive speciesAny species, including noxious and exotic species, that is an aggressive colonizer and can out-compete indigenous species.
InvertebrateAn animal, such as an insect or mollusk, that lacks a backbone or spinal column.
InverterA device that converts direct current electricity (from for example a solar photovoltaic module or array) to alternating current for use directly to…
IrradianceThe direct, diffuse, and reflected solar radiation that strikes a surface.
IrrigationThe controlled application of water for agricultural purposes through manmade systems to supply water requirements that are not satisfied by rainfall.
Irrigation Non-Expansion Area (INA)A geographic area in Arizona that has been designated as having insufficient groundwater to provide a reasonably safe supply for the irrigation of the…