F. X. Browne, Inc. Glossary - J

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JACKSON TURBIDITY UNIT (JTU)—The JTU is a measurement of the turbidity, or lack of transparency, of water. It is measured by lighting a candle under a cylindrical transparent glass tube and pouring a sample of water into the tube until an observer looking from the top of the tube cannot see the image of the candle flame. The number of JTU's varies inversely and nonlinearily with the height of the sample (e.g., a sample which measures 2.3 cm has a turbidity of 1,000 JTU's whereas a sample measuring 72.9 cm has a turbidity of 25 JTU's).

JAR TEST—A laboratory procedure that simulates a water treatment plant's coagulation/flocculation units with differing chemical doses, mix speeds, and settling times to estimate the minimum or ideal coagulant dose required to achieve certain water quality goals.

JET—A forceful stream of fluid (as water or gas) discharged from a narrow opening or a nozzle.

JET STREAM—A high-speed, meandering wind current, generally moving from a westerly direction at speeds often exceeding 400 kilometers (250 miles) per hour at altitudes of 15 to 25 kilometers (10 to 15 miles). In the Western United States, the jet stream's north-south latitudinal position largely determines the application and intensity of precipitation during the winter months when most rain and snowfall occur.

JETTY—A structure extending into a sea, lake, or river to influence the current or tide, in order to protect harbors, shores, and banks.

JIG—An apparatus for cleaning or separating crushed ore by agitation in water.

JOINT-USE CAPACITY—That reservoir capacity which has been assigned to flood control purposes during certain periods of the year and to other purposes during other periods of the year.

JOINT-USE STORAGE—Reservoir storage space which is used for more than one purpose. The operation may follow a fixed predetermined schedule or may be flexible and subject to adjustment, depending upon particular hydrologic conditions.

JOULE—A unit of energy or work equivalent to one watt per second, 0.737 foot-pounds, or 0.238 Calories, or 9.484 X 10-4 British Thermal Unit (BTU).

JURISDICTIONAL WETLAND—An area that meets the criteria established by the U.S. Army Corps of Engineers (Corps or COE) for a Wetlands (as set forth in their Wetlands Delineation Manual). Such areas come under the jurisdiction of the Corps of Engineers for permitting certain actions such as dredge and fill operations. See Wetlands. [Also see Classification of Wetlands and Deepwater Habitats of the United States, U.S. Department of the Interior, Fish and Wildlife Service (USFWS). Appendix W-3 presents a summarization of this Wetland and Deepwater Habitat Classification System based upon USFWS criteria.]

JUVENILE WATER—Water brought to the surface or added to underground supplies from magma.