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<br /> <br />There are a variety of river gage styles in use. Some are very <br />simple, such as staff gages placed on the banks of a river or wire <br />weight gages usually found on bridges. These simple gages must <br />be manually read by trained personnel. Other gages are more <br />complex. These include bubble gages and still-well float gages. <br />The more complex gaging systems are usually automated and <br />continually monitor the water level of the river. River stage <br />information may be transmitted to data sites by telephone or radio <br />systems or stored on site. <br /> <br />Notes <br /> <br />Except staff gages, river monitoring sites are secured to protect <br />the valuable equipment from damage or theft. Local officials may <br />obtain permission to access gage sites from the servicing USGS <br />station, particularly if the sites are not automated. Training should <br />be obtained from the National Weather Service or USGS on proper <br />reading and reporting procedures for the gage sites in their <br />community. <br /> <br />Information from river gages is used by the National Weather <br />Service to determine the volume of water flowing in the river. The <br />water flow is uSually expressed in cubic feet per second (CFS). <br />One cubic foot per second is equivalent to approximately 7.5 <br />gallons per second. Volumetric information can then be used to <br />determine water levels and issue river forecasts. <br /> <br />The National Weather Service also uses data from other <br />sources including, rainfall reports, soil saturation information, <br />snow depth information, temperature readings, etc. to issue river <br />forecasts. Depending on the river system and the amount of data <br />available, these forecasts may be highly detailed stage forecasts or <br />general warning statements on anticipated flood threats. ' <br /> <br />Using this information, the National Weather Service issues <br />two types of emergency flood forecasts. These are the flood watch <br />and the flood warning. A flood watch is issued when conditions <br />are favorable for flooding. The watch does not mean that flooding <br />will definitely occur, but it does give a community an alert of a <br />potential flood threat. <br /> <br />A flood warning is issued when flooding conditions are <br />expected. The flood warning will usually be accompanied by a <br />predicted flood height expressed as river stage or height above <br />flood stage. National Weather Service forecasters strive to issue <br />flood forecasts with an accuracy of plus or minus one foot. <br /> <br />But there are many variables that can enter into this forecast. <br />Some of these variables are difficult to predict, yet have great <br /> <br />Page 1 - 7 <br />