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_. __ __ _ r... _ 1 <; i Memorandum to CWCB Page 4 equipment averages ten years. Therefore, in order to continue using the present system to collect and • transmit basic stream flow data, all sets of electronic equipment must be replaced approximately every 10 years. Since DWR operates over 450 total sets of DCP equipment this equates to an average of about 45 replacements per year. This new standard for faster transmission rates for sending data from the stream gages to the central computer has greatly improved the 'real-time' nature of the system. With new high data rate DCPs in operation, data transmission changes from once every four hours to every hour. The cost of new DCPs with the new radios is $2,700. To replace antennas, batteries, gage height sensors, solar panels, wiring, grounding equipment, etc., the total cost per site averages $4200. Flood HardeninglHigh Flow Measurement Sustainability at Existino Stream Gaoes In 2001, a committee of representatives of DWR, CWCB and the USGS evaluated and ranked, using a set of flood warning/monitoring criteria, all satellite monitoring stream gages throughout the State. This ranking has identified prioritized sites where flood-hardening projects would be useful in flood warning and notification. The cost to modify many of these gages to withstand flood events varies considerably. Each site is being evaluated for required modifications to flood harden the gage. Flood hardening, by definition, allows for stream flow data to continue to be transmitted during a flood event. Flood hardening prevents the need to develop a plan to remove all equipment from stream gages prior to their destruction by floods. While this equipment removal saves equipment costs, this does not allow for data transmission during flood events to emergency managers and the public. Flood hardening involves moving or modifying the existing stream gages so that they can continue to operate during flood events. Some times it may be necessary to add a second gage at the site on higher ground so that the low flows needed for accurate water administration can be measured and the high flows of floods also can be measured. Another form of flood hardening involves rebuilding the stream channel so that accurate data will continue io be available during the flood. Often the stream channel becomes scoured or modified to the point that existing relationships between stage and discharge are no longer valid at high flow. Even if the stage data continues to be available, it is of little or no value in determining the flow of the river. High flow measurement capability varies from gage to gage. High flow discharge measurements at DWR stream gages are important for maintaining/updating the high flow portion of the gage's stage- discharge rela#ionship. This calibration consequently improves the accuracy of high flows reported at the gage(s). High flows at stream gages ace measured from cableways at the gage or from nearby up- or downstream bridges. Cableways at DWR stream gages are given a detailed inspection each four years. During the past 4 years many cableways, primarily because of age, have been found to need replacement of key components of t~i~ ~blesray system, High flow measurement sustainability projects address such ident~ed cableway design/safe use issues. These may include replacement of cable, improvements to the cable anchorage system, replacement of A-frame components, replacement of cable cars, etc. Alternatively, existing cableways found to have design or safe use deficiencies are, under certain site conditions, being replaced with bank-operated cableways. High flow measurements are facilitated with new technology measuring equipment: Acoustic Doppler Current Profilers (ADCPs). This technology provides for more rapid, safer, and often more accurate measurement of stream flow. DWR is employing this technology to help verify and extend the middle and upper ranges of the stage-discharge relationship at key gages. r~ \J