27a (2) - Laserfiche WebLink

Home Browse Search

DWR and CWCB Flood Hardening of Existing Stream Gages Page 3 once per four hours to once per hour) transmission of data from remote sites to the central computer. This has resulted in near ‘real-time’ dat a on the system. The current equipm ent costs of a high data rate DCP upgrade with the new GOES transceivers, antennas, batteri es, gage height sensors, solar panels, wiring, and grounding equipment for a standard stilling well type gage st ation is just under $5000. It is projected that the entire DWR SMS system will be upgraded to high data rate by the end of FY2009-10. Beyond that point in time, requests to CWCB for the SMS satellite teleme try equipment will be of a maintenance nature rather than complete upgrades. Refurbishment of Existing Stream Gages DWR requests $55,000 for refurbishing existing st ream gages in FY2009-10. Approximately 60% of Colorado’s satellite-linked gaging stations are located in the rivers and str eams of the state. The others are located in reservoirs, ditches, and c anals. The electronic equipment is attached to mechanical equipment in and along the stream channel, and electronically rela ys the data sensed by t he mechanical measuring devices. If the mechanical equipment and associated st ream gage structures (shel ters, stream controls, independent reference gages, etc.) ar e not properly maintained and periodically refurbished, data quality and accuracy diminishes. Flood Hardening/High Flow Measurement Su stainability at Existing Stream Gages DWR and CWCB jointly request $50,000 for cont inued flood hardening of existing stream gages and enhanced high flow measurement capacity in FY2009-10. 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 eval uated 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 devel op a plan to remove all equipment from stream gages prior to their destruction by floods. While th is equipment removal saves equipment costs, this does not allow for data transmiss ion during flood events to emergenc y managers and the public. Flood hardening involves moving or modify ing the existing stream gages so t hat they can continue to operate during flood events. In some cases, it may be necessary to add a second gage at the site on higher ground so that the low flows needed for accurate wa ter 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 to be av ailable during the flood. Often the stream channel becomes scoured or modified to the point that existing relations hips between stage and discharge are no longer valid at high flow. Even if t he stage data continues to be available, it is of little or no value in determining the flow of the river. High flow measurement capability va ries from gage to gage. High flow discharge measurements at DWR stream gages are important for maintaining/updat ing the high flow portion of the stage-discharge relationship for the gage. This ca libration consequently improv es the accuracy of high flows reported at the gage(s). High flows at stream gages are measured from cableways at the gage or from nearby up- or downstream bridges. Cableways at DWR stream gages are given a detailed inspec tion 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 he cableway system. High flow meas urement sustainability projects address such identified cableway des ign/safe use issues. These ma y include replacement of cable, improvements to the cable anchor age system, replacement of A-fr ame components, replacement of cable cars, etc. Alternatively, existing cableways found to have desi gn or safe use deficiencies are, under certain site conditions, being replaced with bank-operated cableway s. High flow measurements are facilitated with new technology measuring equipment: Acoustic D oppler Current Profilers (ADCPs).