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3.4 TRANSBASIN DIVERSIONS <br />Transbasin diversion records are important as a basic water resource data need and for use in <br />water rights administration and modeling. Transbasin diversions represent a major inflow <br />component of the South Platte River. As with surface water diversion records, transbasin <br />diversion records will be used in the development of baseflows and will also be used to define <br />inflows to the basin for future conditions modeling. Transbasin diversion records are maintained <br />by DWR and also independently by owners/operators of the diversions. The need for a complete <br />and reliable source of historical diversion records available to the State and water users also <br />applies to transbasin diversion records. <br />3.4.1 Description and Inventory of Available Data <br />There are a total of 19 transbasin diversions in the study area for the SPDSS. Table B-3 in <br />Appendix B summarizes the available records from HydroBase for transbasin imports. <br />3.4.2 Data Assessment <br />The available transbasin diversion records were reviewed for spatial coverage throughout <br />Division 1 and Water District 47, period of available records, completeness of available records <br />and overall reliability of the data. <br />3.4.2.1 Spatial Coverage. The transbasin diversions import water into the South Platte <br />River basin from the Colorado, Arkansas and North Platte (including the Laramie) River basins. <br />Diversion records for the 19 transbasin diversions are included in HydroBase. <br />3.4.2.2 Period of Records. The periods of record shown in Table B-3 are somewhat <br />misleading in some cases because some of the structures have operated for several more years <br />than the data indicate. For example, Roberts Tunnel began delivering water to the North Fork of <br />the South Platte River in 1964 but the HydroBase records begin in 1974. It will be necessary to <br />rely upon the owners' records for such periods. <br />3.4.2.3 Completeness of Records. From inspection of Table B-3, the period of record <br />and the data contained in the DWR files, records are not complete for many of the structures. <br />Table B-3 shows the percentage of missing records within the period of record. <br />3.4.2.4 Reliability of Records. The major transbasin diversions are currently equipped <br />with Parshall flumes or similar devices that accurately measure the flow. The available records <br />identify the point where the imports reach the stream but in many cases do not identify the end <br />user or the delivery point. Many of the smaller transbasin imports have changed ownership and <br />end user. Overall, the quality of the transbasin diversion data will only be adequate after the <br />missing data have been filled or estimated. <br />p:data\gen\spdss~final report\chapter 3.doc 3 -10 <br />October 31, 2001 <br />