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groundwater resources of the South Platte River basin. The data collection effort for the <br />streamflow data should therefore concentrate on identifying the key streamflow gages in the <br />basin and determining missing streamflow records at these key gages. Missing streamflow <br />records could be filled using the same techniques utilized in the CRDSS and RGDSS. <br />3.2.3.2 Real-Time Streamllow and Diversion Gages. Real-time streamflow and <br />diversion data are integral to administration of South Platte River water rights. Interviews of the <br />Division 1 Engineer and water users indicate that there is need for eight new streamflow gages to <br />assist in administration of the basin, as well as satellite-monitoring systems on twelve key <br />ditches in the basin. These ditches have continuous recording capabilities but are not currently <br />on the State's satellite-monitoring network. These ditch monitoring systems are needed to <br />provide better information to water users, assist in administering Water District 64 and provide <br />more accurate and timely data from remote transbasin diversions. Table 3-1 at the end of this <br />chapter summarizes the additional real-time stations required to meet the needs identified in <br />Chapter 2. <br />Real-time streamflow and diversion data are expected to be accessible through an administration <br />tool as part of the SPDSS. This tool could either take a form similar to the Colorado River Water <br />Rights Administration Tool (CWRAT) or the South Platte Water Rights Management System, or <br />simply be an enhancement of these existing tools. Other than the additional streamflow stations <br />indicated in this chapter and real time diversion and call information indicated in subsequent <br />chapters, the administration tool will not require additional streamflow data collection during the <br />Phase I data collection period. <br />3.2.3.3 Rated Control Section Streamllow Gages. The Division 1 Engineer has also <br />expressed the need, if cost effective, for three rated control sections on the mainstem of the South <br />Platte River to replace the existing gages near Kersey, Balzac and Julesburg in support of the <br />administrative and surface water models. These rated control sections are included in Table 3-1. <br />Streamflow gages are currently operated at these sites; however, extensive care is needed at all <br />three locations to maintain reliability, thereby resulting in significant operation and maintenance <br />costs. For water administration, existing gaging stations have been typically located at Water <br />District boundaries. Unfortunately, many of these locations in Division 1 were not hydraulically <br />stable and "shifts" in the rating curves occur every time the stream rises or falls. This instability <br />is especially problematic because the three gages mentioned above are located below bridges, <br />which constrict the flow and aggravate scour/fill processes. The instability also limits the <br />usefulness of these gages to monitor flood flows because flow at a specific flood stage can vary <br />widely from event to event. Flow data during high water will often show discontinuities because <br />of shifts in the rating curve. <br />If implemented, the existing gages would be moved away from the unstable cross-sections below <br />bridges, but there would still be the general instability of gaging a sand channel. Establishing a <br />stable rating curve over a full range of low and high flow conditions in a sand channel can be <br />difficult. Discussions with the USGS have indicated a permanent stable rating curve over a full <br />range of low and high flow conditions may not be achievable at a reasonable cost. However the <br />ability to develop an improved rating curve, particularly at the low flows required for Compact <br />p:data\gen\spdss~final report\chapter 3.doc 3-4 <br />October 31, 2001 <br />