Laserfiche WebLink
<br />. <br /> <br />. <br /> <br />June 2, 1997 <br />Page 2 <br /> <br />On the Purgatoire it was widely believed that transit losses on the lower 100 miles were enol'l11.oU <br />and the PRWCD hoped to establish that a "negative transit loss" should be applied to exchanges th ~ <br />kept water out of that losing reaching (i,e, PRWCD would deliver say 80 AF to JMR via tha <br />mainstem and store 100 AF at Trinidad, since the other 20 AF would have been lost anYway)e <br />Without agreeing that such a negative transit loss was appropriate or feasible the CWCB did agre' <br />that a better understanding of actual losses and traveltimes would be beneficial to improving rive e <br />operations and might assist the Division Engineer in making futile call decisions on the Purgatolrer <br />The CWCB obtained authorization to make grants to defray 50% of the PRWCD's Costs I~ <br />cooperating with USGS on the study (final approximate cost allocation: USGS 50%, ARCA 10/. <br />CWCB 24,5%, PRWCD 24.5%), 0, <br /> <br />Since little was known about the Purgatoire system under a full range of flow conditions It Wa <br />decided to divide the study into two phases, The first phase, just completed, looked at previous <br />studies and perfonned an analysis of existing data in an attempt to synthesize a set of traveltime an~ <br />loss/gain relationships without costly field work and data collection, All parties agreed that a Phas <br />2 Study, using field observation, data collection, and intensive modeling, would only be undertake~ <br />if Phase I indicated that Phase 2 would be warranted and cost-effective, To date no decision 0 <br />Phase 2 has been made pending PRWCD's review of the Phase I final report, CWCB staff believe: <br />based on its initial review of the Phase 1 report, that it is unlikely that a Phase 2 Study WOuld add <br />significant refinements to the Phase I findings in a cost-effective manner. <br /> <br />Phase 1 Findings: <br />The USGS concluded that earlier studies had focused on specific locations and hydrologic conditions <br />and could not be used to establish general relationships between flow, traveltime, and loss/gain OVer <br />the 160 river miles from Trinidad to the confluence with the Arkansas near Las Animas. <br /> <br />USGS divided the 160 mile study area into three reaches: <br />Reach I From Trinidad Reservoir to Thatcher, 60,6 miles with 19,700 acres of land irrigated <br />with the PRWCD, <br />From Thatcher to Rock Crossing, 40,1 miles of the Purgatoire Canyon, <br />From Rock Crossing to the confluence near Las Animas, 58,5 miles with 4,500 <br />irrigated acres at the lower end, <br />USGS looked at two district periods ofrecord, 1984-92 and 1957-67. The period 1968-83 Was <br />excluded due to missing data and Trinidad project development and startup, <br /> <br />Reach 2 <br />Reach 3 <br /> <br />In Reach I, variable diversions and unmeasured return flows occurring within the PRWCD mad <br />analysis of existing data for traveltime and loss/gain impossible, However, in this reach the Proje ~ <br />ditches are generally operated as an integrated system in cooperation with the PRWCD and preci C <br />knowledge of travel times and gains/losses may not have much practical value. se <br /> <br />C:\SRMILLER\ARKANSAS\PROJECTS\TRANSI1\PUROl'Lo <br />J,M13M <br />JIIII'4.1991 <br />