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Key Water Development Events <br />Water resource developments have the potential to complicate data analysis and study period <br />selection. For example, structures and operations that are introduced in the middle of the study <br />period will have implications for definition of the system baseline. Developments in the Rio <br />Grande Basin have included both physical and institutional features, such as additional storage, <br />pumping and conveyance structures, and legal and administrative activities. Table 7 provides a <br />summary of several key water development events occurring in the basin since the mid-1800s. <br />Several of these events are discussed below as they relate to data analysis and selection of the <br />RGDSS study period. <br />Rio Grande Compact <br />The Rio Grande Compact was ratified by the states of Colorado, New Mexico and Texas in 1939. <br />During the period 1939 through the late 1960s, water deliveries by Colorado to the New Mexico <br />state line fell short of the requirements set forth by the Compact. By 1968, Colorado had <br />accumulated a debt of nearly 1 million acre-feet. In 1968, Colorado began efforts to strictly <br />administer water rights such that Compact obligations would be met each year. This <br />administration resulted in the curtailment of numerous water users along the Rio Grande and <br />Conejos River. In 1985, Elephant Butte Reservoir in New Mexico spilled, thereby eliminating <br />(pursuant to the Compact) the large debt accrued through the 1960s. Colorado has continued its <br />administrative practice of meeting state line delivery obligations on an annual basis. <br />It is important to note the differences between early Compact administration and the practices of <br />Colorado since the late 1960s because of their effect on divertable supply available to Colorado <br />water users. These changes in administration have essentially reduced the amount of water that <br />farmers can divert and are so reflected in the historical diversion records. Changes in Compact <br />administration are also reflected in the amount of water measured in the Rio Grande at the state <br />line gage. <br />Closed Basin Project <br />The Closed Basin Project was developed over the period 1985 through 1993. The Project pumps <br />groundwater from the unconfined aquifer underlying the Closed Basin and delivers this water to <br />the Rio Grande. The purposes of the project include supplying additional water to help Colorado <br />satisfy its obligations under the Rio Grande Compact, and providing water supplies for fish and <br />wildlife habitat. As originally envisioned, the project would supply approximately 100,000 acre- <br />feet, thereby reducing the need to curtail water users on the Rio Grande and Conejos River. To <br />date, the project has supplied an average of 35,000 acre-feet for this purpose. <br />As with the change to strict administration of the Compact beginning in the late 1960s, operation <br />of the Closed Basin Project has influenced the amount of water available for diversion by water <br />users in Colorado. Rather than reduce available supply, however, the project has made more <br />water available to Colorado users. The project has effectively reduced the amount and/or <br />duration of diversion curtailment, and the effects are reflected in increased historical diversion <br />records. <br />C:Acdss\Task2-3.doc Identify Study Period April 16, 1999 Page 12 of 18 <br />