RGDSS_Task4_RGWUA_Interview - Laserfiche WebLink

Home Browse Search

in the formulation of any administrative plan for controlling groundwater overdraft in the Closed Basin. The Association is concerned about the long-term viability of the Closed Basin Project. Mechanical problems continue to plague the project, reducing its benefits to Colorado and the Rio Grande. From time to time, there have been suggestions from New Mexico and Texas that the Closed Basin Project should be used to alleviate water shortages or to solve environmental problems in those states. The Association opposes the use of Closed Basin Project water for anything except assisting Colorado to meet its Compact obligations. With respect to the confined aquifer, the Association believes that there is a great lack of knowledge about this aquifer and its connection, if any, to the surface flows of the Rio Grande and the Conejos River. The extent and location of stream depletions to the Rio Grande and Conejos Rivers from confined aquifer diversions is a very contentious issue that was laid aside by the agreement allocating the yield of the Closed Basin Project. If allocation of those depletions between stream systems is made an issue in the RGDSS, then the cooperative nature of and public support for RGDSS may be lost. The Association believes that helpful but limited new information about the confined aquifer will be obtained from the RGDSS drilling program. Therefore, the Association believes the RGDSS modeling effort must recognize these data limitations and not make assumptions that are not well supported by site-specific data. This is particularly important for the extent and location of connections between the confined aquifer and surface streams. Until a good deal more data is collected, there is simply not be enough data to make an accurate assessment of the exact location of that connection and the quantity of any resulting stream depletions. The data gathered from the RGDSS, however, should enable the water-user community to assess the magnitude of impact of substantial new groundwater development from the confined aquifer, and decide if such development is feasible without injury to other water users. The Association's experience with models makes it skeptical about the accuracy and reliability of surface and groundwater models in the San Luis Valley for administrative purposes. Part of this is due to the inexact nature of modeling, part is due to the lack of sufficient data to accurately model the system, and part is due to the continued repackaging of past models into new, but no more reliable, models. The Association would rather see no model than a model using undocumented or poorly documented assumptions that could profoundly change groundwater administration throughout the San Luis Valley. The Association is participating in the technical subcommittee for the RGDSS and has hired highly respected consultants to help it evaluate and provide input on the accuracy and reliability of both the underlying data and the modeling done for the RGDSS. The Association wants the RGDSS to result in a useful tool for better decision making for water resources in the Rio Grande Basin. The Association does not believe, however, that sufficient data is currently available or will be generated by the current RGDSS findings to allow the RGDSS to be used for any water rights decision making requiring a high degree of site-specific accuracy. Accordingly, the Association recommends that the RGDSS be considered as an evolving tool, not aone-time product. Until more data is collected, the RGDSS should be viewed as a means to help make basin-wide assessments and decisions. As more data is gathered for specific areas, the use of the RGDSS can be refined accordingly. The greatest threat to the success of the RGDSS is that its reliability will be overstated and its results will be misused. To avoid this, the inherent limitations of the RGDSS must be recognized C:Acdss\RGWUA3.doc Rio Grande Water Users Association Interview June 21, 1999 -Page 6 of 9