‘The water levels in the San Luis Valley aquifers are dropping, and have been dropping’ — Craig Cotten

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Here’s the latest installment in the Valley Courier’s Colorado Water 2012 series, written by Craig Cotten. Here’s an excerpt:

The Rio Grande is in the fourth year of below average streamflows. Other parts of Colorado are also in a severe drought this year, with some areas having a more severe single year drought than the San Luis Valley. However, much of Colorado had very good precipitation and streamflow last year which filled their reservoirs and aquifers. In fact, some areas in the northern part of the state had one of their best years ever last year in terms of precipitation and streamflow, while this basin languished in the midst of a multi-year drought. Since the extreme drought year of 2002, there have only been three years of above normal flow on the Rio Grande and only two years on the Conejos River. Some smaller streams around the valley have fared even worse, with only one year of above normal flows in the last ten.

The water levels in the San Luis Valley aquifers are dropping, and have been dropping, over the last several years. This drop is in response to the lower than normal recharge into the aquifers from the area rivers, streams, and ditches. After seeing modest gains during the years of 2007 to 2009, the unconfined aquifer is once again dropping substantially.

According to the aquifer study conducted by Davis Engineering, the unconfined aquifer in the West Central part of the San Luis Valley has lost nearly 500,000 acre-feet of water during the last three years. There is not a formal, comprehensive study of the confined aquifer throughout the Valley, but this aquifer is also seeing significant declines in the amount of artesian pressure. While it is not known exactly how much water is in the aquifers, it is obvious that the San Luis Valley cannot continue this drastic drop in the aquifers without severe long-term consequences…

In order to address the problem of injury to surface water users and the decline in the aquifers due to well pumping, the State Engineer is in the process of developing Rules and Regulations concerning the withdrawal of groundwater in Division 3. The State Engineer is being assisted in the development of these rules by a 55 member advisory committee made up primarily of area water users.

While these rules are not completed yet, we do know generally what they will require. In general, the rules will require that large capacity wells in the San Luis Valley repay the injury that they are causing to senior water rights, which are generally ditch and canal rights. In addition, the rules will have a sustainability component which will require that well owners ensure that the underground aquifers are brought back to a sustainable level.

The repayment of injurious depletions and ensuring sustainability can be accomplished by a well owner in two ways. A well owner may choose to implement an individual augmentation plan in which that owner will cover his individual well or wells. Otherwise, a well owner may choose to join a subdistrict, which, in exchange for monetary payment, will provide the repayment of injurious depletions and the sustainability of the aquifers for that owner.

More Colorado Water 2012 coverage here.

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