by Bea Ferrigno
Progress on the Basin Plan
The June 10 meeting of the Rio Grande Interbasin Roundtable (RGRT) was an extended one devoted entirely to a review of the Rio Grande Basin Implementation Plan (RGBP). That plan, together with similar ones for each major river basin in the state, is being developed as part of the statewide water plan mandated last year by Governor Hickenlooper. The staff of Di Natale Water Consultants (DNWC), engaged by the RGRT to help develop the plan, stepped through the entire 142 pages of the current draft, explained the rationale for various sections, and received comments and suggestions from RGRT members and some interested citizens. During the discussion it was noted that
• Irrigated land in the SLV has declined from some 700,000 acres in the 1930s to approximately 600,000 acres today;
• The SLV is home to some 11 listed or endangered species in addition to the Sandhill Cranes; the cranes are not endangered, but could be affected by groundwater rules that will apply to the refuges that host them each spring and fall.
• Although increasing population is not an immediate concern, towns and municipalities in the valley will have to augment their well pumping. Many regional small towns have inadequate resources to address outdated infrastructure as well as water rights issues.
• Compared to hydrologic conditions between 1980 and 1995, streamflow in the SLV has decreased by about 35% due to a number of factors including climate change, early runoff, and dust on snow. Some dust arrives in surrounding mountains from neighboring states, but a significant amount that particularly affects the Sangre de Cristo mountains originates in the SLV.
• Under changing climate conditions, more accurate weather and runoff forecasting is needed. Because downstream deliveries are based on forecasts of flows in the Rio Grande and Conejos rivers, inaccuracies can cause sudden changes in availability and curtailment of irrigation water. The delivery amounts are not fixed, but rather scaled to the amount of water flowing past certain points. If the flow in the Rio Grande increases, for instance, much more of that water has to be passed to New Mexico.
At the May 13 meeting of the RGRT there was also considerable discussion of RGBP and its several objectives which include basin-wide watershed health and a number of projects already contemplated to improve storage capacity at existing reservoirs and upgrade aging delivery infrastructure. Also up for discussion were the impacts of recent fires and ongoing drought; despite the lack of snowpack and rainfall, the risk of flooding is ever-present in a mountainous area with erratic weather.
A follow-up meeting of the RGRT Plan group with DNWC will be held on July 2 beginning at 10:30am at the San Luis Valley Water Conservancy District office, 623 Fourth Street in Alamosa; the monthly RGRT meeting will be on July 8 at 2pm. The public is encouraged to participate on both occasions. The draft plan can be read at www.riograndewaterplan.com.
The long-awaited model runs for Saguache and San Luis creeks were presented at an informational meeting with Saguache Creek water users on May 5. State Engineer Dick Wolfe and staff introduced a chart of depletions that are to be replaced to Saguache, San Luis, and other creeks in the northern San Luis Valley. These figures were based on Rio Grande Decision Support System (RGDSS) model runs that incorporated additional data and the results of recent testing in the Saguache and San Luis creek areas.
A surprise to some was that wells near Saguache creek affect the Rio Grande, the estimated depletion being between 100 and 260 acre feet annually. Similarly, wells near San Luis Creek deplete Crestone Creek by as much as 210 acre feet each year. Total pumping in the Saguache Creek area was stable at about 40,000 acre feet from 2009 to 2013; in the area of San Luis Creek, pumping in the same period averaged 30,000 acre feet, but the major influence on aquifer levels has been lack of inflow. Since 2000, streamflow has been about 14,000 acre feet below average each year, so even if all the wells ceased pumping, the aquifers would not be restored.
A new method of calculating sustainable water use that is applicable in several, but not all, of the Rio Grande basin response areas is based on the ratio of stream flows to pumping from 1978 to 2000. This approach resulted in a reduction of depletions to be replaced during the current irrigation season as compared to those announced last September.
In response to an objection that the Closed Basin Project (CBP) is drawing water away from Saguache and San Luis creeks, Wolfe noted that exempt wells pump about 50,000 acre feet annually while the entire CBP draws about 10,000 to 15,000 acre feet, constituting a small part of the local problem and providing (admittedly expensive) water that helps satisfy Rio Grande Compact obligations, supports wildlife refuges, and that could be available for augmentation.
Similar information, in greater detail, was offered at the San Luis Valley Advisory Committee (aka Rules Committee) meeting the following day in Alamosa. Peggy Godfrey inquired about the depletions to Crestone Creek that had been mentioned in Saguache; Wolfe’s response was that the wells used by the Baca Water and Sanitation District lie close to Crestone Creek and are causing those depletions. James Heath (now the assistant engineer with District 3) added that those wells draw a few hundred acre feet each year, an amount that is in line with the depletion range for the area. He added that the RGDSS model cannot quantify depletions from individual wells.
There was considerable discussion about the potential effectiveness of the new formula for sustainability. Several model runs examined the effects of 10, 20 and 30% reductions in pumping but those would not restore the aquifer to the required average level seen between 1978 and 2000. The inevitable conclusion was that pumping was not the only factor affecting the aquifers.
The Rules Committee meets again July 1, beginning at 10am at the Inn of the Rio Grande in Alamosa. The meeting includes lunch and is open to the public.