@ColoradoWater: #Drought planning showed to lower risks at #LakePowell #ColoradoRiver #COriver

Lake Powell April 12, 2017. Photo credit Patti Weeks via Earth Science Picture of the day.

From the Colorado River District:

The Colorado River Risk Study, commissioned by the Colorado River District and other West Slope parties, forecasts that if another drought like 2002-04 recurs,Lake Powell, now about half full rather than full as it was then, could fall below power generation levels or be drained unless Drought Contingency Plans (DCP) can be put in place.

Should the worst happen, Colorado and its sister Upper Division states (Utah, Wyoming and New Mexico) that are party to the Colorado River Compact of 1922 would be hard pressed to meet compact obligations to the Lower Division states (California, Nevada and Arizona).

The Risk Study is now in Phase II, which is a technical process to learn if federal and state Colorado River computer models can be used conjunctively to better predict what could happen in the state of Colorado. Other partners in the study are the four West Slope Basin Roundtables (Colorado Basin, Gunnison, Yampa-White and South- west) and the Southwestern Water Conservation District– with assistance from the Colorado Water Conservation Board.

At its quarterly meeting on Oct. 17, the Colorado River District Board received an update on the work. John Carron of Hydros Consulting, the study contractor, said the takeaways from the study so far are:

• Should a drought on the order of 2002-04 recur with Lake Powell at its current half-full level, hydroelectric power generation is jeopardized;

• Hydrology, demands and future development levels matter — the higher the consumptive use in the Upper Division states, the higher the risk to existing users;

• The most successful Drought Contingency Planning requires joint participation by both Upper and Lower Division states;

• Drought Contingency Planning is essential;re-operations of reservoirs, such as Flaming Gorge, to move water down to Powell reduces the risk, but in more severe droughts (e.g., 1988-1993 and 2001-2005),demand management (reduced water use) would be necessary in addition to any
reservoir re-operations;

• Some of the volumes of demand management that the model is forecasting are large and may not be feasible, thus the need to consider the trade-offs and alternative strategies;

• Demand management combined with a water bank could limit the impact by spreading conservation over many years and providing greater control over conserved water — a must- have condition.

The four West Slope Basin Roundtables called for the Risk Study at a joint meeting held in December 2014 in order for the West Slope to better under- stand the risks to current water users of future water development and how development, basin by basin, might look against the risk. As Colorado River water is also used on the Front Range of Colorado, drought risk is important to Front Range Roundtables and their future development, but they opted not to participate in the study.

How we got here

Even though there had been some good snow years in the years 2000- 2013, it was clear that dry conditions and overuse of the Colorado River were driving down reservoir levels at Lakes Powell and Mead.

In July 2013, then U.S. Interior Secretary Sally Jewell asked the seven Colorado River basin states if they were prepared to deal with a continuation of these conditions. The answer was no, and the challenge was for the basin states to develop their own DCPs or have the work done for them.

The Upper Division states and the Lower Division states each started work on DCPs for their regions.

Against this backdrop, the four West Slope Basin Roundtables commissioned the Risk Study. In the meantime, Colorado’s Water Plan, released in 2015, calls for actions that will minimize the risk of compact curtailment, embodied in Point 4 of the Seven Point Framework of the plan.

The Upper Basin DCP

The Upper Basin States have a three-pronged DCP, that 1) entails moving water stored in Flaming Gorge, Aspinall and Navajo Reservoirs to Lake Powell as the first line of defense against critical Powell elevations being breached, and modifying releases from Powell to Mead; 2) institutes demand management (reduction of use); and 3) augments river flows through cloud seeding and phreatophyte (primarily tamarisk) reduction.

An agreement between the four Upper Division states and the U.S. Bureau of Reclamation is in the works on how to re-operate the reservoirs. The demand management piece will be controversial among the states and within each state; details are still to be worked out. One policy contention in Colorado is that municipal water users, including those on the Front Range, share the burden of reduced use – and that the reduced uses not all fall on West Slope agriculture.

Demand management in the Upper Basin would be the last action to implement in the “worst of the worst droughts,” General Manager Eric Kuhn said. “The goal is to limit it to that.”

General Counsel Peter Fleming said a Colorado River District policy issue would be implementing demand management at the same time as new and increasing water uses are being developed in the River District, the state of Colorado and throughout the Upper Basin.

Kuhn said that for Colorado, the Seven Point Framework in the 2015 Colorado Water Plan addresses that — calling for any new transmountain diversion to not increase the risk of curtailment, because of Compact or Lake Powell low levels, on current water users.

“It is a major milestone that the state has adopted that in its plan,” Kuhn said. “This is an issue for the Front Range as well. Existing users do not want to see the risk to their projects increase due to new diversions.”

The Lower Basin DCP

The overall goal of DCP in the Lower Division states is to erase the so-called “structural deficit” that over time has showed those three states depleting about 1.2 million acre feet (maf) annually more than their compact entitlement of 7.5 maf, due to use and evaporation. A section of the 2007 Interim Guidelines that pertains to the three states calls for reduction of water use equal to about half of the structural deficit once Lake Meads falls below certain thresholds. Current Drought Contingency Planning specifies further cutbacks would achieve the 1.2 maf goal.

The Lower Division states are nearing finalizing their DCP. As Mother Nature would have it, big rains in California helped to reduce depletions in the Low- er Basin to 6.6 maf this past water year.

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