As Colorado River flows and reservoir levels decline, we face a new era of aridity where we live with what the river offers. Experimentation and adaptation can help us navigate these changes. I want to share three ideas I explored over the past two years to manage the river based on flow and storage rather than storage alone. I hope these ideas can contribute towards more sustainable and equitable river management.
Live within our means
Starting in spring 2020, my colleague Jian Wang and I explored what the Colorado River would look like if we lived within our means.
We programmed a rule that capped basin depletions at an amount equal to average flow over the prior 10 years. The rule triggered when Lake Mead drew down below 1,060 feet, a level that was — at that time — below the actual level. We implemented our proposed rule in a free, downloadable model.
The model simulated the worst recorded flows in the Colorado River from the current day back to A.D. 1416, when flows were reconstructed from tree rings. We then compared depletions and reservoir drawdown for the current rules and our new rule. We found that current operations drew down Lake Powell and Lake Mead to critical levels in just a few years. Living within our means, on the other hand, sustained both reservoirs above their critical levels for long periods of time.
Adapt consumption to reservoir inflows to stabilize Lake Mead’s level
A second free, downloadable model identified the combinations of reservoir inflow and consumption to sustain Lake Mead at its current level of 1,041 feet (Figure 1, dashed blue line). Combinations below the line in the blue fill area will raise Lake Mead’s level while combinations above the line in the pink and red areas will lower Lake Mead’s level. Reduce consumption when Lake Mead inflows decline due to lower Lake Powell releases or a weaker monsoon (pink fill in Figure 1).
Provoke discussion about adaptation
In a third effort, I invited 26 Colorado River managers and experts to allocate water for all regions of the Basin, including First Nations and the Colorado River delta. Using a Google Sheet, they set the annual flow, and then entered the volume of water to consume, save or trade for their account. Next, they decided how much of their collective remaining account balances to leave in Lake Powell and Lake Mead before moving to the next year.
The discussions evoked constructive feedback plus lots of talk about equity, sustainability, hydropower generation, water prices, protecting endangered native fish and other issues. I invite you to virtually manage a Colorado River basin account. Open the repository, download the Excel file, move into Google Sheets, and invite people to start.
These three examples are among numerous possible ways to adapt to low flow and low storage. All three approaches grapple with challenges such as how low a flow to consider, how to divide cutbacks among users, and how to adapt when flow forecasts overestimate actual flow.
These examples give me hope for the future of our Colorado River. Prior generations had the foresight to plan and build the two largest reservoirs in the United States. These reservoirs helped the basin weather a drought that began in 2000. Now we face more years of low flows and low reservoir storage. Our generation will be defined by how we adapt, how we experiment, how we jointly learn, how we collaborate, how we cope with numerous uncertainties and how we pursue goals such as more equity. I hope we are the generation that plans, strengthens and adapts in the face of low flows and low storage.
David Rosenberg is a professor at Utah State University. He can be reached at http://rosenberg.usu.edu.