Water supply in the West
February 09, 2023
Strategic planning and careful designs can ensure water reliability, dam safety, and a low economic, social, and environmental impact
Water is a precious and limited resource that is essential to human life. In the United States (US), western states receive significantly less precipitation compared to the eastern half. And with more than 80 million people living west of the Mississippi River, planning for more drinking water and irrigation are top priorities. With only a few reprieves, the western US has been in a drought since 2000. Combined with climate change and heavy population growth, drought conditions and water supply in the west will continue to be of critical concern.
The crisis is most apparent in the Colorado River basin, which saw one of its driest years on record last year. The nation¡¯s largest reservoir, Lake Mead near Las Vegas, is at its lowest level since the lake filled after the construction of the Hoover Dam in the 1930s. Responsible for supplying water to Arizona, Nevada, California, and portions of Mexico, it¡¯s currently sitting at 35% of its total capacity.
Western water agencies are looking for innovative approaches for new and expanded reservoir storage projects. Building new dams and expanding existing reservoirs is a pragmatic approach to improve resiliency. In fact, it¡¯s been a legacy in the western US for more than a century.
But designing new dams and expanding older ones is not an easy feat. Strategic planning and careful designs are all part of a larger process to ensure water reliability, dam safety, and a low economic, social, and environmental impact.
The crisis is most apparent in the Colorado River basin, which saw one of its driest years on record last year.
Strategic planning to guarantee water supply
Dams and reservoirs have historically been a basis for economic development around the world. At the same time, they are central to debates over the balance between economic development and the health of the natural and social environments on which we depend. The benefits of dams are numerous, including water supply, flood risk reduction, recreation, and hydropower production. But, when poorly planned, dams can also create negative impacts to critical services such as fisheries, floodplain agriculture, and biodiversity.
That¡¯s why the strategic planning of our water resources is essential to the success of new and existing dams. Thoughtful strategic water resources planning justifies these complex projects. These plans develop tradeoffs between providing sustainable water supplies and the social, environmental, and financial costs to do so. Water supply plans benefit most from employing an early focus on understanding risks and mitigating environmental and social impacts. This process identifies critical infrastructure that has the greatest benefits for human safety and prosperity. By evaluating and communicating these tradeoffs, negative outcomes from poorly planned dams can be avoided or reduced.
More responsibly planned and designed dams and reservoirs are necessary to stay ahead in the constant race to provide water to a growing population while maintaining a healthy environment in the US West.
Tying the need for dam projects to future drivers of uncertainty defines what their specific benefits are and identifies barriers to their completion. Important planning drivers for the design of modern dams include climate change impacts that could shift the hydrology, population change requiring more water supply, enhancing environmental conditions, updated dam safety design criteria, and improving infrastructure resiliency, amongst others. Strategic decisions on dams must be justified using objective, quantitative methods employing data analysis and visualization. These decisions then must also be communicated through transparent and equitable stakeholder and community engagement. The process helps develop projects that ensure sustainable water supplies, meet modern design criteria, and align with social expectations.
A great example is the many years and significant financial investment that went into planning and permitting the Gross Reservoir Expansion Project (GRE) outside of Boulder, Colorado. Fortunately, the original design incorporated features for future raising. A decade ago, when it became clear that the growing population required additional storage, engineers were able to provide modern updates to optimize the use of materials while minimizing social and environmental impacts of the construction. The owners developed a deliberate plan for the project organization and ensured collaboration with key project stakeholders to meet project success metrics.?
Gross Reservoir Expansion Project.
Now, after a decades-long permitting process, the 60-year-old reservoir is currently being expanded by raising the existing concrete gravity structure by 131-feet. Once finished, it will be the tallest concrete dam in Colorado and the largest dam to be raised using roller-compacted concrete (RCC) in the world¡ªa much needed water addition to Colorado¡¯s Front Range.
Strong designs for a secure water future
In addition to planning and permitting, careful and strategic design techniques for new and existing dams are allowing for these critical reservoir projects to move forward. Thanks to improvement in technology, dams are being designed to address site-specific constraints and technical challenges during the design phase. Performance and construction risks are also evaluated during this stage. All of these factors within the design process are allowing for the safe construction of environmentally friendly off channel dams. All so these reservoirs can remain one of the primary sources of water supply in the arid West.
The timely construction of the new off channel Chimney Hollow Reservoir Project outside Loveland, Colorado is yet another example of a much-needed water supply project in the West. During a time when the West is using more and more water, the new dam and reservoir project will help provide water for northern Colorado¡¯s growing communities through a partnership of 12 public agencies. The main feature of the new reservoir, part of the Windy Gap Firming Project, will be the approximately 355-foot-tall dam.
A strong design process is key to the successful construction currently going on at the Chimney Hollow Reservoir Project. It will result in the first hydraulic asphalt concrete core rockfill dam in Colorado and the tallest dam of its type in the US.
Chimney Hollow Reservoir Project.
Water security for future generations
Behind every successful construction project is a solid planning, permitting, and design process. And in the fast-growing US West, the time to think about tomorrow¡¯s water supply was yesterday. Many agencies have had plans in the process for years for expanding or developing new critical resource infrastructure projects that are just now coming to fruition.
Moving forward, we must be thinking of future generations and the challenges that they will face with even greater constraints on reliable water supplies. Critical steps must be taken now in securing the region¡¯s water future by continuing to look for more opportunities to conserve and reuse water, expand reservoirs, and build new dams.
Actors at every level¡ªfinanciers, consultants, developers and operators, research agencies, civil society, and government agencies ¡ªcan play a strategic role in promoting and implementing these critical projects.
A secure future for the current and next generations will require the understanding of a changing climate along with engineering innovation in storage, treatment, and delivery of water supplies for irrigation, manufacturing, and drinking. More responsibly planned and designed dams and reservoirs are necessary to stay ahead in the constant race to provide water to a growing population while maintaining a healthy environment in the US West.