Why Dams Won’t Solve Water Supply Needs
The era of widespread construction of large dams for the most part ended in the 1960s and ‘70s. But recently, proposals for new dams have emerged, mostly in the name of improving water supplies strained by urban growth, a desire to irrigate more cropland, or adapting to expected changes in precipitation patterns accompanying climate change.
These new dam proposals don’t have to signal a new dam building era – in the vast majority of cases, water supply alternatives, such as water efficiency and conservation, will prove less costly for taxpayers, rivers, and communities as a whole.
So You’ve Decided to Fight a Dam Proposal…
The era of widespread construction of large dams, for the most part, ended in the 1960s and ‘70s. Or so we thought. Recently, numerous proposals for new dams have emerged, mostly in the name of improving water supplies strained by urban growth, a desire to irrigate more cropland, or adapting to predicted` changes in precipitation patterns accompanying climate change. But new dam proposals don’t have to signal a new dam building era – in the vast majority of cases, water supply alternatives, such as water efficiency and conservation, will prove less costly for taxpayers, rivers, and communities as a whole.
Different Dams, Same Problems
Not all new dam proposals involve traditional dams blocking major rivers – many would dam side canyons or tributary creeks, relying on pumps from a larger river to store water for times of year (typically summer) when more water is desired. These off-channel dams share many of the environmental drawbacks associated with traditional dams: they may block fish migration, harm water quality and temperature, flood valuable riparian and terrestrial wildlife habitat, strain a river basin’s overall water budget, and reduce or alter river flows. And like traditional dams, off-channel dams can cost billions of taxpayer dollars to construct. Off-channel dams can also use a lot of electricity as water usually needs to be pumped uphill to fill their reservoirs. In dry years, the water needed to fill a reservoir may not be available, and if there is water available, much of it will evaporate (an increasingly serious issue as summers grow hotter).
That said, there may be cases where a new off-channel dam makes sense, and could actually help improve seasonal flows for fish and recreation in a nearby river. More often than not, however, the environmental and economic costs of a new dam – whether on- or off-channel – will outweigh any benefits. That’s why the potential of demand reduction strategies and alternative sources of water supply must be thoroughly analyzed and, if there is potential to meet demand, implemented before a new dam proposal receives serious consideration.
So Many Dam Alternatives
Dams are hardly the only way to meet the demand for water, whether it’s new demand due to population growth or to adjust to altered precipitation or runoff patterns resulting from climate change.
The first step in fighting a new dam is to insist that a reasonable assessment of demand for water is made available. Without knowledge of how much water is needed, discussion of tools to meet demand is premature. Any credible demand assessment should assume future implementation of significant conservation and efficiency measures (for more on how to define demand, link to demand fact sheet).
Once demand is nailed down, communities should seek a thorough assessment of supply options to meet that demand.
Water efficiency = Water Supply
- Water efficiency and conservation are the simple, proven, cost-effective, and immediate ways to secure new supply and should always be the first options examined. In the Southeast, on average water efficiency costs $0.46 – $250 per 1000 gallons saved while dams cost $4,000 per 1000 gallons. Communities can also avoid or defer significant infrastructure costs through investing a fraction of the money in water efficiency measures as Seattle did when, in the late 1980s it started investing in water efficiency as water supply and avoided $100 million in long-term water supply costs by investing $30 million in water efficiency. (for more on water efficiency, see American Rivers’ Hidden Reservoir report at www.AmericanRivers.org/WaterEfficiencyReport).
Other supply options may also include:
- Reuse: Also known as water recycling or reclamation, water reuse refers to the use of treated sewage, graywater, or stormwater for non-potable purposes such as irrigation, industrial processes, fire protection, and toilet flushing, among others. There can be drawbacks to water reuse, environmentally and financially, which include costs associated with a municipal scale dual distribution system, and water that would have otherwise returned to the source river/water body once treated is now designated for a consumptive use, in the case of irrigation, that will not return to the river and may result in decreased flows.
- Groundwater recharge: This involves recharging underground water sources during a wet year or a season (often winter) when water is available. Drawbacks of this option can include stormwater infiltration, costs associated with pumping and piping infrastructure, and the effect on instream flows when water is pumped from a river. Also, this is not an option everywhere: many areas have underlying geology that makes aquifer storage infeasible.
- Re-operation of existing dams: Changing the way an existing dam is used is typically cheaper and less environmentally harmful than building a new dam, and in some cases re-operating a dam can provide water for cities, farms, and fish during critical times of year without major environmental, energy-production, or flood protection drawbacks.
- Water markets: In the western U.S., systems that allow for the buying and selling of water rights can, along with conservation and efficiency, help extend the ability of existing water supplies to meet challenges presented by growth and climate change.
In most cases, these water supply tools, whether alone or in combination, will prove far less expensive than building a new dam. These tools also tend to be more flexible than surface storage dams when it comes to adapting water supply systems to a changing climate. For instance, unlike traditional surface storage solutions, conservation, efficiency, …