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.

The high cost of new dams

Not all new dam proposals involve traditional dams blocking major rivers – some 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.

US Army Corps of Engineers contractors work on Folsom Dam spillway.

These off-channel dams share many of the environmental drawbacks associated with traditional dams. For example, they may:

  • Block fish migration
  • Harm water quality and temperature
  • Flood valuable riverside wildlife habitat
  • Reduce or alter river flows

Like traditional dams, off-channel dams can cost billions of taxpayer dollars to construct. Off-channel dams can also use a lot of electricity — typically more than they can generate by releasing water – 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 communities must take a close look at the potential of demand reduction strategies and alternative sources of water supply.

Dams are usually not the best way to meet demand for water. They're often the most costly for communities.Click To Tweet

What are the alternatives to dams?

Dams are hardly the only way to meet 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. Once demand is determined, citizens should call for a thorough assessment of supply options to meet that demand.

If Not Dams, What Other Water supply Options Are Available?

Water efficiency and conservation

These are the simplest, 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 of daily yield.

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.


Also known as water recycling or reclamation, water reuse refers to the use of treated sewage, gray water, or stormwater for non-potable purposes such as irrigation, industrial processes, fire protection, toilet flushing, among others.

Drawbacks of this option can 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 costs associated with pumping and piping infrastructure, and the effect on instream flows when water is pumped from a river.

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, groundwater storage, and western water markets are not vulnerable to increased evaporation as temperatures rise. In addition, conservation and efficiency can be implemented anywhere. New storage projects, on the other hand, only benefit those located within a certain proximity.

Connecticut River case study

In the mid-1980s Boston was faced with the question of how to secure its water supply for a growing city. They examined many options including damming the Connecticut River. After evaluating all their options, the Massachusetts Water Resource Authority (MWRA) decided in favor of aggressively pursuing water efficiency and against the damming of the river.

Shortly thereafter MWRA initiated its conservation program which included a leak detection and abatement program, system-wide residential retrofit programs, changing the state plumbing code from 3.5 gal/flush to 1.6 gal/flush, and industrial audits. Boston successfully secured its needed water supply by reducing its water consumption from 330 million gallons per day in the mid-80s to 205 million gallons per day in 2009, a 35 percent reduction. In fact, the metro area now uses less water than it did in 1911. And while they spent $40 million on these water efficiency measures, given that they were able to avoid the $500 million cost of the dam, overall water efficiency was by far more cost effective.

Stopping a bad dam proposal

In addition to insisting on credible evaluations of water demand and water supply alternatives, citizens should call for any studies of new dams to include ample opportunity for public input, ideally well before it goes through the official federal or state environmental review process. Ample opportunities for public input will allow the public to expose any faulty assumptions regarding demand and supply evaluations as well as any other environmental and economic problems.

Citizens should insist that the beneficiaries of a dam pay for its benefits. Support for a dam can drop off considerably if local water users – who often envision new dams as pork barrel projects paid for by federal or state taxpayers – have to shoulder the burden of dam construction themselves.