JSNH&B home • 2015 • vol. 6 no. 1

On Water, Dams and Restoration

by Joe Medeiros

Sierra College Press, Editor-in Chief

Naturam expelles furca, tamen usque recurret
You can drive out Nature with a pitchfork, but she keeps on coming back
Epistles - Book 1 Epistle 10, 1.24


All life, as we know it, requires water—sometimes only a little, sometimes a lot. Regardless, all living things use water for growth, transport, cooling, reproduction, and for a large variety of metabolic purposes. It didn’t take our prehistoric ancestors long to discover the necessities and values of water. Ever since life first evolved (most likely under water), all species have become specialized to take advantage of this marvelous molecule. For millions of years, primitive aquatic life-forms flourished in this liquid medium—and then came the fishes.

Fish have known about watery things for much longer than we humans, and they’ve taken full advantage of their slippery environment. Evolution enabled them develop gills to extract oxygen from the water, tolerate colder conditions, reproduce without copulatory organs, and even transition from freshwater to saltwater (and back) during their life cycles. Special sensory organs enabled them to relocate their natal streams and nesting locations when they returned to spawn. For millions of years fishes (different species of fish) enjoyed relative freedom, before Modern Man began significantly manipulating their watery environment.trout

Thanks to a few major watersheds (Klamath/Trinity, Sacramento and San Joaquin systems) which were long, voluminous and ecologically complex, California enjoyed the additional benefit of anadromous fishes—those that migrated between fresh and saltwater environments. Rivaling Alaska’s Bristol Bay and the Columbia River of Washington/Oregon, our rivers were once major fish-producers (especially salmon and trout.) Before dams, there were scores of salmon canneries packing millions of fish annually in Sacramento alone.


Before we fully realized the total economic and ecological benefits of free-flowing rivers and intact aquatic ecosystems (including "swamps" like freshwater marshes and salt marshes), we had our eyes on some other properties of water (energy, hydroelectric, agriculture, industry, etc.). Before long, our engineering and entrepreneurial prowess had gotten ahead of us. Dams were built, fish runs demolished, and wetland ecosystems drained or converted to reservoirs.

No doubt that dams and reservoirs have stored water, staved off drought, enabled agriculture in arid lands and during the rainless summers of Mediterranean climates. They have made some enormously rich and helped raise the living standards of the many. They have provided light where it is dark. They have enabled the growth (and sprawl) of many a metropolis. But all of this has come at a cost. These costs, once considered peripheral or external, are now quantifiable and considered crucial. Many of them, when properly analyzed, cause us to scrutinize each new project and design mitigating procedures or technologies to reduce significant negative environmental impacts.

There is no official tally of the number of dams in America, but the US Army Corp of Engineers tells us that there are 75,000 sizable dams (66,000 on rivers) in the country. Of these, 2,540 are licensed to create hydropower. In spite of the fact that California has more than 1,400 larger dams, we defer to Texas as being the most dammed state in the country. The U.S. is not far behind China (80,000 dams) for being the world’s most dammed nation. India is currently building more dams than any other nation, but new dam construction has virtually halted in the United States. Why is this?

Well utilized in California, rivers have been dammed and diverted to harness their energy since before gold was discovered in 1848 (albeit only on a small scale before the Gold Rush). Most larger California dams and watershed diversions are relatively recent (60-70 years old), while few exceed a century’s use. Each and every project, while having clear and measurable utilitarian benefits, has come at some now-equally-measurable environmental cost. This is why we now are beginning to actively examine the real costs and benefits of dams and water diversions throughout the state and the nation—as well as studying many non-dam (and off-stream) alternatives to water storage.

Dam Removals

The environmental organization American Rivers states that 51 dams in the U.S. were removed in 2013 alone. This number will be added to its database of more than 1,000 dams that have been removed in America since 1912 (most of these in the past 20 years).

American Rivers states, "Outdated or unsafe dams came out of rivers in Alabama, California, Colorado, Idaho, Illinois, Maine, Massachusetts, Michigan, New Jersey, North Carolina, Ohio, Oregon, Pennsylvania, South Dakota, Vermont, Virginia, Wisconsin and Wyoming, restoring more than 500 miles of streams for the benefit of fish, wildlife and people."

Their summary includes ranking of dam-removals by state:

Pennsylvania topped the list for the eleventh year in a row. The top three states for river restoration through dam removal in 2013 are: Pennsylvania– 12 dams removed, Oregon– 8 dams removed,
New Jersey– 4 dams removed. Maine, Massachusetts, North Carolina and Vermont all had three dam removals in 2013.

American Rivers also lists 30 dams that have been removed in California, most within the last decade.

So why remove a dam? While they seemed practical and pragmatic at the time, many old dams are outdated, dangerous, or ecologically destructive. Many have simply out-lived their usefulness, and better alternatives for them are found. They are sediment traps—excluding important soil particles from enriching downstream fields. They are fish-passage barriers that significantly reduce or altogether eliminate sustainable fishery economies. They alter or irreparably modify downstream environments, as well as human cultures and communities. In many cases, siltation alone significantly reduces the storage volume, water-holding, and flood-protection capacity of any dam. In time (this varies depending upon the dam and reservoir) a practical reality exists: all dams become completely obsolete—incapable of storing water, generating hydropower, or protecting against floods.

Elwha River Ecosystem Project

One of the most famous dam-removal projects of recent times is the Elwha River Ecosystem Project on the Olympic Peninsula of Washington state. The projects are also within a National Park. However, in this case, the dams were built first (in 1913 and 1927) and Olympic National Park was created around them later in 1938. Elwha and Glines Canyon Dams have since been systematically disassembled, beginning in 2011.

At this time, both dams are gone. The reservoirs (Mills and Aldwell) that formed behind them are drained and pre-existing ecosystems are becoming reestablished. The Elwha River now flows unobstructed from its Olympic Mountain headwaters all the way to Puget Sound. Critical sediments are returning to downstream habitats and anadromous salmon and trout have relocated their ancestral spawning grounds for the first time in a century. Downstream floodplain and delta ecosystems are returning to provide multiple environmental and economic benefits.

While nothing of this magnitude is occurring in California, a somewhat similar river restoration has been proposed, in the northern portion of the state, for four dams on the Klamath River. They are the John Boyle, Copco No. 1, Copco No. 2 and Iron Gate Dams. These dams are up for FERC (Federal Energy Regulatory Commission) relicensing and, if agreements are met, removal of these highly-silted and fish-obstructing dams may begin as early as 2020.

What Would a Hetch Hetchy Restoration Look Like?

Every dam removal and restoration project is different. Some have occurred on small dams that have simply been pushed aside and nature is allowed to "take its course." Larger dam removals require expert designs and well-developed plans to ensure safe and effective results. Costs vary, of course. The Elwha River restoration project costs have exceeded $350 million.

Proposals to restore Hetch Hetchy Valley involve a unique situation—with lots of potential variables. Unlike other dam removal projects, the restoration intent is for Hetch Hetchy Valley alone, within Yosemite National Park, with no other major downstream restoration proposed. The water storage solution (without O’Shaughnessy Dam) resides downstream (at Don Pedro Reservoir and other locations), outside of the National Park. The intent is to allow the Tuolumne River to, once again, run freely through Hetch Hetchy Valley on its way out of the park.

After dam removal, a stump-filled and silty reservoir bottom would appear, encircled by a "bathtub ring" caused by seasonal fluctuations of water levels and chemical weathering of the granite walls. A considerable amount of physical work would need to be done to restore that natural gradient of the river and associated meadow. For example, the site of the dam’s base was excavated more than 100 feet downward from the natural elevation of the river at the meadow’s west end. Gravel and sand pits were dug; piles of materials were left here and there, and railroad beds were cut and established. "Reconstructive surgery" would be required to guarantee a successful restoration of the river and its natural flow through the meadow. Once allowed to run again, the Tuolumne would most likely find its previous course and excavate its new channel.

Previous exposures of the reservoir’s bottom (during droughts) have illustrated that there is relatively little silt accumulation. This is logical as the river has traveled through only high-country granite. As a result, significantly less erosion has occurred, compared to downstream, lower-elevation reservoirs. A draw-down of the reservoir would expose Hetch Hetchy Valley to the sun and the elements. Soon, an artist’s palette (so to speak) would emerge from whatever propagules (seeds and spores) were fortunate enough to light on this newly exposed mudscape.Hetch Hetchy valley one year later

National Park Service Report

In 1988 the National Park Service produced a paper delineating some alternatives for restoration of Hetch Hetchy should the dam and reservoir be removed. Assembled by Richard Riegelhuth, Steve Botti and Jeff Keay, all of Yosemite National Park, the report assumed a number (15) of assumptions that would affect the potential outcomes. The first assumption was probably the most important:

1) 0'Shaughnessy Dam would be removed down to the original level of the river bed. The original stream gradient and water table would be approximated in the restored valley.

The other assumptions dealt with things of which the restoration would have little, some, or great control (seeds being blown in, animals repopulating the new area, weeds, the bathtub ring scar, protection of nesting peregrine falcons, etc.).

Three alternatives were proposed:

  1. Recovery Without Management. The reservoir would be drawn down in one year. No direct management intervention into the successional process would occur.
  2. Recovery With Moderate Management. The reservoir would be drawn down over a 5-year period and some, moderate efforts would be made to control weeds and do some planting.
  3. Recovery With Intensive Management. The reservoir would be drawn down over a 5-year period, weed-control, planting, and even occasional burning would take place.

For each Recovery Alternative, vegetational and wildlife responses were proposed for 5, 10, 50 and 100 year intervals. In all alternatives, monitoring would be conducted. This study is available online for a closer inspection. The document is titled Alternatives for Restoration of Hetch Hetchy Valley Following Removal of the Dam and Reservoir.

Obviously, each alternative has its pros and cons. Costs, available personnel, regional and local climatic conditions, and other major factors will affect the results. Additionally, climate change and changing fire conditions will have to be incorporated into an adaptive management system that allows for modifications to the plans as conditions warrant.

Historic Management of Hetch Hetchy

Assuming that we want Hetch Hetchy Valley to "look just like it used to before the dam," we’ll have to add a few assumptions to our plan. First, and perhaps foremost, we must then assume that Hetch Hetchy was managed by humans, perhaps for hundreds to thousands of years before the Screech Brothers first arrived in 1850. While we can safely assume that most won’t want it populated with hundreds of cattle or sheep (as occurred even before Muir’s first visit), we must review the first photographs and descriptions of the Valley. These will instruct us that fire (both lightning-caused and human ignitions) as well as human management (weeding, pruning, planting, burning, etc.) may well have played major roles in the development of the architecture and structure of the Valley ecosystem before it was observed by modern eyes. Exactly how we achieve this will be a challenge, but it should not require delay or consternation, for, as we know, "nature will return" if we just allow it. For a grand example, take the forests of Mt. St. Helens after its massive eruption in 1980.

The main reason the Yosemite study gives for the slower draw-down of the reservoir, is for a more controlled revegetation scenario. Should the reservoir just be quickly drained and the muddy bottom exposed, there would be a land-grab free-for-all. First-come, first-served, most of the "winners" would be the more aggressive, introduced plants: weeds. There are more than 140 known "invasives" in Yosemite and many of them would love to occupy some new real estate.

As slower draw-down of the reservoir, with moderate or intensive management options, could include the planting of preferred native species, the weeding of unwanted or invasive species and even the light utilization of fire in prescribed and closely-controlled situations. Then, as the meadow and forests were becoming reestablished, work could begin on the dismantling of O’Shaughnessy Dam.

Vegetational Succession

All ecologists know the drill: vegetational succession occurs, step-by-step, from simpler to more complex communities, over time. Unless we want to plant a forest of mature ponderosas, white firs, sugar pines and incense-cedars—as well as some tidy groves of fully grown oaks along with bunches of robust meadow grasses and sedges—we’ll just have to wait. While we can plant, weed, coax, and nudge selected species to increase their chances of survival and maturation, we’ll still have to allow nature to "take its course."

Step by step, one incremental stage after another, a more-or-less "climax" vegetation will eventually emerge in Hetch Hetchy—complete with its attendant fauna—as a late-successional ecosystem. Portions will be grassy meadow, sprinkled with seasonal wildflowers and recolonized by the large and small—insects, worms, voles, squirrels. The newly exposed earth will be naturally inoculated with critical bacteria and fungi, resulting in mature, complex, and life-giving soils. Forests of conifers and broadleaf trees will jockey for position and, in time, will find their perfect niches in the sunny expanse.

Birds will fly over and consider the new digs. Insects, amphibians, reptiles, and mammals will wander through on their way elsewhere. But none will stay until there is food, shelter, and opportunities for them to survive, thrive, and reproduce. All this begins with the establishment of plants, from algae, mosses, lichens, and ferns to flowering plants and towering trees. Fish and aquatic insects that thrive in the upper Tuolumne River drainage will find spacious and new accommodations in the resurrected lower river, now running freely again through Hetch Hetchy Valley. Species of plants and animals will abound, as they find themselves welcomed into niches and habitats denied them for nearly a century.

Paradise regained! Or will it be? Will we want the restored Hetch Hetchy to become another Yosemite Valley? Will we lay down asphalt? Roads? Parking lots? Will we even allow cars or buses? Will we build hotels? Allow camping? How will we treat sacred burial grounds and Native American sites when they are exposed?

We face numerous challenges in this restoration. In addition to the above questions, we must also incorporate climate change, drought, new fire regimes, and a host of newer" inconvenient truths" into the restoration equation.

There are even what one might call "artistic questions" to be considered. Do we want to recreate the Hetch Hetchy that Albert Bierstadt envisioned and articulated on his canvases? Do we see the same, iconic "primeval wilderness" vision portrayed by William Keith? Will we "Photoshop" out the Native Americans setting fires in the new digital images of how we want to see the restored Hetch Hetchy?

The greatest challenges are also the greatest opportunities. We’ve risen to the challenges before. We can certainly do it again.Hetch Hetchy restored

References and Resources

American Rivers – www.americanrivers.org - see their press release - "51 Dams Removed to Restore Rivers in 2013"

Elwha River Restoration Project –

World Commission on Dams -

National Inventory of Dams - https://catalog.data.gov/dataset/national-inventory-of-dams

Richard Riegelhuth, et al. Alternatives for Restoration of Hetch Hetchy Valley Following Removal of the Dam and Reservoir. 1988. National Park Service.

Images Credits

- Trout rising: Joe Medeiros
- Hetch Hetchy one year later: by Laura Cunningham. Courtesy Heyday.
- Artist’s rendition of a 21st century restored Hetch Hetchy Valley in Yosemite (Levelpar) Courtesy of Restore Hetch Hetchy.