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An Assessment of the Removal of Guadalupe Dam as a Restoration Tool for Anadromous Species

Updated: Feb 9, 2019


Theodore Roosevelt proposed the 1902 Reclamation Act which called for snow melt and rain water to be captured and stored for later use (Stanley 2003). In fact, by the time he left office he would have witnessed 30 dams being completed (Stanley 2003). By the end of World War II there were an estimated 5000 dams over 15 meters high worldwide (Stanley 2003). Through the next 80 years the Bureau of Reclamation’s engineers worked tirelessly to tame California’s most wild and scenic rivers (Collier 1996). Dams, locks and diversions now control nearly all rivers in the lower 48 states (Collier 1996). At first we thought dams were beneficial because they provided water supply, recreation, flood control, and hydropower (Collier 1996). As time went on scientific members of the community began to realize that dams actually are very problematic as they degrade habitat downstream and block anadromous fish species such as Steelhead rainbow trout and Chinook salmon from historic rearing habitat. Anadromous species are born in freshwater where they live for 1-3 years before migrating out to sea for 2-4 years, they then return to the same waterway they were born in (Burt 2010). Native anadromous species thrive in cool, clean, well-oxygenated water with stable nutrients (Burt 2010).

Their lifecycle requires a diverse habitat that includes: woody debris, varied rock sizes, and aquatic vegetation for cover. Dams have been known to disrupt these abiotic and biotic elements by blocking the flow of woody debris, substrate and nutrients, thus degrading habitat dynamics crucial to the lifecycle of trout and salmon (Burt 2010). In 1936, Santa Clara Valley Water District built five dams in Santa Clara County in response to land subsidence from over pumping the aquifer since the 1870’s, marking the beginning of “The Valley of Heart’s Delight”. One of the dams constructed was the Guadalupe Dam on Guadalupe Creek.

The problem is that habitat loss, due to the dam and channelization, may have pushed federally threatened Steelhead rainbow trout in the Guadalupe watershed to unsustainable numbers. I feel the solution to restoring Steelhead rainbow trout populations is removing Guadalupe Dam to allow access to historic rearing habitat. According to a report about the historic geographic populations of Steelhead rainbow trout in waterways of the San Francisco Estuary; the Guadalupe River has been monitored for anadromous species sporadically since 1898 (Leidy 2005). The report shows the presence of trout throughout the Guadalupe River watershed in early years that steadily decreased through time (Leidy 2005). The report hypothesizes that considerable amount of conversion of in-stream habitat to cement for flood control purposes as well as the construction of dams that block salmonidae from their historic habitat may be the cause of population decline and diversity loss (Leidy 2005).


Damming of rivers enabled human population growth by allowing people to settle and farm alluvial rich soils, harness energy for industry and to stock water for drinking during drought years (Poff 2002). Reservoirs created by dams provide recreational opportunities such as fishing, boating, water skiing, and swimming and play a part in our water supply infrastructure for residential, industrial and agricultural utilization. Further, dams protect private and public properties by providing flood control from high-water-flow events. Hydropower dams for instance, play a critical role in electricity production in the United States, for example, 75% of America’s Northwest electricity comes from hydroelectric power produced by the Columbia River (Palmer 1991).

It was clear to see the economic and social benefits to dams, but it was hard to see the environmental and ecological adverse effects they create. In the 1880’s; Santa Clara County utilized it rich artesian wells and blossomed into “The Valley of Heart’s Delight”, producing fruit such as prunes, apricots, cherries and plums for most of the world. Amazingly, by 1920, two-thirds of Santa Clara County was being irrigated and 17,000 new wells were drilled annually (United States Geological Services). It wasn’t until 1933 that people began to realize that San Jose was subsiding. Santa Clara Valley Water District responded by installing five dams to capture storm flows and recharge ground water through water releases in the stream bed (United States Geological Services). One of the dams built was the Guadalupe Dam, built in 1936 the Guadalupe Dam has since blocked migrating Steelhead rainbow trout and Chinook salmon from their historic natal spawning grounds. Nutrients, woody debris, substrate and dissolved oxygen are also blocked by the dam and unable to benefit downstream ecosystems.

Degradation of Habitat

The filling of a reservoir upstream of the dam results in the decimation of existing valleys or meadows (Poff and Hart 2002). Habitat downstream is depraved by the lack of the rock cycle, water cycle, and nutrient cycle as the dam blocks the flow of these dynamics.

Upstream Impacts

Natural sediments such as gravel, sand and clay are impeded and create a mound behind the face of the dam decreasing the reservoir’s water carrying capacity. The shallow water is heated faster by the sun and has the potential to foster algae blooms that consume dissolved oxygen and can lead to eutrophication within the reservoir. Additionally, when the landscape upstream of the dam was flooded to create the reservoir, methane formulates from the decomposition of preexisting vegetation as well as from vegetation that grows along the banks as the water level fluctuates seasonally (Yang 2014). This is concerning because not only is methane (CH4) twenty three times more powerful than carbon dioxide (CO2), but it contributes to global warming and climate change.

Downstream Impacts

In addition, degradation of habitat downstream of a dam is caused. Dams disrupt and manipulate natural ecosystem cycles such as: temperature, woody debris, nutrients, and alluvial transport (Poff and Hart 2002). Water released warm from reservoirs is low in dissolved oxygen due to decomposition within the reservoir (Kittrell 1959) and physiologically stresses resident fish populations and jeopardizes egg survival rate. In addition, restricted downstream movement of sediment and woody debris (Pess 2014) reduces habitat complexity. For example, woody debris provides shade and predatory cover for fish species throughout their lifecycle increasing survival rate and populations. Dams block anadromous species access to pristine, historic rearing habitat (Pess 2014).

Anadromous Steelhead Rainbow Trout and Chinook Salmon

Before the existence of dams, native anadromous species such as salmon and steelhead rainbow trout have been migrating between freshwater and saltwater biomes for hundreds of thousands of years. Anadromous in Greek means “running upward”. Anadromous species are born in freshwater rivers and creeks; they migrate out to sea before returning to spawn in the same freshwater river or creek they were born in. Steelhead rainbow trout and Chinook salmon spawn between fall and spring with a majority of the salmon spawning in September and a majority of the Steelhead rainbow trout spawning during December and March (Moyle 2002). Anadromous species have an important role of providing nutrients for the entire watershed, for example, more than 90% of a salmon’s biomass is acquired in sea waters, accumulating high volumes of marine-derived nitrogen, phosphorous, and carbon (Kline 1990). When salmon return to their natal stream to spawn, they die soon after, delivering marine derived nutrients (MDNs) to freshwater systems that are not able to provide large loads of nutrients naturally (Hocking 2002). The female steelhead rainbow trout for example, which is known as a hen, will build a nest called a redd bed (Burt 2010). She prepares her redd bed (nest) by lying on her side and flapping her tail (Burt 2010). She does this to clean out any sediment that may be in the gravel and rock she has chosen for her redd bed (Burt 2010). Once her redd bed is free of sediment she deposits between 2– 5 thousand pink, bead sized eggs in the interstitial spaces of the rocks (Burt 2010). She then covers them with a thin layer of sediment so that the eggs don’t get washed away during high-water-flow events. Too much sediment from unnatural river dynamics could be fatal to eggs as it impedes water flow and oxygen and does not allow cleansing of waste from the redd bed. Eggs prefer temperatures ranging from 53-59 degree Fahrenheit (Pess 2008) to hatch, temperatures above could be fatal.

For an anadromous species to have a successful egg to spawner lifecycle they need specific habitat dynamics. Factors that can directly affect species survival rate are: water temperatures, dissolved oxygen, nutrients, substrate, and woody debris. Rivers naturally provide ecosystem services beneficial to trout and salmon that are degraded or eliminated by the presence of barriers. Dams are currently being removed as a restoration tool for aquatic ecosystems (Stoecker 2016). There has been an up rise in dams being removed for numerous reasons such as:

  1. they are unable to serve their original purpose, or

  2. maintenance expenditures outweigh their economic value, and

  3. dams fragment habitat range, which leads to loss of genetic diversity, community compositions and species loss (Santucci 2005).

Removal of the 104 foot Elwha Dam began 2012 on the Elwha River in Washington, becoming the largest dam removal in United States history. Ecologist, fisheries managers and environmentalist around the world looked upon this project with scientific eyes, curious of the environmental outcome (Tonra 2015). It didn’t take long for fisheries managers to witness that if you remove a dam, anadromous species will naturally utilize the area upstream. In 2013, a year after the dam was removed, 85% of redd beds (McHenry 2015) were located upstream of the previous location of Elwha Dam as 4,000 Chinook salmon (Oncorhynchus tshawytscha) spawners swam their way up stream (Denton 2014). We need to consider removing the Guadalupe Dam to restore native anadromous species and aquatic and riparian habitats. Scientific data has concluded that fish return after dam removal (Pess 2008). After the Elwha Dam removal, sediment, woody debris, substrate and nutrient flows have reestablished within complex ecosystem and food webs leading to a more diverse biological biome.

With habitat loss being an important factor in the population of anadromous species, it is important to look at the overall habitat available to anadromous species after taking into consideration habitat loss due to channelization and inability to access habitat upstream due to Guadalupe Dam.

Study Area

The Guadalupe River Watershed (see figure 1) encompasses approximately 171 square miles (Santa Clara Valley Urban Runoff Pollution Prevention Program). Loma Prieta in the eastern Santa Cruz Mountains is where the headwaters begin but the Guadalupe River doesn’t actually begin until Guadalupe Creek and Alamitos Creek join, just downstream of Coleman Road in San Jose (Santa Clara Valley Urban Runoff Pollution Prevention Program). The river flows through the heart of San Jose before joining San Francisco Bay through Alviso Slough (Santa Clara Valley Urban Runoff Pollution Prevention Program). Historic documents reveal local populations of salmon in the “Rio Guadalupe” dating as far back as the 1700’s (SCBWMI 2001).

Figure 1. Map of Guadalupe River watershed. Source: Map by Oakland Museum of California


I used Santa Clara Valley Water District’s Watching Our Watersheds (WOW) program to measure linear in-stream habitat length, habitat channelization and linear in-stream habitat in the upper watershed not accessible to migrating fish on Guadalupe River, Guadalupe Creek, Rincon Creek and Los Capitancillos Creek. I used Dr. Hobbs’ “Steelhead Smolt Outmigration and Survival Study: Pond A8, A7 & A5 Entrainment and Escapement Final Report” (Hobbs 2014) to calculate, through extrapolating data, the potential rainbow trout population upstream of the dam once removed.

To assess the existing impacts due to the Guadalupe River Dam I used: 1.) existing information (e.g., peer reviewed publications, gray literature reports, historic survey information; 2.) web data from local water district.

For clarification we assume the following biological abiotic and biotic factors are necessary criteria when we mention habitat: (stable water temperature, spawning gravel, dissolved oxygen, nutrient flow, minimal pollution, log jams/wood debris, predatory cover in the form of undercuts and aquatic vegetation, riparian shade and habitat i.e. riffle, pool, tailout)


Using GIS to Determine Habitat and Channelization

The habitat up stream of the dam is made up three main creeks, Los Capitancillos 1.41mi, Guadalupe Creek 5.07mi, and Rincon Creek 4.74mi (see figure 2) that equal 11.22 miles. The habitat downstream of the dam, Guadalupe River 16.78mi and Guadalupe Creek 5.0mi equal 21.86mi for a total of 33.09mi of habitat upstream and downstream of the dam (see figure 2). Of the 33.09 miles of habitat, 11.23 miles or 34% is being blocked by the dam. Downstream of the dam, 10.25 miles or 47% of Guadalupe River and Guadalupe Creek’s stream bed has been channelized for flood control. Of the 33.09 miles of habitat upstream and downstream of the dam, 65% is currently being blocked by the dam or channelized, leaving Steelhead rainbow trout and Chinook salmon with only 35% of their historic habitat.

Figure 2. Above left, map of Guadalupe Creek, Rincon Creek and Los Capitancillos Creek – above dam site; above right, map of habitat blocked by dam and in-stream channelization. Source: Santa Clara Valley Urban Runoff Pollution Prevention Program.

Extrapolating Data to Predict Potential Fish Population When Dam is Removed

On January 17, 2014 (see table 1) Dr. Hobbs and his team electrofished nine juvenile rainbow trout per 100 linear feet on Guadalupe Creek downstream of Guadalupe Dam (see figure 3). I extrapolated Dr. Hobb’s data to predict the potential population of rainbow trout in the 11.22 miles of habitat upstream of Guadalupe Dam once removed. The results suggest that removing the dam would increase carrying capacity and thus allow 5,328 additional rainbow trout to recolonize substantial habitat in the upper watershed.

11.22mi x 5,280ft = 59,241ft/100ft = 592 x 9 juvenile trout per 100ft = 5,328 juvenile trout

Table 1. Dates of electrofishing at Guadalupe River, Guadalupe Creek and Los Gatos Creek.

Source: Hobbs, James, Ph. D, 2014. Steelhead Smolt Outmigration and Survival Study: Pond A8, A7 & A5 Entrainment and Escapement. Final Report. Prepared for: NOAA/NMFS

Figure 3. Juvenile rainbow trout electrofished per 100 linear feet of stream on Guadalupe River, Guadalupe Creek and Los Gatos Creek. Source: Hobbs, James, Ph. D, 2014. Steelhead Smolt Outmigration and Survival Study: Pond A8, A7 & A5 Entrainment and Escapement. Final Report. Prepared for: NOAA/NMFS


After dam removal, studies show not only federally threatened and endangered species recolonizing above dam habitat, but also restoration of habitat downstream of the dam. It’s time we reassess Guadalupe Dam. Of the 10 reservoirs Santa Clara Valley Water District manages, Guadalupe Reservoir is one of the smaller reservoirs with a minor holding capacity of acre feet of water. More importantly, Guadalupe Dam no longer functions for its original purposes. For example, the dam was built for water storage during “The Valley of Heart’s Delight” (Santa Clara Valley Water District 2014). Today, 55% of Santa Clara County’s water supply is imported from state and federal water infrastructure such as the State Water Project (SWP) and Central Valley Project (CVP) (Santa Clara Valley Water District 2014). The remaining local water supply is extracted from underground aquifers (Santa Clara Valley Water District 2015). The other original function of the dam was to allow water releases into the stream bed for groundwater recharge (Santa Clara Valley Water District 2016). Today, 65% of Guadalupe River and Guadalupe Creek directly below the dam are channelized with cement, reducing impermeable surface area and thus water infiltration and groundwater recharge. It is important for our growing community to find a sustainable source of water supply to replenish our groundwater. Being Silicon Valley we can use technology and engineering to minimize our environmental impact on our ecosystem and supply water to the residents of Santa Clara County. I believe we should invest in the Silicon Valley Water Purification Center.

Silicon Valley Water Purification Center

Santa Clara Valley Water District partnered with the City of San Jose and Santa Clara to meet the water demand of Santa Clara County residents. The facility cost $72 million to build and is designed to receive and purify water from the San José-Santa Clara Regional Wastewater Facility (RWF) that would have otherwise been released in to the San Francisco Bay. The purified water is currently being used for irrigation in local parks and community gardens, businesses and industrial sectors, but the goal is to expand Santa Clara Valley’s drinking water supply by pumping the water to local groundwater recharge ponds. The purification center uses a three step process (microfiltration, reverse osmosis and ultraviolet light) that mimics the process of how Mother Nature cleans water naturally and is expected to exceed California drinking standards.

State-of-the-art Water Purification Process

First, microfiltration is the process where treated wastewater is pushed through filtration membranes made of thousands of very fine pores 1/300th the width of a human hair. Bacteria, protozoa, solids and some viruses are filtered out.

Second, the reverse osmosis process forces water using very high pressure through holes so small only H20 molecules can fit through. This removes salts, viruses and most but not all contaminants such as pharmaceuticals, personal care products and pesticides.

Third, now that the water is clean ultraviolet light is used as an additional safety procedure to inactive any viruses and any trace organic elements. There are 6 UV trains each having two vessels, each vessel holds 40 high-intensity UV bulbs for a total of 480 high-intensity UV bulbs.

Meeting and expanding Santa Clara Valley’s drinking water supply using the SCVWPC would relieve our communities of any dependence on local reservoirs that degrade our local rivers and creeks.

Removing Guadalupe Dam

Removing Guadalupe Dam would open 11.29 miles of rich spawning habitat to trout and salmon and would allow complex ecosystem processes to cycle again. Given this opportunity, I predict anadromous species within the Guadalupe River watershed will be able to reproduce sustainably. When the Elwha River Dam was removed in Washington the river was able to repair itself and thousands of trout and salmon returned to spawn in the area upstream of the old dam site the following year. In my opinion, by removing Guadalupe dam, we can restore Guadalupe River’s historic population of Steelhead rainbow trout and Chinook salmon. More and more dams are being demolished because they are no longer economically viable, unsafe to the public or as a tool for restoration (Bednarek 2001).

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