About Stream Bypass

Water Audit California inspects reservoir operations in sensitive environments to ensure adequate stream bypass to support aquatic species. When operators are recalcitrant, WAC litigates to compel compliance with public trust obligations.

  1. Fish are part of the public trust.
  2. Every dam owner is a trustee.
  3. FGC 5937 is the quantification of their trust duty.
  4. Trustees must account for their conduct.
  5. Every Californian has standing to protect the public trust.
  6. We manage what we measure.

California has been built on water diversions

The prosperity and habitability of much of California requires the diversion of great quantities of water from its streams. California has over 1,500 jurisdictional dams, and uncounted non-jurisdictional dams. Jurisdictional dams alone are authorized to store 126 million-acre feet (about 41 trillion gallons). But size is not everything. Even an inopportunely placed and poorly designed non-jurisdictional dam can destroy a migration run.

While public attention is focused on water served in restaurants and other such matters, the majority of human water consumption, about 75%, is utilized by agricultural irrigation. Low value crops (alfalfa, corn, rice, and cotton) consume about two-thirds of the agricultural supply while generating only 14% of farm income. As a UCD Watershed Sciences publication dryly stated: “These statistics imply significant potential for reducing farm water use without incurring overwhelming consequences for the state’s economy.”

Unnecessary harm is caused to the fishery by improper dam operations

While public attention is focused on the conflict between urban and rural users, scant notice is paid to the unnecessary harm being caused to our state’s fishery by improper operation of hundreds of small to medium size dams.

While attention is focused on the large reservoirs such as Oroville, Shasta and Trinity, the state’s fishery is suffering the death of a thousand cuts. With modest physical plant and operations modifications substantial progress could be made in the near-term to reverse the course to extinction.

Water, Fish and the Public Trust

It often seems that our contemporary society is mono-focused on private property and personal liberties, but there is another critical component to our existence: those things that we do not own individually, but share rights to in common. Rich or poor, we all have equal right to breathe the air, or to sail across the oceans, or to catch a fish.

Courts and legal scholars came to describe these common rights as a “public trust.” Our fishery belongs to all of us and none of us. We are all the beneficiaries of the public trust.

The first duty of a trustee is to preserve the trust delivered into their care. Some dam operators have discharged this duty with thoughtful integrity, and many others much less so.

Fish and Game Code 5937 is the statutory codification of a dam operator’s duty to the public trust.

It places upon the dam operator the duty to bypass “sufficient” water to maintain the downstream fishery in good condition. Three things are necessary to perform this duty. First, water flows must be properly measured. Second, the needs of the downstream fishery must be determined. Thirdly, the dam must have adequate capacity to bypass “sufficient” flows into the downstream reach.

All usufructuary water allocations are subject to reconsideration as time passes and circumstances change. California courts have held that dam operations are subject to review to determine if unreasonable harm is being caused to public trust resources.

“Fill and Spill” dams

Early in the last century, California had a rich fishery and little human development. Until 1914 we had no formal water allocation mechanisms.

In that pro-growth environment numerous “fill and spill” dams were built to provide water to urban and agricultural interests. Inadequate attention was paid to the unmitigated effects on the fisheries, perhaps because the effect of any individual project was not thought to be important. Although versions of FGC 5937 have been the law almost since statehood, in the 20th century the real estate developer was in the driver’s seat.

A consequence of this imbalance is that our commercial fishery has been largely lost, and the few surviving natural fish are in grave peril. Continuing expensive and genetically dangerous intervention has become necessary to stave off total collapse.

This is not a sustainable course. We must strike a more balanced course, not with any one dam, but throughout the state.

Rainfall in California is not evenly distributed throughout the year. Dams are designed to capture the high flows of winter to sustain during the dry summer season.

Our native anadromous fishery is well accustomed to this seasonal variation, with immature fish migrating to the ocean to become adult, and mature fish returning to their birthplace to reproduce, drawn by the initial heavy winter “attraction” flows.

The operation of a “fill and spill” dam is simple. Rainfall fills the reservoir formed by the dam until it flows over the spillway and into the downstream reach.

If the reservoir is full, the flow into the downstream reach equals the inflow, and a natural condition exists, but for the impact of the dam on the fishes’ ability to spawn upstream of the dam. However, if the reservoir is not full, a dam without bypass precludes any downstream flow. Even a short interruption in water flow can eliminate a fishery.

Absent bypass, from the end of the rainy season through until the winter rains fill the reservoir no water is released into the downstream reach.

It is evident that if the reservoir is empty when the rains start, as is usually the case, attraction flows will be delayed until after the reservoir fills. Dependent on the rain pattern in any particular year, and the size of the reservoir, this delay may, or may not, significantly delay attraction flows.

Proper dam operation is not a “set it and forget it” activity. The variation of the natural environment requires continual management of the water resource and balancing of numerous interests. There are two components to success in this effort: good monitoring of flows and a well constituted active management team, comprising of representatives from all critical interests.

Even in mid-winter, if direct diversion is greater than rainfall, “fill and spill” dam operations repeatedly de-water the downstream reach. This is perhaps the cause of the greatest damage to the fishery from improperly operated dams.

Imagine this common scenario. The winter rains arrive, fill the reservoir, and water flows over the spillway, successfully creating an attraction flow. Fish do as fish will, and migrate upstream. Then, as happened in February 2016, the rains stop. The water level in the reservoir drops, downstream flows cease, and the spawning fish are left to die. Although subsequent rains refill the reservoir to overflowing, the damage is done.

The impact on the fishery is devastating, particularly during the spawning and migration season.

There is no benefit to human uses from the environmental damage caused in the scenario described above. At the end of March the reservoir would still be full, whether or not sufficient bypass is made in February.

The only difference is that with bypass in February the fishery could survive, and without it, it cannot. Thoughtful management is the solution.

We manage what we measure

Without adequate monitoring dam operators are unable to model the consequences of any bypass regime, and often protest that any bypass will adversely impact human uses. Our examination of monitored and bypassing dams has thus far proved that not to be the case.

Under California law all dam operators are trustees of the public trust, and as such all must account for their conduct to be able to demonstrate that they are bypassing “sufficient” flow to support the fishery.

The monitoring of downstream flows below California dams is incomplete and disjointed, with few mid-size dam operators adequately reporting their dam operations.