Across the world and throughout history, people have settled next to rivers to take advantage of their water for transportation, fish and wildlife productivity, and the naturally fertile soils of adjacent floodplains.
Floodplains should be thought of as nature’s pantry; they are among the most productive ecosystems in nature and provide the supply of nutrients and food resources necessary to keep rivers, and the many species dependent on them, healthy.
Changing with the seasons, floodplains serve as “cooking pots” for the complex food chains that rivers support. They hold concentrations of life that are found at no other time in the hydrologic cycle and act as a food supply for rivers, which need floodplain inputs to sustain the resident fish and wildlife populations until the cycle can be repeated the following year. However, rivers must have access to floodplains during the right times of year to receive these annual injections of beneficial nutrients.
In California’s Central Valley, the Sacramento River originally evolved with, and benefited from, annual flooding. But that natural cycle no longer functions due to the manmade levees and water-control structures that keep the river’s rising water from naturally entering the floodplain. Today, it takes the combination of flooded agricultural lands and managed wetlands to provide the food resources necessary to support the millions of waterfowl, shorebirds and other waterbirds that call California home for a significant portion of their life cycle. I was personally involved with this complex management system during my time with the United States Fish and Wildlife Service, and have seen how important these floodplain inputs are for wildlife.
Now that natural flooding no longer occurs and millions of acres of natural wetlands have been lost because of development and other impacts, seasonally flooded rice fields have become a critical resource for waterfowl and other wildlife species. The 300,000 acres of winter-flooded rice in the Sacramento Valley during a “normal” winter are needed to provide the food resources necessary to help support nearly 7 million waterfowl (60 percent of all waterfowl in the Pacific Flyway) and 300,000 shorebirds.
The Nigiri Project, which is a partnership of farmers and researchers, including California Trout, has shown that flooded rice fields benefit fish populations. In the winter, the project floods farmland used for crops during the summer, and creates a kind of “surrogate” floodplain for juvenile salmon. Results from the project have shown an increase in growth and health of salmon inside seasonally flooded rice fields, which dramatically demonstrates the need for more connectivity between the river and adjacent floodplains.
California’s Central Valley contains approximately 206,000 acres of managed wetlands, covering just 5 percent of the historic 4 million acres of wetlands that once existed in the region. These remaining managed wetlands need water, for both summer irrigation and winter flooding, to provide their maximum benefits to birds and other wildlife.
The provision of this water and the habitat values it provides is reliant upon the ability of Sacramento Valley water districts and companies to divert and deliver surface water resources year-round in accordance with their contracts and water rights.
Rice fields and wetlands provide the basis for nutrients and the ensuing explosion of life that still occurs, but these fields are largely disconnected from rivers and can’t currently provide nursery habitat for salmon and smelt. This impacts the food available for salmon and smelt, with the most concerning outcome being possible starvation. And it’s not just fish that are at risk.
During normal years in which wetlands are managed properly and typical rice acreage is winter-flooded, there is enough food to maintain waterfowl populations throughout the winter months. However, during times of drought, models predict that food resources may run short in the middle of winter right when bird numbers are at their peak and food demand is highest. This will likely result in substantial losses of birds that rely upon this Pacific Flyway habitat.
Ducks Unlimited and our partners are convinced this problem can be reversed and, if we desire to have healthy populations of salmon, smelt, waterfowl and the remainder of Sacramento River ecosystem constituents, it must be reversed. It is vitally important that we allow the food produced in the floodplain, along with the healthy growth of fish, to provide much-needed biological relief and support the sustainability of our rivers.
This can only occur by having water available for the floodplain and by encouraging water users and managers involved with the Central Valley’s water to provide functional and targeted flows that are directly tailored for specific purposes and benefits to “nature’s pantry.” Continuing to develop voluntary agreements, consistent with a functional flow approach, will ensure that this important work in the Sacramento Valley will benefit fish and wildlife.
The views expressed in this article belong to the author and do not necessarily reflect the editorial policy of Water Deeply.