Dams show promise for sustainable food systems, but we should tread lightly

Dams show promise for sustainable food systems, but we should tread lightly

Dams are an engineering marvel generating energy for millions people around the globe. However, some dams have negative environmental side effects. They can cause more inbreeding in livestock by seperating their populations to causing sediment to flow in rivers , which deprives wetlands from resources.

In Washington, the Snake River, the Columbia River’s largest tributary is home to four controversial dams, known as the Lower Snake River Dams . For decades, environmentalists have been calling for their removal due in large part for the effects on the region’s salmon population. While the dams include ladders and other fish passages, they still have made it difficult for the fish to make it to the Pacific Ocean. Three of the river salmon species have been declared endangered or threatened. Meanwhile, the orca whales in the area are running out of salmon . A 2022 report from NOAA said that rebuilding the area’s salmon population will require large-scale actions, including breaching the dams.

While every dam and related water basin is different, some existing dams could be part of a more sustainable future when water from their reservoirs is used in irrigation for farming, according to a study published today in the journal Proceedings of the National Academy of Sciences (PNAS). The study examines how much water storage is needed to maximize crop irrigation without depleting water supplies or encroaching upon nature. It also explores how many people this watering method could feed. They found that dammed reservoirs could be used to store more than 50 percent of the water needed for such irrigation.

[Related: Dams are hurting this enigmatic Australian species. ]

The researchers analyzed the natural hydrological cycle (or water cycle) to see how much freshwater in both surface and groundwater bodies is created and renewed by this natural process, and how it compares to the water needs of current farmland. They found that storage-fed irrigation could be used to grow enough food for about 1. 15 billion people around the world

The authors also found that if all of the 3,700 potential dam sites that have previously been mapped out to generate hydroelectricity throughout the globe were built and partially used for crop irrigation, they could supply enough water storage to irrigate crops for about 641 million people.

While dams have potential, the authors caution against relying on them as a major sustainable solution, due to their socio-environmental consequences. In some circumstances, dams have fragmented rivers and displaced people. They are also more expensive, cause high levels of water loss, and have negative ecological consequences.

“Amongst all supply and demand side options to increase food and water security, building more dams should be the last resort,” the researchers said in a joint statement.

The authors also stress that even large reservoirs can only make up a small part of the solution. Instead of building new dams, they recommend a serious evaluation of other options.

According to the researchers, some alternative solutions for more environmentally sound water storage for irrigation are using small dams to harvest water, recharging groundwater systems with water from winter storms or snow melt in the spring, and better management of soil moisture on fields. The team points out that better irrigation techniques and crops that are more in line with water availability can help reduce the need for stored water.

“There is an urgent need to explore alternative water storage solutions, but we have to acknowledge that many dams are already in place,” said study lead author Rafael Schmitt, a research engineer with the Stanford Natural Capital Project, in a statement. “Our research reveals their critical role in ensuring food safety in the future .”

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Better water storage techniques using dam reservoirs could help create a more sustainable agricultural future. Farming practices in many parts of the world pollute and deplete water resources, can damage natural landscapes, and generate about one-third of global greenhouse gas emissions. Roughly two-thirds of cropland around the world depends on rainfall, and in times of drought the deficit is made up via non-sustainable water resources such as non-renewable groundwater or impeding environmental flows.

[Related: How AI could help bring a sustainable reckoning to hydropower. ]

“Nutritional security is a core challenge for sustainable human development,” said study senior author Gretchen Daily, co-founder and faculty director of the Stanford Natural Capital Project, in a statement. “Our study highlights the urgent need and opportunity for nature-positive investments into irrigation and water management to reduce harmful impacts of agriculture while supporting other vital benefits of farmland and freshwater ecosystems.”

Eric Edwards, an assistant professor at North Carolina State University’s Department of Agricultural and Resource Economics who was not involved in the study told PopSci that this paper is tackling an important food production issue, “Focusing on irrigation is a key question as a changing climate will make patterns of precipitation more variable, which could affect the security of the world’s food supply.”

Edwards warns that this study does not provide a benefit-cost analysis. He also points out that water problems are localized and therefore more global solutions may not be as effective. He stated that individual dam projects could still create large ecological problems or be too costly relative to the financial benefits they provide. Dams and the associated irrigation water distribution infrastructure are very costly. These projects are often not justified on the basis of improvements in agricultural production. They can instead be explained as governmental subsidies .

According to Edwards, this paper could also be used by policymakers and researchers to conduct further research on how to use the water basin.

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