Blossoming friendships across two nations

Arakawa-Potomac Sister River Agreement

Throughout the years, the blooming cherry trees along the Tidal Basin have become the harbinger of spring in the District of Columbia. The same holds true for the residents of the Potomac’s sister river in Japan.

In 1912, First Lady Helen Taft planted the first of what would end up being more than 3000 cherry trees along the Potomac River. The trees were a generous donation from Mayor Yukio Ozaki of Tokyo in honor of the lasting friendship between the United States and Japan.

These majestic pink blooms also tie us to a river across the world known as the Arakawa.

 Sister River Agreement

More than 80 years after that first sapling was put in the ground, an even deeper connection was made by citizens of the two countries. The Arakawa-Potomac Sister River Agreement, co-signed by the Interstate Commission on the Potomac River Basin and the Arakawa Sakura Club in March of 1996, set in motion efforts to actively develop international friendship between residents and communities of the Arakawa and Potomac watersheds. In 2012, Society of Arakawa River succeeded the Arakawa Sakura Club and we reestablished a sister river partnership ever since. To this day, it still fosters information and friendship across the two nations.

The two rivers mirror each other in many ways. A combined 16 million people rely on these two watersheds for drinking water. Each watershed also provides countless ecosystem services and recreation opportunities to its residents and visitors alike. People fish and boat between its riverbanks, and enjoy picnics, soccer games, and other diversions below the cherry trees along the river.

About the Arakawa

A member of the Arakawa River Society (left) and Dann Sklarew of George Mason University (right) hold the signed Arakawa-Potomac Sister River Agreement.

Just as the Potomac begins its journey in the scenic mountains, flowing into a busy metropolis, so does the Arakawa.

Heavy agricultural irrigation upstream as well as metropolitan water use strain the resources of the river. Historically, flooding has been a major problem in the area. Several reservoirs and retaining walls within the city have helped to alleviate these problems but have also degraded the natural beauty of the river.

Just like the Potomac River, a resurgence in an environmental ethic has led to a river renaissance for the Arakawa. An expansion of open spaces, a focus on riparian buffers, and a renewed interest in recreation have improved this essential resource. In 2024, The Arakawa River Society held a successful swimming competition.

Arakawa—also known as Kantō and roughly translates to “Wild River”—flows from the center of the island of Japan off Mount Kobushigatake. The river flows through the capital city of Tokyo into Tokyo Bay as the Potomac flows through Washington, D.C. into Chesapeake Bay.

The Arakawa watershed includes the Arakawa spillway, which was constructed in 1924 to control dangerous flooding, and the Sumida River, which branches off the Arakawa and flows through central Tokyo. Like the Potomac, the Arakawa provides the majority of drinking water to the residents of its capital region.

The symbolic tie between the two groups grows along the Tidal Basin in Washington, D.C., where cherry trees from the banks of the Arakawa were planted more than a century ago as a gift of friendship. Later in the century, cuttings of the D.C. trees were taken back to Japan to replace diseased trees.

Trees tie us together

Cherry tree planting during Arakawa-Potomac partnership visit (2001). Photo credit: ICPRB

In 2001, our friends from the Arakawa River Society in Japan visited the Potomac watershed, planting a new cherry tree with ICPRB at Hains Point. Arakawa Society members learned from science educators at area high schools, visited the Hard Bargain Farm run by the Alice Ferguson Foundation, went on a boat tour with the Anacostia Watershed Society, visited historic Occoquan, and Harpers Ferry. A similar trip was held in 2019. Members of ICPRB’s staff have visited Japan over the years as well.

The Arakawa-Potomac Sister River Agreement has helped all involved to exchange new ideas about each watershed. As there are concerns about certain contaminants such as bacteria, algae, and PFAS in the Potomac, there are concerns about the same substances in the Arakawa. As there are efforts to make the urban Potomac swimmable, there are efforts to make the Arakawa swimmable. Though on opposite ends of the world, both water bodies face similar challenges. Fortunately, both watersheds benefit from a myriad of organizations and individuals who take up the cause of improving the river.