"Mainstem" honors the legacy of the Pick-Sloan Flood Control Act of 1944, under which South Dakota gave up nearly 595,000 acres for the creation of four mainstem dams. In return, South Dakota was promised irrigation and water access. Today, rural systems like WEB, Mid-Dakota, Mni Wiconi, and Lewis & Clark are the true beneficiaries — yet only 5.5% of the water allocated to South Dakota under Pick-Sloan is currently used. Dakota Mainstem seeks to fulfill that promise more fully.

The Missouri River accounts for 80% of all flowing water in South Dakota. Accessing additional groundwater in the future is complicated by its variable quality, which makes collection and treatment challenging. The river’s storage capacity and water quality are unmatched. 

The Appraisal Study will explore:

·       Identify the needs

·       Available alternatives

·       Environmental impacts

·       Cultural impacts

·       Site and route determination

·       Best practices and design

·       Treated water standards

·       Pipeline materials

·       Pumping and storage strategies

·       Financing options

The Feasibility study would follow by exploring:

·       Project justification

·       Engineering concepts

·       Cost estimates

·       Environmental and cultural findings

·       Governance recommendations

·       Funding strategies

This foundational work is essential for securing federal and state support and aligning the project with the region's long-term water infrastructure needs.

The project will provide an abundant supply of clean, safe water to areas in need. It will support sustainable growth, strengthen economic development, and attract water-intensive industries to member locations.

The Missouri River offers reliable, high-quality water. With existing resources and infrastructure, South Dakota is well-positioned to draw, treat, and distribute water from the river efficiently and cost-effectively over the long term.

·       Addressing Water Scarcity and Building a Sustainable Future

The Upper Midwest is not immune to the challenges of water scarcity facing much of the nation. While our region has historically relied on groundwater, this resource is increasingly at risk—overdrawn, degraded in quality, and susceptible to drought. Many communities are already encountering insufficient water supplies to meet current needs, let alone future demand driven by population growth, agriculture, and industry.

·       Dakota Mainstem is a sustainable solution.

By leveraging the Missouri River—a renewable, high-quality source that accounts for 80% of South Dakota’s flowing water—we can build a water system that is not only resilient to climate change but also scalable to serve generations to come. This project would draw less than 1% of the river’s average daily flow, making it environmentally responsible and operationally feasible.

·       Regional water systems are the future of sustainability.

Dakota Mainstem would reduce reliance on vulnerable aquifers, spread costs across multiple users, and allow for consistent, regulated surface water treatment. WEB, Mid-Dakota, Mni Wiconi, and Lewis & Clark have proven that surface water systems can transform regional economies and public health.

The Missouri River's flow downstream of South Dakota varies due to factors such as dam releases, seasonal changes, and weather conditions. On average, the river's discharge at Sioux City, Iowa—just downstream of South Dakota—is approximately 26,614 cubic feet per second (cfs). This flow rate translates to about 17.2 billion gallons per day.​ While DMRWS does not yet know how much water the project will require to withdraw from the river to meet its needs, it’s safe to say that it will be a small fraction of the water flowing out of South Dakota each day. By way of example, a need to divert even 200 million gallons of water per day, which is likely on the high side, translates to about 1% of the water flowing out of the state each day.

Other states, upstream, downstream, and out of the Missouri River basin, are already exploring ways to access the Missouri River to service their own communities. South Dakota and the region nearby must work together to assert a right to this resource.

With more frequent droughts, unpredictable weather, and rising demand, the time to act is now. Dakota Mainstem will ensure that our region has access to clean, reliable water while respecting environmental and cultural resources. Water is the backbone of public health, economic vitality, and national security—this system will help us protect all three.

Institutional memory in Congress about the 80 (+)-year-old Pick-Sloan Flood Control Act is fading, and with it, the understanding of the promises made to impacted communities—particularly in rural and tribal areas. If we don’t bring those commitments back into today’s conversations, we risk losing the opportunity to fulfill the original vision of Pick-Sloan and the equitable development it was meant to deliver.

Although the source of all water from the Missouri River hasn’t yet been determined, it is the most likely source. The Missouri River is naturally high-quality. When treated as a surface water source, it produces clean, safe, and healthy drinking water, a fact proven by several large regional water systems already operating in South Dakota.

Yes. Dakota Mainstem Regional Water System is rooted in the spirit of collaboration and stewardship. This effort honors the legacy of past regional water systems—like WEB, Mid-Dakota, Mni Wiconi, Randall, and Lewis & Clark—demonstrating how surface water from the Missouri River can strengthen communities. We acknowledge the sacrifices made by the people and lands of South Dakota during the construction of the Missouri River’s mainstem dams, and we are committed to enforcing the promises made under the Pick-Sloan Missouri Basin Program.

Acknowledgement:

While the Missouri River is anticipated to be a primary source due to its abundance and quality, the feasibility study will also consider other viable sources. These may include additional surface water supplies, groundwater resources, wheeling arrangements, and purchased water agreements. All potential options will be thoroughly evaluated based on sustainability, availability, and cost-effectiveness. This study will result in a unified step toward a more secure, equitable, and sustainable future for all who depend on this critical resource.

A detailed cost estimate will be developed during planning. Funding is expected to come from a combination of federal and state investments, local cost shares, and low-interest loans — modeled after successful projects like WEB, Mid-Dakota, Mni Wiconi, and Lewis & Clark.

Ensuring Safe, Clean, and Affordable Drinking Water

The federal government has a longstanding role in ensuring all U.S. citizens have access to safe and affordable drinking water, as codified in the Safe Drinking Water Act (SDWA) of 1974 (Public Law 93-523). The U.S. Environmental Protection Agency (EPA) sets and enforces drinking water standards. Federal engagement in Dakota Mainstem helps ensure communities meet these standards, protecting the health and well-being of citizens across multiple states.

Supporting rural infrastructure under the Bipartisan Infrastructure Law

The Bipartisan Infrastructure Law (BIL) reinforced commitments to provide clean water to rural areas by making historic investments in water infrastructure, including dedicated funding for underserved rural areas. Supporting rural water projects through the BIL not only aligns with its goals of equity and modernization but also delivers long-term national benefits—strengthening communities, creating jobs, and securing water resources for future generations. Federal involvement is not just support—it’s a partnership that empowers rural America and reflects the values of shared prosperity and sustainable development.

Interstate Coordination and Cooperation

Dakota Mainstem’s membership encompasses South Dakota, Nebraska, Minnesota, and Iowa communities, making it an inherently interstate water system. The Constitution grants Congress the authority to regulate interstate commerce, and interstate water projects often fall under federal purview to coordinate agreements and mitigate conflicts among multiple states.

Federal Oversight of the Missouri River

The Missouri River—the project’s primary water source—flows through seven states (Montana, North Dakota, South Dakota, Nebraska, Iowa, Kansas, and Missouri). Because the river is a major interstate waterway, federal agencies (including the BoR and the U.S. Army Corps of Engineers) have long managed aspects of its development and flow. Dakota Mainstem cannot proceed effectively without federal oversight to balance the interests of multiple states, tribes, and stakeholders.

Fulfilling Trust Responsibilities to Native American Tribes

The Santee Sioux Tribe of Nebraska is already a member of Dakota Mainstem, and other tribes in South Dakota may soon join. By law and established court precedent, the federal government has a trust responsibility to Native American tribes. Through the Department of the Interior, the United States must ensure that tribes have access to essential resources—particularly clean water—and that tribal interests are protected.

Pick-Sloan Act (1944). Obligations

Under the Pick-Sloan Flood Control Act of 1944 (Public Law 78-534), the federal government promised water resource development projects to the region, especially in South Dakota, to compensate for the impacts of constructing mainstem dams and reservoirs. Many communities in South Dakota have never fully received the promised benefits. Dakota Mainstem is an opportunity for the BoR to fulfill lingering obligations and provide long-delayed infrastructure improvements.

Support for National Security and Strategic Industries

Reliable water supplies are critical for numerous industries vital to national security, such as ethanol production, agricultural processing, semiconductor manufacturing (where large-scale data centers depend on ample water), and military installations. By investing in robust regional water infrastructure, the federal government helps ensure the upholding of both economic and national security interests.

Climate Resilience and Drought Preparedness

As climate patterns shift, states along the Missouri River have increasingly experienced droughts, floods, and other extreme weather events. A regional water system improves resilience to these events, mitigating economic losses and human suffering. Federal support is crucial in planning and investing in large-scale infrastructure to ensure climate-change preparedness across state lines.

EPA Regulatory Mandates and Funding Assistance

Federal regulations (administered by the EPA) set limits on drinking water contaminants, yet many rural and tribal communities lack the tax base or technical resources to upgrade infrastructure. Helping fund and build the Dakota Mainstem Project, the BoR and other federal agencies can ensure these communities meet EPA standards, reducing potential public health risks and federal enforcement actions.

Promotion of Economic Development and Rural Vitality

Water-intensive development projects—ranging from agriculture, livestock operations, and food processing to high-tech industries—rely on abundant and safe water. These industries create jobs and sustain rural communities across multiple states. Ensuring water availability through a federal-state partnership will create jobs and help prevent population decline in rural areas, supporting the broader national economy.

Equitable Water Allocation and Regional Stability

Federal involvement helps ensure that water resources are allocated fairly across communities and states. An independent federal agency such as the BoR can be an impartial party that balances competing interests (e.g., upstream vs. downstream users, agricultural vs. municipal needs), reduces interstate disputes, and fosters regional stability.

Leveraging Federal Expertise and Resources

The BoR has over a century of experience planning, designing, and constructing large-scale water infrastructure projects in the western United States. By engaging federal engineers, hydrologists, and technical specialists, Dakota Mainstem gains access to expertise, research, and financial resources far beyond what individual states or local entities typically muster.

Ensuring Long-Term Public Health and Safety

Large-scale water systems such as Dakota Mainstem serve populations across broad geographic areas, where local water sources may be vulnerable to contamination, drought, or poor infrastructure. A robust regional water supply reduces public health risks, enhances firefighting capabilities, and ensures safe water for future generations, further justifying the federal government’s role as a public health and safety guarantor.

These reasons underscore the federal government’s legitimate and necessary stake in the Dakota Mainstem Regional Water System. By supporting and funding this multi-state, multi-tribal undertaking, the U.S. Bureau of Reclamation and other federal agencies uphold their legal obligations, promote interstate cooperation, and secure economic, public health, and national security benefits for present and future generations.

No. Dakota Mainstem is intended to supplement—not replace—existing supplies. Local systems will maintain ownership and control. Dakota Mainstem’s Bylaws protect the provider/customer relationship. If a member opts to replace their supply due to quality or capacity issues, that choice is theirs.

A 1989 study near Yankton recorded the 57-year average flow of the Missouri River at 17.2 billion gallons per day. While flow may have slightly declined since, this figure remains valid for planning. The water used by Dakota Mainstem would represent less than 1% of that flow — truly, a drop in the bucket.

We encourage all interested systems and communities to contact the Dakota Mainstem planning team. Letters of support, participation in stakeholder meetings, and formal expressions of interest will help guide design and routing decisions.