Cheyenne Bottoms, located in central Kansas, is the largest inland marsh in the United States. However, in recent years, this important wetland area has often been unusually dry. There are several factors that have contributed to the drying of Cheyenne Bottoms.
Declining Water Inflows
Cheyenne Bottoms depends on water flows from the Arkansas River to maintain its wetland ecosystem. There are three main sources of river water that fill the marshes:
- Walnut Creek
- Blood Creek
- Deception Creek
These creeks channel water from the river into the wetland area. However, river flows have declined over the years due to drought, water diversions, and reservoir construction upstream. Less water reaching the sources of the creeks means less water making it to Cheyenne Bottoms.
Drought
Periods of drought in the Arkansas River basin lead to reduced water flows. Multi-year droughts, like those experienced in the 2010s, severely limit the amount of water entering Cheyenne Bottoms. During drought years, the area may receive only 10-25% of normal inflows.
Water Diversions
Over 300 ditches, canals, and pipelines divert water from the Arkansas River basin for irrigation and municipal use before it reaches Cheyenne Bottoms. It is estimated that 57% of the river’s flow is lost to diversion and consumption above the wetland. As water demands increase upstream, less water is left to maintain the marsh ecosystem.
Reservoir Construction
Large reservoirs built on the Arkansas River over the past 60 years capture water before it can reach Cheyenne Bottoms. For example, the construction of Cedar Bluff Reservoir in the 1950s led to noticeable drying of the wetlands. Reservoirs hold back peak flows needed to flood the marshes.
Sedimentation
Another factor contributing to the drying of Cheyenne Bottoms is sedimentation. Over time, soil particles carried in the incoming water have accumulated on the marsh bottom. This has gradually made the wetland shallower. It is estimated that sedimentation has reduced the maximum depth of Cheyenne Bottoms by 75%. With less capacity to hold water, the area dries out faster between infrequent flood events.
Climate Change
Climate change may also be exacerbating drying at Cheyenne Bottoms. Rising temperatures increase evaporation from the open water and soils of the marsh. At the same time, climate models project decreases in total precipitation and river flow for the region. Drier overall conditions due to climate change make it harder to maintain proper water levels in the wetland.
Efforts to Restore Water Flows
Government agencies and conservation groups are working to restore normal water flows to Cheyenne Bottoms. Some of the strategies being implemented include:
- Constructing small dams and levees to retain more water in the marsh
- Diverting flows from other rivers and creeks into the wetland area
- Building sediment traps to reduce accumulation on the marsh bottom
- Purchasing water rights to guarantee minimum inflows
- Removing invasive plant species that use excess water
However, fully restoring the marsh to historic water levels has proven difficult given all the factors involved. Completely offsetting declining river flows and increasing sedimentation remains challenging.
Impact on Wildlife
Drying of Cheyenne Bottoms has significantly impacted the wildlife populations that depend on the wetland ecosystem. During dry periods, there is a drastic reduction in the number of migratory birds that use the area for resting and feeding. The table below shows declines in peak shorebird numbers during recent drought years compared to normal years:
| Year | Peak Number of Shorebirds |
|---|---|
| Normal | 250,000-500,000 |
| 2012 (drought) | 25,000 |
| 2013 (drought) | 70,000 |
| 2017 (drought) | 18,000 |
In addition to birds, fish populations crash during dry times as the remaining marsh pools grow shallow, hot, and crowded. For example, massive fish kills involving hundreds of thousands of individuals have occurred during recent droughts.
Other Effects of Drying
Beyond impacts to wildlife, drying also affects the area in other ways:
- Exposes more open soil to wind erosion
- Allows expansion of invasive plant species
- Reduces natural water filtration and flood control capacity
- Decreases recreational opportunities like fishing and bird watching
These effects demonstrate the importance of maintaining proper water levels at Cheyenne Bottoms for ecological and economic reasons.
Conclusion
In summary, Cheyenne Bottoms has been drying in recent decades due to declining inflows from the Arkansas River basin. This is driven by a combination of factors including drought, water diversions, reservoir construction, sedimentation, and climate change. Drying has had major negative impacts on wildlife populations that depend on the marsh ecosystem. Restoration efforts have so far been unable to replicate historic water levels and flooding cycles. Managing water use and sediment accumulation in the Arkansas River watershed will be key to returning Cheyenne Bottoms to a healthy wetland system.
