The hydroperiod of the Mississippi River is an important part of understanding the flow and health of the river. The hydroperiod is a term to describe the average timing of river flooding and low flow periods. It helps to understand how water is available for human use, how sediment moves and how wetland ecosystems change over time. This article looks at the hydroperiod of the Mississippi River and its influence on the Mississippi Delta.
The Mississippi River has an average hydroperiod of 7850 days, with a range between 650 days at the northern end of the river to 10620 days at the mouth of the river in its delta. This means that seasonal floods occur every 10-12 years – flooding providing essential nutrients that help wetland vegetation to survive in both summer and winter months. The winter floods deposit sediment on the banks of the river and its distributaries, forming the delta.
The flooding event in 2019 was recorded as one of the most extensive and broad flooding in the past 200-250 years. Scientists believe it was due to climate change involving warmer ocean temperatures, increased precipitation and subsequent evaporation. The increased river levels affected wildlife, agricultural activities, drinking water supplies and human health. The flooding exposed a number of identifying features of the Mississippi River, including shallow water depths and exposed woody debris.
The flooding also threatened wetlands, an important ecosystem for the Mississippi Delta. Wetland plants are adapted to handle frequent flooding, the lowering of water levels and the fluctuating temperature and salinity of the water. These plants provide vital food and habitat to fish, waterfowl and other wildlife species, as well as protecting shorelines from erosion. The process of sedimentation in the Mississippi Delta helps in the formation of deltaic landforms and wetlands. Migration of wildlife also increases after flooding, which increases the available food sources.
Interactions between the Mississippi River, its tributaries, wetlands and coastal waters are the cornerstone of the hydroperiod of the Mississippi River. The wide range of hydroperiod values is a result of the large range in lengths, fluxes and levels of complexity of the rivers. The hydrodynamics of the river, including the mixing and transport of materials, is affected by the hydroperiod of the river. This affects changes in water levels and the sediment deposition at the mouth of the delta.
The flooding of the river has a significant role in regulating water levels and the transport of materials from the catchment areas, which affects the vegetation and water chemistry of the deltaic environment. Human activities can also have an effect on the hydroperiod. Dams and navigation locks on the river have been used to regulate river flows, but this can reduce the water level volatility and can affect the functioning of the deltaic ecosystems.
Effects on Human Health and Economies
Flooding of the Mississippi River can cause hazardous health conditions and damage properties, structures and infrastructure. Inhabitants of the Mississippi Delta can face various health issues associated with water-borne diseases, arising from the flooding. These include diarrhoea, typhoid, cholera, Hepatitis and dengue fever – the effects of which can be long-lasting and expensive.
Flooding events can bring about economic problems for the local population. Businesses can be affected by disruption in transport and power supplies, leading to loss of revenue and jobs. Road and rail transport can be difficult, leading to higher transport costs, and the power supply can be affected. Crop damage can occur, and the value of land can drop, leading to lower levels of income for the people. The total damages due to flooding in 2019 amounted to $208 million.
The future of the Mississippi Delta is therefore heavily dependent upon thehydroperiod of the Mississippi River. Increasing climate variability and sea level rise is likely to make flooding events more severe and frequent. To cope with this, the river must remain in balance and the management of the river must be managed in such a way that it allows the ecosystem to continue to function.
Environmental Strategies and Solutions
The US Environmental Protection Agency has policies in place to reduce the impact of flooding on the region. This includes new regulations on floodplain management activities and evacuation procedures. The US Army Corps of Engineers is also charged with the task of reducing the harm caused by flooding by constructing levees, floodwalls and floodgates, in addition to other physical measures. These strategies help to protect people, buildings and land from harm.
To reduce the impact of flooding on the deltaic ecosystem, projects have been developed to restore areas of freshwater cover and to reconnect vegetation to the land-water interface. By placing shoals, islands and marshes in the river, the river’s velocity can be reduced. This encourages sediment deposition, which decreases the effects of erosion and increases nutrients available to the ecosystem.
The US Department of Agriculture offers a range of cost-share programs to provide financial assistance for the conservation of wetland areas in the delta. These funds can be used to develop Wetland Reserve Program (WRP) projects to restore the habitats that are important for wildlife. This can help to maintain a healthy and functioning deltaic environment.
Public Involvement in Conservation
The public can also play a role in the conservation of the Mississippi Delta. Projects such as the Million Pines initiative, have been established to raise awareness of the importance of wetland conservation and of the hydroperiod of the Mississippi River. Educational programs are also in place to encourage people to take part in conservation efforts and increase their appreciation of the Delta’s natural resources.
Organizations such as The Nature Conservancy (TNC), work with local communities, businesses and government to develop adaptation strategies and solutions to help reduce the impact of floods on the Mississippi Delta. TNC is involved in projects designed to enhance and restore wetlands and protect water resources. These include the Mississippi Delta and Lower Atchafalaya River Conservation Program, and the Lower Mississippi Floodplains Conservation Program.
The Delta Environmental Society also works to promote conservation of the Mississippi Delta. Public outreach activities, such as camping and birdwatching, are organized to raise awareness of the importance of the Mississippi Delta and encourage public participation in protecting it.
Climate Change Adaptation
To protect the Mississippi Delta from increasing floods, the US government have implemented a range of strategies to mitigate the effects of climate change and water management. These tactics involve the design of integrated hydrological systems, development of regulations for water storage, and improved water quality control. These strategies are complemented by monitoring and interpreting the hydrology of the river.
The US Army Corps of Engineers is also working to improve the functionality of the region’s infrastructure, by improving the design of levees, floodwalls and floodgates. The FEMA disaster relief fund has been used to protect communities and economies from the effects of floods and to create flood resilience plans. A range of projects are currently underway to reduce the impacts of flooding on vulnerable populations in the region.
Adaptation strategies must also consider the effects of climate change on the hydrological cycle. Climate change is likely to reduce the water levels in the rivers, leading to higher salinity levels in the delta and an increase in frequent floods. To counter this, the US Army Corps of Engineers uses long-term modeling to understand the impacts of climate change and develop solutions for protecting the region from floods.
Conclusion
As the hydroperiod of the Mississippi River has implications for the environment, human health and economies, it is important to understand the dynamics of the hydroperiod and the changing climate. The US government have implemented a series of strategies to reduce the impacts of flooding and to build the region’s resilience to climate change. The public can also play a role in the conservation of the Mississippi Delta, by participating in conservation activities and lending their support to wetland conservation initiatives.
