Modeling climate change impacts on a Vermont watershed

Oct. 15th 2018
Instrumenting for watershed modeling

Climate change will impact human and environmental systems in complicated ways that are still being explored. This includes sediment transport and mobilization within watersheds. In the northeastern U.S., trends of increasing precipitation are outpacing those of other regions in North America. Examining local and regional climate trends is vital to better understand how humans and local ecosystems will be impacted by climate change.

The U.S. has already seen increases in the frequency of extreme precipitation events (the heaviest 1% of rainfall events). These extreme events can cause streambank erosion and failure. Sediment is mobilized, and sediment yields increase when streambanks erode, which can exceed the capacity of current infrastructure. Extreme precipitation events can also carry excess nutrients, like phosphorous, into waterbodies. The movement of soil and excess water and nutrients contribute to a decrease in water quality, and land and habitat loss. Furthermore, erosion, undercutting of streambanks, and incision of streams can reduce flood resiliency of the surrounding area.

A recent study by Stryker, Wemple and Bomblies from the University of Vermont used models on the Mad River watershed in Vermont to assess the impacts of local temperature and precipitation trends on discharge and sediment loads. The Mad River drains into Lake Champlain, which has experienced an increase in harmful summer cyanobacteria algal blooms. The watershed is representative of other northeastern watersheds, where steep headwaters drain to floodplains with a history of deforestation for agriculture. This study helps researchers understand how potential changes in temperature and precipitation can affect water quality of streams, rivers and receiving waters.

The study used mechanistic hydrological and sediment transport models driven by temperature and precipitation data. Streambank erosion and failure was simulated using temperature and precipitation scenarios developed to represent potential future climate conditions in the northeastern United States. Overall, results clearly showed that precipitation and temperature both significantly influenced discharge and sediment mobilization. Specifically, the study concludes that local increases in temperature and precipitation will likely increase sediment loading in the watershed as a result of changes in snow melt and an overall increase in wetter conditions, and in response to increases in extreme precipitation and flow events. These influences will likely create significant instances of streambank erosion and sediment loading, which would affect ecosystems, water quality, infrastructure, and overall watershed health and sustainability.

Studies like this help offer new opportunities for identification of high risk areas and for further work simulating potential climate change impacts, including examining targeted mitigation and management practices.