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Projecting the Impacts of Land Cover Change on Drinking Water Treatment in Minneapolis Minnesota
Citation:
Woznicki, S., J. Wickham, AND G. Kraynick. Projecting the Impacts of Land Cover Change on Drinking Water Treatment in Minneapolis Minnesota. ACES 2018 – A Community on Ecosystem Services, Washington, DC, December 03 - 06, 2018.
Impact/Purpose:
This research provides a case-study for the EnviroAtlas while filling a knowledge gap in drinking water source protection by developing a modeling framework using an ecosystem goods and services approach and land cover change forecasting. The research is centered on an EnviroAtlas community (Minneapolis, MN), with an engaged community partner (Minneapolis Drinking Water Treatment) and local stakeholders. The community partner and local stakeholders are concerned with land cover change in their source watershed and its potential impact on water quality and drinking water treatment. They need EPA ORD expertise in developing a modeling framework to aid their future planning and decision-making processes at the treatment plant scale and landscape scale. Community participation is a key component of this research: the drinking water treatment plant and local stakeholders provide data (e.g. drinking water treatment chemical usage and costs) and direction (e.g. expertise on local conditions and concerns). This research is an opportunity to use EnviroAtlas data to aid the decision-making process at the community and watershed levels, while collaborating with the community to define the research goals to better fit their needs
Description:
Source protection is a critical aspect of drinking water treatment. The benefits of source water quality protection on reducing drinking water treatment costs are clear. However, forecasting the impacts of environmental change on source water quality and its potential to influence drinking water treatment processes is rare. The Minneapolis, MN drinking water treatment plant recognized the threats of land cover change on source water quality in their drinking water watershed, the Upper Mississippi River Basin (UMRB). Consistent losses of forests, wetlands, and grasslands in the watershed, coupled with a projected population increase of one million people by 2030, is of great concern to the drinking water treatment plant with respect to meeting water quality standards in the future. The objective of this study was to relate forecasted land cover change (forest and wetland loss, agricultural expansion, urbanization) to changes in source water quality and drinking water treatment for Minneapolis. The Soil and Water Assessment Tool (SWAT) watershed model was driven with historical land cover change using all eras (2001, 2006, 2011) of the National Land Cover Database (NLCD) to understand the impact of recent change on water quality and drinking water treatment. Then, mid-century projections of land cover change from the the FOREcasting SCEnarios of Land-use Change (FORE-SCE) model were used in SWAT to characterize potential future water quality conditions. The spatially-explicit land cover change projections are based on the A1B, A2, B1, and B2 emissions scenarios from the Special Report on Emissions Scenarios (SRES). In-stream water quality (sediment, nitrogen, and phosphorus) was linked to chemical treatment data at the treatment plant (e.g. alum and powder activated carbon). The land cover change scenarios demonstrate uncertainty in projecting the magnitude of change, although all capture the trend of forest and wetland loss. The “A” scenarios translate these losses to urbanization and agricultural expansion, while the “B” scenarios also lose agricultural lands to urbanization. Forest loss projections range from 390 to 1,370 km2, while urban growth ranges from 330 to 860 km2 and agricultural change from 220 km2 of loss to 610 km2 of expansion. This translates to an additional 22,000 to 216,000 metric tons of sediment erosion to rivers in the watershed annually, up to 940 metric tons of total nitrogen, and 60 metric tons of total phosphorus, highlighting the potential increases in drinking water treatment chemical input requirements. These analyses will contribute to determining the value of natural landscapes in protecting drinking water quality, while providing the Minneapolis drinking water utility with information critical to their planning process.
