The MRB, which overlaps the Northern Great Plains (NGP), functions as the “life zone” for the larger Mississippi River Basin, providing grassland habitat that infiltrates precipitation and recharges groundwater, reduces sediment erosion, filters nutrients, stores carbon, and provides critical habitat for wildlife. However, most of the terrestrial land in the NGP is used for agricultural purposes, either as cropland or rangeland for livestock. This creates a unique challenge for conservation. WWF is interested in understanding the impact on water resources when grassland is converted to cropland, to help inform conservation priorities.
We developed a large-scale, screening level Soil and Water Assessment Tool (SWAT) to estimate the impact of avoided conversion of grassland on water quantity and quality. LimnoTech acquired data and information for the study area, developed the model and compared a “baseline” scenario to a “grassland conversion” scenario in terms of water, sediment and nutrient (phosphorus and nitrogen) yields from the landscape to determine the benefits of conserving grasslands.
Study results suggest that the avoided conversion of grasslands to cropland could potentially save billions of gallons of water in the basin, and prevent additional sediment, phosphorus, and nitrogen loading. The avoided conversion of grassland will likely result in additional environmental benefits that have not been quantified as part of this work, including preservation and protection of terrestrial and aquatic habitats, maintenance and protection of biodiversity of plants, terrestrial wildlife, and aquatic life, flooding mitigation and recreational benefits.