Modeling the effects of future land use change on water quality under multiple scenarios: A case study of low-input agriculture with hay/pasture production

• Interchanges of land use classes are analyzed using FORE-SCE projections in 2011–2091.
• Land use for year 2091 under three scenarios are incorporated in SWAT modeling.
• Low-input agriculture with increased hay/pasture cultivation improves water quality.

Understanding the relationship between land use and freshwater quality is necessary for effective water management. This study sought to evaluate the impacts of future land use change on water quality in an agriculture dominated watershed in South Dakota. Taking into account three cases (A1B, A2 and B1) of the FOREcasting SCEnarios (FORE-SCE) of Land use Change modeling framework, possible changes in surface runoff, sediment, nitrate and total phosphorus by the end of the 21st century were assessed relative to the baseline (National Land Cover Database 2011) comprising a multi-year period from the recent past (2006–2014). The Soil and Water Assessment Tool (SWAT) was used for simulating hydrology and water quality, where particular attention was given to land transformation from “high-input” to “low-input” agriculture. The analysis revealed that urban areas and low-input hay/pasture production would expand from conversion of forest, grassland and high-input cultivated cropland. While afforestation might also occur under certain future scenario assumptions such as B1, all the three scenarios are suggestive of complete grassland depletion by the first quarter of this century. Simulation results suggested that water quality would improve with expansion of hay/pasture production (as low-input agriculture), reducing surface runoff volume, sediment, nitrate and total phosphorus loads by 3–14% across all three future scenarios of land use change. This study provides an example on how physically-based land use projections can be ingested in SWAT modeling to identify possible environmental implications of future land use changes. Similar studies adopted on large scales would be useful to support holistic water resources management strategies and associated policy interventions.