Streamflow response to changes in land cover and climate in Lower Michigan
Hook, James C., III
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Studies of the influence of basin land use on the hydrologic response of streams to climate change are limited, and have generally focused on individual land use types in isolation. Prediction of future hydrologic change requires a comprehensive understanding of the relative influence of multiple land cover classes on streamflow response to changes in climate. A statistical analysis of 20 Lower Michigan watersheds spanning various environmental gradients was used to determine the influence of land cover and climate on streamflow change during the period 1935-2008. A second analysis, a temporal, pairwise comparison of neighboring basins with similar climatic and environmental characteristics and different land use histories, was used to further refine the impacts of land cover change on stream hydrology and to identify explanatory trends. Urbanization and agriculture were found to have significant effects on streamflow response to climate changes. Urbanized and agricultural basins were both observed to exhibit increases in baseflow and overall average streamflow, and declines in peak flows. Urbanization was found to generally contribute more significantly to these trends than agriculture. Peak flows were found to be negatively affected by urbanization, a likely consequence of increased stormwater management and retention capacity later in the study period. These findings suggest that conservation measures and increased outflows associated with human activity, coupled with significant increases in precipitation, have contributed to both higher delivery of water and reduced flood volumes to Lower Michigan streams.