CHARACTERIZATION OF SUGAR RIVER WISCONSIN HYDROLOGY: A 95-YEAR ASSESSMENT OF THE IMPACTS OF SHIFTING CLIMATE AND LAND-USE

Land-use change and climate change are both well known drivers in fluvial systems. However, non-stationarity of the hydrologic signal poses significant problems to the larger scale analysis of hydrologic records, including the ability to quantifiably identify the impacts of land-use change and climate change. A combination of traditional statistical methods with wavelet analysis helps better understand recurring periodicities of flow, without the assumption of a stationary signal. In turn, wavelet-defined periodicities facilitate better resolution of influences of changes in land use and climate.

In this study, the continuous 95-year record of the Sugar River (1914-2009) and associated weather stations located in south-central Wisconsin were analyzed using wavelet analysis . The records were also temporally stratified and analyzed using other standard statistical techniques. Results indicate that changes in agricultural land-use since the early 20th century, including a pronounced shift in agricultural practice during the mid-century, altered the discharge pattern of the Sugar River during its 95 year record. Notable changes include magnitude of the base flow, timing and magnitude of floods, and annual average peak in discharge. However, long term trends in flow are contradictory to shifting temporal precipitation patterns, with local peaks in precipitation shifting from June to September pre-1970s, to February to June post-1970. We suggest that the changes in agricultural land-use and agricultural practice mitigated what could otherwise have been larger spring peak flows within the Sugar River catchment.