The temperature and surface geophysical data contained in this release have primarily been collected to support groundwater/surface water methods development, and to characterize the hydrogeological controls on native brook trout habitat. All data have been collected since 2010 along the Quashnet River corridor located on Cape Cod, MA, USA. Cape Cod is a peninsula in southeastern coastal Massachusetts, USA, composed primarily of highly permeable unconsolidated glacial moraine and outwash deposits. The largest of the Cape Cod sole-source aquifers occupies a western (landward) section of the peninsula, and is incised by several linear valleys that drain groundwater south to the Atlantic Ocean via baseflow-dominated streams. Strong groundwater discharge to the Quashnet River supports a relatively stable flow regime, as monitored by USGS gage 011058837, located at the downstream end of typical field research focus areas. The lower Quashnet River emerges from a narrow sand and gravel valley to a broader area with well-defined lateral floodplains. Historical cranberry farming practices, abandoned in the 1950s, have modified the stream corridor as described by: Barlow, P. M. and Hess, K. M.: Simulated Hydrologic Responses of the Quashnet River Stream-Auquifer System to Proposed Ground-Water Withdrawals, Cape Cod, Massachusetts, U.S. Geol. Surv. Rep. 93-4064, 51, 1993. The Massachusetts Division of Fisheries and Wildlife has been monitoring brook trout populations in the Quashnet River since 1988 and movement since 2007. Groundwater influence on stream temperature is pronounced, particularly over the 2-km reach above the USGS gage, below which stream stage is tidally affected.