Study area precipitation.

<p>Study area precipitation.</p

BACI analysis of reach scale stream temperature.

<p>BACI analysis of reach scale stream temperature.</p

Change in wetted channel area.

<p>Change in wetted channel area.</p

Beaver dam increase.

<p>Total number of intact natural dams and BDA structures actively maintained by beaver in the 34-km study area (a), and number of intact natural dams and BDA structures within 500 m upstream of stream temperature monitoring sites that spanned the entirety of the study period (b). Vertical hashed line shows date of BDA structure installation.</p

Regression analysis of longitudinal temperature change.

<p>Linear regressions showing the seasonal relationship between the mean daily longitudinal change in minimum, mean, and maximum temperature and the density of intact beaver dams (dams/km) between each temperature monitoring site. Grey hashed line at 0 provided as a reference for no longitudinal temperature change. Positive regression lines indicate increasing and negative lines indicate decreasing temperatures from up to downstream.</p

Distribution of daily stream temperature differences before and after beaver dam increase.

<p>Gaussian distribution of the seasonal difference in daily stream temperatures between the control site with no beaver dams (Rkm 32.39), and sites where dam abundance increased dramatically during the study period. Difference are expressed for each season before (grey curve) and after (black line curve) increased dam abundance for minimum, mean, and max daily stream temperature.</p

Moderation of maximum summer temperature by beaver dams.

<p>Linear relationship between August maximum daily temperatures measured below the control site with no upstream beaver activity (x-axis, rkm 32.39) and at a site (y-axis, rkm 6.16) prior to (open circles, 2008 and 2010) and following (black circles, 2013 and 2014) development of beaver dam complexes. This regression serves to demonstrate how buffering of daily temperature maxima by beavers minimizes the number of days that temperatures are above or approaching critical thresholds for juvenile steelhead (<i>O</i>.<i>mykiss</i>) during periods of extreme summer temperatures.</p

Channel scale stream temperature heterogeneity.

<p>High-density temperature monitoring locations (upper panels) and hourly stream temperature (lower panels) within the beaver dam/BDA impounded reach (left panels– 22 locations) and the unimpounded reach (right panels– 10 locations). Inset box shows narrow range of stream temperatures observed within the unimpounded reach due to lack of surface water—groundwater exchange.</p

Climate, discharge, and stream temperature for the study period.

<p>Seven-day minimum and maximum air temperature range at the study area (a). Seven-day mean discharge measured near the mouth of Bridge Creek (b). Minimum, mean, and maximum daily stream temperatures for monitoring sites located in the cooler upstream (c, river km 32.39) and warmer downstream (d, river km 3.00) reaches of the study area. Gaps in temperature data indicate when a site was not operational, when a logger may have been lost during high flow, or was suspected to have been out of the wetted channel. Right panels show a more detailed view of a single year (2013) of air temperature, discharge, and stream temperatures, with vertical black lines representing astronomical seasons.</p

Regression analysis of longitudinal temperature change.

<p>Regression analysis of longitudinal temperature change.</p