Field validation sites in the Skykomish subbasin.

<p>Field validation sites in the Skykomish subbasin.</p

BIP model in the Snohomish Basin.

<p>Large, low-gradient rivers and small, high-gradient streams are grouped as having low or no BIP, while small to mediums sized low-gradient streams have moderate or high BIP.</p

Geomorphic characteristics of stream segments in the Snohomish River Basin occupied by beaver.

<p>(A) Valley widths versus slope, (B) valley width v. bankfull width. Crosshair lines represent the standard deviations, and square symbols are the means. Note that the scale is logarithmic. The data show that dam-building beaver generally prefer streams with percent slope < 0.04, bankfull width < 8 m, and valley width > 30 m.</p

The Snohomish River Basin, Washington State (USA), showing the Skykomish River sub-basin, with major and minor river bodies.

<p>BIP was modeled in the entire Snohomish Basin and validated using survey data from the Skykomish sub-basin. Input data to inform model variables was derived from stream segments in the Snohomish watershed, but excluded the Skykomish sub-basin where model validation occurred.</p

Model validation contingency table and supporting test statistics, comparing field-observed BIP with modeled BIP (left), and evaluation of model prediction at sites currently or historically occupied by beavers (center), and actively occupied sites (right).

<p>Model validation contingency table and supporting test statistics, comparing field-observed BIP with modeled BIP (left), and evaluation of model prediction at sites currently or historically occupied by beavers (center), and actively occupied sites (right).</p

Study area precipitation.

<p>Study area precipitation.</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

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

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

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