IMPACTS OF BEETLE KILL ON MODELED STREAMFLOW RESPONSE IN THE NORTH PLATTE RIVER BASIN

A beetle epidemic across the western United States has resulted in the death of millions of acres of forests. This beetle outbreak, referred to as “beetle kill”, has caused many to believe that such dramatic changes in land cover could potentially alter the hydrology of the impacted regions. One of the most important hydrological processes that beetle kill has the potential to impact is streamflow. This research evaluates the hydrologic impacts on streamflow from land cover change due to beetle kill in the North Platte River Basin (NPRB) (Colorado and Wyoming, USA) by utilizing the Variable Infiltration Capacity (VIC) hydrologic model. Utilizing the National Agricultural Imagery Program (NAIP) dataset from 2005 / 2006 (onset of “beetle kill”) to more current conditions (2009), a decrease in tree cover of 16% to 40% was estimated. This decrease in tree cover was applied to VIC modeled streamflow from 1950 to 2000. The VIC model predicted a minimal increase in streamflow of approximately 5% which was not statistically significant.

RECONSTRUCTIONS OF HYDROLOGIC VARIABLES IN THE NORTH PLATTE RIVER BASIN

Reconstructions of hydrologic variables are commonly created using tree-ring chronologies (TRCs) to generate information about historic climate and potential future variability. This study used TRCs to reconstruct annual streamflow, April 1st Snow Water Equivalent (SWE), and soil moisture in the North Platte River Basin (NPRB). Stepwise linear regression was performed to determine which of the 55 moisture sensitive TRCs were the best predictors of hydrologic variation. The regressions explained 63% of the variability in streamflow, 55% of the variability in SWE, and 66% of the variability in soil moisture. This study then maximized the overlapping period of records which resulted in a decrease in the percent of variability explained but indicated that the regression models were stable for long reconstruction periods. This study successfully reconstructed all three hydrologic variables for NPRB to 1438 or earlier. Temporal wet and dry periods for streamflow and SWE were closely aligned while soil moisture did not follow similar temporal patterns. This was likely due to a natural “lag” between soil moisture and streamflow / SWE given soil moisture tends to retain antecedent signals. The availability of reconstructed hydrologic data in NPRB allows for a better understanding of the long-term hydrologic variability in the region.

Quantifying 87Sr/86Sr temporal stability and spatial heterogeneity for use in tracking fish movement

The specificity and accuracy of inferred fish origin and movement relies on describing spatial heterogeneity and temporal stability of environmental signatures. But the cost and logistics of sample collection often precludes the complete quantification of environmental signature temporal stability and spatial heterogeneity. We used repeated sampling and a novel approach (Bayesian ridge regression, BRR) to quantify the temporal stability and spatial heterogeneity of 87Sr/86Sr, respectively. We explained 86% of observed variation in 87Sr/86Sr using a BRR model and estimated 87Sr/86Sr throughout the Upper North Platte River Basin with high accuracy (±0.00106). Year to year variation in 87Sr/86Sr signatures ranged from 0.00007 to 0.00073 (SD), while seasonal variation ranged from 0.00091 to 0.00134 (SD). We then assessed the specificity and discussed the accuracy of inferring movement using three scenarios of described spatial heterogeneity. Our results indicate reliable inference of fish movement requires comprehensive quantification of spatial heterogeneity and temporal variation in environmental signatures.

Cutthroat Trout: Evolutionary Biology and Taxonomy

<em>Abstract</em>.—Despite major declines in distribution and abundance of Cutthroat Trout <em>Oncorhynchus clarkii </em>across their native range since European settlement, substantial morphological and genetic diversity remains. For example, recent molecular investigations revealed the presence of six discrete lineages of Cutthroat Trout native to the Southern Rocky Mountains rather than four as previously thought. These include the previously recognized Yellowfin Cutthroat Trout <em>O. c. macdonaldi </em>(extinct) and Rio Grande Cutthroat Trout <em>O. c. virginalis</em>, as well as the true native of the South Platte River basin, located east of the Continental Divide, which we continue to refer to as Greenback Cutthroat Trout. Within the range of Colorado River Cutthroat Trout <em>O. c. pleuriticus</em>, which is located west of the Continental Divide, we highlight two divergent clades that historically occupied upstream, coldwater reaches of the Green River and Colorado River basins. Both are also found outside their historical ranges as well, due to extensive, mostly undocumented stocking in the early 20th century that served to conceal native diversity in the region. An additional clade closely aligned with those two Colorado River groups historically occupied the San Juan River basin. In this chapter, we discuss both molecular and morphomeristic evidence that indicates distinct lineages are aligned with major drainage basins, information that guides ongoing conservation actions.

Streamflow Depletion

Much of the book’s discussion thus far has focused on groundwater depletion. However, as wells continue to pump, the source of water increasingly comes from surface water. This chapter examines how depletion of even a small part of groundwater storage can have large impacts on surface-water resources. Yet despite this critical connection, different laws govern surface water and groundwater. Solving this complex water resource relationship also involves accounting for the delayed effects of pumping on surface-water resources. The ongoing challenges for conjunctive management are illustrated by the South Platte River basin of Colorado, as well as the Arkansas and Republican Rivers.