Brian G. Laub | USGS Science

USGS2018

Evaluating the conservation potential of tributaries for native fishes in the Upper Colorado River Basin

We explored the conservation potential of tributaries in the upper Colorado River basin by modeling native fish species richness as a function of river discharge, temperature, barrier‐free length, and distance to nearest free‐flowing main‐stem section. We investigated a historic period prior to large‐scale water development and a contemporary period. In the historic period, species richness was log‐linearly correlated to variables capturing flow magnitude, particularly mean annual discharge. In the contemporary period, the log‐linear relationship between discharge and species richness was still evident but weaker. Tributaries with lower average temperature and separated from free‐flowing main‐stem sections often had fewer native species compared to tributaries with similar discharge but with warmer temperature and directly connected to free‐flowing main stems. Thus, tributaries containing only a small proportion of main‐stem discharge, especially those at lower elevations with warmer temperatures and connected to free‐flowing main stems, can support a relatively high species richness. Tributaries can help maintain viable populations by providing ecological processes disrupted on large regulated rivers, such as natural flow and temperature regimes, and may present unique conservation opportunities. Efforts to improve fish passage, secure environmental flows, and restore habitat in these tributaries could greatly contribute to conservation of native fish richness throughout the watershed.

Upper Colorado River Basin↗

USGS2015

Application of science-based restoration planning to a desert river system

Persistence of many desert river species is threatened by a suite of impacts linked to water infrastructure projects that provide human water security where water is scarce. Many desert rivers have undergone regime shifts from spatially and temporally dynamic ecosystems to more stable systems dominated by homogenous physical habitat. Restoration of desert river systems could aid in biodiversity conservation, but poses formidable challenges due to multiple threats and the infeasibility of recovery to pre-development conditions. The challenges faced in restoring desert rivers can be addressed by incorporating scientific recommendations into restoration planning efforts at multiple stages, as demonstrated here through an example restoration project. In particular, use of a watershed-scale planning process can identify data gaps and irreversible constraints, which aid in developing achievable restoration goals and objectives. Site-prioritization focuses limited the resources for restoration on areas with the greatest potential to improve populations of target organisms. Investment in research to understand causes of degradation, coupled with adoption of a guiding vision is critical for identifying feasible restoration actions that can enhance river processes. Setting monitoring as a project goal, developing hypotheses for expected outcomes, and implementing restoration as an experimental design will facilitate adaptive management and learning from project implementation. Involvement of scientists and managers during all planning stages is critical for developing process-based restoration actions and an implementation plan to maximize learning. The planning process developed here provides a roadmap for use of scientific recommendations in future efforts to recover dynamic processes in imperiled riverine ecosystems.

San Rafael River watershed↗