Science and Resource Management, Grand Canyon National Park, Tusayan, USA.
Kentucky Geological Survey, University of Kentucky, Lexington, USA.
Environ Manage. 2019 Jun;63(6):718-731. doi: 10.1007/s00267-019-01157-8. Epub 2019 Apr 10.
Water infrastructure updates at Grand Canyon National Park (GRCA) provide an opportunity to restore natural flow to Bright Angel Creek, adding an additional ~20% to baseflow. This creek provides habitat for endangered humpback chub (Gila cypha) and invasive brown trout (Salmo trutta). We assess how increased flow may alter habitat and how that change may impact native and nonnative species using physical habitat modeling and statistical analysis of stream temperature data. We used System for Environmental Flow Analysis to calculate the change in habitat area for both species in the lower 2.1 km of the creek before and after the increased flow. Results indicate a slight increase in available habitat for juveniles of both species and a slight decrease for spawning brown trout. We used regression modeling to relate daily average air temperature to stream temperature and periods of increased discharge during water system maintenance were used to model the temperatures during likely future conditions. Both high and low stream temperature were dampened due to the added water resulting in fewer days with suitable spawning temperature and more days with suitable growth temperature for humpback chub. Fewer suitable days for growth upstream but more suitable days downstream, were predicted for brown trout. Compared to other streams that sustain populations of humpback chub, flow conditions for Bright Angel Creek provide fewer days throughout the year with suitable temperatures, particularly during the winter months. Juvenile humpback chub rearing may improve through the restoration of flow however the presence of predatory brown trout complicates the net beneficial impact.
大峡谷国家公园（GRCA）的水资源基础设施更新提供了一个机会，将自然水流恢复到布莱斯天使溪，增加大约 20%的基流。这条溪流为濒危的弓背鲑（Gila cypha）和入侵的褐鳟（Salmo trutta）提供了栖息地。我们评估了增加的水流如何改变栖息地，以及这种变化如何影响本地和非本地物种，使用物理栖息地建模和溪流温度数据的统计分析。我们使用环境水流分析系统（System for Environmental Flow Analysis）来计算在增加水流前后，溪流下游 2.1 公里处两种物种的栖息地面积变化。结果表明，两种物种的幼鱼可利用栖息地略有增加，而产卵褐鳟的栖息地略有减少。我们使用回归模型将每日平均空气温度与溪流温度相关联，并利用水系统维护期间增加的流量期来模拟未来可能的条件下的温度。由于增加了水量，高和低的溪流温度都有所降低，导致适合产卵的温度天数减少，适合弓背鲑生长的温度天数增加。预测褐鳟的上游适宜生长天数减少，但下游适宜生长天数增加。与其他维持弓背鲑种群的溪流相比，布莱斯天使溪的水流条件全年提供适宜温度的天数较少，尤其是在冬季。然而，通过恢复水流，幼鲑的饲养可能会得到改善，但捕食性褐鳟的存在使净有益影响变得复杂。
