Doctoral Dissertation Research: Advances in the Methodologies and Implications for Hydrologic Responses to Climate Change in the Upper Colorado Watershed, UT and CO

大量证据表明，科罗拉多流域下游的地表水文变化与厄尔尼诺-南方涛动（ENSO）之间存在联系。一条证据，古森林记录，说明了极端洪水对厄尔尼诺事件频率的依赖性。在科罗拉多流域上游，这些气候异常与ENSO并不呈正相关，在某些情况下呈负相关。该地区没有古气候研究，因此导致极端洪水的水文气候机制是基于时间有限的计量记录。这项研究的主要目标是通过在多洛雷斯流域开发流域尺度的古森林年表来解决空间差距，以了解极端洪水如何应对气候变化。该流域包括科罗拉多西南部和中西部的广阔地区，然后在犹他州摩押附近排入科罗拉多河。它是该地区的一部分，与ENSO的相关性非常弱，因此它对气候变化的反应可能与上科罗拉多流域的大部分相似。这项研究强调地质年代学，以创建非常可靠的洪水年代学。 有问题的有效性，使用“光释光”（OSL）的方法来测定古森林水文。本研究将为OSL在古森林水文学中的应用提供分析评估。此外，本研究旨在通过调查冲积层来评估河道稳定性，以评估古流量估计的不确定性程度。 洪峰流量估算将通过一维水文模型完成，研究结果将为科罗拉多上游流域洪水状况对气候变化的响应提供更深入的了解。过去气候变化的水文响应是现代和未来全球变暖的水文响应的一个潜在合理的类比。此外，多种年龄控制和现场技术的集成将减少古生物研究中的不确定性。选择多洛雷斯流域进行这项研究是因为其独特的位置：在一个气候区域，水流与厄尔尼诺事件的相关性非常差，使其成为科罗拉多流域上游其他子流域的原型。该流域的自然地理是这项研究的理想选择，因为河流混合了基岩和冲积河道，古生物证据的保存潜力很高。该地区的古洪水记录表明，发生过多次极端洪水，每次都大大超过历史上的最大洪水。水资源管理人员可以利用这些信息来减轻未来洪水的直接影响，特别是在现代和未来气候变化的背景下。

Numerous lines of evidence have highlighted the relationship between the variability of surface hydrology and the El Niño-Southern Oscillation (ENSO) within the lower Colorado Watershed. One line of evidence, the paleoflood record, illustrates the dependence of extreme flooding on the frequency of El Niño events. Within the upper Colorado Watershed, these climatic aberrations are not positively correlated with ENSO, and in some cases, inversely correlated. There are no paleoflood studies in this region, so the hydroclimatic mechanisms responsible for driving extreme flooding is based on temporally limited, gaged records. The primary goal of this research is to address the spatial gap by developing a watershed-scale, paleoflood chronology in the Dolores Watershed to understand how extreme flooding has responded to shifts in climate. The watershed encompasses a broad region of southwestern and west-central Colorado, before draining into the Colorado River near Moab, UT. It is part of the region that correlates very weakly with ENSO, so its response to climate shifts may act as an analog to the majority of the Upper Colorado Watershed. This research places an emphasis on geochronology to create a very robust flood chronology. There are questions about the validity of using "optically stimulated luminescence" (OSL) methods for dating paleoflood hydrology. This research will provide an analytical assessment of OSL for its application to paleoflood hydrology. In addition, this study is designed to evaluate the degree of uncertainty in paleodischarge estimations by investigating the alluvial stratigraphy to assess channel stability. Peak discharge estimates will be completed with a one-dimensional hydrological model.Results from this research will provide a more thorough understanding of flood regime responses to climate change in the upper Colorado Watershed. Hydrological responses to past climate shifts are a potentially reasonable analog for modern and future hydrologic responses to global warming. In addition, the integration of multiple age-control and field techniques will reduce uncertainty in paleoflood research. The Dolores Watershed has been selected for this study because of its unique position: in a climatic region where stream flow is very poorly correlated with El Niño events, making it a prototype for other sub-basins within the upper Colorado Watershed. The physiography of the watershed is ideal for this study because the rivers are mixed with both bedrock and alluvial channels, and the preservation potential for paleoflood evidence is high. The paleoflood record in this region indicates that numerous extreme floods have occurred, each of which greatly exceeds the maximum flood during historical times. Water managers may apply this information to mitigate the direct impacts of future flooding, especially in the context of modern and future climate change.