Rapid Assessment of Hydrologic Controls on Mountain Water Resources

Hill, Alice Frances

Graduate Thesis Or Dissertation

Rapid Assessment of Hydrologic Controls on Mountain Water Resources Public Deposited

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Citeable URL: https://scholar.colorado.edu/concern/graduate_thesis_or_dissertations/kd17cs96z

Abstract

The water stored in mountain snowpacks and glaciers provides an important water resource, seeding river systems that serve major populations centers and globally important ecosystems downstream. Mountain river systems are facing potential hydrologic changes imposed from a warming climate and hundreds of recent hydropower development proposals. The melt-dominated hydrologic regimes of mountain river systems are prone to a gradual shift due to change imposed by increasing temperatures as glacier masses decline and snowpack accumulation is altered, whereas dam development in remote mountain basins would impose a more abrupt transformation. Since these river systems play an important role in water supply and provide key ecosystem services, it is important to clarify their governing hydrologic processes. Despite their high societal value, we know little about many remote mountain rivers and they are notoriously data scarce. To advance our understanding of remote mountain hydrologic processes over regional scales, this research develops a hybrid field-satellite methodology called Rapid Hydro Assessment (RHA) for data scarce mountain regions facing imminent change. This method 1) clarifies the role of climate-sensitive snow and ice source waters to river flow and 2) characterizes regional hydrologic controls within a study timescale of months-to-years, not decades. RHA uses targeted water chemistry and isotope data to elicit hydrologic insights not available from, but complemented by, remote sensing imagery. RHA methodology is initially informed by headwater scale streamflow separation work at the Niwot Ridge Long Term Ecological Research site in the Colorado Rocky Mountains, and is further developed via two case studies in Kyrgyzstan’s Tien Shan mountains and in the Peruvian Andes. Results of the case studies demonstrate the complex and varied role of meltwater across scales and sites. Meltwater plays a critical role in surface flow and groundwater recharge in arid mountain areas like Colorado and Central Asia where snow makes up the vast majority of inputs. In contrast, in the more hydro-climatically variable Andes and Amazon, melt’s role is less directly important to river flow. High storage capacity in alpine wetlands provides a reservoir for wet season rain that appears to source baseflow through the dry season, and Amazon moisture systems deliver lower lying tributaries with major rain inputs. The importance of melt in the Andes is instead indirectly connected to river flow, with the diminishing extent (size) of alpine wetland reservoirs connected to declining melt inputs as tropical glaciers melt out. The case studies demonstrate the ability for the overarching RHA framework to be applied across diverse sites with varying levels of data availability, field access, sampling configurations and mixing model techniques. This work serves as an example of the creative approaches needed to address mountain hydrologic knowledge gaps that will allow us to better anticipate future water vulnerabilities, and to inform holistic, basin-wide development strategies.

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