Projected Effects of Temperature and Precipitation Variability Change on Streamflow Patterns Using a Functional Flows Approach

Abstract

Streamflow patterns are shifting with climate change, and these shifts pose increasing risk to freshwater ecosystems. These emerging changes must be linked with ecological functions of river systems to understand how climate change may affect freshwater biota. In this study we used a functional flows approach to analyze the ecological effects of changing streamflow patterns in snowmelt‐dominated watersheds of the Sierra Nevada mountains of California. Our climate change modeling method combined ensemble Global Climate Models (GCMs) and decision scaling methods to incorporate the effects of GCM‐projected changes in precipitation variability on streamflow patterns. Of climate parameters explored, air temperature causes the most change in functional flows, although precipitation variability compounds changes driven by air temperature. The greatest changes in ecologically‐relevant streamflow patterns manifest as longer and drier dry season conditions, earlier snowmelt recession, and higher‐magnitude peak flows. Although the directions of changes in functional flow metrics are largely consistent across models and watersheds, the magnitude of change depends strongly on human emissions levels. The analytical approach used in this study can serve as a model for integrating multiple approaches in hydroclimatic assessment of ecological change, and the results can help prioritize specific aspects of the flow regime for restoration efforts.

Multi-scale drivers of daily flow intermittency in a regulated desert river

“…For example, we calculated how much 100 m 3 /s decrease in diversion, increase in discharge, or increase in returns would reduce daily accumulated flow intermittency at the two-and ten-subreach scales. Importantly, these finding can contribute to development of options that can bridge the gap between providing environmental flows based on the natural flow regime and implementing emerging concepts like "designer flows" that are being developed to incorporate the realities of anthropogenically altered freshwater ecosystems and human needs (Poff et al, 1997;Poff 2018;Tonkin et al, 2021;Patterson et al, 2022).…”

Riparian cottonwood mortality following compound impacts from river water withdrawal and hydroclimatic variation

“…Dam operations may provide the major tool to address the ecological challenges from river flow depletion due to climatic variation and change and human uses (Hall & Fagre, 2003; MacDonald et al, 2011; Nazemi et al, 2017). Environmental flow strategies, including functional flows, could provide instream flow patterns that support the essential life history processes (Foster et al, 2018; Patterson et al, 2022; Yarnell et al, 2015). Through wet intervals, when there is abundant water for irrigation and other human demands, deliberate flow alterations to provide ramping flows and avoid irregular spikes could enhance seedling recruitment and invigorate established woodlands.…”

“…The studies were generally intended to coordinate the system hydrology and woodland ecophysiology (Cooper et al, 2003; Gazal et al, 2006; Horton et al, 2001; Schook et al, 2020; Stromberg & Patten, 1996). This knowledge provides a foundation for environmental flow regimes to sustain and even restore cottonwoods and other native riparian trees and shrubs (Foster & Rood, 2017; Patterson et al, 2022; Stella et al, 2010; Yarnell et al, 2015).…”

Optimizing Reservoir Operation With Demand Uncertainty and Internal Climate Variability

“…Thus, the significance of reservoir operation becomes even more pronounced considering shifts in precipitation and temperature patterns, which alter the timing and quantity of water inflows into reservoirs. [15,7,16,17,18,19,20,21]. These variabilities in water availability changes become essential to adapt to evolving trends and maintain a sustainable water supply for various sectors reliant on reservoirs [22].…”