Spatial Patterns and Sensitivity of Intermittent Stream Drying to Climate Variability

Abstract

Intermittent streams are common throughout the world, and are characterized as having variable cycles of wetting and flow cessation (Busch et al., 2020). Though intermittency is a natural phenomenon, projected changes in temperature and precipitation patterns are expected to prolong the dry season and increase the frequency of multi-year droughts in many parts of the world (Dai, 2011). This, in turn, is predicted to intensify the low-flow period and exacerbate the duration and severity of intermittent conditions (Grimm & Fisher, 1992;Larned et al., 2010). Changes to streamflow patterns can profoundly influence ecological functioning of streams by disrupting evolutionary cues (Heim et al., 2016), altering nutrient cycles (von Schiller et al., 2011), and increasing the risk of invasion by nonnative species (Larson et al., 2009). Many endemic and imperiled species that are adapted to natural intermittency may be placed at risk of extirpation from these shifts (Jaeger et al., 2014). Furthermore, changes to hydrological regimes may reduce the ecosystem services provided by intermittent streams, such as drinking water resources (Marshall et al., 2018) and nutrient cycling (Datry, Foulquier, et al., 2018), which may exacerbate stressors faced by human populations (Datry, Boulton, et al., 2018). Understanding the drivers of intermittent stream dynamics, as well as their sensitivity to climate variability, is critical for predicting how functioning of these systems may change under a volatile climate future.Previous studies on temperate and arid intermittent stream dynamics have shown that as the dry season progresses, the wetted channel contracts from the full extent of the geomorphic channel network in response to declining stream discharge (Godsey & Kirchner, 2014). The spatial and temporal patterns of intermittency are affected by meteorologic, geologic, and land cover conditions (Costigan et al., 2016), with topographic relief and lithology playing a particularly important role in influencing the spatial patterns of wetted channel contraction in intermittent stream networks (Jensen et al., 2017;Lovill et al., 2018;Prancevic & Kirchner, 2019). Growing insight into the mechanisms that control wetted channel dynamics has led to attempts to model and predict intermittent stream expansion and contraction (Pate et al., 2020;Ward

Migration in drought: Receding streams contract the seaward migration window of endangered salmon

“…Because fish are planted in the previous fall and most often experience >50% overwinter mortality (California Sea Grant, 2021b), we could not test whether the total number of outmigrating smolts was lower in drought versus non‐drought years. Nevertheless, we can assume that smolts that do not outmigrate in the spring are unlikely to survive until the rainy season, owing to the extensive stream drying that occurs in tributaries of the Russian River watershed (Moidu et al, 2021).…”

The salmonid and the subsurface: Hillslope storage capacity determines the quality and distribution of fish habitat

“…Recent work by Vorste et al (2020), however, highlights that some intermittent systems provide reliable habitats for juvenile coho rearing. For example, across the geologically complex Russian River watershed in Sonoma County, California, interannual variation in summer survival was high at some sites, but much more stable at other sites, hinting at the importance of CZ properties in influencing the sensitivity of different systems to interannual variation in rainfall and consequences for salmon survival (e.g., Figure 8; see also Moidu et al, 2021).…”

Harnessing hyperspectral imagery to map surface water presence and hyporheic flow properties of headwater stream networks

“…As hydrological regimes shift in response to increasing anthropogenic pressures and a changing climate, so too will the wetted extent of channel networks (Lapides et al, 2021), with consequences for food webs, sedimentation, riverine nutrient cycling, habitat extent/quality, and other ecological processes (Bernal et al, 2004;Hwan & Carlson, 2016;Sabo et al, 2010;Larned et al, 2010;Arthington et al, 2005). A remote-sensing based framework for detecting the absence or presence of water in (often difficult-to-access) headwater stream networks would contribute to ongoing efforts to address this significant challenge in watershed management (Moidu et al, 2021).…”

“…However, these surveys are limited in their spatiotemporal coverage: less than 0.0001% of Earth's ice-free land area has been repeatedly mapped (Lapides et al, 2021), underscoring the status of headwater stream networks as aqua incognita (Bishop et al, 2008). Sparse observations have limited exploration of the physical controls on channel growth and contraction (Moidu et al, 2021).…”