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Natural springs in water‐limited landscapes are biodiversity hotspots and keystone ecosystems that have a disproportionate influence on surrounding landscapes despite their usually small size. Some springs served as evolutionary refugia during previous climate drying, supporting relict species in isolated habitats. Understanding whether springs will provide hydrologic refugia from future climate change is important to biodiversity conservation but is complicated by hydrologic variability among springs, data limitations, and multiple non‐climate threats to groundwater‐dependent ecosystems. We present a conceptual framework for categorizing springs as potentially stable, relative, or transient hydrologic refugia in a drying climate. Clues about the refugial capacity of springs can be assembled from various approaches, including citizen‐science‐powered ecohydrologic monitoring, remote sensing, landowner interviews, and environmental tracer analysis. Managers can integrate multiple lines of evidence to predict which springs may become future refugia for species of concern, strengthening the long‐term effectiveness of their conservation and restoration, and informing climate adaptation for terrestrial and freshwater species.

Springs ecosystems are globally abundant, geomorphologically diverse, and bioculturally productive, but are highly imperiled by anthropogenic activities. More than a century of scientific discussion about the wide array of ecohydrological factors influencing springs has been informative, but has yielded little agreement on their classification. This lack of agreement has contributed to the global neglect and degradation of springs ecosystems by the public, scientific, and management communities. Here we review the historical literature on springs classification variables, concluding that site-specific source geomorphology remains the most diagnostic approach. We present a conceptual springs ecosystem model that clarifies the central role of geomorphology in springs ecosystem development, function, and typology. We present an illustrated dichotomous key to terrestrial (non-marine) springs ecosystem types and subtypes, and describe those types. We identify representative reference sites, although data limitations presently preclude selection of continentally or globally representative reference springs of each type. We tested the classification key using data from 244 randomly selected springs of 13 types that were inventoried in western North America. The dichotomous key correctly identified springs type in 87.5% of the cases, with discrepancies primarily due to differentiation of primary vs. secondary typology, and insufficient inventory team training. Using that information, we identified sources of confusion and clarified the key. Among the types that required more detailed explanation were hypocrenes, springs in which groundwater is expressed through phreatophytic vegetation. Overall, springs biodiversity and ecosystem complexity are due, in part, to the co-occurrence of multiple intra-springs microhabitats. We describe microhabitats that are commonly associated with different springs types, reporting at least 13 microhabitats, each of which can support discrete biotic assemblages. Interdisciplinary agreement on basic classification is needed to enhance scientific understanding and stewardship of springs ecosystems, the loss and degradation of which constitute a global conservation crisis.

Regulated river restoration through planned flooding involves trade-offs between aquatic and terrestrial components, between relict pre-dam and novel post-dam resources and processes, and between management of individual resources and ecosystem characteristics. We review the terrestrial (wetland and riparian) impacts of a 1274 m 3 /s test flood conducted by the U.S. Bureau of Reclamation in March/April 1996, which was designed to improve understanding of sediment transport and management downstream from Glen Canyon Dam in the Colorado River ecosystem. The test flood successfully restored sandbars throughout the river corridor and was timed to prevent direct impacts to species of concern. A total of 1275 endangered Kanab ambersnail (Oxyloma haydeni kanabensis) were translocated above the flood zone at Vaseys Paradise spring, and an estimated 10.7% of the total snail habitat and 7.7% of the total snail population were lost to the flood. The test flood scoured channel margin wetlands, including potential foraging habitats of endangered Southwestern Willow Flycatcher (Empidonax traillii extimus). It also buried ground-covering riparian vegetation under Ͼ1 m of fine sand but only slightly altered woody sandbar vegetation and some return-current channel marshes. Pre-flood control efforts and appropriate flood timing limited recruitment of four common nonnative perennial plant species. Slight impacts on ethnobotanical resources were detected Ͼ430 km downstream, but those plant assemblages recovered rapidly. Careful design of planned flood hydrograph shape and seasonal timing is required to mitigate terrestrial impacts during efforts to restore essential fluvial geomorphic and aquatic habitats in regulated river ecosystems.

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Near-natural springs provide vital ecosystem goods and services (Knight 2015;Mueller et al. 2017). For example, many farms, ranches, small towns, and several national capitals (e.g., Rome, Vienna, Beirut, Damascus) use springs for potable and agricultural water (Kresic & Stevanovic 2010). Springs also have tremendous cultural, social, and economic significance. They have played important roles throughout human evolution and history (Cuthbert & Ashley 2014). Many of them have substantial recreational value (Glazier 2014; Knight 2015) (Fig. 1a, b), and the economic value of bottled spring water is enormous (Gleick 2010). Most human cultures consider springs places of vital importance for physical and spiritual well-being (Fig. 1k). Impacts, Management, and Global Conservation StatusAlthough abundant worldwide, many springs are disappearing or are impaired by local to global anthropogenic stressors, including habitat alteration, recreational use, groundwater depletion, pollution, and climate change (Glazier 2014; Knight 2015) (Fig. 1im). At local scales, individual springs are directly impaired by flow abstraction and manipulation, road and 378

Ground water/surface water interaction in rivers is dependent on the hydraulic conductivity of sediments lining the streambed. This study was designed to determine the temporal and spatial variability of the hydraulic conductivity of active sedimentary deposits lining the streambed of the Colorado River in the Grand Canyon. These reattachment bars form aquifers and create return‐current channels that are critical for supporting terrestrial and aquatic ecosystems. Monitoring wells were placed in five separate reattachment bars over a 200 mile long reach of the Colorado River below Glen Canyon Dam. Hydraulic conductivity was measured in all wells with the pneumatic slug test method. There is no significant difference in hydraulic conductivity among the five reattachment bars in the Grand Canyon. Hydraulic conductivity is bimodally distributed within a reattachment bar because of differing sizes of sediments deposited under different eddy velocities. A major controlled release of water from Glen Canyon Dam in March 1996 redistributed the sediments in the reattachment bars and compressed sediments deposited during previous floods. Hydraulic conductivity was significantly lower in these sediments after the flood due to the increased effective stress from the newly deposited sediment. A year later, after the sediments had drained and some deflation had occurred, hydraulic conductivity of sand deposits returned to values similar to pre‐flood values, whereas fine‐grained sediments that compressed weren't able to elastically respond.