Subsurface Controls and Characteristics for Gaining and Losing Segments of Streams
Additional Funding Sources
The project described was supported by the Ronald E. McNair Post-Baccalaureate Achievement Program through the U.S. Department of Education under Award No. P217A170169 and the National Science Foundation via the CAREER grant (Award NSF EAR-1653998).
Abstract
Mountainous headwater streams represent a substantial proportion of the global stream network, though more than half of them may only flow periodically. Moreover, downstream water quantity and aquatic habitat largely reflect the condition of upstream contributing headwaters and subsurface-surface water exchange occurring in these reaches. Indeed, understanding the dynamics and controls on this exchange is crucial for predicting drying patterns and resulting water quality. Drying patterns may present as discontinuities in surface flow where all water in the stream corridor is completely flowing in the subsurface. Discontinuities occur either because of variations in flow along the stream corridor or because the proportion of flow in the subsurface is heterogeneous. We test both of these hypotheses in Gibson Jack watershed in southeastern Idaho by taking measurements of changes in flow along a discontinuous stream segment and by collecting geophysical measurements to infer subsurface heterogeneity. Initial results suggest that flows change by as much as 40 L/s along the length of the stream and that inferences from different geophysical techniques must be reconciled to infer changes in subsurface flow capacity. Once we understand subsurface heterogeneity, we can distinguish among the drivers of stream intermittency and make more accurate subsurface flow models.
Subsurface Controls and Characteristics for Gaining and Losing Segments of Streams
Mountainous headwater streams represent a substantial proportion of the global stream network, though more than half of them may only flow periodically. Moreover, downstream water quantity and aquatic habitat largely reflect the condition of upstream contributing headwaters and subsurface-surface water exchange occurring in these reaches. Indeed, understanding the dynamics and controls on this exchange is crucial for predicting drying patterns and resulting water quality. Drying patterns may present as discontinuities in surface flow where all water in the stream corridor is completely flowing in the subsurface. Discontinuities occur either because of variations in flow along the stream corridor or because the proportion of flow in the subsurface is heterogeneous. We test both of these hypotheses in Gibson Jack watershed in southeastern Idaho by taking measurements of changes in flow along a discontinuous stream segment and by collecting geophysical measurements to infer subsurface heterogeneity. Initial results suggest that flows change by as much as 40 L/s along the length of the stream and that inferences from different geophysical techniques must be reconciled to infer changes in subsurface flow capacity. Once we understand subsurface heterogeneity, we can distinguish among the drivers of stream intermittency and make more accurate subsurface flow models.