Walvoord, M.A., and B.L. Kurylyk (2016), Hydrologic Impacts of Thawing Permafrost-A Review, Vadose Zone Journal, 15, doi:10.2136/vzj2016.01.0010
Summary: Thawing permafrost is leading to changes in soil moisture, connectivity of inland waters, streamflow seasonality, and the partitioning of water stored above and below ground. The field of permafrost hydrology is undergoing rapid advancement with respect to multiscale observations, subsurface characterization, modeling, and integration with other disciplines. However, gaining predictive capability of the many interrelated consequences of climate change is a persistent challenge. Observations of hydrologic change have been causally linked to permafrost thaw, but applications of process-based models needed to support and enhance the transferability of empirical linkages have often been restricted to generalized representations. This review highlights promising advances in characterization and modeling of permafrost regions and presents critical gaps and research challenges in projecting hydrologic and ecologic consequences of permafrost thaw at time and spatial scales that are useful to managers and researchers.
Meixner, T., A.H. Manning, D.A. Stonestrom, D.M. Allen, H. Ajami, K.W. Blasch, A.E. Brookfield, C.I. Castro, J.F. Clark, D.J. Gochis, A.L. Flint, K.L. Neff, R. Niraula, M. Rodell, B.R. Scanlon, K. Singha, and M.A.Walvoord (2016), Implications of projected climate change for groundwater recharge in the western United States, Journal of Hydrology, 534, 124-138, doi:10.1016/j.jhydrol.2015.12.027
Summary: This review paper provides a regional analysis of the potential impacts of climate change on groundwater recharge across the western United States. The analysis was performed by synthesizing existing studies, with a focus on eight representative groundwater basins in the region, and by applying current knowledge of recharge processes. Future changes in four separate recharge mechanisms as well as total recharge were estimated for each basin. In general, less groundwater recharge is expected in southern aquifers, whereas recharge to northern aquifers may increase slightly in the future. Mountain system recharge is likely to decline due to reduced snowpack, however this effect is projected to lessen with higher elevation and latitude. This synthesis is a product of a USGS John Wesley Powell Center working group. (Figure from Meixner et al., 2016)
Jepsen, S.M., M.A. Walvoord, C.I. Voss, and J. Rover (2016), Effect of permafrost thaw on the dynamics of lakes recharged by ice-jam floods: case study of Yukon Flats, Alaska, Hydrological Processes, doi:10.1002/hyp.10756
Summary: A recent ice-jam flooding event near Fort Yukon, Alaska (USA) that resulted in substantial recharge of a lake declining in level for the past 38 years prompted an integrated remote sensing and hydrologic modeling analysis to gain insight into the evolving hydrologic connectivity of lowland lakes in discontinuous permafrost. Model results demonstrate how climate-driven permafrost degradation can reduce the dependence of typical lowland lakes on sporadic flooding events. Study results also suggest that river flooding may recharge a more spatially widespread zone of lakes and wetlands under future scenarios of permafrost table deepening and enhanced subsurface hydrologic connectivity.
Ebel, B.A., F.K. Rengers, and G.E. Tucker (2015), Aspect-dependent soil saturation and insight into debris-flow initiation during extreme rainfall in the Colorado Front Range, Geology, 43, 659-662, doi: 10.1130/G36741.1
Summary: Extreme rainfall events in interior continental areas can cause widespread slope failures, leading to threats to life and property. These events can be especially threatening because emergency preparation for slope failure is minimal and knowledge of the landscape conditions that make particular locations vulnerable is poorly characterized. In September of 2013 a storm event in the Colorado Front Range, USA produced rainfall totals with a 1,000 year recurrence interval caused flooding and debris flows that took 8 lives and damaged nearly 19,000 homes spreading over 320 km and 17 counties. Here we show aspect-dependent hydrologic behavior may result from (i) a larger gravel/stone fraction, and hence lower soil-water storage capacity, on south-facing slopes, and (ii) lower weathered-bedrock permeability on south-facing slopes, because of lower tree density and associated deep roots penetrating bedrock as well as less intense physical weathering, inhibiting soil drainage.
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