Permafrost Hydrology: Linkages and Feedbacks

In the cold regions, hydrological regime is closely related with permafrost conditions, such as permafrost extent and thermal characteristics. Ice-rich permafrost has a very low hydraulic conductivity and commonly acts as a barrier to deeper groundwater recharge or as a confining layer to deeper aquifers. In regions underlain by permafrost, the active layer is the upper layer of the soil near the surface that undergoes thawing in the summer and freezing in the fall. The thawing starts from the surface in the spring, and the active layer reaches its maximum in late summer. The lower boundary of this layer is the top of the permafrost layer. The active layer is considered to produce base flow (or low flow) during the ice-free season. In this chapter, we discuss relationship between permafrost coverage and streamflow regime, detection of permafrost thawing trends from long-term streamflow data, determination of permafrost groundwater age, and water balance of northern permafrost basins.