Headwater lakes and their influence on downstream discharge

Abstract

Small headwater lakes are common water features in northern environments. These small lakes are often reported to have an influence on downstream water quality; however, few studies have addressed the underlying hydrology of these systems and how small lakes influence downstream discharge or how far downstream these influences persist. We show that catchments with small lakes sustain baseflows compared to catchments without lakes. In addition, small lakes have limited influence on the magnitude and timing of peakflow events, except for immediately downstream of the lake where peakflow hydrographs are characterized by low magnitude and long duration. The relative contribution of lake water to downstream discharge can vary widely in time (between 0% and 75%) and be detectable when lakes make up as little as 0.5% of catchment area. This variability and persistence of lake water in stream networks may have important implications for how we interpret water quality patterns downstream of small lakes.

How catchment characteristics influence hydrological pathways and travel times in a boreal landscape

“…Our assumption is further based on modelling studies of weathering rates in a soil transect in the Krycklan catchment, which indicates that there is a kinetic control of the release of BCs in the soils (Erlandsson et al, 2016). Since all BCs behave relatively conservatively in these environments (Ledesma et al, 2013;Lidman et al, 2014), we used their combined concentration as a proxy for soil contact time. However, the assumption is only valid when the water is in contact with mineral soils, not with peat in mires, which are abundant in some of the investigated sub-catchments.…”

Describing alpine lake influence on stream network temperatures: A statistical modelling approach

“…Previous studies have the examined the spatial extent of lake influence on stream water characteristics. One such study used measurements of streamflow and water isotopes to examine the direct contributions of lake water to streams, and found that these contributions constitute a declining fraction of stream water across a distance from 1.4 to 4.2 km downstream of a lake (Leach & Laudon, 2019). An additional study examining sediment dynamics in a montaine stream‐lake network suggested that lakes act as sediment sinks, and thereby deplete the sediment content of lake outlet streams (Arp et al, 2007).…”

“…Previous studies have also examined temporal variations in the contributions of upstream lakes to stream water. Measurements of streamflow and water isotopes performed by Leach and Laudon (2019) estimated that these direct contributions of lake water to streams are greatest during periods of moderate to high discharge. This may seem contrary to our findings of higher stream temperature response to lakes are at low discharge.…”

“…Lake influence on stream temperature may be substantial where a large portion of stream water has originated from an upstream lake, but will be absent where no upstream lakes are present. This fundamental hydrologic partitioning may influence many stream characteristics, and has been reflected in observed patterns of stream sediment load (Arp et al, 2007) and the composition of water isotopes (Leach & Laudon, 2019) along streams draining lakes. Lake‐sourced contributions to streamflow at any single point may also vary over time due to changing amounts of runoff from above‐lake and below‐lake contributing areas (Leach et al, 2017).…”

Linking groundwater travel times to stream chemistry, isotopic composition and catchment characteristics

“…There should, therefore, be a significant relationship between the simulated travel times a nd the observed winter isotopic stream signature provided that the model performs well. Some of the sub-catchments are, however, affected by evaporation from lake surfaces that result in isotopic fractionation (Leach and Laudon, 2019). Th is fractionation must be accounted for in order to use the signature as a representation of the groundwater.…”