An Application of the T‐TEL Assessment Method to Evaluate Connectivity in a Lake‐Dominated Watershed after Drought

• Published in: Journal of the American Water Resources Association 2019-04, Vol.55 (2), p.318-333
• Main Authors: Spence, C., Ali, G., Oswald, C.J., Wellen, C.
• Format: Article
• Language: English
• Subjects: Coastal inlets; connectivity; Data processing; Drought; Duration; Evaporation; Flow duration; Flow duration curves; Hydrology; Lakes; Methods; Outlets; Rain; Rainfall; Rivers; Runoff; Stability; Surface runoff; surface water hydrology; Upstream; Watersheds
• ISSN: 1093-474X; 1752-1688
• DOI: 10.1111/1752-1688.12702

Lakes are landscape features that influence connectivity of mass and energy by being foci for the reception, mixing, and provision of water and material. Where lake fractions are high, they influence hydrological connectivity. This behavior was exemplified in the Baker Creek watershed in Canada's Northwest Territories during a two‐year drought in which many lake levels declined below outlet elevations. This study evaluated how lakes controlled surface runoff connectivity reestablishment following the drought using a new assessment method, T‐TEL (time scales — thresholds, excesses, losses). Analysis of daily data showed that during a summer period following the drought, connectivity occurred between 0% and 41% of the time. The size of run‐of‐the‐river lakes relative to their upstream watershed area, and the upstream lake fraction, are two factors for connectivity. These terms represent a lake's ability to control the size of storage deficits relative to rainfall, and evaporation and storage losses along pathways. The connectivity magnitude–duration curve only aligned with the watershed flow duration curve during high‐water conditions, implying lakes functioned as individuals rather than as part of a perennial watercourse during much of the study. The T‐TEL method can be used to quantify consistent metrics of hydrologic connectivity that can be used for regionalization exercises and understanding hydrologic controls on material transport. Research Impact Statement: This research demonstrated the T‐TEL method can be used successfully to quantify hydrological connectivity in a lake‐dominated watershed.