Functional Lake‐to‐Channel Connectivity Impacts Lake Ice in the Colville Delta, Alaska

Abstract

Arctic deltaic floodplains consist of complex river and lake systems that transport and store both inorganic and organic materials. The connectivity of Arctic floodplain lakes to nearby channels determines how much river water these lakes receive each year (

Remote Sensing of Multitemporal Functional Lake‐To‐Channel Connectivity and Implications for Water Movement Through the Mackenzie River Delta, Canada

“…If fewer than 50% of the lake's open water pixels were cloud-free in a given Landsat observation, we removed that observation from analysis. While Dolan et al (2021) used ratios of lake reflectance to channel reflectance to determine connectivity, we found that this method overestimated the movement of high sediment water into lakes in the Mackenzie Delta, specifically during periods of low sediment transport. Therefore, this analysis instead uses the optical properties of each lake as input to a random forest model.…”

“…Next, we paired same‐day near‐infrared lake reflectance with same‐day nearby channel near‐infrared reflectance, resulting in a total of 1,694,790 matchups (60% of all observations) of 10,024 lakes (97% of all lakes), and divided lake reflectance by channel reflectance, which we refer to as the lake‐to‐channel ratio (Dolan et al., 2021). We flagged any observations in which both the lake‐to‐channel ratio was greater than 1.3 and the connectivity classification was a class 2, indicating high lake reflectance relative to nearby channel reflectance.…”

“…Lake connectedness can be defined as “structural” or “functional.” Structural connectivity refers to physical connectedness of the lake, often based on connected channel presence/absence or the water elevation needed to induce flow of water into a lake (Lesack & Marsh, 2010; Marsh & Hey, 1988, 1989; Passalacqua, 2017; Piliouras & Rowland, 2020). Functional connectivity specifically refers to the movement of water and sediment from a river channel into a lake (Dolan et al., 2021; Long & Pavelsky, 2013). For example, a lake with a consistent but indirect structural connection to the channel network (e.g., a lake that is structurally connected to the distributary channel network via a chain of other structurally connected lakes) could be high functional connectivity when freshet‐related elevated discharge carries high sediment water into the lake but low functional connectivity during other periods.…”

“…Long and Pavelsky (2013) and Dolan et al. (2021) demonstrated the efficacy of tracking high sediment river water recharge to detect functional connectivity, and it is on this idea that we build our methods. Our method does not require channel detection, nor does it require frequent aerial monitoring of lakes, and it is spatially applicable across all 10,362 Landsat‐observable Mackenzie Delta lakes.…”

“…In this analysis, we use Landsat imagery to investigate patterns, trends, and drivers of lake-to-channel functional connectivity in the Mackenzie River Delta between 1984 and 2022. Long and Pavelsky (2013) and Dolan et al (2021) demonstrated the efficacy of tracking high sediment river water recharge to detect functional connectivity, and it is on this idea that we build our methods. Our method does not require channel detection, nor does it require frequent aerial monitoring of lakes, and it is spatially applicable across all 10,362 Landsat-observable Water Resources Research 10.1029/2023WR036614 Mackenzie Delta lakes.…”