The River Corridor's Evolving Connectivity of Lotic and Lentic Waters

Abstract

River corridors supply a substantial proportion of the fresh water for societal and ecological needs. Individual functions of flowing (lotic) streams and rivers and ponded (lentic) waterbodies such as lakes and reservoirs are well-studied, but their collective functions are not as well understood. Here we bring together nationally consistent river corridor datasets to characterize the contributions of lotic and lentic features and to estimate changes over the past centuries. High-resolution datasets describing waterbodies across 10 million kilometers of the conterminous U.S. (CONUS) river network were classified by waterbody type and origin (historic vs. human-made or intensively managed), surface areal coverage, and degree of connectivity as estimated by a change in water residence timescale in river corridors. Four centuries of human disturbance drove large swings in river corridor makeup, with a transition toward more lotic systems caused by beaver extirpation and abandonment of waterwheel mill ponds by end of the nineteenth century. The twentieth century saw a vast expansion (49%) in river corridor areal coverage resulting from construction and management of small ponds and reservoirs for drinking water, hydropower, irrigation and livestock watering, and stormwater control. Water residence timescale in river corridors doubled or quadrupled over large areas, and more in specific locations, during the twentieth century as a result of the increased coverage of reservoirs and managed small ponds. Although reservoirs and lakes now dominate river corridor surface areas, we found that the growing number of small ponds impacts a greater proportion of network length through their influence on headwater streams where most water and chemical runoff enters the river corridor. We close with an agenda for integrated modeling of the physical, biogeochemical, and ecological drivers of river corridor functions, trajectories of change, and management opportunities.

Lakes protect downstream riverine habitats from chloride toxicity

“…Processes like deposition and evapoconcentration can impact chloride concentrations, but are unlikely to be of any consequence in the Yahara lakes (Kirchner et al 2010; Svensson et al 2012). However, since lakes slow down the movement of water, it was expected that the presence of a lake in a river network should fundamentally change the salinity regime in downstream river reaches (Harvey and Schmadel 2021). In the case of Lake Mendota, with an average water residence time of 4 yr (Brock 1985), the long‐term increase in chloride concentrations in the lake demonstrates that the lake is acting as a chloride reservoir (Fig.…”

“…The degree of connectivity in a watershed results in solutes either moving quickly downstream (short residence time) or being retained in the watershed (long residence time). The presence of lakes in river networks slow water movement, and results in high rates of biogeochemical processing and sedimentation (Harvey and Schmadel 2021). Lentic environments thus act as moderators of solute transport and have been shown to buffer downstream nutrient delivery (Goodman et al 2011; Kalinin et al 2016; Schmadel et al 2018; Stachelek and Soranno 2019).…”

Spatial Microbial Respiration Variations in the Hyporheic Zones Within the Columbia River Basin

“…Lastly, our HZ respiration estimates are limited in the lotic (or flowing) stream/river systems, and do not account for the respiration process in water column. Lentic waters, including reservoirs or small ponds and wetlands, impact the downstream water quality and regional nutrient budgets (Harvey & Schmadel, 2021; Schmadel et al., 2019). Schmadel et al.…”

“…Lastly, our HZ respiration estimates are limited in the lotic (or flowing) stream/river systems, and do not account for the respiration process in water column. Lentic waters, including reservoirs or small ponds and wetlands, impact the downstream water quality and regional nutrient budgets (Harvey & Schmadel, 2021;Schmadel et al, 2019). Schmadel et al (2019) showed that small ponds influences the retention of nitrogen, phosphorus, and sediment, depending on their spatial location, especially for the headwater catchment.…”

Freshwater corridors in the conterminous United States: A coarse‐filter approach based on lake‐stream networks

“…Many studies have demonstrated the importance of hydrologic connectivity for maintaining freshwater populations and community structure across taxa (Altermatt & Fronhofer, 2018; de Mendoza et al, 2018; Schmera et al, 2018). Of existing freshwater corridor mapping studies, the majority has focused on river and stream networks at landscape, watershed, or regional scales, without incorporating lentic waterbodies (Collier, 2011; Saunders et al, 2016; but also see Gardner et al, 2019; Harvey & Schmadel, 2021).…”