Guest Editors' Introduction to Special Issue on Water and Rivers in the South (Part 1)

Guest Editors' Introduction to Special Issue on Water and Rivers in the South (Part 1) Sarah Praskievicz (bio), Joann Mossa (bio), and Johanna Engström (bio) issue 1 Water is an omnipresent feature of the physical and cultural landscapes of the US South. From the mountains' springs and waterfalls to the great rivers making their way through forests, farmland, and cities, to the estuaries and wetlands fringing the coast, water takes various forms in the region. This physical diversity translates into biological diversity as well. The South is a globally significant hotspot of freshwater biodiversity, with nearly two-thirds of all US fish species and over 90% of all US freshwater mussel species found in the region (Baer and Ingle 2019). Throughout history, water has taken on a variety of meanings for the region's human inhabitants. Since the time of the mound-building Mississippian civilization, fertile river valleys have been prime locations for agriculture and settlement. Later, Euro-Americans concentrated their own settlements along those same rivers, building ports near the river mouths and water-powered mills along the fall line. From New Orleans to Norfolk and from Washington, DC, to Tuscaloosa, Alabama, the geography of Southern cities is a function of the geography of its rivers. Those rivers have provided, and continue to provide, transportation, energy, water supply, and recreation, all important components of the region's economic development. Water is just as integral to the cultural identity of the region. In imagining the South, water-related imagery invariably comes to mind: the steamboats rolling along the Mississippi, the dark waters of a cypress swamp, the babbling of a rushing Appalachian stream. There are also images of water rising out of riverbanks to submerge towns and of storm-driven waves wearing away at shorelines. Whether a comfort, a resource, or a danger, water never seems far away. This dominant perception of abundant water resources in the South gives a misleading impression of the state of those resources (Praskievicz 2019). Just as water has shaped the region's cultural landscape, humans have in turn massively transformed water systems in a variety of ways both visible and invisible. To make rivers navigable, huge quantities End Page 4 of wood were removed (Wohl 2014) and significant channel dredging was undertaken (Mossa et al. 2017). Thousands of dams have been constructed on Southern rivers, from ubiquitous small mill dams (Walter and Merritts 2008) to large flood-control and hydroelectric projects built by the US Army Corps of Engineers and the Tennessee Valley Authority (Graf 2005). Intensive agriculture in the 1800s and early 1900s resulted in the widespread deposition of large quantities of sediment in Piedmont streams (Jackson et al. 2005). The legacies of these impacts continue to shape Southern landscapes today. These landscape changes have been accompanied by hydrologic alterations associated with flow regulation, water withdrawals, inter-basin transfers, increased impervious surfaces, and climate change (Baer and Ingle 2019). Water quality has been degraded by agricultural, industrial, and urban pollution (Alnahit et al. 2020). Invasive aquatic species have been introduced that can outcompete or prey upon native species, resulting in biotic homogenization (Rahel 2007). Due to these collective physical, chemical, and biological impacts, the South is the US region with the most highly threatened freshwater biodiversity (Master et al. 1998). More than two-thirds of the region's native freshwater mussel species and half of its crayfish species are either extinct, imperiled, or vulnerable (Smith et al. 2002). Pervasive though water may be in the South, its fragility is just as much a part of the region's story. This special issue is the first of two focusing on Water and Rivers in the South, and it addresses the multifaceted dimensions of water in the region, including the physical complexity of rivers, impacts on rivers by human activities, efforts made to restore river systems, and water as an essential but vulnerable resource for human populations across several study sites in the South (Figure 1). First, Hess et al. (this issue) examine one element of complexity in river systems, namely large wood, in their paper "Large Wood Distribution and Volume using UAV Imagery: Ground Truthing Results and Sources of Error". These pieces of...