Benefits of State and Private Forest Lands for the South

Forests provide the most stable and highest quality water supplies among all land uses. The Southern United States is heavily forested, and most of the forests are owned and managed by State and private entities, thus it is critical to understand the role of these forest lands in providing water across the region, the fastest growing in the Nation. We quantified surface water supply originating on State and private forest (SPF) lands in the 13 Southern States at the 12-digit Hydrologic Unit Code watershed scale between 2000 and 2010, using the Water Supply Stress Index (WaSSI) hydrologic model. Water originating on seven forest ownership types was tracked through the river network and linked to a database of surface drinking water intakes to quantify the population served by water from SPF lands across the South.

We found that the area of SPF lands was 44.2 percent of the total land area and that SPF lands contributed 44.3 percent of the 836 billion cubic meter per year total available surface water supply in the region. Of the 7,582 surface drinking water intakes in the study area, 6,897 (91.0 percent) received some portion of their water from SPF lands, with 4,526 (65.6 percent) receiving >20 percent of their water from SPF lands. Approximately 55.3 million people in the South and 1.8 million people outside the 13 Southern States derived some portion of their surface water supply from SPF lands. These results highlight the importance of southern State and private forests in providing drinking water to downstream communities. 

The Authors:

 Ning Liu , Postdoctoral Research Fellow, U.S. Department of Agriculture Forest Service, Southern Research Station, Coweeta Hydrologic Lab, and University of Minnesota, College of Natural Resources, Department of Forest Resources, 301H Green Hall, St. Paul, MN 55108;

 G. Rebecca Dobbs , Geospatial Research Associate, U.S. Department of Agriculture Forest Service, Southern Research Station, Coweeta Hydrologic Lab, Otto, NC 28763, and North Carolina State University, College of Natural Resources, Department of Forestry and Environmental Resources, Center for Geospatial Analytics, Raleigh, NC 27695;

 Peter V. Caldwell , Research Hydrologist, U.S. Department of Agriculture Forest Service, Southern Research Station, Coweeta Hydrologic Lab, Otto, NC 28763;

 Chelcy Ford Miniat , Research Ecologist, U.S. Department of Agriculture Forest Service, Southern Research Station, Coweeta Hydrologic Lab,Otto, NC 28763;

 Paul V. Bolstad , Professor, University of Minnesota, College of Natural Resources, Department of Forest Resources, St. Paul, MN 55108;

 Stacy Nelson , Professor, North Carolina State University, College of Natural Resources, Department of Forestry and Environmental Resources, Center for Geospatial Analytics, Raleigh, NC 27695;

 Ge Sun , Research Hydrologist, U.S. Department of Agriculture Forest Service, Southern Research Station, Eastern Forest Environmental Threat Assessment Center, Forestry Sciences Laboratory, Research Triangle Park, NC 27709. 

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Mean annual  water yield  ranged from < 200 mm/yr (7.9 inches per year) in western Texas to > 1000 mm/yr (39.4 inches per year) in the high-elevation Southern Appalachian Mountains.  Water supply  originating on SPF lands in the 13 Southern States made significant contributions to the total water supply across the region in comparison with other land cover and ownership types. State and private forest land area in the South was 44.2 percent of the total land area, and SPF lands contributed 44.3 percent of the 836 billion cubic meter per year (220,848 billion gallons per year) total available water supply generated in the region.

Approximately 55 million people in the South derived some portion of their drinking water (> 0 percent of the total supply) from SPF lands. This represents 49 percent of the total population in the region. In addition, approximately 1.8 million people outside the 13 Southern States received some portion of their drinking water from SPF in the South. State and private forest lands in the South provide more than half of the available water supply for 14.0 million people in the region and beyond.

Forest land area in the South and the proportion of water supply originated on forest lands were closely linked at the State level. For the 13 Southern States, Alabama had the highest percentage (~66 percent) of SPF lands and the highest percentage (~60 percent) of water supply from SPF lands. Although Oklahoma had the lowest percentage (~23 percent) of SPF lands, > 30 percent of water supply originated from SPF.

 Nonindustrial private forest was the dominant source of water supply from SPF for 11 of the 13 Southern States (the exceptions being Florida and Louisiana), followed by corporate forest. In Kentucky, nonindustrial private contributed > 80 percent of water supply originating on SPF, while > 70 percent of water supply originating on SPF was from State and corporate forest in Florida.

Water from State and private forest lands served the largest population in Texas among all 13 Southern States; 16.7 million people in Texas (59.0 percent of the total population) derived some portion of their water from SPF lands. The majority (> 50 percent) of people in Texas (2.5 million people) received their water from SPF lands, followed by North Carolina (1.54 million) and Alabama (1.48 million). In other States that have relatively low forest cover (e.g., Oklahoma) and/or relatively low population served by surface water supply (e.g., Mississippi), < 0.2 million people received the majority of their drinking water supply from SPF. While these populations may be small relative to other States, water originating on SPF lands is critical for meeting the water supply needs of specific downstream communities.

 Alabama ,  Arkansas ,  Florida ,  Georgia ,  Kentucky ,  Louisiana ,  Mississippi ,  North Carolina ,  Oklahoma ,  South Carolina ,  Tennessee ,  Texas , and  Virginia