Water Balances of Two Piedmont Headwater Catchments: Implications for Regional Hydrologic Landscape Classification

Abstract

In the Piedmont of North Carolina, a traditionally water‐rich region, reservoirs that serve over 1 million people are under increasing pressure due to naturally occurring droughts and increasing land development. Innovative development approaches aim to maintain hydrologic conditions of the undisturbed landscape, but are based on insufficient target information. This study uses the hydrologic landscape concept to evaluate reference hydrology in small headwater catchments surrounding Falls Lake, a reservoir serving Raleigh and the greater Triangle area. Researchers collected one year of detailed data on water balance components, including precipitation, evapotranspiration, streamflow, and shallow subsurface storage from two headwater catchments representative of two hydrologic landscapes defined by differences in soils and topographic characteristics. The two catchments are similar in size and lie within the same physiographic region, and during the study period they showed similar water balances of 26‐30% Q, −4 to 5% ΔS, 59‐65% evapotranspiration, and 9‐10% G. However, the steeper, more elevated catchment exhibited perennial streamflow and nongrowing season runoff ratios (Q/P) of 33%, whereas the flat, low‐lying stream was drier during the growing season and exhibited Q/P ratios of 52% during the nongrowing season. A hydrologic landscape defined by topography and soil characteristics helps characterize local‐scale reference hydrology and may contribute to better land management decisions.

Clearcutting upland forest alters transpiration of residual trees in the riparian buffer zone

“…We report the average value between the two locations and depths to capture integrated soil moisture across space and with depth. Because of missing soil moisture data at the beginning of the monitoring period, 15% of our HF1 2010 growing season data (June and July 2010) was supplemented with moisture readings measured reported in Dreps et al ., . The riparian buffer net radiation was measured next to the monitored trees every 10 min with a Kipp & Zonen long and short wave net radiometer (CNR2‐L) (Campbell Scientific, Logan, UT).…”

Variability of tree transpiration across three zones in a southeastern U.S. Piedmont watershed

“…Soil moisture and sap flux density were measured in the riparian buffer, mid-hillslope, and upland-hillslope zones of the watershed from May 2015 to December 2016. The definition of the riparian buffer was based on field observations of sandy loam soils in the flat (i.e., <12% slope) stream valley bottom (Dreps et al, 2014). Mid-hillslope units correspond with the Tatum soil series and are on relatively steep (i.e., 12-50%) slopes with eroded soils that have a shallow depth to bedrock.…”

“…Mid-hillslope units correspond with the Tatum soil series and are on relatively steep (i.e., 12-50%) slopes with eroded soils that have a shallow depth to bedrock. Shallow-to-deep water tables and upland-hillslope units are relatively flat slopes on deep soils that correspond to Cecil, Appling, and Georgeville soil series (Dreps et al, 2014). Volumetric soil moisture (m 3 m -3 or %) readings were taken using a water content reflectometer (CS 615; Campbell Scientific, Logan, UT, USA).…”

“…The same species sapwood area and tree counts were used for each zone to scale J s to T z to avoid over-or under-emphasizing watershed sapwood area for each zone. Weighted area percentages for each zone was estimated based on landscape units that included percent slope, soil type, and unsaturated zone depth (Dreps et al, 2014) and field observations of species across the watershed (Boggs et al, 2015). The weighted area average (i.e., 10% buffer, 45% mid-hillslope, and 45% upland-hillslope) ofT z from each zone was then used to compute the average riparian buffer, mid-hillslope, and upland-hillslopeT w .…”

Climate Change in the Lumbee River Watershed and Potential Impacts on the Lumbee Tribe of North Carolina

“…The highest elevations of the southern Appalachian Mountains receive, on average, 2500 mm or more of annual precipitation (Swift et al ), and this precipitation helps sustain headwater streams of major river basins throughout the region (Nippgen et al ; Singh et al ). The driest parts of the Piedmont and Atlantic Coastal Plain regions receive approximately half as much precipitation as the Appalachian Mountains (Dreps et al ). To meet growing societal demands for water, major reservoirs were constructed along Piedmont rivers during the 20th century to capture runoff from mountains and store it for human use (Sun et al ).…”