Hydrology and Water Quality

WeyCo PineForest

Managing forested wetland landscapes for water quality improvement, quantity control, and productivity requires a detailed understanding of functional linkages between ecohydrological processes and management practices.

Watershed-level hydrologic and nutrient cycling processes are complicated by the presence of varied land features such as natural and managed forests, depressional wetlands, pine flatwoods, riparian buffers, bottomland hardwoods (BLH) on brackish waters, uplands and water bodies, and multiple land uses increase this complexity still further. These watersheds are characterized by low topographic relief, slow drainage with poorly drained high water table soils and wet sites where mean annual rainfall exceed potential evapotranspiration. Some of these forested wetlands have been drained artificially to lower water tables for trafficability and reduction of excessive moisture for increased crop growth.

Agricultural and silvicutural developments together with recent population growth in the region have not only caused a decrease of forested headwater wetlands but also altered the hydrology and water quality of these eco-systems. The consequence of wetland loss in the headwaters and alteration in hydrologic pathways may include increases in flash flooding, water quality decline, and alteration in hydroperiod and flow regime.

The focus of the Center’s program is to understand the hydrologic and nutrient cycling and transport processes of these low-gradient forested wetlands and evaluate the impacts of natural and anthropogenic factors on hydrology and water quality by using both the long-term monitoring and modeling approaches on field and watershed scales.

Physical Hydrology

Lowland Forest Hydrology Procedure

Hydrology of the forest ecosystem plays a critical role not only in ecosystem structure and functions but also in regulating the water cycle and pathways.

Read more about Physical Hydrology here

Water Quality

Turkey Creek Outlet Station

Research that focuses on water quality has three principal facets.

The first relates to hydrologic and soil processes that affect water quality flowing through a wetland. This line of research is fundamental to designing effective buffer zones for ameliorating non-point runoff from adjoining uplands.

The second facet considers the interaction of land management practices and water quality, as a basis for designing management practices that do not degrade water quality.

The third part is the in-stream transformation and transport processes along the streams that impact the ultimate water quality at the watershed outlet or a receiving water body. Research is considering the effects of harvesting on a riverine wetland, and other studies are considering the effects of harvesting and site preparation on basin wetlands.

Selected Publications

Modeling Applications

Modeling

Models are a useful tool for assessing hydrology, water quality, in-stream transport and biogeochemistry. They also provide a basis for evaluating silvicultural and water management plans, identifying information gaps, and addressing hypothetical scenarios on land use and climate change impacts.

Our modeling research focuses on linking hydrologic and biogeochemical processes in managed forested landscapes. We are collaborating with North Carolina State University scientists on application of DRAINMOD-based models to forested landscapes in the southeast. DRAINMOD was originally developed for design and evaluation of agricultural drainage and related water management systems.

DRAINMOD is a field-scale, one dimensional model that simulates water and heat flow for high water table soils with artificial drainage systems. Recently, the model has been modified to describe the hydrology of pine forests, and research to extend it to predict nutrient fate and transport in the forest ecosystems is underway. To that extent, researchers and modelers from various institutions gathered at the Center for disseminating current state-of-art modeling efforts on forest nutrient cycling and their fate and transport. Workshop presentations can be accessed at Forest Nutrient Cycling and Transport Modeling Workshop, March 6-7, 2008

Selected Publications
DNDC
Map of Watersheds

Forest-DNDC, a computer simulation model of carbon and nitrogen in terrestrial ecosystems, is a member of DNDC (DeNitrification-DeComposition) family.

It was developed by Complex Systems Research Center, EOS, University of New Hampshire, USA, and lots of support and cooperation from the Center for Forested Wetlands Research, USDA Forest Service, USA and the Institute for Meteorology and Climate Research, Atmospheric Environmental Research, Germany.

Forest-DNDC is a process-based biogeochemical model, coupling with soil carbon and nitrogen dynamics model DNDC and forest carbon model PnET. It integrates photosynthesis, decomposition, nitrification-denitrification, carbon storage and consumption, and hydro-thermal balance in forest ecosystems.

The model is used to predict plant growth and production, soil temperature and moisture regimes, carbon and nitrogen balance, and generation and emission of soil-borne trace gases in soils, including carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), nitric oxide (NO) and dinitrogen (N2). The model components are mainly driven by environmental factors, including climate, soil, vegetation and human activities.

Selected Publications
DRAINMOD
DRAINMOD Forest Dialogue

DRAINMOD was developed to simulate the performance of drainage and related water management systems (Skaggs, 1978) on afield scale.

It is based on a water balance in the soil profile and predicts water table depths, soil water conditions, and drainage rates on a continuous basis. Input data include soil properties, crop parameters, drainage design parameters, weather and irrigation data.

The model conducts a water balance on an hour-by-hour, day-by-day basis and calculates infiltration, ET, drainage, surface runoff, subirrigation, deep seepage, lateral seepage, water table depth and soil water status at each time step.

Later DRAINMOD was modified as DRAINLOB to simulate forest hydrology based on canopy interception, forest evapotranspiration (ET) and subsurface drainage characteristic to widely spaced ditches in drained pine forests (McCarthy et al., 1992; Amatya and Skaggs, 2001).

Predictions of daily water table elevations (left) and daily flows (right) for a drained pine forest, NC.

DRAINLOB was able to capture the daily water table and flow dynamics. A watershed−scale hydrologic model DRAINWAT (Amatya et al., 1997; 2004) is a further expansion of DRAINLOB by linking it with field and stream routing submodels (Konyha and Skaggs, 1992) to predict cumulative outflows flows from all fields through the canal−stream network reaches to the watershed outlet.

Selected Publications

Turkey Creek Working Group

Turkey Creek Watershed Location Map

The low-gradient forested wetland landscapes of the Coastal Plain of the Southeastern United States represent important eco-hydrologic systems, yet there is a very little information on ecologic, hydrologic and biogeochemical processes and transport, flooding pattern, and water and nutrient balances.

In 2004, with support from the U.S. Forest Service (FS) Southern Research Station and the National Council for Air and Stream Improvement, (NCASI), Inc., a watershed scale eco-hydrological monitoring and modeling study was re-established on a predominantly forested 7,260 ha coastal watershed on the Francis-Marion National Forest in Coastal South Carolina.

The main goal of the Turkey Creek watershed initiative is to develop a multi-cooperative research collaboration to address the critical issues of sustainable water management for low-gradient forested wetlands. in goal of the Turkey Creek watershed initiative is to develop a multi-cooperative research collaboration to address the critical issues of sustainable water management for low-gradient forested wetlands.

Selected Publications
Turkey Creek Watershed
TCWatershed WS77 & WS80 Image

Managing forested wetland landscapes for water quality improvement, quantity control, and productivity requires a detailed understanding of functional linkages between ecohydrological processes and management practices.

Watershed-level hydrologic and nutrient cycling processes are complicated by the presence of varied land features such as natural and managed forests, depressional wetlands, pine flatwoods, riparian buffers, bottomland hardwoods (BLH) on brackish waters, uplands and water bodies, and multiple land uses increase this complexity still further.

These watersheds are characterized by low topographic relief, slow drainage with poorly drained high water table soils and wet sites where mean annual rainfall exceed potential evapotranspiration. Some of these forested wetlands have been drained artificially to lower water tables for trafficability and reduction of excessive moisture for increased crop growth.

Agricultural and silvicutural developments together with recent population growth in the region have not only caused a decrease of forested headwater wetlands but also altered the hydrology and water quality of these eco-systems. The consequence of wetland loss in the headwaters and alteration in hydrologic pathways may include increases in flash flooding, water quality decline, and alteration in hydroperiod and flow regime.

The focus of the Center’s program is to understand the hydrologic and nutrient cycling and transport processes of these low-gradient forested wetlands and evaluate the impacts of natural and anthropogenic factors on hydrology and water quality by using both the long-term monitoring and modeling approaches on field and watershed scales.

Selected Publications
Watershed Characteristic & Monitoring
CR10X Weather Station

Turkey Creek (WS 78) Watershed Characteristics

  • Established in 1964 mostly within US Forest Service’s Francis-Marion National Forest, SC
  • ~ 5000 ha, 3rd order watershed, tributary of Huger Creek within the Cooper River Basin
  • Surface elevations from 4.0 to 15.0 m a.m.s.l. Less than 0.1% slope
  • Soils: Primarily poorly drained clayey soils of Lenoir-Lynchburg series and sandy/loamy soils.
  • Vegetation: Loblolly pine, Longleaf pine, Bottomland Hardwood, Gum/Oak/Willow, Shrubs and Scrubs, Bay/Cypress/Tupelo, Maple
  • Land Use: Forest (52%), Shrubs/scrubs (28%), Wetlands (14%), Ag/developed -lands (6%)
  • Mean annual rainfall: 1220 mm; Mean annual temperature: 18oC

Watershed Monitoring

  • Nearest meteorological monitoring stations at adjacent Santee Experimental Forest Head Quarter (since 1946) and experimental watersheds (WS 77 and WS 80) (since 1997)
  • Flow gauging stations at the outlet of WS78 established in 1964 and discontinued in 1984.
  • New real time stream flow monitoring station re-established in January 2005 (shown below)
  • Automatic water quality sampling at the outlet planned to be started in Fall 2005

Carteret

Carteret Ditch Outlet

The Carteret study site on a drained loblolly pine forest of mid-rotation age, located in Carteret county, North Carolina, is owned and operated by Weyerhaeuser Company.

The research site consists of three artificial experimental watersheds, each about 25 ha in size. The site is poorly drained and nearly flat with shallow water table under natural conditions.

The soil is a hydric series, Deloss fine sandy loam (fine-loamy mixed, Thermic Typic Umbraquult). Each watershed is drained by four 1.4 to 1.8 m deep parallel lateral ditches spaced 100 m apart.

Three rectangular experimental plots (each about 0.13 ha in area) located in each watershed were used to collect data on hydrology, soil and vegetation parameters. The three experimental watersheds have been instrumented since 1988 for continuous monitoring of precipitation, complete weather parameters, stage heights at watershed outlets equipped with V-notch weirs for estimating flow rates, and shallow ground water wells for measuring mid-point water table elevations.

The watersheds have also a long history of measurements for tree physiological parameters such as leaf area index (LAI), stomatal conductance, tree heights, and dbh. These artificially drained watersheds are typical of other managed pine forests in the Coastal Carolinas.

Studies on this site were conducted between 1988 and 2008 in cooperation with North Carolina State University and Weyerhaeuser Company with a support from National Council for Air & Stream Improvement (NCASI), Inc.

In 2009 a new long-term study has been initiated to the study of the effects of managing forests and bioenergy crops on the site water balance, and water quality at this study site. The main objectives are to quantify and evaluate the effects of cultivating loblolly pine (Pinus taeda), switchgrass (Panicum virgatum), and interplantings of switchgrass and loblolly pine on hydrology (surface and groundwater), water quality, and the site water and nutrient balance on drained forest lands.

Carteret Bioenergy & Forest Water Management
Viewing Setup

A vast area of the forests in the southeastern U.S. is on pine plantation forests. Among that about 1 million hectares of plantation pine in the coastal plain region are drained to improve soil trafficability for harvesting and planting operations and to improve soil moisture growth conditions throughout the year.

These lands on poorly drained soils are being intensively managed with pine forests for maximum timber production. Intensive forest management activities include access, drainage, harvest, site preparation, regeneration, fertilization, tending, protection, and utilization.

These lands drain a large amount of freshwater outflows into ditches and canals discharging ultimately into downstream nutrient sensitive estuaries and water bodies.

As a result there has been a public concern about the potential impacts of these operational silvicultural treatments on drainage water outflow and quality from these drained plantations.

In 1988 North Carolina State University together with Weyerhaeuser Company initiated a long-term forest water management study on three experimental watersheds at Weyerhaeuser’s drained pine plantations to evaluate the effects of both water and silvicultural management treatments on the drainage outflow and quality of water drained to downstream ditches discharging to the nearby estuary at Carteret county in eastern North Carolina coastal plain.

The water management treatments included controlled drainage with raised weir at the watershed outlet to hold more water during the spring spawning period for reducing potential offsite impacts and summer-fall tree growing season for maximizing tree growth. This treatment was evaluated for the period from 1990-94.

One of the treatment watersheds was harvested in June 1995 followed by bedding and site preparation in 1996 and re-planting in 1997 to study the effects of harvesting and regeneration on hydrology and water quality. The second treatment watershed underwent controlled drainage with an orifice hole in the weir plate from 1995 to 1999 to release a uniform pressurized discharge downstream during high flow events to minimize downstream impacts of flow and water quality.

The second watershed was later thinned in July 2002 to evaluate the thinning effects on hydrology and water quality. Both of the treatment watersheds were later fertilized in September 2005 to study the effects of fertilization and the water quality of these drained pine plantations through 2007.

Finally in early 2009, a new Catchlight funded collaborative study with North Carolina State University, Forest Service, and Weyerhaeuser Company has been initiated at the same site to study the hydrologic and water quality impacts of switch grass as a bioenergy-based crop intercropping between the beds of pine plantations. This study is currently ongoing.