M.L. Jaynes | USGS Science

USGS1994

Hydrologic, water-quality, and meteorologic data from selected sites in the Upper Catawba River Basin, North Carolina, January 1993 through March 1994

Hydrologic, water-quality, and meteorologic data were collected from January 1993 through March 1994 as part of a water-quality investigation of the Upper Catawba River Basin, North Carolina. Specific objectives of the investigation were to characterize the water quality of Rhodhiss Lake, Lake Hickory, and three tributary streams, and to calibrate hydrodynamic water-quality models for the two reservoirs. Sampling locations included 11 sites in Rhodhiss Lake, 14 sites in Lake Hickory, and 3 tributary sites. Tributary sites were located at Lower Creek upstream from Rhodhiss Lake and at Upper Little River and Middle Little River upstream from Lake Hickory. During 21 sampling visits, specific conductance, pH, water temperature, dissolved-oxygen concentration, and water transparency were measured at all sampling locations. Water samples were collected for analysis of biochemical oxygen demand, fecal coliform bacteria, hardness, alkalinity, total and volatile suspended solids, suspended sediment, nutrients, total organic carbon, chlorophyll, iron, calcium, and magnesium from three sites in each reservoir and from the three tributary sites. Chemical and particle-size analyses of bottom material from Rhodhiss Lake and Lake Hickory were performed once during the study. At selected locations, automated instruments recorded water level, streamflow, water temperature, solar radiation, and air temperature at 15-minute intervals throughout the study. Hydrologic data presented in the report include monthly water-level statistics and daily mean values of discharge. Diagrams, tables, and statistical summaries of water-quality data are provided. Meteorologic data in the report include monthly precipitation, and daily mean values of solar radiation and air temperature.

North Carolina↗

USGS1994

Effects of water-control structures on hydrologic and water-quality characteristics in selected agricultural drainage canals in eastern North Carolina

November of water into and out of tidally affected canals in eastern North Carolina was documented before and after the installation of water-control structures. Water levels in five of the canals downstream from the water-control structures were controlled primarily by water-level fluctuations in estuarine receiving waters. Water-control structures also altered upstream water levels in all canals. Water levels were lowered upstream from tide gates, but increased upstream from flashboard risers. Both types of water-control structures attenuated the release of runoff following rainfall events, but in slightly different ways. Tide gates appeared to reduce peak discharge rates associated with rainfall, and flashboard risers lengthened the duration of runoff release. Tide gates had no apparent effect on pH, dissolved oxygen, suspended-sediment, or total phosphorus concentrations downstream from the structures. Specific conductance measured from composite samples collected with automatic samples increased downstream of tide gates after installation. Median concentrations of nitrite plus nitrate nitrogen were near the minimum detection level throughout the study; however, the number of observations of concentrations exceeding 0.1 milligram per liter dropped significantly after tide gates were installed. Following tide-gate installation, instantaneous loadings of nitrite plus nitrate nitrogen were significantly reduced at one test site, but this reduction was not observed at the other test site. Loadings of other nutrient species and suspended sediment did not change at the tide-gate test sites after tide-gate installation. Specific conductance was lower in the Beaufort County canals than in the Hyde County canals. Although there was a slight increase in median values at the flashboard-riser sites, the mean and maximum values declined substantially downstream from the risers following installation. This decline of specific conductance in the canals occurred despite a large increase of specific conductance in the tidal creek. Flashboard risers had no significant effect on concentrations of dissolved oxygen, suspended sediment, total ammonia plus organic nitrogen, or phosphorus. Maximum concentrations of ammonia nitrogen were smaller at both test sites after riser installation. In addition, concentrations of nitrite plus nitrate nitrogen exceeding 1.0 milligram per liter rarely occurred at the flashboard-riser test sites following installation of the risers. Median loadings of nitrite plus nitrate nitrogen and total nitrogen decreased at one riser test site following flashboard-riser installation. Tide gates and flashboard risers were associated with reductions in concentrations and export of nitrite plus nitrate nitrogen; however, these changes should be interpreted cautiously because reductions were not observed consistently at every site. The hydrology and baseline water-quality characteristics of the two study areas differ, making comparisons of the effectiveness of the two types of water-control structures difficult to interpret. The effects of water-control structures on the hydrology of the drainage canals are more meaningful than the changes in water quality. Tide gates and flashboard risers altered the hydrologic characteristics of the drainage canals and created an environment favorable for nutrient loss or transformation. Both structures retained agricultural drainage upstream, which increased potential storage for infiltration and reduced the potential for surface runoff, sediment, and nutrient transport, and higher peak outflow rates.

North Carolina↗