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Nutrient loading to Lewisville Lake, north-central Texas, 1984-87

Water-Resources Investigations Report 95-4076

Prepared in cooperation with the City of Dallas
By:
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Abstract

Concentrations of nutrients in the streams of the 1,660-square-mile Lewisville Lake drainage basin have some association with the two types of physiographic regions in the basin prairie regions and cross timbers regions. Total nitrogen and phosphorus concentrations generally are larger in streams draining the prairie regions than in streams draining the cross timbers regions, a characteristic that might be accounted for in part by the fact that prairie regions tend to have more nutrient-rich, less-permeable soils than cross timbers regions. Most of the variability in nutrient loads is associated with variability in discharge. During a low-flow synoptic survey, the largest contributor of total nitrogen and total phosphorus (at the downstream-most site) was Isle du Bois Creek (815 pounds per day of total nitrogen and 146 pounds per day of total phosphorus). During a high-flow synoptic survey, the largest contributor of total nitrogen and total phosphorus (at the downstream-most site) was Elm Fork Trinity River (4,620 pounds per day of total nitrogen and 210 pounds per day of total phosphorus).

On the basis of results of stormflow and periodic sampling, the total nitrite plus nitrate nitrogen that entered the reservoir on the average each day during 1986 was 5,640 pounds per day, and during 1987,4,480 pounds per day. During the same period, about one and one-half as much nitrogen in the form of total ammonia plus organic nitrogen entered the reservoir (8,530 pounds per day in 1986 and 7,020 pounds per day in 1987); and about one-fourth as much total phosphorus entered the reservoir during the period (1,310 pounds per day in 1986 and 1,080 pounds per day in 1987).

Point sources accounted for small fractions (probably less than 10 percent) of the total nutrient load from Clear Creek, Little Elm Creek, Hickory Creek, and Elm Fork Trinity River.

Most of the point-source load to Lewisville Lake could originate at a few sewage-treatment plants discharging to ungaged streams close to the reservoir.

The estimated long-term (1974-89 water years) average annual total nitrogen load (excluding loads from sewage-treatment plants in ungaged areas) is 11,800 pounds per day. The estimated long-term (1974 89 water years) average annual total phosphorus load (excluding loads from sewage-treatment plants in ungaged areas) is 1,100 pounds per day.

Additional publication details

Publication type:
Report
Publication Subtype:
USGS Numbered Series
Title:
Nutrient loading to Lewisville Lake, north-central Texas, 1984-87
Series title:
Water-Resources Investigations Report
Series number:
95-4076
Year Published:
1995
Language:
English
Publisher:
U.S. Geological Survey
Publisher location:
Austin, TX
Contributing office(s):
Texas Water Science Center
Description:
iv, 25 p.
Country:
United States
State:
Texas
Other Geospatial:
Lewisville Lake
Online Only (Y/N):
N
Additional Online Files (Y/N):
N