Leon River, Texas
An ARS Benchmark Research Watershed
Collaborators and cooperating Agencies and Groups
LeonRiver, above LakeBelton, consists of 735,600 ha, predominately in the Grand Prairie MLRA and
West Cross Timbers (Fig. B8). The watershed area to be evaluated is 607,000
ha above Gatesville in Coryell County Texas. The area is well dissected
with steams. Numerous small flood control dams (exact number unknown at
this time) have been constructed in the watershed. Two reservoirs, LakeLeonand LakeProctor, are located in the watershed. The watershed drains into LakeBelton, a large reservoir that provides domestic water for about one-half million
people. Soils in the watershed are divided into two major groups. In the
upper portion of the watershed, soils are generally lighter textured with
loamy fine sands and sand soils occurring near the streams. In the lower
portion of the watershed, soils are finer textured, with clays and clay
loam soils occurring most often. About 68% of the land area is either in
pasture or rangeland. Agricultural cropland makes up about 10% of the total
watershed land area, although this amount is decreasing due to a decrease
in peanut production in the area. Forestland makes up 17% of the land area.
Mean annual rainfall decreases from east to west, but averages about 800mm
per year near the center of the watershed. There are 55 concentrated animal
feeding operations (CAFOs) in the watershed, mostly dairy operations or
replacement heifers. There are about 66,000 dairy cattle in the watershed.
Most of the dairy operations are in ErathCountyin the eastern portion of the watershed located on tributaries of Resley
Environmental concerns in the watershed are generally associated with
the CAFO units and the management and disposal of animal wastes, and municipal
wastewater. Land application of the animal wastes can potentially have
many positive aspects, including increasing soil organic matter content
with associated increased soil aggregation, water holding capacity, and
improved soil fertility. There are potentially problems of over application
of waste products with excess application of phosphorus and nitrogen, resulting
in excessive nutrient loss in surface runoff, and also the potential of
pathogen contamination of surface waters. As a result, the environmental
issues of concern and under evaluation are:
1. Water Quality: Runoff contaminated with pathogens and /or nutrients.
2. Soil Quality: Carbon and nutrient availability and distribution in
3. Changes in soil water holding capacity.
1. Nutrient Management (590)
2. Prescribed Grazing (528A)
3. Brush Management (314)
4. Grassed Waterway (412)
The objective is to quantify the effects of management practices on soil
quality and water quality and quantity. Watersheds with a wide range of
sizes (0.5 to 607,600 ha) are being studied to examine scale impacts and
transport mechanisms. Paired watersheds have also been established to determine
the field-scale effects of selected management practices.
The upper Leon River Watershed is a new area for ARS research, and few
structures are in place. The U.S. Geological Survey (USGS) has a long history
of monitoring flow in the LeonRiverwith records dating back to 1925. Monitoring stations have been operated
by the USGS in to watershed, resulting in a nest of sub-watersheds of 68,400,
124,000, and 489,700 ha. These records will be invaluable in developing
and evaluating models of the hydrology of the watershed. Instruments for
sampling stream flow and for measuring flow from smaller areas will be
installed to determine how conservation practices associated with manure
and nutrient management impact water and soil quality. A watershed model
will be used to evaluate the watershed and potential management scenarios.
Selected soil properties will be determined for a range of management
properties, concentrating on manure management and tillage practices. If
possible, properties for a range of management intensity and length of
management on similar soils will be determined. In one particular study,
recently sampled soil properties will be compared to those of archived
soil samples that are over 50 years old. The data obtained will provide
a basis for computer simulation modeling and/or to verify model results.
In the Mustang Creek watershed (a subwatershed in the LeonBasin), water quality and quantity are being measured for three 1 ha tilled
field plots, two 0.5 ha pasture field plots, and one 17 ha tilled field
with previous animal byproduct application. Two monitoring sites (1467
and 5506 ha) have also been installed on Mustang Creek. In addition, two
large-scale monitoring sites (approximately 500,000 and 600,000 ha) have
been established on the LeonRiver. At each of these sites, automated samplers are collecting storm data
on the following parameters: dissolved nutrients (NO
-P), particulate N, particulate P, and suspended sediment. Grab samples
for bacteria and dissolved nutrients are being collected on weekly or biweekly
schedule. All data will be used to support the CEAP modeling efforts.
Collaborators and Cooperating Agencies and Groups
USGS, USDA-NRCS, BrazosRiverAuthority, TexasAgricultural Experiment Station, TexasCooperative Extension, TexasSoil and Water Conservation Board.