Scope of
Work
Funding Source
Funding provided by the Texas State Soil and Water Conservation
Board as part of a Clean Water Act Section 319(h) Grant.
Background
The Arroyo Colorado flows through Hidalgo, Cameron and Willacy
Counties in the Lower Rio Grande Valley of Texas into the Laguna
Madre (Figure 1). Flow in the Arroyo Colorado is sustained by
wastewater discharges, agricultural irrigation return flows, urban
runoff, and base flows from shallow groundwater. The Arroyo is the
major source of fresh water to the lower Laguna Madre, an
economically and ecologically important resource to the region. The
Laguna Atascosa National Wildlife Refuge and several county and
city parks are located within the Arroyo watershed. The mild
climate, semi-tropical plants and animals, and many recreational
opportunities draw large numbers of people to the Arroyo Colorado
watershed. One third of the stream is also used for shipping from
the Gulf Intracoastal Waterway to the Port of Harlingen.
As a result of low dissolved oxygen levels, the tidal segment of
the Arroyo Colorado (2201), does not currently meet the aquatic
life use designated by the State of Texas and described in the
Water Quality Standards. This has been the case for every 303(d)
list prepared by the state since 1986. There have also been
concerns for high nutrient levels in this river as documented on
every 305(b) assessment prepared by the state since 1988. In order
to meet the dissolved oxygen criteria (24-hour average of 4.0 mg/L
and minimum of 3.0 mg/L) at least 90% of the time between the
critical period of March through October, TCEQ (2003) estimates a
90% reduction in nitrogen, phosphorous, oxygen demanding substances
and sediment will be necessary.
In response to this impairment, a local effort has been
initiated to develop a watershed protection plan (WPP) to improve
conditions in the Arroyo Colorado. Working with the TCEQ, the
TSSWCB, and other agencies, a local steering committee will devise
and implement strategies to increase dissolved oxygen in the Arroyo
and improve its environmental condition.
The Arroyo Colorado Watershed Steering Committee has established
several work groups to address the six major components of the
watershed plan: wastewater infrastructure; agricultural issues;
habitat restoration; refinement of the TMDL analysis; land use; and
public education. The project has significant financial support
from federal nonpoint source grants under CWA Section 319(h).
Already, the stakeholders have made great progress. The Education
and Outreach Work Group has developed an outstanding multimedia
presentation about pollution problems in the Arroyo and how to get
involved in addressing them. In May 2004, the TCEQ and the Habitat
Restoration Work Group established contracts with Texas A&M's
Sea Grant program and the Texas Parks and Wildlife Department to
provide an independent watershed coordinator and a habitat
restoration specialist to assist in the development of the WPP.
TPWD has contracted with Alan Plummer Associates, Inc. to develop a
habitat restoration feasibility study. Funding for this study was
obtained from NOAA through GLO. A Draft Wastewater Infrastructure
plan has been developed. In September 2005, the TSSWCB and the
Agricultural Issues Work Group established contracts with (1)
Hidalgo and Southmost SWCDs to provide technical and financial
assistance to landowners to aid in the development and
implementation of WQMPs and (2) the Texas Water Resources Institute
and Texas AgriLife Extension Service to provide education on best
management practices. The Draft WPP is expected to be completed
February 2006.
Goals and Objectives
The primary focus of this 319(h) project is to better
characterize agricultural runoff in the Arroyo Colorado, assess and
demonstrate the effects of BMP implementation at the field and
sub-watershed level, and measure progress towards meeting WPP
goals. A secondary focus is to evaluate the natural phosphorus
reduction capabilities of drainage ditches on runoff from irrigated
cropland in the Arroyo Colorado watershed.
This project will provide storm and routine monitoring of
drainage ditches that contribute nonpoint source loadings to the
Arroyo Colorado in order to better assess agricultural NPS loadings
and reductions resulting from BMP implementation. Monitoring will
primarily be directed at evaluating areas with significant
irrigated cropland acreage to evaluate nonpoint source pollution
(NPS) contributions and determine NPS reductions resulting from
BMPs.
A final report will be developed assessing the effects of the
conservation practices. Soil sampling and water quality monitoring
will be utilized to gauge the impacts on water quality.
This project will be consistent with the Watershed Protection
Plan and highly coordinated with the Arroyo Partnership and Arroyo
Ag Steering Committee as well as the educational and implementation
projects already underway in the watershed. These groups and
projects will provide for a great deal of public participation and
many opportunities for public input.
In this project, TAMUK and TAES will provide assessment
activities at 4 sub-watershed sites within the Arroyo Colorado:
- Mile 4 North FM 491 in Hidalgo County (Lat. 26 06 47.8758, Long
-97 53 27.8602)
- +/- 3 miles north of the intersection of US Military Highway
281 and 493 in Hidalgo County (Lat. 26 06 44.6665, Long -98 02
14.987)
- Harding Ranch Road approximately 3 miles north of 508 and 1420
in Cameron County (Lat.26 16 47, Long 97 43 27)
- ABD Road and FM 1479 about 4 miles south of Highway 83 in
Cameron County (Lat. 26 08 06 Long 97 43 27)
The monitoring effort will make use of numerous automated
sampling systems in TAMUK's possession that will be made available
to this project. Historical or nondirect data obtained from other
projects with QAPPs approved by EPA or the State of Texas will also
be used to supplement this project. The data collected for this
project will be used to determine the reduction of NPS pollution
associated with implementation efforts and provide data to inform
TSSWCB of areas where focused reduction efforts are most needed.
This project will also support the educational efforts in the
watershed.
The four sub-watersheds chosen for this study represent
predominately irrigated cropland within the Arroyo watershed with
two sites being located in Cameron County and two sites in Hidalgo
County. The two stream sites in Cameron County were monitored from
2000 to 2002. The historical water quality data available at these
sites will be made available as non-direct data to this project for
use in the assessment of water quality.
The sub-watershed monitoring activities of this project will
consist of automated stormwater sampling, monthly ambient grab
sampling, and instantaneous streamflow measurements. Field
measurements of dissolved oxygen, water temperature, specific
conductance, and pH will occur with all grab sampling. Stormwater
samples will be retrieved on a daily basis during storm events and
flow composited into a single sample. All water samples will be
analyzed for various nutrient forms (i.e., total phosphorus,
dissolved orthophosphate phosphorus [frequently referred to as
soluble reactive phosphorus], total Kjeldahl nitrogen, dissolved
ammonia, dissolved nitrite plus nitrate), and total suspended
sediments (TSS). In addition, monthly grab samples will be analyzed
for BOD5. The nitrogen forms are included in the laboratory
analyses to provide a more complete indication of macronutrient
conditions in the watershed, to evaluate whether agricultural BMPs
are reducing both nutrients (nitrogen and phosphorus), and to
ensure that efforts to reduce one nutrient is not inadvertently
increasing another.
This project will provide result demonstrations to landowners in
the Arroyo Colorado watershed. This edge of field monitoring will
represent both tiled and non-tiled irrigated cropland fields that
drain to both drainage ditches and directly into the Arroyo.
Surface runoff, along with outflow from the tile drainage system,
will be monitored. Surface runoff and tile drain samples will be
retrieved on an event basis and flow composited into a single
sample. All water samples will be analyzed for various nutrient
forms (i.e., total phosphorus, dissolved orthophosphate phosphorus
[frequently referred to as soluble reactive phosphorus], total
Kjeldahl nitrogen, dissolved ammonia, dissolved nitrite plus
nitrate), and total suspended sediments (TSS). In addition, monthly
grab samples will be analyzed for BOD5.
This project is dependent upon and is an important component of
the larger project effort in the Arroyo Colorado described above.
It is closely linked to the CWA ยง319 funded FY05 Arroyo BMP
Education Project being conducted by TWRI and AgriLife Extension,
the FY05 Arroyo WQMP Implementation Project being conducted by the
TSSWCB and Hidalgo and Southmost SWCDs, and the Arroyo Watershed
Coordination Project being conducted by TCEQ and Texas Sea Grant.
The results of this study will be used to support ongoing
educational and implementation efforts and future modeling efforts
planned for the watershed.
Task 1: Project Coordination and Administration
Objective: TWRI will organize an An Monitoring
Oversight Committee to coordinate projrect efforts with all project
participants. In addition, TWRI will ensure project goals are
achieved in the manner proposed, summarize activities and
achievements made throughout the course of the project by
developing and submitting quarterly progress reports and a final
report, hold regular meetings and maintain communication among all
personnel involved.
Task 2: Compilation and Evaluation of Prior Studies and
Data
Objective: TWRI, with assistance from members
of the Ag Monitoring Oversight Committee, will compile historical
water quality data and information from previous studies and
conduct a detailed analysis of the most significant water quality
parameters to investigate the trends and the different biological
and physical process taking place in the watershed that contribute
to changes in water quality in the Arroyo. These results will be
organized and summarized for project participants to identify
critical data gaps and these results will be provided to project
personnel and for development of education materials.
Task 3: Inventory Conservation Practice Implementation
Objective: TAES-Temple, with assistance from
TCE, USDA-NRCS, USDA-FSA, the TSSWCB Harlingen Regional Office, and
the SWCDs, will identify all producers in the watershed, compile
information on the location and types of Conservation Practices
implemented in the Arroyo Colorado Watershed since 1995, assemble a
geo-referenced database and develop a map (hard copy and
electronic) displaying conservation practice implementation
information collected, and transfer all information to use in
targeting educational activities and identifying areas needing
priority implementation work.
Task 4: Update Land Use/Land Cover Data
Objective: The Spatial Sciences Lab (SSL) will
obtain data for the Arroyo Colorado Watershed including: 1998 LULC
and major LULC changes since 1998; 2003 LANDSAT ETM+ Data, Path 26/
Row 42 and Path 27/ Row 42; applicable digital data on cropland
from USDA - FSA; digital location data on citrus production from
USDA-APHIS; digital data on locations of sugarcane fields from
sugar mill; 2004 1m DOQ for Cameron, Hidalgo and Willacy counties;
most recent digital data from irrigation districts; 1998 tile
drainage data and if available, obtain updated data from TSSWCB and
TCE; 1998 data on colonia and if available, obtain updated data
from TWDB; 1998 data on non-colonia septic systems and if
available, obtain updated data from Lower Rio Grande Valley
Development Council (LRGVDC); and 1998 data on land Application and
if available, obtain updated data from NPDES Permits.
Task 5: Develop Quality Assurance Project Plan
Objective: TWRI will develop a project QAPP and
submit it to TSSWCB and EPA for approval. TWRI will and provide
annual revisions and necessary amendments as needed.
Task 6: Perform Sub-Watershed Monitoring and Measure Pollutant
Attenuation in Drainage Ditches
Objective: TAMUK will perform water quality
monitoring and develop Stage-discharge relationships at four
drainage ditch sites. The data will be summarized in a report. In
addition, TAMUK will assess the ability of the drainage ditches to
mitigate nitrogen and phosphorus and with this information, TAMUK,
with assistance from TAES, will develop a suite of suitable
BMPs.
Task 7: BMPs to Reduce NPS Pollution at the Farm Level
Objective: TCE, TAES-Weslaco, and TAMUK will
select suitable demonstration sites to assess loadings from
agricultural runoff and leachate produced by different BMPs and
compare traditional practices with innovative BMP for the 3 most
representative crops of the watershed at 6 representative sites.
Runoff and leachate samples will be collected by TAES-Weslaco for
the different practices and laboratory analyses will be performed
to determine agricultural loadings such as nutrients and solutes.
TCE will conduct one field day and one result demonstration per
year to demonstrate and transfer the results to farmers and
interested persons.
Task 8: Develop Final Report
Objective: TWRI, with assistance from TAES and
TAMUK, will prepare final report for submittal to the TSSWCB.