Watershed Protection Plan - Lower Rio Grande Valley Development ...

WATER QUALITY MONITORING PLAN
Table 21. Nutrient and Bacteria Parameters Monitored
Under the Arroyo Colorado Pollutant
Reduction Plan (PRP)
Parameter Parameter .
Code
Total Phosphorus as P (mg/l) 00665
Total Phosphate as PO4-3 (mg/l) 00650
Total Ammonia Nitrogen as N (mg/l)* 00610
Total Kjeldahl Nitrogen as N (mg/l) 00625
Total Nitrite + Nitrate Nitrogen
as N (mg/l) 00630
E. coli (#/100ml)* 31648
* Monitoring is only required if this parameter is not already being
monitored
TMDL Monitoring
Despite the development of predictive water
quality models for the Arroyo Colorado in 2001 and
2002, efforts to develop a TMDL for DO in the Arroyo
Colorado have been limited by the availability of
physical, biological and biochemical data for critical
areas of the tidally infl uenced segment. Information on
hydrodynamics, primary productivity, the dynamics of
biochemical oxygen production/consumption, nutrient
cycling and the relationship between these processes
and dissolved oxygen dynamics in Segment 2201 is
very limited. These data limitations have contributed to
a signifi cant level of uncertainty associated with existing
water quality models developed in 2001 and 2002.
In 2004 the TCEQ entered into a cooperative funding
agreement with the USGS to collect the information
necessary to address the current data limitations
and information gaps associated with the topics of
hydrodynamics, primary productivity, biochemical
oxygen demand dynamics and nutrient cycling in the
Arroyo Colorado. The purpose of the study was to:
1. Characterize water quality of the Arroyo Colorado
by measuring hourly temperature, pH, DO and
conductivity at two depths at four locations in the
Arroyo Colorado over two 24-hour periods during
two synoptic events.
2. Characterize the nutrient and carbon fl ux through
a study reach including pertinent nitrogen and
phosphorus species, BOD, total organic carbon
(TOC), TSS and volatile suspended sediment
(VSS).
3. Measure the seasonal, nutrient-dependent algal
growth and algal productivity rates in the water
column for each study reach.
4. Measure biochemical oxygen consumption and
production rates, respiration rates and sediment
and carbon deposition rates.
To complete these tasks, the USGS and TCEQ are
collecting surface water quality data and biological
data to produce estimates of rates and constants
necessary for detailed calibration of hydrodynamic and
water quality models that will be used to determine a
TMDL for the Arroyo Colorado, which is scheduled to
be completed in 2009. Data collection for this project
began in 2006.
Continuous Meteorological, Stage and Water
Quality Monitoring in the Zone of Impairment
In 2006 the TCEQ, in cooperation with the IBWC,
installed and began testing a continuous monitoring
station capable of monitoring air temperature, wind
speed, wind direction, water surface elevation, water
temperature, pH in water, specifi c conductance in
water and dissolved oxygen at two water depths in the
Zone of Impairment of the Arroyo Colorado near Rio
Hondo (Station 13072). When testing is completed,
the automated measurements taken hourly at the site
will be transmitted directly to the TCEQ via telephone
modem. The data will be displayed in near real-time on
a dedicated TCEQ website.
The data generated by the continuous water quality
monitoring station will be used to increase current
understanding of the role of physical factors such
as meteorological conditions and tidal cycling in the
occurrence of low DO in the Zone of Impairment and
the relationship between hydrodynamics and in-stream
biochemistry in the Arroyo Colorado.
Monitoring of Agricultural Activities
The ACW Partnership will monitor water quality
resulting from agricultural activities to:
• better characterize pollutant loading from
agricultural runoff
• evaluate/demonstrate agricultural BMP
effectiveness
• measure progress toward meeting ACW
Protection Plan goals
To accomplish these objectives, ACW Partnership
member organizations will conduct monitoring on three
different scales: 1) at the sub-watershed scale, 2) at the
transitional fl ow zone scale and 3) at the edge-of-fi eld
January 2007 123 Arroyo Colorado Watershed Protection Plan