Oklahoma Conservation Commission (OCC) Rotating Basin Monitoring Program
Recent changes in EPA regulations have increased the amount of funds that can be used
for monitoring for nonpoint source pollution in Oklahoma. In response to this change,
the OCC evaluated existing monitoring programs in the state and developed a program
best suited to fill the gaps and to monitor the impact of nonpoint source pollution on
Oklahoma’s water resources.
The OCC is charged with monitoring, assessing, and evaluating waters of the state for
impacts of nonpoint source pollution. Nonpoint Source pollution is difficult to monitor
for because it comes from diffuse, diverse, and often intermittent sources. Because
nonpoint source pollution is often delivered to waterbodies during rainfall events as
runoff, it is difficult to pinpoint its origin. Historical studies and the nature of nonpoint
source pollution suggest the best way to monitor, assess, and characterize nonpoint
source pollution is to work on a small scale, in small watersheds, close to the source.
With this in mind, along with the need for statewide coverage, the OCC developed a
program to monitor approximately 150 sites in smaller watersheds across the state on a
five year interval. The OCC plans to sample streams in each of the 11 major basins in the
state for a 2 year period once every five years. Sites will be located at the approximate
outlet of every 11-digit HUC watershed and at least one site higher up in the watershed
(Figure 1).
Water quality samples will be collected ten times per year on a fixed interval basis.
Parameters to be tested for include turbidity, pH, dissolved oxygen (DO), alkalinity,
conductivity, water temperature, instantaneous discharge, nitrate (NO3) plus nitrite
(NO2), ortho phosphate (PO4), total phosphorous (TP), total Kjeldahl nitrogen (TKN),
ammonia (NH4), chloride (Cl), sulfate (SO4), total suspended solids (TSS), total dissolved
solids (TDS), 5-day biochemical oxygen demand (BOD5), and total hardness.
Enterococcus, Escherichia coli will be monitored during the summer months only.
Sites will be monitored twice yearly for benthic macroinvertebrates and benthic habitat
during the 2-year collection period. The sample collections are evenly divided between
the winter and summer dry periods; thus utilizing the most stable index periods. Fish and
fish habitat will be monitored once during each rotation cycle. This period was selected
to minimize the impact on fish populations within small streams. Additional information
on the geomorphology of the stream will be collected on selected streams. Specifically,
width-to-depth ratios, bank full estimations, entrenchment calculations, and substrate type
and size distribution will be estimated. This information will be used to develop a
correlation with Rosgen stream type classification (Rosgen, 1996).
When results of bioassessment indicate that toxic compounds have affected the fish and
wildlife propagation beneficial use, the water and sediments will be sampled for
biologically available forms of metals (Ag, As, Cd, Cr, Cu, Hg, Ni, Pb, Se, and, Zn). In
addition, pesticides will be measured when biological and habitat assessments indicate
the presence of unknown toxicity. Since there are over 50 modern pesticides in common
use and many more in minor use, it is not cost effective to monitor for all of them. When
pesticides are suspected to be a contaminant, a cooperative effort with the local districts
and the local extension agents will be undertaken to identify which pesticides are used in
the area of concern and at what time of the year. Monitoring for the suspect pesticides
will occur during the application periods throughout the year. (As a caveat, financial
resources will limit the degree and magnitude to which toxic evaluation will occur.)
Additional parameters that will be monitored in association with this program include
landuse/land cover, human population factors such as population density, urban
expansion, and septic tank density, agricultural use such as crop type and acreage,
domestic animal type and population as well as farm size, and climatic information.
The data will be collected using EPA approved methods, following guidelines in EPA
approved Quality Assurance Project Plans. This data will be stored in a single,
geographically linked database such that it can easily be used in geographical information
systems analysis such as identification of areas contributing to nonpoint source pollution
and effects of landuse changes on water quality over time.
It is anticipated that this program will evolve over time. Some of the upper watershed
sites might change as warranted by certain interests in the watershed. Additional
parameters may be added relative to future concerns. It is anticipated that in the near
future, the data will all be available via internet access in GIS layers such that a person
can go to a map of sites, click on a site or group of sites, and obtain all the data for that
selection. When technology, information, and financial resources become available, the
monitoring program will be expanded to include other potential NPS pollutants such as
endocrine disrupters. In addition, the program will be revamped to address the 3dimensional nature of NPS pollution. Eventually, the monitoring program will be
designed to identify surface water, groundwater, and aerial borne NPS pollution causes
and sources.
Figure 1. Approximate Location of Rotating Basin Program Monitoring Sites.