AGRICULTURAL USE PROTECTION POLICY – ANNUAL MONITORING, POWDER RIVER BASIN (CAMPBELL AND JOHNSON COUNTIES) WYOMING
In 2006 the Wyoming Department of Environmental Quality (WYDEQ) – Water Quality Division (WQD) finalized the Agricultural Use Protection Policy (AUPP) requiring the annual monitoring of soil quality and crop productivity in areas throughout the Powder River Basin (PRB) of northeastern Wyoming receiving irrigation water containing coalbed methane (CBM) produced water discharges. The goal expressed in the Chapter 1, Section 20 standard of the Wyoming Water Quality Rules and Regulations is simply to “maintain surface water quality at a level that will continue to support the local agricultural uses that have developed around it.”
CBM produced water, a by-product of CBM gas extraction, is typically stored in on-channel reservoirs with releases to the channel when natural storm flows cause the on-channel reservoirs to overflow. The goal of annual monitoring is to protect agricultural uses of downstream soils from the potential degradative effects of irrigation water resources associated with saline/sodic CBM produced water discharges. Elevated salinity and sodicity in irrigation waters may impair agronomic soil properties and reduce crop growth and productivity.
Annual soil and vegetation monitoring is conducted on 15 to 18 fields, located along seven tributaries of the Powder and the Little Powder Rivers. Agricultural productivity evaluations include assessing soil quality and vegetative properties including cover, diversity, and production data from irrigated fields downstream of CBM produced water discharge points. Selected fields are within stream floodplains and naturally or sub-irrigated.
Soil samples are collected using a truck-mounted, hydraulically powered Giddings soil probe to comply with regulatory requirements and to establish current soil physicochemical properties within crop rooting zones. Soil sample analytical results are also used to monitor trends in soil physicochemical properties and to proactively determine any deleterious effects on soil quality from the application of irrigation waters receiving CBM produced water discharges.
Vegetation data is collected by clipping frames along transects to estimate crop biomass, yield, and moisture content. Tissue analyses are conducted and include crude protein levels and nutrient analyses. Canopy cover estimates by species and lifeform are also collected to estimate vegetative cover and species composition over time.
Technical annual reports are provided for each drainage following monitoring activities to fulfill agency reporting requirements and to discuss monitoring results and any changes/trends in soil chemistry (i.e., soil salinity, soil sodicity). Monitoring results are evaluated by the agency and used for adjusting future monitoring frequency as needed.