Land application of coalbed natural gas (CBNG) co-produced water is a popular management option within northwestern Powder River Basin (PRB) of Wyoming. This study evaluated the impacts of land application of CBNG waters on soil chemical properties at five sites. Soil samples were collected from different depths (0-5, 5-15, 15-30, 30-60, 60-90, and 90-120 cm) from sites that were irrigated with CBNG water for 2 to 3 yr and control sites. Chemical properties of CBNG water used for irrigation on the study sites indicate that electrical conductivity of CBNG water (EC(w)) and sodium adsorption ratio of CBNG water (SAR(w)) values were greater than those recommended for irrigation use on the soils at the study sites. Soil chemical analyses indicated that electrical conductivity of soil saturated paste extracts (EC(e)) and sodium adsorption ratio of soil saturated paste extracts (SAR(e)) values for irrigated sites were significantly greater (P < 0.05) than control plots in the upper 30-cm soil depths. Mass balance calculations suggested that there has been significant buildup of Na in irrigated soils due to CBNG irrigation water as well as Na mobilization within the soil profiles. Results indicate that irrigation with CBNG water significantly impacts certain soil properties, particularly if amendments are not properly utilized. This study provides information for better understanding changes in soil properties due to land application of CBNG water. These changes must be considered in developing possible criteria for preserving fragile PRB ecosystems.

Land application of co-produced waters from coalbed natural gas (CBNG) wells is one management option used in the Powder River Basin (PRB) of Wyoming and Montana. Unfortunately, the co-produced CBNG waters may be saline and/or sodic. The objective of this study was to examine the effects of irrigation with CBNG waters on soils and plants in the PRB. Soil properties and vegetation responses resulting from 1 to 4 yr of saline-sodic water (electrical conductivity [EC], 1.6-4.8 dS m(-1); sodium adsorption ratio [SAR], 17-57 mmol(1/2) L(-1/2)) applications were studied during 2003 and 2004 field seasons on sites (Ustic Torriorthent, Haplocambid, Haplargid, and Paleargid) representing native range grasslands, seeded grass hayfields, and alfalfa hayfields. Parameters measured from each irrigated site were compared directly with representative non-irrigated sites. Soil chemical and physical parameters, including pH, EC, SAR, exchangeable sodium percent, texture, bulk density, infiltration, and Darcy flux rates, were measured at various depth intervals to 120 cm. Multiple-year applications of saline-sodic water produced consistent trends of increased soil EC and SAR values to depths of 30 cm, reduced surface infiltration rates, and lowered Darcy flux rates to 120 cm. Significant differences (p < or = 0.05) were determined between irrigated and non-irrigated areas for EC, SAR, infiltration rates, and Darcy flux (p < or = 0.10) at most sites. Saline-sodic CBNG water applications significantly increased native perennial grass biomass production and cover on irrigated as compared with non-irrigated sites; however, overall species evenness decreased. Biological effects were variable and complex, reflecting site-specific conditions and water and soil management strategies.

Management of large volumes (60,000 ha-m) of co-production water associated with coal bed natural gas (CBNG) water extraction is a potential concern in the Powder River Basin (PRB) of Wyoming and Montana due to elevated water salinity and sodicity levels. Land application of saline-sodic CBNG water is a common water management method being practiced in the PRB, which can result in deterioration in soil quality. The objective of this study was to evaluate effects from 1 to 4 yr of land application with CBNG water on soil chemical properties at six study sites (fine to loamy, mixed to smectitic, mesic, Ustic Ardisols and Entisols) in the Wyoming PRB region. Changes in chemistry of soils collected from six depths irrigated with CBNG water were compared with representative nonirrigated soils. Applications of CBNG water significantly increased soil EC, SAR, and ESP values (up to 21, 74, and 24 times, respectively) compared with nonirrigated soils. Differences in soil chemical properties between an irrigated and nonirrigated coarse-textured soil were less than that of fine-textured soils, emphasizing texture as an important factor for salinity buildup. Pretreatment of CBNG water using a sulfur burner and application of gypsum and elemental S soil amendments reduced soil pH but did not prevent the build-up of salts and sodium. Study results suggest that current CBNG water management strategies are not as effective as projected. Additional research is needed to develop management strategies appropriate for mitigating adverse effects of CBNG water irrigation.

Saline/sodic waters derived from wells associated with coalbed methane (CBM) gas production are being applied to rangelands and to lands used for production agriculture within the Powder River Basin (PRB) of Wyoming and Montana. Our study areas represent variable vegetation types, soil textures, treatment strategies and water application methods on sites impacted by up to 3 years of land application of saline/sodic CBM water. Vegetation parameters evaluated were forage quality, above ground biomass production, aerial cover, species diversity and infectivity of arbuscular mycorrhizae (AM) fungi. Soil data from six depth intervals to 120 cm were collected early summer, mid/late summer and fall during the 2003 water application season. Samples were analyzed for texture, bulk density, pH, electrical conductivity (EC), and sodium adsorption ratio (SAR). Infiltration and hydraulic conductivity rates were also measured. Waters from CBM gas wells in the PRB vary in quantity and quality, with average flows of around 30 liters per minute, salinity levels of about 2 dS/m and SAR's ranging from low (e.g., 5) to extremely high (e.g., 70) levels. Variable water application methods including center-pivot and side-roll irrigation and "mister" evaporation systems are utilized for land application. Common CBM water treatment strategies include: 1) varying application rates; 2) chemically treating water to adjust for SAR, salinity, pH and bicarbonate levels; and 3) chemically treating soil surfaces to minimize sodicity and salinity conditions. Potential advantages and disadvantages of various management strategies are discussed based on soil and vegetation data analyses. With about 20,000 CBM gas wells currently permitted or drilled in the PRB and estimates of at least 50,000 future new wells, proper CBM product water utilization is warranted.

Changes in soil physical and chemical properties due to land application of coalbed methane (CBM) waters were investigated in study sites located in northwest Powder River Basin (PRB) of Wyoming. Samples of CBM water used for land application and analyzed for pH, electrical conductivity (EC), and sodium adsorption ratio (SAR) values. Water quality data indicated that EC and SAR values of CBM water samples were greater than the recommended values for irrigation use (0.75 dS m-1 and <10 SAR). Impacts of these poorquality CBM waters on soil physical and chemical properties were evaluated by collecting soil samples during the 2003 irrigation season from 6 depths (0-5, 5-15, 15-30, 30-60, 60-90 and 90-120 cm) from 6 sites that received CBM water applications for up to 3 years, which were compared to control sites. Changes in soil physical (e.g., infiltration rates, bulk density) and soil chemical (pH, EC, and SAR of saturation paste extracts) properties were determined. Our study indicates that the pH values are significantly (p = 0.05) greater in irrigated plots than control plots at depths of 0-5 and 30-60 cm in site 1 and 0-60 cm in site 4. The EC values were significantly greater in irrigated sites than control plots at 0-60 cm depth in sites 1, 4 and 6, 5-30 cm in site 3, and 0-15 cm in site 5. SAR values were significantly greater in irrigated sites than control plots in the upper 60 cm in sites 1 and 5, 0-5 cm site 4, and 5-30 cm in site 6. Irrigated sites 1, 3, and 4 had significantly lower %clay. Hydraulic conductivity in sites 1 and 5 were significantly lower than control plots. Thus, irrigation with poor-quality CBM water had significant impacts on soil chemical and physical properties. It has been estimated that over the next 15 years CBM water production in the PRB will exceed 366,000 ham. The results of this study will be useful to understand the potential changes in soil properties due to land application of CBM waters and to develop possible mitigating criteria for preserving impacted PRB ecosystems.

With about 20,000 coal bed natural gas (CBNG) wells currently permitted or drilled in the Powder River Basin (PRB) of Montana and Wyoming and projections of more than 50,000 future wells, CBNG water production in the PRB over the next 15 years will exceed 366,000 ham. Therefore, proper CBNG product water utilization is warranted. Land application using conventional center-pivot and side-roll irrigation systems is a common strategy for managing saline-sodic waters derived from CBNG production within the PRB. Various soil and plant impacts resulting from 1 to 4 years of saline-sodic water (EC = 1.8 to 4.0 dS m-1 ; SAR =15 to 38) applications were examined during the 2003 and 2004 field seasons on 6 (2003) to 8 (2004) study sites representing native range grasslands, seeded grass hayfields and alfalfa hayfields. Because soil and plant types, water application rates and water and soil treatment strategies were variable across study sites, parameters measured from each treated (irrigated) site were compared directly to those from representative control (non-irrigated) sites. Soil chemical and physical parameters including pH, EC, SAR, texture, bulk density, surface infiltration rate and Darcy flux rates were measured at various depth intervals to 120 cm. Multiple year applications of saline-sodic water produced consistent trends of increased soil EC and SAR values at depths to 30 cm, reduced surface infiltration rates and reduced Darcy flux rates to 120 cm. Significant (P=0.05) differences in EC, SAR, infiltration rates and Darcy flux (P=0.10) were determined at most sites. Up to 4 years of saline-sodic water applications significantly (P=0.05) increased native perennial grass biomass production and cover on treated vs. control sites. However, overall species evenness was reduced. Biological effects were variable and complex, reflecting site specific conditions and management strategies.

Irrigation with coalbed natural gas (CBNG) co-produced water is a popular management option used by many gas companies operating in northwestern Powder River Basin (PRB), Wyoming. Depending upon local conditions and production rates, a CBNG well may be productive for 2 to 20 years, with an average lifespan of 7 years. At present there are over 20,000 CBNG wells permitted or drilled in the PRB region and it is estimated that another 50,000 to 100,000 new wells will be drilled in the future. The total CBNG water production in the PRB is expected to peak at about 47,000 ha-m in 2006 and the cumulative CBNG-water production during the period 2002-2017 is estimated to be 366,000 ha-m. CBNG water is dominated by sodium (Na + ) and bicarbonate (HCO 3 -) ions and the average discharge of a single CBNG well ranges from <1 to 100 liter per minute, with pH ranging from 6.8 to 9.0, electrical conductivities (EC) from 0.4 to 4 dS/m, Na adsorption ratio (SAR) from a low of 5 to an extreme high of 70 and total dissolved solids (TDS) concentrations from 270 to 2720 mg/L. Application of poorer quality CBNG water can have significant impacts on soil physical and chemical properties. Changes in soil chemistry due to land application of CBNG waters were investigated using lysimeters installed at depths of 15, 30, and 60 cm. Soil solutions collected during June to August 2004 from soil solution lysimeters were analyzed for EC and SAR. Soil solution chemistry data were compared with EC and SAR data from saturated paste extracts of CBNG irrigated soil samples collected at the same depth. Preliminary data indicate the build up of salts and Na in the upper horizons of irrigated fields. The EC values of lysimeter soil solution samples were greater than those of saturated paste. However, SAR of lysimeter soil solution and saturated paste extracts were comparable. The results of this study will be useful to understand potential changes in soil properties due to land application of CBNG waters and to develop possible mitigating criteria for reclaiming impacted PRB ecosystems. Additional

Aggressive coalbed natural gas (CBNG) development in the Powder River Basin (PRB) of Montana and Wyoming is driven by the Nation's growing demand for energy. Wyoming's PRB had over 13,000 CBNG producing wells in 2004 with more than 50,000 future wells projected. Extraction of CBNG is associated with production of significant volumes of saline-sodic co-produced water in the PRB, estimated to exceed 162,000 ham by 2020. Suitable water-management strategies will need to be developed and implemented to address long-term soils impacts from these large water volumes. Land application with sprinkler irrigation systems is a common method for managing these waters. This study examined various soil and native vegetation impacts resulting from up to 5 seasons of land application with saline (EC = 1.6 to 4.8 dS m-1) and sodic (SAR =17 to 56) CBNG water. Treated (irrigated) and representative control (non-irrigated) areas were established at several study sites and examined through the 2003-2005 field seasons. Soil and vegetation types, water application rates, and water and soil treatment strategies were variable across study sites so parameters from each treated area were compared directly to those from representative control areas. Soil texture, pH, EC, SAR, bulk density, surface infiltration rate and Darcy flux rates were measured at various depth intervals to 120 cm. Multiple year applications of CBNG water produced consistent trends of increased soil EC and SAR values at depths to 60 cm, reduced surface infiltration rates and reduced Darcy flux rates to 120 cm. These differences were significant (P<0.05 or P<0.10) at most depths on most sites. CBNG water applications also resulted in significant (P<0.05) increases in native perennial grass biomass production and cover (treated vs. control areas). However, species diversity as measured by evenness was reduced. Biological effects were variable and complex, reflecting site specific conditions and management strategies. These findings indicate concern for effective Na + and soluble salt leaching success with current management and treatment strategies on these study sites. Degraded soil physical and chemical properties will require mitigation during reclamation efforts following cessation of CBNG water applications.