No abstract

Efficient use of water, particularly in the western U.S., is an increasingly important aspect of many activities including agriculture, urban, and industry. As the population increases and agriculture and energy needs continue to rise, the pressure on water and other natural resources is expected to intensify. Recent advances in technology have stimulated growth in oil and gas development, as well as increasing the industry's need for water resources. This study provides an analysis of how efficiently water resources are used for unconventional shale development in Northeastern Colorado. The study is focused on the Wattenberg Field in the Denver-Julesberg Basin. The 2000 square mile field located in a semiarid climate with competing agriculture, municipal, and industrial water demands was one of the first fields where widespread use of hydraulic fracturing was implemented. The consumptive water intensity is measured using a ratio of the net water consumption and the net energy recovery and is used to measure how efficiently water is used for energy extraction. The water and energy use as well as energy recovery data were collected from 200 Noble Energy Inc. wells to estimate the consumptive water intensity. The consumptive water intensity of unconventional shale in the Wattenberg is compared with the consumptive water intensity for extraction of other fuels for other energy sources including coal, natural gas, oil, nuclear, and renewables. 1.4 to 7.5 million gallons is required to drill and hydraulically fracture horizontal wells before energy is extracted in the Wattenberg Field. However, when the large short-term total freshwater-water use is normalized to the amount of energy produced over the lifespan of a well, the consumptive water intensity is estimated to be between 1.8 and 2.7 gal/MMBtu and is similar to surface coal mining.

The development of unconventional resources in tight shales has stimulated considerable growth of oil and gas production in Northeastern Colorado, but has led to concerns about added demands on the region's strained water resources. Northeastern Colorado's semi-arid environment, population growth, competing water demands and uncertainty about drilling and hydraulic fracturing water requirements have resulted in scrutiny and conflict surrounding water use for tight shales. This study collects water use data from wells in Northeastern Colorado to improve water estimates and to better understand important contributing factors. Most water resource studies use estimates for the number of future wells to predict water demands. This study shows that the number of hydraulic fracturing stages is a better measure of the future water demands for horizontal wells. Vertical wells use significantly less water than horizontal wells and will be less prevalent in the future.

Excess nutrients are among the leading sources of water quality impairment in the Unites States, and the USEPA has been working with state regulatory agencies to develop nutrient criteria for wastewater treatment plants (WWTPs). The Colorado Department of Public Health and Environment is scheduled to establish nutrient regulations in 2013, and stream total P (TP) concentration standards of 0.16 mg L in warm water and 0.11 mg L in cold water have been proposed for the rivers in the state. The objectives of this study were to monitor TP concentrations and loads along the Cache La Poudre River as it flows from the pristine upstream area through urban regions and finally through a mixture of agricultural and urban land uses. The study attempts to evaluate the sources and influences of TP under different hydrologic conditions. Twelve sampling events were completed from April 2010 to August 2011 to assess the influence of various flow and precipitation conditions on aqueous TP concentrations. During midrange flows and dry conditions, WWTPs were the major sources of TP, but other sources were more significant under high-flow and wet conditions according to a load analysis. The analysis indicates that reducing the TP load from WWTPs will only marginally affect the TP load in the river, and therefore it appears that other sources (e.g., stormwater and agricultural runoff) need to be addressed before the aquatic life-based stream standard can be achieved.

The objectives of this study were to monitor total phosphorus concentrations and loads along the Cache la Poudre River in Northern Colorado as it flows from a pristine area through urban regions and, finally, through mixed land uses. The study attempted to evaluate the sources and influences of total phosphorus under different hydrologic conditions. Nine sampling events were completed from April 2010 to May 2011 to assess the influence of various hydrologic conditions on aqueous and riverbed sediment total phosphorus concentrations. Total phosphorus concentrations and loads exceeded the in-stream limits proposed by the Colorado Department of Public Health and Environment in all observed hydrologic conditions, and nonpoint sources were significant in high-flow conditions. Reducing nutrients only at water resource recovery facilities (WRRFs) could not achieve the in-stream limits without substantial reduction of non-pointsource loads. The study exposed a need for flexibility in WRRF discharge limits based on the overall total phosphorus load in the river from other sources. Water Environ. Res., 87, 169 (2015).KEYW ORDS: Cache la Poudre River, load analysis, nutrient regulation, total phosphorus, water resource recovery facilities.