27 research outputs found
Geochemical detection of carbon dioxide in dilute aquifers
<p>Abstract</p> <p>Background</p> <p>Carbon storage in deep saline reservoirs has the potential to lower the amount of CO<sub>2 </sub>emitted to the atmosphere and to mitigate global warming. Leakage back to the atmosphere through abandoned wells and along faults would reduce the efficiency of carbon storage, possibly leading to health and ecological hazards at the ground surface, and possibly impacting water quality of near-surface dilute aquifers. We use static equilibrium and reactive transport simulations to test the hypothesis that perturbations in water chemistry associated with a CO<sub>2 </sub>gas leak into dilute groundwater are important measures for the potential release of CO<sub>2 </sub>to the atmosphere. Simulation parameters are constrained by groundwater chemistry, flow, and lithology from the High Plains aquifer. The High Plains aquifer is used to represent a typical sedimentary aquifer overlying a deep CO<sub>2 </sub>storage reservoir. Specifically, we address the relationships between CO<sub>2 </sub>flux, groundwater flow, detection time and distance. The CO<sub>2 </sub>flux ranges from 10<sup>3 </sup>to 2 × 10<sup>6 </sup>t/yr (0.63 to 1250 t/m<sup>2</sup>/yr) to assess chemical perturbations resulting from relatively small leaks that may compromise long-term storage, water quality, and surface ecology, and larger leaks characteristic of short-term well failure.</p> <p>Results</p> <p>For the scenarios we studied, our simulations show pH and carbonate chemistry are good indicators for leakage of stored CO<sub>2 </sub>into an overlying aquifer because elevated CO<sub>2 </sub>yields a more acid pH than the ambient groundwater. CO<sub>2 </sub>leakage into a dilute groundwater creates a slightly acid plume that can be detected at some distance from the leak source due to groundwater flow and CO<sub>2 </sub>buoyancy. pH breakthrough curves demonstrate that CO<sub>2 </sub>leaks can be easily detected for CO<sub>2 </sub>flux ≥ 10<sup>4 </sup>t/yr within a 15-month time period at a monitoring well screened within a permeable layer 500 m downstream from the vertical gas trace. At lower flux rates, the CO<sub>2 </sub>dissolves in the aqueous phase in the lower most permeable unit and does not reach the monitoring well. Sustained pumping in a developed aquifer mixes the CO<sub>2</sub>-affected water with the ambient water and enhances pH signal for small leaks (10<sup>3 </sup>t/yr) and reduces pH signal for larger leaks (≥ 10<sup>4</sup>t/yr).</p> <p>Conclusion</p> <p>The ability to detect CO<sub>2 </sub>leakage from a storage reservoir to overlying dilute groundwater is dependent on CO<sub>2 </sub>solubility, leak flux, CO<sub>2 </sub>buoyancy, and groundwater flow. Our simulations show that the most likely places to detect CO<sub>2 </sub>are at the base of the confining layer near the water table where CO<sub>2 </sub>gas accumulates and is transported laterally in all directions, and downstream of the vertical gas trace where groundwater flow is great enough to transport dissolved CO<sub>2 </sub>laterally. Our simulations show that CO<sub>2 </sub>may not rise high enough in the aquifer to be detected because aqueous solubility and lateral groundwater transport within the lower aquifer unit exceeds gas pressure build-up and buoyancy needed to drive the CO<sub>2 </sub>gas upwards.</p
Controlling Groundwater Exploitation Through Economic Instruments: Current Practices, Challenges and Innovative Approaches
Groundwater can be considered as a common-pool resource, is often overexploited and, as a result, there are growing management pressures. This chapter starts with a broad presentation of the range of economic instruments that can be used for groundwater management, considering current practices and innovative approaches inspired from the literature on Common Pool Resources management. It then goes on with a detailed presentation of groundwater allocation policies implemented in France, the High Plains aquifer in the USA, and Chile. The chapter concludes with a discussion of social and political difficulties associated with implementing economic instruments for groundwater management
TO ENERGY POLICY AND DECISION MAKING: THE USER'S VIEW
This paper presents an approach to the development and use of management information systems that is particularly applicable to systems with the following characteristics:- several classes of users, each of which has a different degree of sophistication- complex and changing security requirements- data exhibits complex and changing inter-relationships- changing needs to be met by information system,- must be built quickly and inexpensively- complex data validation requirements The approach is hierarchical from the user's view in that he may access the system at distinct levels, corresponding to his degree of computer sophistication. A casual user has high level primitives to work with, while an experienced user has more flexible but more detailed low-level primitives. also We/have advocated that such systems be implemented in a hierarchical fashion, because this technique provides for ease of debugging, independence of hardware, and a basis for investigating properties of completeness, integrity, correctness, and performance
Groundwater economics: an object-oriented foundation for integrated studies of irrigated agricultural systems
An integrated foundation is presented to study the impacts of external forcings on
irrigated agricultural systems. Individually, models are presented that simulate
groundwater hydrogeology and econometric farm level crop choices and irrigated water
use. The natural association between groundwater wells and agricultural parcels is
employed to couple these models using geographic information science technology and
open modeling interface protocols. This approach is used to study the collective action
problem of the common pool. Three different policies (existing, regulation, and incentive
based) are studied in the semiarid grasslands overlying the Ogallala Aquifer in the
central United States. Results show that while regulation using the prior appropriation
doctrine and incentives using a water buy-back program may each achieve the same level
of water savings across the study region, each policy has a different impact on spatial
patterns of groundwater declines and farm level economic activity. This represents the first
time that groundwater and econometric models of irrigated agriculture have been
integrated at the well-parcel level and provides methods for scientific investigation of this
coupled natural-human system. Results are useful for science to inform decision
making and public policy debate
Recommended from our members
Unpublished letter from US Geological Survey Scientists to the editor of the New York Times Magazine regarding William J. Broads` November 18, 1990 article on Yucca Mountain
This letter documents objections of a group of US Geological Survey Scientists to an article appearing November 18, 1990 in New York Times Magazine. The article was written by William J. Broad and dealt with a hypothesis of Jerry S. Szymanski. The letter addressed areas of concern; including hydrology, geology, tectonics, and the integrity of the scientists and their conclusions. (SM