AQUIFER SYSTEMATICS
This general procedure has been applied for decades. A great many places have advanced models that facilitate integrating the above steps. There are historical examples of decision sup- port using analytical methods that have been borne out by later post-audits of data and by repeat models. Examples include the intensively-studied Gnangara aquifer for municipal supply in Western Australia (Balleau 1972) and the equally significant Albuquerque Basin wellfield in New Mexico (Reeder et al. 1967). The conditions anticipated for both were initially pro- jected using analytical calculations. The early projections were verified decades later (Vogwill et al. 2008; McAda and Barroll 2002). Seward et al. (2014) provide case studies of applying the radius of influence for planning purposes.
Hydrogeologists can support water planning and water policy with projections that answer the important questions. They have done so. It is critically important to recognize that distant areas of the aquifer, the basin, or the hydrologic system outside the quasi-radial area of influence do not contribute to restoring balance.
Current efforts sometimes apply simple measures such as footprints (Gleeson et al. 2012) or indexes of recharge to pumping (Scanlon et al. 2012). Those approaches cover large aquifer and drainage basin areas not focused on the area of influence of wellfields. Where the stress is not tied to the adja- cent supply available to respond via capture, then those efforts must mislead. Safe outcomes require plans that account for the location of wellfield stress and the corresponding area of hydrologic response. Footprints and indexes might have a role to play when tied to the availability of supply to be captured inside the limited area of response to a specific wellfield stress. The useful comparison is between withdrawals and available capture within a responsive distance, not between withdrawals and the natural recharge to the entire aquifer or basin area.
Conclusions
1. Aquifers display systematic responses to the stress of development. These responses can be anticipated for use in basin water planning and policy.
2. Critical concerns involve the dewatering of the aquifer and the depletion of interrelated surface water and
wetlands.as a foreseeable effect of beneficial use of aquifers for water supply.
3. This technical comment is offered to promote further thinking about the ways that hydrogeologists address or aid in answering questions of aquifer policy and planning. Attention is directed toward understanding the radial area that encloses surface water features balancing wellfield withdrawal.
References
Balleau, W.P., 1972, North Gnangara Sand Beds Aquifer, Tentative Water Balance and Yield Analysis: Geological Survey, West Australia Rec. 1972/14, 23p.
Cooper, H.H. Jr., and C.E. Jacob 1946, A Generalized Graphical Method for Evaluating Formation Constants and Summarizing Well-field History: American Geophysical Union, v. 27, No. 4, pp. 526-534.
European Commission, 2009, Common Implementation Strategy for the Water Framework Directive (2000/06/EC): Guidance Document No. 18, Guidance on Groundwater Status and Trend Assessment, Technical Report – 026.
Franke, O. L. and Reilly, T.E., 1987, The Effect of Boundary Conditions on the Steady-State Response of Three Hypothetical
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Ground-Water Systems – Results and Implications of Numerical Experiments: U.S. Geological Survey Water- Supply Paper 2315.
Gleeson, T., Wada, Y., Bierkens, M., 2012, Water balance of global aquifers revealed by groundwater footprint: Nature 488, p.197–200,
doi.org/10.1038/nature11295.
Glover, R.E., 1974, Transient Ground Water Hydraulics: Department of Civil Engineering, Colorado State University, 413p.
Harbaugh, A.W. 2005, MODFLOW-2005, The U.S. Geological Survey Modular Ground-Water Model - the Groundwater Flow Process: U.S. Department of the Interior, Chapter 16 of Book 6. Modeling Techniques, Section A. Ground Water, U.S. Geological Survey Techniques and Methods 6-A16, vari- ously paginated.
Konikow, L.F, and Leake, S.A., 2014, Depletion and Capture: Revisiting: “The Source of Water Derived from Wells”: Groundwater, Vol. 52, S1, p. 100-111. doi: 10.111/gwat.12204.
Lohman, S. W., 1979, Ground-Water Hydraulics: U. S. Geological Survey, Professional Paper 708, 78p.
McAda, D.P. and Barroll, P., 2002, Simulation of Ground-Water Flow in the Middle Rio Grande Basin Between Cochiti and San Acacia, New Mexico: U.S. Geological Survey Water-Resources Investigations Report 02-4200, 81p.
Reeder, H.O., Bjorklund, L.J., and Dinwiddie, G.A., 1967, Quantitative Analysis of Water Resources in the Albuquerque Area, New Mexico: New Mexico State Engineer Office Technical Report 33, 34p.
Scanlon, B. R., Faunt, C. C., Longuevergne, L., Reedy, R. C., Alley, W. M., McGuire V. L., McMahon P. B., 2012, Groundwater depletion and sustainability of irrigation in the US High Plains and Central Valley: Proceedings of the National Academy of Sciences, v.109 (24), p. 9320-9325; DOI: 10.1073/pnas.1200311109.
Seward, P., Xu, Y., and Turton, A., 2015 Investigating a spatial approach to groundwater quantity management using radius of influence with a case study of South Africa: WaterSA, v.41, No.1, p. 71-78.
Theis, C.V., 1940, The Source of Water Derived from Wells: American Society of Civil Engineers, Civil Engineering, Vol. 10, No. 5, pp. 277-280.
Theis, C.V., 1941, The Effect of a Flow on a Nearby Stream: Transactions, part 3: American Geophysical Union.
Western Water Policy Review Advisory Commission, 1998, Water in the West: The Challenge for the Next Century.
Zektser, I.S. and Everett, L.G., 2004, Groundwater Resources of the World and Their Use: IHP-VI, Series on Groundwater No. 6, United Nations Educational, Scientific and Cultural Organization.
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