Modified use of the "SDF" semi-analytical stream depletion model in bounded alluvial aquifers
Date
2005
Authors
Miller, Calvin P., author
Durnford, Deanna S., author
Colorado State University, publisher
Journal Title
Journal ISSN
Volume Title
Abstract
A widely used semi-analytical model quantifying stream depletions and accretions induced by groundwater pumping and augmented groundwater recharge was reviewed for accuracy when applied in bounded alluvial aquifers. The method is based on the analytical Glover method, but uses a model-derived input parameter to account for mathematically non-ideal conditions such as variable transmissivities and nearby aquifer boundaries. Using this parameter, called the stream depletion factor (SDF) with units of time, often improves estimates and is an approximation that produces only small errors near the time of the SDF. However, recent experience has highlighted the significant errors introduced at larger times, especially in narrow aquifers. This paper reviews the approximations inherent in the method and presents expanded response curves and error curves as functions of well position within the bounded aquifer. It is shown the SDF values mapped in the half of the aquifer nearest the river do not account for aquifer boundaries, and that values in the other half follow a predictable adjustment. By removing the boundary adjustments, the method of images can be legitimately combined with the SDF method, thereby improving estimates in bounded aquifers while still benefiting from the additional information contained in SDF maps and retaining their value as standardized references for water rights administration.
Description
2005 annual AGU hydrology days was held at Colorado State University on March 7 - March 9, 2005.
Includes bibliographical references.
Includes bibliographical references.