- Assumptions Supporting Response Functions
functions cannot be universally applied to all situations. The validity
of response functions is linked to the concept that responses, such as river depletion
from pumping, are additive and proportional to the pumping or recharge rate.
This assumption is valid in many ground water environments. Each situation
should be evaluated by a qualified professional hydrologist, however, to determine
if any of the following excluding conditions are likely to have a significant
effect on the ground water flow system in the area of interest.
aquifer thickness changes, resulting in a significant change in aquifer properties,
need to be evaluated, not just for the development of response functions, but
for their application to each specific circumstance. If ground water elevations
are changing dramatically in a given situation, then the above conditions are
more likely to occur, and response functions should not be used.
either begin or cease flowing as a result of natural or man-imposed changes
in aquifer water level.
transition between perched and hydraulically connected with the aquifer.
or other water consumption varies non-linearly with aquifer head.
water is flowing in the river to meet demands in losing reaches.
Response functions generated
by field measurements, analytical techniques, or numerical models will be burdened
with all of the assumptions of the method used in their development. For
example, if the Jenkins (1968) analytical technique is used to generate the
response functions, then one of the assumptions underlying the response functions
is that the stream is straight and fully penetrating. If a numerical model
is used to generate the response functions, then the accuracy of the response
functions is directly dependent on the accuracy of the numerical model's calibration
and the underlying conceptual model. In many cases, this will be the greatest
source of error in application of response functions.
Information supplied by Idaho
Water Resource Research Institute, University of Idaho December 1998
Authors: Dr. Gary Johnson, Donna Cosgrove, and Mark Lovell.
Graphics: Sherry Laney and Mark Lovell of Idaho Water Resources Research Institute.
All State of Idaho images and graphics created with GIS files obtained through
Idaho Department of Water Resources Public Domain GIS unless otherwise noted.