These conditions (steady-state flow to a pumping well with no nearby boundaries) never truly occur in nature, but it can often be used as an approximation to actual conditions; the solution is derived by assuming there is a circular constant head boundary (e.g., a lake or river in full contact with the aquifer) surrounding the pumping well at a distance R. Sources of error Of critical importance in both aquifer and well testing is the accurate recording of data. Not only must water levels and the time of the measurement be carefully recorded, but the pumping rates must be periodically checked and recorded. An unrecorded change in pumping rate of as little as 2% can be misleading when the data are analysed. References Further reading The US Geological Survey has some very useful free references on pumping test interpretation: Some commercial printed references on aquifer test interpretation: Good summary of the most popular aquifer test methods, good for practicing hydrogeologists Thorough, a bit more mathematical than Batu Excellent treatment of most aquifer test analysis methods (but it is a hard-to-find book). On line : On line ANSDIMAT user's guide : . More book titles can be found in the further reading section of the hydrogeology article, most of which contain some material on aquifer test analysis or the theory behind these test methods. Analysis software Water Resources Applications Software from the US Geological Survey Schlumberger Water Services – Pumping test and slug test data analysis software ANSDIMAT – advanced commercial software AQTESOLV – standard commercial software MLU for Windows LT – Free software for pumping test and slug test analysis in one or two aquifer systems VINMOD Multi-Well – Groundwater pollution analysis using pumping tests and pollution parameters from pumped groundwater Hytool - Open source toolbox for pumping and build up tests interpretation on Matlab SmartGEO - advanced commercial software for heterogeneous aquifers characterization, hydraulic tomography and multiple pumping tests See also Dupuit–Forchheimer assumption Groundwater Water well Aquifers Hydrology Hydraulic engineering Water wells