In a third-party groundwater related project, a consultant prepared several versions of groundwater elevation maps. One map was produced on the basis of the average groundwater elevation of each well, measured trimonthly over two years. The second map was for each of the eight quarters, but with the groundwater elevations being measured within a month’s period.
There are so many conditions that can render your data completely useless if collected over a time frame of three to four weeks, and all these would need to be interpreted. Data should be collected within a day or two, to reflect a “point in time” as closely as possible, thus leaving no room or need for assuming, guessing or interpreting. This goes for shallow and deep wells alike.
Taking into account fracture zones, surface water etc. should be part of the measurements. If there are any surface water bodies in the area, the expert should also take readings of water levels there.
If the work has to take place in a large area and/or on a large number of wells, the contractor either needs to send more staff to the field, or should apply water level loggers inside the wells.
The scientific value of groundwater contour maps from the average over eight quarters in my opinion is zero. I have completed monitoring campaigns in areas where the groundwater flow direction turned by 180° depending on summer or winter, the average would have indicated that there is no groundwater flow at all.