4.3.3.4

Seasonal and Temporal Factors

The water level monitoring program should be structured to provide precise water

level measurements in a sufficient number of piezometers or wells at a sufficient frequency to

gauge both seasonal average flow directions and temporal fluctuations in ground water flow

directions ( 264.97(f)). The owner/operator should determine and assess seasonal/temporal,

natural, and artificially induced (e.g., off site production well pumping, agricultural use) short 

term and long term variations in ground water elevations, ground water flow patterns, and

ground water quality. Such factors that may influence ground water elevations and flow

include:

Barometric effects;

Variations in precipitation and runoff/recharge rates;

On site or off site well pumping, recharge, and discharge;

Tidal processes or other intermittent natural variations (e.g., river stage);

Off site or on site construction, or changing land use patterns;

Off site or on site lagoons, ponds, or streams;

Deep well injection;

On site waste disposal practices; and

Other anthropogenic effects, such as a nearby passing train;

Ground water flow may exhibit significant seasonal variations. For example, in the

humid eastern regions of the United States, heads are generally highest in late winter or

spring and lowest in late summer or early autumn. However, short term processes may create

ground water flow patterns that are markedly different from ground water flow patterns

determined by seasonal averages. Such processes include changes in river stage, tides, and

storm events.

Changes in land use may affect ground water flow by altering recharge or discharge

patterns. Examples of such changes in land use patterns include the paving of recharge areas

or damming of waterways. Municipal, industrial, or agricultural off site or on site well

pumping may affect both the rate and direction of ground water flow. On site and off site

well pumping may be seasonal, or dependent on more complex water use patterns.

November 1992

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