Groundwater well measurements

We use water quality indicators, such as pH, temperature, conductivity (specific conductance), dissolved oxygen, oxidation-reduction potential (ORP), and turbidity, as groundwater well stabilization parameters. Stable values of three consecutive measurements of these parameters are considered an indication of a stabilized well. 

The measurement of pH is one of the most important measurements in water chemistry. The value of pH defines the types and the rates of chemical reactions in water, and the fate and bio availability of the living organisms. Together with temperature measurements, pH values serve as groundwater well stabilization indicators. 

Turbidity is a drinking water quality parameter and a groundwater well stabilization indicator. The clarity of water defines a physical property of turbidity. Suspended matter, such as clay and silt particles, organic matter, microscopic organisms, and colloids, causes natural waters to be turbid. Turbidity is measured optically as a lightscattering property of water. 

A map showing sampling points (groundwater well field a grid from which samples were collected a drawing of an excavation with measurements etc.)... 

To characterize flow in the subsurface environment, groundwater wells often are installed. Wells can be used to measure hydraulic head gradients, and thus to determine the direction of groundwater flow to conduct aquifer tests to... 

When the well depth or diameter is unknown or a water-level measurement is not possible, purging should be carried out by pumping the well for a pre-determined period of time (e.g., at least 30min). Measurement of groundwater parameters should be monitored at intervals during the purging process and at the time of sample collection (Figure 3). 

As discussed before, groundwater samples can be collected when a sufficient volume of water has been removed from the well (e.g., three to five well volumes) and groundwater parameters have stabilized. If parameters have not stabilized after five well volumes have been removed, then the well may be sampled (acceptance of sampling following the fifth purge volume is dependent on the study objectives). Table 1 summarizes the criteria used for establishing the stability of groundwater parameters. The time intervals between the parameter measurements depend on the well characteristics and the hydraulic properties of the aquifer and must be sufficiently spaced to provide results representative of aquifer properties. ... 

The minor amounts of Mg++, Ca++, and Fe++ in the fluid might easily be accounted for by contamination by a small volume of a shallow groundwater or even by dissolution of concrete and steel in the wellbore. If we discount the results for minerals containing these components, we arrive at a well-defined equilibrium temperature slightly above 200 °C (Fig. 23.9). Again, the equilibrium temperature is slightly higher than the temperature measured in the wellbore. 

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