A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

TDS (Total Dissolved Solids)
The amount of dissolved material in water usually measured in milligrams per liter (mg/L).

Test Hole
Test holes are typically used in applications of engineering geology whereas test wells are used in gorund water investigations to obtain information about geologic and/or hydrologic conditions. Test holes are usually drilled at a small diameter. Based on the information obtained, productions wells of a larger diameter may be installed.

Test Well
A well used to assess and/or test the geologic and hydraulic properties of an aquifer. A series of test wells may be drilled in order to determine the most effective location for a (much more expensive) production well. Test wells are usually of a smaller diameter than production wells.

Till (see Glacial Till)


Transmissivity
The capacity of a rock to transmit water under pressure. The rate at which water moves through a unit width of an aquifer under a unit hydraulic gradient. The coefficient of transmissibility is the rate of flow of water, at the prevailing water temperature, in gallons per day, through a vertical strip of the aquifer one foot wide, extending the full saturated height of the aquifer under a hydraulic gradient of 100 percent. A hydraulic gradient of 100 percent means a one foot drop in head in one foot of flow distance.

Transpiration
The process by which water that is absorbed by plants, usually through the roots, is evaporated into the atmosphere from the plant surface, via stomata (tiny pores) on the leaves and stems. See also evapotranspiration.

Tremie Pipe
A pipe used to carry materials (usually grout) to a specific depth in a drilled hole. Tremie pipes are slowly withdrawn as the grout is placed in the well.

Tributary
A smaller river or stream that flows into a larger river or stream. Usually, a number of smaller tributaries merge to form a river.

Turbidity
The amount of solid particles that are suspended in water and that cause light rays shining through the water to scatter. Thus, turbidity makes the water cloudy or even opaque in extreme cases. Turbidity is measured in nephelometric turbidity units (NTU).