Unit 2. Surface Runoff and Ground Water Exercises (a)

1. Learn new words:

rate of precipitation – норма porous strata – пористый пласт

осадков artesian – артезианский

water body – водоем, водная масса well – колодец

to exceed – превышать to define – определять

to infiltrate – просачиваться to lie – лежать

to reach – достигать soil moisture deficit – дефицит

bottom – дно почвенной влаги

portion – часть stream bad – речное русло

to penetrate – проникать, stream channel – русло потока

просачиваться loss – потеря

To absorb – всасывать, впитывать

porous rocks – пористые породы

water table – водное зеркало

to intersect – пересечь, разделить

2. Read and translate the following international words:

infiltrate [¢infiltreit]; cycle [saikl]; channel [¢tòænl]; system [sistim]; zero [¢ziərəu]; agriculture [¢ægrikÙltòə]; transit [trænzit]; structure[¢strÙktòə].

3. Translate the following word combinations:

rate of precipitation; may infiltrate into the soil; this part of the precipitation; the surface depressions; over the surface of the ground; the beginning of a definite stream channel system; to be discharged ultimately into the ocean; some inland water body; some loss in transit; because of evaporation to the atmosphere; infiltration to the bottom and sides of the channel; to lie within the zone of saturation; major importance in connection with agriculture; to return to the atmosphere without penetrating; a portion of the precipitation; to percolate into the ground; to be absorbed by soil deficient in moisture; by porous rocks; to reach a level; may intersect a stream bed; will be returned to a body of surface water; to flow through porous strata; may be confined by tighter soils; may be artesian; the same pressure zone; may contact the ocean bed; various lengths.

Text (a)

Read the text «Surface Runoff and Ground Water»:

When the rate of precipitation exceeds the rate at which water may infiltrate into the soil (infiltration capacity), surface runoff usually occurs. This part of the precipitation after filling the surface depressions finds its way over the surface of the ground until it reaches the beginning of a definite stream channel system, through which it passes and is discharged ultimately into the ocean or some inland water body. There is some loss in transit because of evaporation to the atmosphere and infiltration to the bottom and sides of a definite stream channel. The latter may vary from practically zero to nearly 100 %.

Ground water as defined by geologists and engineers, comprises only that portion of the water which lies within the zone of saturation or below the water table. It does not include the suspended water which is held in the ground above that zone but does include the water which lies below a perched water table. Water above the zone of saturation and near the ground surface is of major importance in connection with agriculture because of its relation to plant growth. Much of this water, of course is utilized and transpired by vegetation and is thus returned to the atmosphere without penetrating deeply below the surface or becoming a part of the body of ground water.

A portion of the precipitation penetrating the ground surface as infiltration will percolate into the ground. If not absorbed by soil deficient in moisture, or by porous rocks, this water eventually reaches a level which is completely saturated — the «ground water table». The slope and confining structure surrounding the ground water body may be such as to prevent its immediate release; or the ground water body may intersect a stream bed where part of it will be returned to a body of surface water. Ground water may also flow through porous strata and reach a level where it may be confined by tighter soils and thus subjected to pressure. If a well penetrates to this level, it may be artesian and the water discharged will like wise become part of the surface water. The same pressure zone may contact the ocean bed and discharge water into the sea.

Thus, the atmospheric moisture with which this description of the cycle started may follow paths of various lengths and complexity before it can complete the circuit.