Members of the Merl Grove High quiz team at TVJ's School Challenge Quiz at TVJ, on Monday, March 6. - Ricardo Makyn Photo

OBJECTIVES

You need to be able to:

1.14 Describe and explain the relationship between surface water and underground water within the hydrological cycle.

1.15 Describe and explain the occurrence of springs and artesian basins and major features formed by underground water.

1.16 Describe the value of underground water as a direct source of water supply and locate areas in the Caribbean where underground water is utilised.

1.17 Describe and explain the ways in which surface water and underground water is/are polluted, and the methods used to conserve the quality and supply with specific reference to the Caribbean.

I have been reviewing the topics under geomorphic system through answering questions on them taken from past examination papers. However, before presenting the questions on underground water, let me first share with you some general information on the topic. My source of reference is the text Morphology And Landscape written by Harry Robinson. This source tells us that The term ground water simply means water that is underground or beneath the surface in contrast to the water that occurs on the earth's surface. We are also told of the origin of ground water. Water, in lesser or greater quantities, is almost everywhere present in the soil, subsoil, and bedrock; it is this water, beneath ground level, that we call ground water. It is of either external origin, i.e., derived from the atmosphere or surface waters or of internal origin, i.e., derived from the rocks forming the crust.

The information that follows is from the same source. The quote is a bit lengthy but I think you will find it useful in helping you to understand the factors contributing to ground water:

Three things happen to the rain or other forms of atmospheric precipitation which fall onto the land surface:

(i) It may evaporate directly into the air or be returned to the atmosphere through transpiration by plants.

(ii) It may flow over the land surface and be collected by streams and rivers and carried to the sea.

(iii) It may sink into the ground and percolate through the soil and rock to form ground water where it remains unless it reaches the surface again as spring water.

The proportionate amounts evaporating, running off, and sinking into the ground vary widely between place and region according to the influence of several factors.

The factors which determine the amount of surface moisture entering the ground may be enumerated as:

(i) The abundance and nature of the rainfall: Gentle or drizzly rains will allow the moisture to sink in gradually, whereas heavy, torrential rains produce much run-off.

(ii) The slope of the land surface: Steep slopes induce rapid run-off whereas fairly level land prevents run-offs and assists percolation.

(iii) The porosity and permeability of the surface layers: If the soils and rocks have few openings in them, the water will not be able to seep downwards.

(iv) The rate of evaporation: If the air is dry and warm and there is much wind, surface moisture will be readily evaporated and hence, less will be able to sink in.

(v) The nature and extent of the vegetative cover: A thick mat of vegetation will help to protect the soil surface from evaporation while roots and stems will assist percolation; on the other hand, plants draw water up from the soil and readily evaporate it from their leaf surfaces.

(vi) The amount of moisture already in the soil: If the soil is dry it will absorb moisture readily, but if it is already saturated, it will be unable to take in further water.

As usual, I encourage you to read on the topic from whatever available source you can find.