Groundwater Management

What is Groundwater?  (Click here to download)

Groundwater is best described as the world’s real hidden treasure. Almost everywhere it has made a difference in providing safe drinking water and livelihood security in times of drought. Groundwater is the earth’s largest accessible store of fresh water (excluding ice sheets and glaciers) and constitutes about 94% of all fresh water. The volume of groundwater is almost 100 times that of surface water. It is the most reliable source of supply for potable water and supports a wide array of economic and environmental services.

·        Groundwater is the water found underground in the cracks and spaces in soil, sand and rock. It is stored in and moves slowly through geologic formations of soil, sand and rocks called aquifers.

·        Groundwater is a source of recharge for lakes, rivers, and wetlands

What are the properties of groundwater?

·        Groundwater is in constant motion, although the rate at which it moves is generally slower than it would move in a stream.

·        Groundwater moves downward due to the pull of gravity.

·        It can also move upwards because it will flow from higher-pressure areas to lower pressure areas. 

·        Some of the most typical characteristics of groundwater are weak turbidity

·        A constant temperature and chemical composition and almost overall absence of oxygen.

·        Circulating groundwater can have extreme variation in the composition with the appearance of pollutants and various contaminants.

·        Groundwater is often very pure microbiologically.

Groundwater Table:

Water table, also called Groundwater Table, upper level of an underground surface in which the soil or rocks are permanently saturated with water. The water table separates the groundwater zone that lies below it from the capillary fringe, or zone of aeration, that lies above it. The water table fluctuates both with the seasons and from year to year because it is affected by climatic variations and by the amount of precipitation used by vegetation. It also is affected by withdrawing excessive amounts of water from wells or by recharging them artificially

Groundwater Pollution:

Sources of pollution:

·        Water is said to be polluted when its quality is degraded as a result of man’s activities to an extent that it becomes less suitable for its intended use.

·        The foreign substances that impair or degrade the water quality are referred to as pollutants and may be of organic, inorganic, biological or physical origin.

·        The deleterious effect of pollutions include harm to human health, hindrance to aquatic activities and the inability of the water to support agriculture, industrial and other related economic activities.

·        A noted source of pollution in groundwater supplies is the latrine/septic tank, causing an increase in biochemical oxygen demand BOD, chemical oxygen demand COD, nitrate, inorganic chemicals and pathogens thus leading to outbreak of diseases common in developing nations like Africa, Asia and South America.

·        Unsanitary mode of disposal of wastes, such as defecation in streams and the dumping of refuse in pits, rivers and drainage channels could be expected to affect surface and groundwater quality.

·        The degree of pollution (contamination) will depend on the efficiency of the waste disposal methods, safety of land use patterns, density of disposal systems in an area, composition of waste and soil and a number of other site-specific information.

·        Industrial waste disposal method of discharging effluents unto land, stream and sanitation sewers also have potential of polluting ground water.

·        Other sources of groundwater pollution include tank and pipeline leakage and mining activities.

·        Oil and gas production is often accompanied by substantial discharges of wastewater called brine, which is disposed of using methods such as abandoned pits, evaporation ponds and streams.

·        Agricultural sources of pollution include irrigation with a lot of return flow back into the ground  

·        The possible effect on the ground water include an increase in ground water salinity, due to inadequate drainage and direct evapotranspiration of irrigation return flow from soils whose salinity has been increased by salts from fertilizers.

·        Others include animal waste from animal pens and slaughter houses where they are confined for purposes of meat and milk production and may carry through storm run-offs, significant amounts of nitrates, salts, organic loads and bacteria to surface and sub-surface water (Sangodoyin and Agbawhe, 1991).

·        Agrochemicals such as fertilizer, pesticides and insecticides also pollute ground water. Nitrate based fertilizers are a significant contribution to groundwater pollution. This is because nitrogen in solution is neither fully utilized by plants nor absorbed by the soils.

·        Stock piles of solid materials from construction sites, individual’s plants residue are potential groundwater pollutants when precipitation falls on these piles, causing a leaching of heavy metals, salts and other organic and inorganic constituents.

Groundwater management:

By Aquifer System

An aquifer is an underground layer of water-bearing permeable rock. An aquifer is an underground layer of water-bearing permeable rock, rock fractures or unconsolidated materials (gravel, sand, or silt) from which groundwater can be extracted using water well.

 By groundwater recharge technique

Recharge occurs both naturally (through the water cycle) and through anthropogenic processes (i.e., "artificial groundwater recharge"), where rainwater and or reclaimed water is routed to the subsurface.

Other useful steps to manage groundwater:

·        Decide groundwater ownership rights

·        Prioritize inter-sectorial groundwater uses

·        Initiate process for comprehensive water act

·        Fix operational range of groundwater reservoir

·        Rationalize canal water allowances

·        Revise gypsum marketing policy

·        Strictly enforce EPA regulations to protect groundwater quality

·        Strengthen water related institutions

·        Prepare a drought contingency plan in view of climate change

·        Start water management in pilot projects