UNESCO/IHP Statement

World Water Day 1998
Groundwater:
the Invisible Resource

key information - potential actions - effects of falling water tables

The sixth annual World Water Day (WWD) was celebrated on 22 March 1998. As per the recommendations of the 17th meeting of the ACC Sub-Committee on Water Resources, UNICEF and the United Nations Division of Economic and Social Affairs (UNDESA), took the lead in organizing the observance of World Water Day in 1998. IRC is acting as a focal point for information dissemination about WWD activities.

The theme “Groundwater - the Invisible Resource” was selected for 1998 as the UN system has expressed its concern about three principal gaps in groundwater management which have enormous implications for sustainable development :

• The accelerated degradation of groundwater systems, through pollution of aquifers.
• The lack of both professional and public awareness about the sustainable use and economic importance of groundwater resources generally.
• The economic implications of not resolving groundwater demand and supply management.

Nearly half of the world's population depends on groundwater sources for drinking water supply and for other uses. In India nearly 50 percent of the irrigated land depends on groundwater. Almost 80 percent of the world's rural population receives a safe supply of water only because it comes from a groundwater aquifer safe from surface pollution.

UNICEF's and IRC's interest in celebrating World Water Day this year rests on three premises:

• The importance of groundwater is not generally recognized; it is in fact taken for granted. Yet, if the entire world's water supply were based on treated surface water, then the cost would be increased by 20 times. Groundwater is affordable and close to the community who can manage it.
• The protection of groundwater from pollution, particularly biological contamination, will become critical in the coming years due to the increasing problem of lack of adequate sanitation. Promotion of environmental sanitation is not possible without a linkage with groundwater quality control and protection.
• Conflicting uses of groundwater, e.g., for drinking for households, irrigation for farmers and/or water for cities, can only be tackled through dialogue between all stakeholders.

In the five years since its inception, the WWD has been successfully celebrated in a majority of countries. Many countries have been able to promote awareness of major issues at the national and local levels. The event has provided opportunities to national health authorities and water agencies to organise a large number of educational activities on the benefits of clean water, and on the problems of water supplies. On a country-by-country basis, comprehensive programmes for WWD have been developed, which have attracted attention and participation at the highest political levels, as well as at the level of school children and the media.

This sixth celebration will allow countries to broaden the scope of their activities. WWD has proven to be an important vehicle for mobilising a majority of the population about the importance of water management and conservation, while reinforcing to the authorities the urgency of addressing water problems in urban marginal and rural areas.

Key information on Groundwater

Groundwater is one of the most valuable natural resources possessed by many developing nations. Without pro-active management and protection there is a serious risk of irreversible deterioration on an increasingly widespread basis. Under the pressure of the need to rapidly develop new water supplies, there is rarely adequate attention to, and investment in, the maintenance, protection and longer-term sustainability of groundwater.

Advantages

Groundwater has many advantages over surface water for water supply:

• It is reliable in dry seasons or droughts because of the large storage.
• It is cheaper to develop, since, unpolluted, it requires little treatment.
• It can often be tapped where it is needed, on a stage-by-stage basis.
• It is less affected by catastrophic events.

As a result groundwater has become immensely important for human water supply in urban and rural areas in developed and developing nations alike. Countless large towns and many cities derive much of their domestic and industrial water-supply from aquifers, both through municipal wellfields and through very many private bore holes.

More and more farmers all over the world are using groundwater to irrigate their crops during the dry season. In the more arid areas, where rainfall is low and less predictable, groundwater may be the only source of supply for all types of agricultural activity, including watering livestock.

Resource under pressure

Groundwater resources are coming under increasing pressure from a rapidly growing human population - both through an ever-increasing demand and through a contaminant load on the land surface which is steadily growing in volume and chemical complexity, especially in Southeast Asia and Latin America.

Despite their importance, there is still not enough concern about protecting groundwater resources. The fact that they are 'out of the public sight' has caused them also to be 'out of the political mind' and they are too often abandoned to chance.

Groundwater is now being abstracted at unsustainable rates in many areas, seriously depleting reserves. This happens when uncontrolled drilling of wells causes the overall rates of withdrawal from aquifers greatly to exceed their replenishment from rainfall and other sources over decades or more. This ‘over-abstraction’ causes many serious problems. Often the yield of wells is reduced and the cost of pumping increased. In extreme cases, this may lead to the wells being abandoned, with premature loss of infrastructure investment.

Deterioration and pollution

In some geological conditions, the falling groundwater level induces compaction of underground strata and serious subsidence of the land surface, causing costly damage to urban infrastructure and increasing the risk of flooding. On many coasts and small islands, over-abstraction is leading to the intrusion of saline water inland, causing effectively irreversible deterioration of groundwater resources.

Groundwater is becoming increasingly polluted. The most common causes are:

• nitrate,
• salinity,
• soluble organic compounds (including synthetic toxic species) and, in certain conditions,
• some fecal pathogens.

The subsoil and the underlying soil and rock formations can eliminate or attenuate many water pollutants by natural physical, chemical and biological processes. But this natural capacity does not extend to all types of water pollutants and varies widely in effectiveness under different hydrogeological conditions, being rather limited in the more vulnerable areas. In parts of West Bengal and Bangladesh this phenomena has contributed to arsenic pollution of water from hand pumps serving hundreds of thousands of people.

Serious pollution of groundwater occurs when contaminants are discharged to, deposited on, or leached from the land surface, at rates significantly exceeding the natural attenuation capacity. This is occurring widely as a result of both the indiscriminate disposal of liquid effluents and solid wastes from urban development with inadequate sanitation arrangements, and of uncontrolled effluent disposal and leakage of stored chemicals into the ground from industrial activity.

Intensification of agricultural cultivation can also lead - and has led - to significant and widespread deterioration in groundwater quality in some conditions. The principal problems are the leaching of nutrients and pesticides, and increasing salinity in the more arid environments.

Groundwater pollution is insidious and expensive; insidious because it takes many years to show its full effect in the quality of water pumped from deep wells; expensive because, by this time, the cost of remediating polluted aquifers will be extremely high. Indeed, restoration to drinking water standards is often practically impossible.

What can be done

Rapid surveys of the state of groundwater exploitation, aquifer pollution vulnerability and subsurface contaminant load are urgently needed. The risk of pollution and the susceptibility of aquifers to the effects of over-abstraction can then be assessed and protection measures can be prioritized and initiated. In some cases abstraction must be better controlled, through a combination of regulation, pricing and incentives.

Similarly the risk of pollution must be reduced by incorporating groundwater vulnerability as a factor in land use planning and environmental controls. Many countries need better focused monitoring of groundwater levels and quality so that a clearer picture can be painted of the actual state of resources and of what must be done to use them more effectively - and to preserve them for future generations.

Potential actions

In many developing countries actions around World Water Day have been undertaken by related water organizations. They include:

• articles in local newspapers
• articles in newsletters and other (governmental) periodicals
• TV feature programmes on water resources
• TV interview of senior spokes person for water
• school competitions
• distribution of brochures and posters to secondary schools
• water quiz programmes on radio
• photo exhibits
• water seminars and symposia
• water cleaning or saving campaigns.

United Nations focal points for WWD 1998 are local UNICEF offices. In many countries national members of the International Water Supply Association, National Committees of the UNESCO International Hydrology Programme, of the International Commission on Irrigation and Drainage and International Association of Water Quality are focal point for World Water Day activities.

Effects of falling water tables

Lowering the groundwater level by one metre adds one metric ton of load per square metre to the subsoil.

In Gujarat in northern India, groundwater supplies most domestic and more than three quarters of irrigation water. Over-abstraction has caused the water table to fall, in some places by as much as 40 metres. This has deprived many poor farmers of water since they can afford only dug wells, which are usually limited to depths of 10 metres. Equity issues are accentuated by the fact that the poor have little representation in the government organizations that develop groundwater policies.

In Mexico City the water table has fallen so low that there has been widespread ground subsidence, involving costly rebuilding. Subsidence is caused by water draining from the porees in underground strata, causing the subsurface layers to compact.

Parts of the Las Vegas valley, in the United States have fallen by more than 1.5 metres as a result of over-abstraction in an area where annual rainfall averages only 100 mm. Arizona is marked by a series of hundreds of fissures in the ground, which have disrupted roads, railways and housing.

In the southern province of Brabant, in the Netherlands farmers are not allowed to use groundwater for irrigation in part of the year, as over-abstraction is causing drying out of the local ecology.

Bangkok is suffering from severe water problems as a result of the over-exploitation of the water table beneath the city. In Beijing recently, over-abstraction caused the water table to drop by more than four metres in a year. According to the Chinese National Environment Protection Agency, as many as 45 Chinese cities are now experiencing some form of land subsidence as a result of the over-abstraction of groundwater.

In many places of the world salt water has been moving in land and polluting coastal aquifers. This saltwater intrusion problem is for example happening in India, China, Mexico and the Philippines. In Metropolitan Manila groundwater abstraction has lowered the water level by 50-80 metres. As a result, salt water has seeped into the Guadelupe aquifer that lies under the city, reaching as far as 5 km inland. In Madras in India salt water intrusion has moved 10 km inland, causing many irrigation wells to be abandoned.

A number of the world's major wetlands are now under threat from the over-abstraction of groundwater. Spain, Algeria, Cyprus, Tunisia, Egypt and Turkey are among the countries where increasing salinity and changing water levels are leading to vegetation changes in wetlands.

In some areas of Africa and south Asia, a succession of years of below-average rainfall has caused severe water shortages. The effect of these extended dry periods may be worsened if excessive groundwater abstraction depletes aquifer storage further.

The shallow, sandy coastal aquifer that underlies the Gaza strip is heavily over-pumped and becoming polluted. Faecal contamination among the 800 000 people in this area is widespread and nitrate concentrations in some parts of the aquifer are reported to be 10 times the WHO guideline. Pesticide levels are also believed to be high and there is indiscriminate dumping of solid wastes throughout the area. Groundwater is no longer potable in some central areas.