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1999
Volume 2, No. 4

The Challenge of Water in Central America
The chapter of this document dedicated to water underscores that Central American populations are beginning to suffer problems with drinking water supplies, and proceeds to analyze the situation of some of the region's freshwater systems, both surface and groundwater.

First there is a discussion of regional water resources without reference to national borders or political-administrative divisions, and then the author zeroes in on three sites considered critical: the Lempa River Basin (El Salvador), Río Grande de Tárcoles (Costa Rica) and the Managua aquifer (Nicaragua).

The document points out that 71% of the 629 billion cubic meters of water draining into the region's oceans runs into the Caribbean, and 29% into the Pacific. This means the isthmus' wealth of water resources is mostly in the Caribbean zone. However, the bulk of the population resides on the Pacific slope, where water has historically been drawn from extensive aquifers.

There is a risk that in the near future groundwater will be pumped up at a higher rate than it can be replaced. Because systems for evacuating waste are poor, there is an additional risk of these sources becoming contaminated.

In the case of the Lempa River, a trinational resource, this basin is the largest on the region's Pacific slope. Even though the country has important aquifers, El Salvador is critically dependent on this basin. However, the paucity of conservation practices results in a poor use of resources as water flows down rapidly from the higher regions, carrying topsoil toward the coastal zones and ocean.

The Grande de Tárcoles River Basin has the largest demographic and economic density in the region, is the most polluted in Costa Rica and represents a critical case of unsound management.

The Managua aquifer is a typical example of overexploitation of water resources. Available information indicates that in the medium range, this aquifer will be unable to satisfy demand for the city of Managua, and the population will have to make more use of the extensive reserves of surface water (Lake Managua and Asososca). Because of their advanced state of pollution, use of these lakes in the future poses a serious challenge.

What is needed is a systematic compilation of the information available in each country to use for planning at the regional scale.

Barry, D. et al. 1999. El Desafío del Agua en Centro América. In: Informe Estado de la Región en Desarrollo Humano Sostenible. San José: Proyecto Estado de la Nación Chapter 4. 101-126.

The Crisis of Water Resources and Aquatic Ecosystems in the Countries of Latin America and the Caribbean
The water crisis in Latin America and the Caribbean has generated and continues generating adverse forces that threaten aquatic ecosystems. These threats must be fought with vigorous initiatives to preserve and protect this vital resource for the development of the region's countries. Governments must take the initiative in establishing effective regulations and planning programs to promote efficient water use and to protect the environment and water quality and quantity. If governments wish to manage and protect their aquatic resources it will be necessary to launch educational campaigns and convince users of the importance of conserving water and preventing pollution.

To keep this crisis from escalating, an action plan should be adopted with three simultaneous phases of planning, regulation and efficient use. Each and every conservation effort should be based on the planning and integrated management of river basins as units of nature. But along with planning and scientific management of water resources, systems for the production and distribution of potable water must be developed and optimized, as well as for preventing pollution and investing in wastewater treatment plants. It is imperative to create strong institutions with the backing of a legal framework and multidisciplinary support. This could be obtained by transferring, adapting and testing experiences and technology from developed nations.

Special problems are posed to the conservation of resources and aquatic ecosystems when river basins are international. For effective protection of these ecosystems, the nations involved must sign and comply with multilateral agreements for integrated catchment management and water use.

Vázquez, A. 1997. The Crisis of Water Resources and Aquatic Ecosystems in Latin American and Caribbean Countries. In: The Impact of the Water Crisis on Freshwater Ecosystems in Latin America and the Caribbean. Washington, D.C.: WWF. 45-49

The Application of Ecological Indicators to Assess the Ecological Condition of a Lake
There is a growing interest in the use of ecological indicators to assess what is known as the health and integrity of an ecosystem. In brief, the objective is to find an index that explains or clarifies the crucial properties of ecosystems. This article proposes using "exergy" (the quantity of work potential the system possesses), structural exergy (exergy/biomass) and buffer capacity as indicators to measure ecosystem health. The relevancy of these three concepts for practical management of lakes was examined in fifteen case studies.

Joegensen, S. 1995. The Application of Ecological Indicators to Assess the Ecological Condition of a Lake. In: Lakes and Reservoirs: Research and Management. 1: 177-182

Ecological Indicators for Assessing Freshwater Ecosystems Health
This paper presents the structural, functional and system-level effects of four chemical stresses (acidification, copper, oil and pesticide contamination) in freshwater ecosystems. Exergy, structural exergy and zooplankton buffer capacity were used as ecological indicators for the measurement of ecosystem-level responses to the four chemical stresses. The results showed that changes in ecosystems were highly related to changes in the structure and functions of the systems studied, and that these indicated the effects of chemical stress on the health of freshwater ecosystems.

Exergy, structural exergy and zooplankton buffer capacity revealed significant decline of zooplankton biomass (Bz/Bp ratio), species diversity and resource use efficiency caused by chemical stress. A slight change in the structure and function of local ecosystems was accompanied by little or no change in exergy, structural exergy, or zooplankton buffer capacity.

The results strengthen use of these ecological indicators as a means of assessing the impact of chemical stress on freshwater ecosystem health. The indicators were applied successfully to assess the health of a lake.

Fu-Liu Xu; Jorgensen, S. y Shu Tao. 1999. Ecological Indicators for Assessing Freshwater Ecosystem Health. In: Ecological Modeling. 116, 77-106

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