Water Needs

Water Needs of Earth's Ecosystems

The primary and most critical water need is the need for sufficient water at the appropriate time and in the required amount to sustain Earth's ecosystems, of which humans are a part and on which all life depends. As water moves through the hydrologic cycle, not only is water itself transported but also energy and materials are moved through their own biogeochemical cycles, habitat is provided for aquatic organisms, and terrestrial systems are sustained. Water and freshwater ecosystems provide numerous ecosystem services to people worldwide. Ecosystem services are the wide range of benefits provided to people through the functioning of Earth's ecosystems. This includes many types of services such as provisioning services that provide food, water, and fiber; supporting services such as transportation and cycling of materials; preservation services such as preserving plant and animal species; and cultural and aesthetic services that include social, economic, spiritual, and recreational benefits.

The allocation and management of water resources, especially in international river basins, are becoming more difficult. Increasing demands are being placed on human and environmental systems by competing water uses that include hydropower generation; flood control; agricultural, industrial, municipal, and industrial water use; flows for water quality; fish habitat and fish passage; and recreational and cultural uses. Competing interests for water are taxing the limited water supplies. The water needs of agriculture, industry, and urban areas compete with environmental claims for in-stream water or the water rights of indigenous people. Traditional water governance structures are not well suited to address the complex issues and needs of competing agents to resolve the emerging problems over water quantity and quality, nor are they flexible enough to address the projected rapid changes in the timing and delivery of water as the world's climate changes.

As part of the Pilot Analysis of Global Ecosystems, the World Resources Institute (WRI) assessed the condition, status, and trends in the world's freshwater ecosystems. WRI selected and [Page 3063]analyzed both quantitative and qualitative information and developed five indicators of the condition of the world's freshwater

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