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United Nations Environment Programme
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Freshwater Management Series No. 7

Phytotechnologies

A Technical Approach in Environmental Management

II. Global Issues Requiring Innovative Sollutions >

C. Integrated Water Resources Management and Ecohydrology

Over a billion people worldwide lack access to adequate water, and close to two billion suffer the consequences of poor sanitation; millions of people die each year from contaminated water. Water quality, expressed as secondary pollution and toxic algal blooms, continues to decline in aquatic ecosystems around the world. Furthermore, thousands of rivers, lakes and reservoirs are continuously affected directly or indirectly by human activities causing enormous environmental problems related to biodiversity, ecosystem functioning and preservation of the water cycle. These impacts are sobering evidence that the prevailing approach to catchment-scale water management does not guarantee sustainable water use. Technical approaches to pollution control, such as sewage treatment plants and regulation of hydrological processes for flood and drought control, are important but by themselves not sufficient. Purely technical controls, without understanding and consideration of biota dynamics, reflect a trial and error approach to water management rather than the implementation of a policy toward sustainable use of water resources.

River rapids

In most parts of the world, urbanisation has caused progressive occupation and development of open land and land reclamation from water basins, causing changes in ecology and hydrology. Heavy consumption of water in cities, combined with suburban sprawl resource overexploitation and the technical, political and economic challenges of meeting water demands, has created growing pressure to build in new areas and maintain older systems. In developing countries, providing enough safe water to meet basic human needs is a serious problem. Areas without adequate water supply tend to remain underdeveloped because of widespread disease and unsanitary living conditions. Where infrastructure does exist, water resource managers are struggling to meet more stringent water quality goals and regulations.

Historically, problems of poor water supply and inadequate wastewater treatment have persisted because of limited resources and funding, and an absence of effective policies, planning, management practices and regulations. Even when funding has been available, the conventional response has been to build large, centralised treatment plants, often without sufficient consideration of the need to overhaul and maintain existing supply infrastructure. The potential for degraded infrastructure to jeopardise safe water supply is often ignored. For example, it is not unusual for poor distribution systems to leak 50% or more. Similarly, the construction and operating costs of conventional wastewater treatment systems are often too high, and much of the world's wastewater is discharged untreated. As a result, there is growing interest in developing more affordable, decentralized solutions based on natural systems which combine natural wastewater purification and nutrient recycling, including the use of phytotechnologies, such as constructed wetlands, for wastewater treatment.

A watershed planning and management strategy within a hydrologically defined area provides a coordinating framework for water supply protection, pollution prevention and ecosystem preservation. Although watershed strategies vary, they should be based on ecohydrology, the integrated study of ecosystems and hydrological characteristics and processes and their combined potential to influence water dynamics and quality. Ecohydrology requires an understanding of the temporal and spatial patterns of catchment-scale water dynamics which are determined by four fundamental components: climate, geomorphology, plant cover/biota dynamics and anthropogenic modifications. A more efficient approach to water quality and ecosystem integrity requires not only the reduction or elimination of pollution, but in parallel, an augmentation of the effectiveness of potential tools to manage the dynamics of excess nutrients, pollutants, mineral and organic matter in the landscape. This can be done by reducing human impacts and by regulating the aquatic and terrestrial biota in the catchment. One of the most efficient ways to control biota dynamics is through the regulation of hydrological processes by:

increasing watershed water retention through reforestation and restoration of land/water ecotones,
enhancing in-stream retention of water sediments and nutrients through river renaturisation and wetland restoration,
amplifying biogeochemical cycles such as denitrification through wetland inundation.

Recent and ongoing research has greatly increased our understanding of hydrological dynamics, as well as the biotic and biogeochemical dynamics in freshwater ecosystems and land/water ecotones. The application of biotic processes can facilitate self-purification in aquatic ecosystems, significantly reduce the costs of water quality maintenance, and expand the repertoire of management tools which can be applied to freshwater resources. The application of ecohydrological concepts in watershed management also relies on the existence and manipulation of plants understood in terms of species distribution and interactions.

The United Nations Governing Council has directed IETC to play a central role in the transfer of ESTs for freshwater management in developing countries. As part of this responsibility, IETC is working with the Ecohydrological Programme of the United Nations Educational, Scientific and Cultural Organization (UNESCO) and other organisations to promote a broader understanding of the combined benefits of phytotechnologies and ecohydrological applications.

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