[[Image:water reuse1.png|thumb|right|200px|Source: [http://bebuffered.com/downloads/3R_managing_the_water_buffer_2010.pdf bebuffered.com]]]Water reuse can include reusing water from many sources. Sometimes it is used water from showers bathing or dishwashing, and other times it is managing agricultural runoff. Reusing waste water is also very popular worldwide. Other names include “water recycling,” “water purification,” “reclaimed water,” “recycled water,” “reuse water,” and “repurified water.”
Water reuse is a well-known concept and part of the [[3R (water) – Recharge, Retention and Reuse|3R process (recharge, retention, reuse)]]. In this way, managing water well is thought of as a "buffer" to insure consistent supplies - A buffer between the user and the bad effects of drought or an unreliable water resource.
By ponding up groundwater and slowing down lateral movement, retention can create or enlarge such saturated zones. These nuances must be appreciated in order to avoid the assumption that because a basin is a hydrological unit all water related processes in the basin are one and the same.
===Reuse around the world===
The following analysis of regions for reuse of water is an introduction to this subject. A full report with specific countries highlighted can be found in the Status and Role of Water Reuse reference at the bottom of the page.
====Latin America (Central and South America)====
More than 80% of the 700 million people in Latin America live in urban areas, making large quantities of treated and untreated wastewater available for reuse, principally for agricultural irrigation. Drivers for water reuse include wastewater availability, seasonal variations in water availability and use, low or no cost of wastewater to farmers, high salinity of many natural waters, and soil and crop benefits associated with organic matter and nutrients in wastewater used for irrigation. Water availability varies dramatically throughout the region, with countries in Central America generally having larger volumes of natural water resources than some countries in South America such as Peru and Chile.
====Middle East and North Africa====
The drivers for water reuse in developing countries in the Middle East vary but are principally related to population growth, climate, limited water resources, and socio-economic conditions. Agricultural irrigation is the leading use of reclaimed water in the Middle East. Unplanned reuse is common, where untreated or minimally-treated wastewater is discharged into watercourses and subsequently withdrawn by farmers with or without mixing with water that may be present in the rivers. Farmers are often unaware that the irrigation water they draw to irrigate food crops
is grossly contaminated; the link between high disease incidence and wastewater is seldom recognized.
In some countries, untreated or partially treated wastewater is preferred over more highly treated wastewater for irrigation due to its low (or no) cost and high organic and nutrient value. In some Muslim countries, the use of wastewater for irrigation has been opposed on religious grounds (i.e., that the water originated from wastewater and is therefore contaminated). This resistance has been relieved in some cases by religious scholars who have issued fatwas (i.e., legal pronouncements issued by religious specialists on specific issues, usually at the request of an individual or judge to settle questions where Islamic jurisprudence is unclear) stating that wastewater reclamation and reuse can result in a “pure” water source of water that is safe and adequate for different applications.
====South Africa====
South Africa is a semi-arid country with limited water resources, and it is projected that water demand will exceed available supplies around 2020. The main drivers for water reuse in South Africa include: variable and uneven distribution of rainfall; high evaporation rates; low-yielding aquifers; and growing industrial and urban development. In the past, many of the investigations have been directed at potable reuse. Intensive research has been conducted at the Stander reclamation plant in Cape Town and demonstration plants in Pretoria and Athlone, but planned direct potable reuse projects have yet to be implemented and more attention has recently been given to nonpotable reuse.
====Far East====
Population increase is the main driver for water reuse in most of the Far East, although rapid industrial growth in some areas, such as China, have drastically increased the need for water and at the same time has resulted in gross pollution of many of the existing water resources. Water is
scarce in many parts of the Far East, particularly in the northern and western regions of China, India, and Pakistan. Almost two-thirds of China’s 668 cities have limited water resources and 136 cities experience severe water shortages. The tropical countries in the Far East generally have abundant water resources and have limited water reuse.
====India and Pakistan====
'''India:''' Only about 72% of the 17 Mm3 (4.5 billion gallons) of wastewater generated annually in India is collected, and less than 25% of the collected sewage is treated. This has resulted in a high number of waterborne disease cases in the country. Sewage farms irrigating salad crops
with low quality wastewater are prevalent even though irrigation wastewater is forbidden. India does provide high levels of treatment of industrial wastewater for reuse. In some cases, reverse osmosis treatment is provided for industrial wastewater, but tertiary treatment of municipal wastewater is rare.
'''Pakistan:''' The use of untreated wastewater for the irrigation of all types of agricultural crops is common. About 80% of the urban communities use untreated wastewater for agricultural irrigation, including vegetables. In the City of Faisalabad, for example, more than 2,000 ha (4,900 ac) of agricultural land is irrigated with untreated wastewater. Farmers prefer to use untreated wastewater because of its high nutrient value and, although there is one small wastewater treatment facility in the City, all wastewater used for irrigation is untreated. Wastewater is sold to the farmers; the revenues generated are used to operate and maintain the drinking water and sewage disposal systems.
===Water reuse links===
* [http://www.gwp.org/en/gwp-in-action/Mediterranean/News-and-Activities-GWP-Mediterranean/Non-Conventional-Techniques-for-Water-Reuse-in-the-Mediterranean/ Non-Conventional Techniques for Water Reuse in the Mediterranean]
* [http://www.limpoporak.com/en/management/water+demand/conservation+and+reuse.aspx Limpopo river awareness kit: Conservation and reuse].
* [http://www.unep.or.jp/Ietc/Publications/Water_Sanitation/wastewater_reuse/Booklet-Wastewater_Reuse.pdf WATER AND WASTEWATER REUSE]. UNEP & GEC.
* [http://scerpfiles.org/cont_mgt/doc_files/W-03-13-report.pdf AN EVALUATION OF AGRICULTURAL WATER REUSE PRACTICES IN THE ARID U.S.-MEXICO BORDER REGION—MEXICALI, BAJA CALIFORNIA, MEXICO]. Universidad Autonoma de Baja California & Arizona State University.
===Acknowledgements===
* [http://bebuffered.com/downloads/3R_managing_the_water_buffer_2010.pdf Managing the Water Buffer for Development and Climate Change Adaptation: Groundwater Recharge, Retention, Reuse and Rainwater Storage], Frank van Steenbergen and Albert Tuinhof.
* [http://www.watereuse.org/files/images/04-007-01.pdf Status and Role of Water Reuse], Global Water Research Coalition.