A valley, gully, or streambed in northern Africa and southwest Asia that remains dry except during the rainy season. Wadis are often used for spate irrigation. Synonyms: Vadi
Someone who prefers to use water to cleanse after defecating, rather than wipe with dry material.
Waste Stabilisation Pond
Waste stabilisation ponds are large, manmade water bodies used for the treatment of wastewater by the means of naturally occurring processes, such as solar light, wind, and microbial activity. There are three types of ponds, anaerobic ponds, facultative ponds and aerobic or maturation ponds, each with different treatment and design characteristics. The ponds can be used individually, or linked in a series for improved wastewater treatment. Investment and operation costs are relatively low, but large surface areas far from housings are required. Synonyms: Waste Stabilization Pond, WSP
Used water from any combination of domestic, industrial, commercial or agricultural activities, surface runoff/stormwater, and any sewer inflow/infiltration. Wastewater from sanitation contains one or more of the following products: excreta, faeces, urine, blackwater, brownwater, flushwater, dry cleansing material, cleansing water.
Wastewater Collection
In order to facilitate treatment and reuse of wastewater, it has to be collected. Wastewater can either be collected in a centralised sewer system, or, in the absence of this, with a system of human-powered or mechanised vehicles (cartage). Synonyms: WWC
Abbreviation: WWC

Wastewater Reuse at Home
This is the title of the factsheet that describes the various ways that wastewater reuse can be practiced at the household level. Water use optimisation means resistance to chronic and short-term water scarcity and cost and energy savings for water supply and wastewater treatment as less water is required and less polluted water produced. Besides installing water saving appliances, source separation and reuse of different types of wastewater is a way to optimise water use at home. Depending on the type, quality and quantity of water, wastewater can either be reused directly, or treated and reused (recycled). Synonyms: Reuse at home

Wastewater Treatment
Wastewater treatment means the treatment of wastewater and related products (e.g. blackwater, faecal sludge, greywater, non-biodegradable waters, etc.) for safe reuse or disposal in order to minimise health risks for people and protect the environment from pollution.

Water Allocation
Water allocation makes trade-offs between the priorities of stakeholders, profitability and economic returns, reliability of water supply, equity, and sustenance of ecosystems to ensure that good quality water is allocated in a manner that achieves economic efficiency, social equity and environmental sustainability.

Water and Sanitation Program
Water and Sanitation Program
Abbreviation: WSP

Water Charge
Water charges are a widely used economic instrument to better control water use and water pollution by imposing a price on the use of the environment. The goal of such measures is to internalise negative externalities related to water use. Charges can be placed on emissions, users, the product, or on administrative services. Apart from influencing the amount of consumption, water charges can also activate innovation processes. Synonyms: Water Pollution Charge
Water Closet
Water closet or WC describes either a toilet or the room where the toilet is located. Synonyms: WC
Abbreviation: WC

Water Distribution
The act of distributing water to different users (household, agriculture, industry). Water distribution can either be done by centralised pipe systems or by cartage, in the absence of a centralised system.
Abbreviation: WD

Water Distribution Networks
In order to bring collected water sources to the users, a distribution network is required. This network, according to a given context, can be designed taking into account different parameters.

Water Footprint
The water footprint expresses human appropriation of freshwater in volume terms. It counts the direct and indirect freshwater (blue water, grey water and green water) used to produce a product, but can also be applied to consumers, companies, nations, areas. It can be used as an indicator that provides information on the volume, location, time and source of water used and can be compared to water availability at the affected water bodies in order to assess risk of water scarcity and pollution.

Water Footprint Assessment
Water Footprint Assessment refers to a whole range of activities that comprise: 1) Quantification and location of the water footprint of a product, process, person, nation etc., 2) Assess the environmental, social and economic sustainability of this water footprint and 3) formulate a response strategy. It is useful for analysing how human activities relate to water scarcity and pollution and on this basis improve the sustainability of water use.
Water for basic Human Needs
Quantitatively, this is 50 litres of water per day.
Water Frameworks and Approaches
To manage water resources sustainably, various approaches have been developed. These approaches include guidelines on how to conceptualise, plan and carry out project that aim at a improved management of water resources.

Water holding capacity
The ability of the soil to bind water due to its structure and amount of organic matter. Synonyms: Field capacity
Water kiosk
A water kiosk is an outlet through which formal water providers deliver safe and reliable water at affordable prices to residents of low-income areas.
Water Management
Water management means to plan, develop, and optimise the use of the water resources, taking into account the needs of present and future uses, different user groups, as well as the environment.
Abbreviation: WM
Water Pasteurisation Indicator
A Water Pasteurisation Indicator (WAPI) is a simple thermometer that indicates when water has reached pasteurisation temperature and is safe to drink. It consists of a small polycarbonate tube that contains a soybean wax that melts when water or milk is heated enough to be pasteurised (65˚C/149˚F). Since water pasteurises at temperatures well below its boiling point, WAPIs save time and fuel. Synonyms: WAPI, Water Pasteurization Indicator
Water Productivity
Productivity is the ratio of a unit of output to a unit of input.The term water productivity is used exclusively to denote the amount or value of product over volume or value of water depleted or diverted.
Water Purification
Water purification describes a process during which contaminants such as organic material, pathogens or chemical substances are removed from raw water. Water purification can either denominate the process of making water safe for human consumption, but the term is also used for other cleansing processes to make water suitable for e.g. industrial or agricultural uses. Water purification includes physical processes such as filtration or sedimentation, or chemical processes such as chlorination or use of sunlight which contains ultraviolet light.
Abbreviation: WP

Water Quality Testing
In many parts of the world, water is not safe enough to drink. There are basic qualitative observations that quickly determine if water is not safe. However,there are many “invisible” substances that must be tested for professionally to identify the contaminants and to figure out how the specific polluted water can be purified. Testingcan be done in the fieldwith portable test kits or mobile laboratories. Water samples can also be collected and sent to a professional laboratory.

Water Risk Map
A Water Risk Map gives an overview of the water risk in a geographic area with regard to for example baseline water stress, seasonal variability, drought severity, groundwater stress and flood occurrence. Various Water Risk Maps are open source available online.

Water Sanitation and Hygiene
Water Sanitation and Hygiene Synonyms: WASH
Water Sanitation and Hygiene Education
Water Sanitation and Hygiene Education Synonyms: WASHE
Abbreviation: WASHE

Water Seal
Because of its shape, the trap retains a small amount of water after the fixture's use. This water in the trap creates a seal that prevents sewer gas from passing from the drain pipes back into the occupied space of the building. Essentially all plumbing fixtures including sinks, bathtubs, and toilets must be equipped with either an internal or external trap. Synonyms: Liquid Trap Seal, Plumbing Trap
Water Sources
This term denominates the different sources of water, including shallow or deep groundwater, precipitation, surface water, or desalinised seawater. Preserving existing water sources (e.g. through moisture control techniques or water-saving technologies in households, industry and agriculture), resulting in a decreased water use, can also be considered part of water sources, as water saved becomes available for other purposes.
Abbreviation: WS

Water Supply and Sanitation
Water Supply and Sanitation Synonyms: WSS
Abbreviation: WSS

Water Supply and Sanitation Collaborative Council
Water Supply and Sanitation Collaborative Council Synonyms: WSSCC
Abbreviation: WSSCC

Water Table
The level below the earth’s surface, which is saturated with water. It corresponds to the level where water is found when a hole is dug or drilled. A groundwater table is not static and can vary by season, year or usage. Synonyms: Groundwater level
Water Truck
Trucks equipped with a tank to deliver big amounts of fresh and/or drinking water. Synonyms: Cistern Truck, Tank Truck

Water Use
This term denominates the consumption of water for different purposes, without which no life would be possible on earth. Water use is generally divided into household use, industrial and commercial use, and agricultural use.
Abbreviation: WU

Water Use Efficiency
Water use efficiency includes any measure that reduces the amount of water used per unit of any given activity, consistent with the maintenance or enhancement of water quality. Generally, efficient water use is defined as the ratio between the actual volume of water used for a specific purpose and the volume extracted or derived from a supply source for that same purpose.
Water vendors
Water vending refers to the formal or informal reselling or onward distribution of utility water, or water from other sources by small-scale vendors for domestic use. E.g. water kiosks, water carriers, tanker trucks, households reselling water from their utility water connections, etc. Synonyms: independent water provider, small-scale providers, small-scale water provider, small-scale water supply, vended water, vendor-provided water, water entrepreneurs, water vending

Water, Sanitation and Hygiene
Global access to safe water, adequate sanitation, and proper hygiene education can reduce illness and death from disease, leading to improved health, poverty reduction, and socio-economic development. WASH stands for water, sanitation and hygiene and has become a popular notion. It is used worldwide to show that all three are interrelated and therefore have to be tackled together to reach the millennium development goals. Synonyms: WASH
Abbreviation: WASH
Water-borne diseases
Water-related diseases include: those due to micro-organisms and chemicals in water people drink; diseases like schistosomiasis which have part of their lifecycle in water; diseases like malaria with water-related vectors; drowning and some injuries; others such as legionellosis carried by aerosols containing certain micro-organisms. Synonyms: Water borne disease, Water borne diseases, Water related disease, Water related diseases, Water-borne disease, Water-related disease, Water-related diseases
This is the most basic irrigation technique. A sprinkler can be added at the outlet to create a rain effect.

Waterless Urinal
Waterless urinals function without water. They have two important advantages compared to flush urinals: They save water and they allow the collection of undiluted urine, which is a valuable resource as fertiliser in agriculture. Synonyms: waterless urinals

A watershed is where all the water supplies of a particular region originate from Synonyms: Drainage basin, river catchment, river basin
What is a Watershed
Well Casing
Casing used in boreholes is tubular material that provides support to the walls of the borehole and may be either temporary (used by the driller during drilling of the borehole and subsequently withdrawn) or permanent (forming part of the final construction of the completed borehole). Selection of casing material should be based upon water quality, borehole depth and diameter, drilling methods, local regulations and cost. Synonyms: Casing
Well Development
All drilling methods alter the hydraulic characteristics of formation materials in the vicinity of the borehole. Development of a borehole after completion of drilling forms part of the normal drilling procedure. Development procedures are designed to restore or improve these characteristics to maximise the performance of the borehole by improving specific capacity and hydraulic efficiency. Well development methods include: overpumping, surging, jetting, hydro-fracturing, and other supplementary development methods.
Well Rehabilitation
Well rehabilitation of dug or drilled wells becomes necessary if operating wells lack in providing adequate water quality or quantity as the well becomes contaminated or clogged through natural processes or in consequence of emergencies (e.g. floods, seawater intrusion, etc.). It involves the cleaning and disinfection of the well and sometimes the application of well development procedures. Synonyms: Well Cleaning, Borehole Rehabilitation, Borehole Cleaning

Well Remediation
The term well remediation is used in the oil industry. It refers to the cleaning of oil wells to improve performance and requires utterly different methods than the rehabilitation of water wells.

Well Screen
A well screen is a filtering device that allows groundwater to enter the well. It provides structural support but prevents sediment from entering, especially in unconsolidated strata. Proper screen design and selection is important for the hydraulic efficiency of the well, as well as for the longevity and long-term cost of the structure. Screens should have maximum open area to create minimum resistance to flow into the hole, but at the same time must minimise sediment ingress and provide adequate structural strength. Optimising each of these criteria for a particular well is the essence of screen design. Synonyms: Screen
Wet Well
Sewage is fed into and stored in an underground pit, commonly known as a wet well. The well is equipped with electrical instrumentation to detect the level of sewage present. When the sewage level rises to a predetermined point, a pump will be started to lift the sewage upwards.
Windrow Composting
Windrow composting is a simple, but slow composting process. The material is piled up in heaps or elongated heaps (called windrows). The size of the heaps ensures sufficient heat generation and addition of bulky materials, passive or active ventilation or regular turning ensures aeration. Systems with active aeration by blowers are usually referred to as forced aeration systems and when heaps are seldom turned, they are referred to as static piles. Leachate control is provided by a sloped and sealed or impervious composting pad (the surface where the heaps are located) with a surrounding drainage system. Synonyms: Open Composting
Someone who prefers to use dry material (e.g., toilet paper or newspapers) to cleanse after defecating, rather than wash with water.
World Health Organisation
World Health Organisation Synonyms: WHO
Abbreviation: WHO