Stormwater harvesting or
Stormwater reuse is the collection, accumulation,
treatment or purification, and storage of
stormwater
Stormwater, also spelled storm water, is water that originates from precipitation (storm), including heavy rain and meltwater from hail and snow. Stormwater can soak into the soil ( infiltrate) and become groundwater, be stored on depressed la ...
for its eventual reuse. While
rainwater harvesting
Rainwater harvesting (RWH) is the collection and storage of rain, rather than allowing it to run off. Rainwater is collected from a roof-like surface and redirected to a tank, cistern, deep pit (well, shaft, or borehole), aquifer, or a reservoir w ...
collects precipitation primarily from rooftops, stormwater harvesting deals with collection of runoff from creeks, gullies, ephemeral streams, underground conveyances ( pipes ). It can also include catchment areas from developed surfaces, such as roads or parking lots, or other urban environments such as parks, gardens and
playing fields
A pitch or a sports ground is an outdoor playing area for various sports. The term ''pitch'' is most commonly used in British English, while the comparable term in American and Canadian English is playing field or sports field.
For most sports t ...
.
Water that comes into contact with
impervious surface
Impervious surfaces are mainly artificial structures—such as pavements (roads, sidewalks, driveways and parking lots, as well as industrial areas such as airports, ports and logistics and distribution centres, all of which use considerable p ...
s, or saturated surfaces incapable of absorbing more water, is termed
surface runoff
Surface runoff (also known as overland flow) is the flow of water occurring on the ground surface when excess rainwater, stormwater, meltwater, or other sources, can no longer sufficiently rapidly infiltrate in the soil. This can occur when th ...
. As the surface runoff travels greater distance over impervious surfaces it often becomes contaminated and collects an increasing amount of
pollutant
A pollutant or novel entity is a substance or energy introduced into the environment that has undesired effects, or adversely affects the usefulness of a resource. These can be both naturally forming (i.e. minerals or extracted compounds like oi ...
s. A main challenge of stormwater harvesting is the removal of pollutants in order to make this water available for reuse.
Stormwater harvesting projects often have multiple objectives, such as reducing contaminated runoff to sensitive waters, promoting
groundwater recharge
Groundwater recharge or deep drainage or deep percolation is a hydrologic process, where water moves downward from surface water to groundwater. Recharge is the primary method through which water enters an aquifer. This process usually occurs in ...
, and non-potable applications such as toilet flushing and irrigation.
Stormwater harvesting is also practiced in areas of the
United States
The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territorie ...
as a way to address rising water demands as population rises.
Internationally,
Australia
Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...
is notable in its active pursuit of stormwater harvesting.
![CatchingHillRunoffwater](https://upload.wikimedia.org/wikipedia/commons/9/9d/CatchingHillRunoffwater.svg)
Systems
Ground catchments systems channel water from a prepared catchment area into storage. These systems are often considered in areas where rainwater is scarce and other sources of water are not available. If properly designed, ground catchment systems can collect large quantities of rainwater. In arid ranch land, a
catchwater
A catchwater device is a large-scale man-made device for catching surface runoff from hills and the sky from precipitation by channeling it to reservoirs for commercial and domestic use later. Freshwater is a scarce natural resource due to pollutio ...
or
cattle tank can be constructed across shallow ephemeral washes to impound and collect what little stormwater does generate there. This untreated water is easily accessed and utilized by livestock. More intricate collection and processing systems are necessary for stormwater harvest to be reused for human uses.
Stormwater Capture
![Infiltration Basin at Anawan Street Pocasset Street (September 14, 2016) (29856364125)](https://upload.wikimedia.org/wikipedia/commons/a/a0/Infiltration_Basin_at_Anawan_Street_Pocasset_Street_%28September_14%2C_2016%29_%2829856364125%29.jpg)
Five Core Steps: End Use, Collection, Treatment, Storage, and Distribution
* End Use
** Water resources become more scarce as the human population grows. Populations need to create systems and methods to minimize water consumption at all levels, while simultaneously engineering new methods of
water reuse
Water reclamation (also called wastewater reuse, water reuse or water recycling) is the process of converting municipal wastewater (sewage) or industrial wastewater into water that can be reused for a variety of purposes. Types of reuse include: ...
. For non-potable water purposes with lower water quality needs, people can use stormwater for toilet flushing, gardening,
fire fighting
Firefighting is the act of extinguishing or preventing the spread of unwanted fires from threatening human lives and destroying property and the environment. A person who engages in firefighting is known as a firefighter.
Firefighters typicall ...
,
irrigation
Irrigation (also referred to as watering) is the practice of applying controlled amounts of water to land to help grow Crop, crops, Landscape plant, landscape plants, and Lawn, lawns. Irrigation has been a key aspect of agriculture for over 5,00 ...
, etc. For potable water use of higher water quality, stormwater needs to be highly treated before final use. The latter has rarely been used around the world.
Some stormwater collection systems aim to simply reduce the amount of stormwater runoff that flows to a nearby waterway. The benefits of these systems include reducing pollution in streams, lakes, and nearshore coastal environments, as well as promoting groundwater recharge. The intended end use of a system will determine the level of treatment and processing of collected stormwater.
* Collections
** Stormwater collection is a process of directing water into storage from stormwater gathering, such as
urban runoff
Urban runoff is surface runoff of rainwater, landscape irrigation, and car washing created by urbanization. Impervious surfaces (roads, parking lots and sidewalks) are constructed during land development. During rain , storms and other precipit ...
. Generally, there are two types, online storages and offline storages. Online storages are a conventional way of acquiring stormwater directly from waterways or drains. For instance, the urban drainage system of channels and pipes conduct stormwater into storage facilities,
often with treatment at or just prior to storage. One drawback of this collection design is the required maintenance that systems may require for structural integrity to prevent conduit failure resulting in stormwater leakage. Water Sensitive Urban Design, or
WSUD , is one comprehensive planning and design process that incorporates online stormwater storage into urban development models. Offline storages require additional facilities to conduct water from waterways indirectly, and can serve as storage for stormwater prior to treatment. For instance, weirs divert flows into stormwater containment and contribute to a large part of stormwater catchment for a city, where it is then stored for future treatment and distribution. Stormwater collection is widely practiced for purposes of urban runoff and flood mitigation as well.
* Treatment
**
![The top of the SMURRF](https://upload.wikimedia.org/wikipedia/commons/1/16/The_top_of_the_SMURRF.jpg)
Stormwater treatment is the greatest challenge for stormwater harvesting. Water treatment processes depend on the intended end use and the catchment equipment, which determines the level of pollutants to be filtered and removed. For instance, construction uses may only require non-potable water where the water processing includes only
filtration
Filtration is a physical separation process that separates solid matter and fluid from a mixture using a ''filter medium'' that has a complex structure through which only the fluid can pass. Solid particles that cannot pass through the filter ...
and
disinfection
A disinfectant is a chemical substance or compound used to inactivate or destroy microorganisms on inert surfaces. Disinfection does not necessarily kill all microorganisms, especially resistant bacterial spores; it is less effective than st ...
. However, for potable uses of higher water quality, the treatment process requires screening, coagulation,
filtration
Filtration is a physical separation process that separates solid matter and fluid from a mixture using a ''filter medium'' that has a complex structure through which only the fluid can pass. Solid particles that cannot pass through the filter ...
, carbon adsorption, and
disinfection
A disinfectant is a chemical substance or compound used to inactivate or destroy microorganisms on inert surfaces. Disinfection does not necessarily kill all microorganisms, especially resistant bacterial spores; it is less effective than st ...
.
* Storage
** There are three factors to consider in terms of storage: function, location, and capacity. The planner is responsible for determining the end use of the stored stormwater, such as fire fighting, industrial water supply, farming and irrigation, recreation,
flood mitigation
In environmental engineering, the flood mitigation involves the management and control of flood water movement, such as redirecting flood run-off through the use of floodwalls and flood gates, rather than trying to prevent floods altogether. It a ...
, groundwater recharge, etc. Regarding location of a system and its storage, a water tank in proximity to the waters' end use may be the best design. If the collection system is intended to slow runoff and/or recharge an aquifer, an on-site, below ground infiltration systems may be considered. Choices between online and offline storages can affect the surrounding natural aquatic systems and yields different maintenance costs and
flood mitigation
In environmental engineering, the flood mitigation involves the management and control of flood water movement, such as redirecting flood run-off through the use of floodwalls and flood gates, rather than trying to prevent floods altogether. It a ...
effectiveness. The capacity of a storage system will be determined by the type of end use in a particular climate or period of time.
* Distribution
** Generally, there are two types of stormwater distribution systems. The first is open space irrigation systems.
This application uses treated stormwater to irrigate open spaces such as parks, municipal green spaces, golf courses, etc., and can be implemented at a hyper-local scale (ie catchment and reuse occurs at the same park). Another system is a non-potable distribution system which distributes treated stormwater to be used for things like toilet flushing, fire fighting, and some industrial uses. This system may require additional infrastructure such as a third-pipe network for distribution.
Concerns
Major concerns for stormwater harvesting projects include cost effectiveness as well as quality, quantity, and reliability of the reclamation, as well as existing water management infrastructure and
soil
Soil, also commonly referred to as earth or dirt, is a mixture of organic matter, minerals, gases, liquids, and organisms that together support life. Some scientific definitions distinguish ''dirt'' from ''soil'' by restricting the former te ...
characteristics. Some projects have estimated stormwater harvesting to be twice as expensive per unit -when including operating costs- versus other
potable water
Drinking water is water that is used in drink or food preparation; potable water is water that is safe to be used as drinking water. The amount of drinking water required to maintain good health varies, and depends on physical activity level, ag ...
alternatives. New construction of third-pipe networks in urban settings can be prohibitively expensive; therefore the ideal project will produce recycled stormwater of potable quality in order to take advantage of existing distribution infrastructure. Attaining quality as well as useful quantity water from stormwater harvesting presents challenges of filtration efficacy as well as source reliability and predictability. However, other valuable (and hard-to-calculate) benefits include reducing
soil erosion
Soil erosion is the denudation or wearing away of the upper layer of soil. It is a form of soil degradation. This natural process is caused by the dynamic activity of erosive agents, that is, water, ice (glaciers), snow, air (wind), plants, and ...
by slowing flow rates and reducing demands on local
aquifer
An aquifer is an underground layer of water-bearing, permeable rock, rock fractures, or unconsolidated materials (gravel, sand, or silt). Groundwater from aquifers can be extracted using a water well. Aquifers vary greatly in their characterist ...
s, as well as reduction of pollution into local waterways.
See also
*
Rainwater Hog
Early life and education
Sally Dominguez was born in Australia on 24 October 1969. She attended the Sydney Church of England Grammar School – an all girls preparatory school located in Sydney, New South Wales, Australia – from 1978 to 198 ...
*
Stormwater detention vault
A stormwater detention vault is an underground structure designed to manage excess stormwater runoff on a developed site, often in an urban setting. This type of best management practice may be selected when there is insufficient space on the si ...
References
{{Wikiversity, Stormwater Harvesting and Management
Stormwater management
Water supply
Water conservation
Hydrology and urban planning
Appropriate technology