Stormwater harvesting and management

Stormwater Harvesting and Management refers to the broad practices, systems, techniques, laws and strategies used to handle stormwater, or rainwater that has flowed over land, including but not limited to roads, agricultural areas, gardens and sidewalks. Stormwater harvesting differs from rainwater harvesting in that runoff from non-building surfaces is collected. However there is some overlap, and definitions for what kind of system is what varies from area to area.

Stormwater harvesting can be considered a technique and one out of many approaches to stormwater management, but for the sake of clarity, we will define stormwater harvesting most simply as the act the collection, storage and reuse of stormwater and stormwater management as strategies dealing with the management of the quantity and quality of stormwater.

Stormwater that has come in contact with impervious surfaces can become polluted and is denoted as surface runoff. The more impervious surfaces that the water travels over, the more pollutants accumulate in the water.

Stormwater Harvesting
Major concerns in new projects for stormwater harvesting include cost effectiveness as well as quality, quantity, and reliability of the reclamation, as well as existing water management infrastructure and soil characteristics. Some project cost estimates have produced results for stormwater being around twice as expensive factoring operating cost per unit versus potable water alternatives. However, other benefits include reducing soil erosion and reducing demands on local aquifers, as well as reduction of pollution into local waterways.

Stormwater Harvesting Systems
Ground catchments systems channel water from a prepared catchment area into storage. Generally they are only considered in areas where rainwater is very scarce and other sources of water are not available. If properly designed, ground catchment systems can collect large quantities of rainwater.

Stormwater Management
The term Best Management Practice (BMP) or stormwater control measure (SCM) is often used to refer to both structural or engineered control devices and systems (e.g. retention ponds) to treat or store polluted stormwater, as well as operational or procedural practices (e.g. street sweeping). Stormwater management includes both technical and institutional aspects.

Increasingly, communities and governments require that developers account for and reduce the impact of stormwater run-off on either the municipal or other local treatment systems.

Technical Approaches

 * control of flooding and erosion;
 * control of hazardous materials to prevent release of pollutants into the environment (source control);
 * planning and construction of stormwater systems so contaminants are removed before they pollute surface waters or groundwater resources;
 * acquisition and protection of natural waterways or rehabilitation;
 * building nature-based solutions such as ponds, swales, constructed wetlands or green infrastructure solutions to work with existing or "hard" drainage structures, such as pipes and concrete channels (constructed wetlands built for stormwater treatment can also serve as habitat for plants, amphibians and fish)

 

Institutional and Policy Aspects

 * development of funding approaches to stormwater programs potentially including stormwater user fees and the creation of a stormwater utility;
 * development of long-term asset management programs to repair and replace aging infrastructure;
 * revision of current stormwater regulations to address comprehensive stormwater needs;
 * enhancement and enforcement of existing ordinances to make sure property owners consider the effects of stormwater before, during and after development of their land;
 * education of a community about how its actions affect water quality, and about what it can do to improve water quality.

Stormwater management system maintenance
Proper service and maintenance schedules on a regular basis are sometimes required of applicable federal, state and local laws, codes and regulations. Maintenance ensures that pollutants are separated or removed from stormwater before entering further water connections downstream. If incorrect or insufficient maintenance is provided, back ups can occur, causing flooding and allowing pollutants to bypass treatment sections and flow downstream. This is no better than if there no system in the first place.