Harvesting Water
Rainwater Run off
Geology, Ground water, India
Ground water Recharge
Rainwater Harvesting methods
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Urban Rainwater Harvesting- Water Sensitive Urban Designing
Water Sensitive Urban Design (WSUD)
         is a relatively new approach to water management in urban areas. The objective of WSUD is to maintain or replicate the pre-development water cycle through the use of design techniques to create a functionally equivalent hydrological landscape. When urban development occurs, the natural water cycle is altered to the extent that stormwater runoff from individual properties and roads intensify, flows usually increase and potential contaminants from residential and commercial activity and associated vehicle use flow into the streams and watercourses. The effect of this type of water management approach on natural systems has included: • an increase in the use of water resources for domestic, commercial/industrial uses as well as outdoor irrigation of gardens and open space areas; and • an increased tendency for more severe flooding and increased areas of flooding.
Components
 Catchments: -
                      
It is the surface that directly receives the rainfall and provides water to the system. It can be in the form of a terrace or a lawn or open ground. A roof made up of reinforced cement concrete (RCC), galvanized iron or corrugated sheets can also be used for rainwater harvesting.

Coarse mesh: -
It is present at the roof and it functions as a barrier to the passage of the debris.
Gutters: -
The channels around the edge of a sloping roof are called as gutters. The main functions of gutters are to collect and transport rainwater to the storage tank. Gutters can be in semi – circular or rectangular in shape. It could be made either using galvanized iron sheets or PVC material. The size of the gutter should be according to flow during the highest intensity rain. It is advisable to make them 10 to 15 % oversize. It is important to support the gutters so as to prevent them from falling off due to water load.
Conduits: -
These are the pipelines or drains used to carry rainwater from the catchment area to the storage tanks. Polyvinyl chloride (PVC) and galvanized iron are the common material used to prepare the conduits.
First flushing: -
A first flush device is a valve that ensures that runoff from the first spell of rain is flushed out and do not enter the system. The first spell of rain carries large amount of pollutants from the air and catchment area and hence first flushing is very essential.
Filter: -
The filter is used to remove suspended matter present in the rainwater. A filter unit is a chamber filled with filtering media such as fibre, coarse sand and gravel layers to remove debris and dirt from water before it enters the storage tank or recharges structure. Charcoal can be added for additional filtration. When rainwater is harvested in a large rooftop area, the filtering system consists of 3 concentric circular chambers in which the outer chamber is filled with sand, the middle one with coarse aggregate and inner most layer with pebbles.
Storage facility: -
The shape of these tanks can be cylindrical, rectangular or square. Commonly used material of construction includes reinforced cement concrete (RCC), plastic and metal sheets. Depending upon the availability of space, these tanks could be constructed above ground, partly underground or fully underground.
Recharge structures: -
The ground aquifers may be recharged by the rainwater through suitable structures like dugwells, borewells, recharges trenches and recharge pits.
WSUD Measures Included in the Design Specifications
1. Vegetated Swales
2 Vegetated Filter Strips
3 Sand Filters
4 Bioretention Systems
5 Permeable Pavements
6 Infiltration Trenches
7 Infiltration Basins
8 Rainwater Tanks (single lot above ground)
9 Landscape Developments
Artificial recharge to groundwater
         Artificial groundwater recharge is an important technology in water resources management, particularly for utilizing excess surface water. This technology can increase the water reserve of underground aquifers and utilize surface water that would otherwise be lost or contaminated.

Technology Description
      
A number of artificial recharge concepts currently exist, and they also intermix with other concepts related to groundwater storage or to drainage of liquid wastes into different aquifers. Accordingly, artificial recharge of groundwater refers here to the process of feeding surface water into a groundwater aquifer, utilizing different artificial methods to increase the safe freshwater yield from the aquifer. When an aquifer is supplied with new quantities of freshwater that are not possible with natural recharge, the result is an increase in the quantity of water available to be extracted for beneficial human uses.
       With this perspective, the goal of artificial recharge is to increase the volume of freshwater reaching an aquifer, with the smallest environmental impact. Thus, artificial recharge can achieve one or more of the following objectives:

  • Relieving overdrawn aquifers by limiting their depletion and deterioration of water levels, increasing their well productivity, and improving their water quality. This is also known as well field management; 
  • Conserving and controlling groundwater levels; 
  • Preventing surface runoff flow and floodwater from being lost, evaporated, contaminated or released into the ground;
  • Storing water to reduce the costs of transporting and pumping it to other locations;
  • Conveying water from where it is available to where it is to be used; 
  • Improving water quality by removing suspended solids, organic pollutants and microbes, and by cooling it via infiltration through ground layers; 
  • Preventing seawater intrusion into freshwater, and extending the boundary between the salt and freshwater.
What is WSUD? 
          WSUD is the integration of various Best Planning Practices (BPPs) and Best Management Practices (BMP) for the sustainable management of the urban water cycle. WSUD is concerned with the design of urban environments to be more “sustainable” by limiting the negative impacts of urban development on the total urban water cycle. Therefore WSUD is about:
         1. trying to more closely match the pre-development stormwater runoff regime, in both quality and quantity;2. reducing the amount of water transported between catchment, both in water supply import and wastewater export; and3. Optimizing the use of rainwater that falls on the urban areas.
Source of Urban Rainwater Harvesting
Rainwater Harvesting: Micro-catchment Systems  
      Rainwater Harvesting is the technique of collection and storage of rainwater at the surface or in sub-surface aquifers, before it is lost as surface runoff.Uncovered areas, particularly in urban and semi-urban localities, are continuously diminishing due to phenomenal pace of industrialization and urbanization and massive use of concrete all around in the country. This phenomenon is constantly causing reduced scope for percolation of rain waters to the ground during monsoon and thus perpetual reduction in ground water recharge year after year.
     The water harvesting system makes use of the surface, which directly receives the rainfall and provides water to the system.

• Roof top/terrace catchments
• Surface runoff catchments
Technology Description  
As with most of the water harvesting technologies, this technology consists of three components, including
(1) collection,
(2) conveyance and
(3) storage systems.
What is WSUD? 
         The rooftop constitutes the rainwater collection system. The rooftop surface should
        (1) be smooth,
        ( 2) not absorb large amounts of dust,
         (3) of uniform slope, and
         (4) not covered with harmful paint especially those made of bitumen. If the roof is painted, the paint should not contain significant amounts of any heavy metals (lead, mercury). The direction of the prevailing winds should be considered in determining the location of the rooftop. Application of chemical fertilizers via aircraft should be avoided in agricultural areas. Routine cleaning of the rooftop also is required to maintain an acceptable quality of the collected rainwater. The conveyance system usually consists of gutters to receive the rainwater flow from

the rooftop, and convey it to vertical pipes leading to the storage tank. The slope of the gutters and pipes should be adequate to ensure the immediate drainage of the rainwater. The pipes should be constructed of non-toxic material, such as aluminum, plastic or fiberglass. They should also be equipped with screens, to prevent debris, sand and other dirt from entering the cistern. The storage tank (for Holding peak rainfall water) should be constructed of different storage capacity and on the specific site conditions, and can be constructed either above or below the ground surface. It is usually equipped with a device to indicate the existing storage inside the cistern. A cistern typically consists of
(1) storage tank,
(2) sediment trap (to receive the rainwater and retain sediment and other debris before entering the storage tank), and (3) extraction opening (manhole) at the top of the cistern, compatible with convention extraction methods. Protection measures should be taken to prevent all water pollutant sources from entering the cistern, especially for underground cisterns, which should be situated 20-30 cm above the ground level. Debris Separation and Water Filtration Manual, semi-automatic or automatic mechanisms can be used to separate the settled and deposited material that accumulates on the rooftop during the dry season. The first  flush of rainwater is directed away from the cistern. Special manual valves to divert the flow at the feeding pipe to the cistern can be provided. Special
drainage of the dirt settled at the bottom of the cistern also can be incorporated. A small sand filter also can be attached to the cistern to secure better water quality in it.
Drainage ditch
It is essential to design the cistern to prevent the release of sediments with the water. This can be done with drainage water openings in the floor of the cistern.
Water Treatment The water settlement process constitutes a part of the cistern system. The infiltration mechanism can be a sand filter attached to the cistern structure, or a separate filter device in which the water drawn from the cistern is treated and chlorinated.
  Copy Rights :Amar Joshi