Does this sound like an impossible task? Is there any village that does not have this land availability? India's total land area is over 300 million hectares. Let us assume that India's 587,000 villages can harvest the runoff from 200 million hectares of land, excluding inaccessible forest areas, high mountains and other uninhabited terrains, that still gives every village on average access to 340 hectares or a rainfall endowment of 3.75 billion litres of water. These calculations show the potential of rainwater harvesting is enormous and undeniable.
Alternate technologies
1. water harvesting
water harvesting can be undertaken through a variety of ways
Capturing runoff from rooftops
Capturing runoff from local catchments
Capturing seasonal floodwaters from local streams
Conserving water through watershed management
Runoff Collection Using Surface Structures
Technical Description
Water storage is an important method for artificially regulating natural water circulation to harmonize society's demands for water with the availability of surface water resources that change in time and space due to climate and topography. This storage is often accomplished through the construction of dams to create reservoirs of surface water along a naturally occurring watercourse. Reservoirs may be divided into different types on the basis of site (highland and lowland reservoirs), size (small, medium, and large reservoirs), intended purpose (irrigation, water supply, fish production, hydropower generation), and technical design (river dam reservoirs and retention/detention water storage ponds).
Reservoirs serve not only as water storage facilities, but also work as biological wastewater treatment systems, places for recreation, and aesthetic landscape elements.
Operation and Maintenance
The major element in the operation of surface water storage ponds in the construction and maintenance of the hydrological structures, including the barrier wall, water control gates, and associated canals and outlet pipes. In multi-purpose reservoirs, maintenance may also include the upkeep of turbines or other equipment.
Level of Involvement
Costs
Costs depend upon scale of a given project. Construction costs range from $0.16/m3 to $0.60/m³ for large dams, and from $1/m3 to $5/m3 for smaller sized structures. If large dams are built in an environmentally sound manner, and have no significant hydraulic problems, maintenance costs are low and the structures can be operated without specialized staff. Small dams have few costs, although they must be inspected periodically to ensure that they are not subject to siltation or misuse.
Effectiveness of the Technology
Effectiveness is determined by the hydrological regime, scale, and design of the project. Generally, well-designed and sited reservoirs are very effective means of storing freshwater.
Suitability
Technology suitable for most of geographic and hydrological areas excluding sites with unfavourable geology; i.e., those areas with fractured or porous bedrock that cannot be sealed to retain surface water or support a structure.
Advantages
The main goals of reservoirs are storage of excess surface water and flood control by attenuating the downstream effects of the flood peak. In turn, the reservoir provides water suitable for irrigation use and support of fish stocks. Recreational activity is also possible on and around reservoirs. Because of the head differential between the water surface and the river bed, most reservoirs also have the capacity for power generation, a capacity enhanced by the development of low-head turbines in recent years (see below). Construction of smaller reservoirs for fire protection not only provided increased resistance for forest fires due to their microclimatic effects, but also make available additional water for use during extreme droughts. Disadvantages Reservoirs create extensive land-use changes, wherein agricultural bottomlands are inundated and habitat is disturbed. Such disturbances lead to potentially severe environmental impacts depending on the size of the impoundment, including changes in the microclimate in the vicinity of large impoundments and both terrestrial and aquatic ecological disturbances. Because they are artificial structures, reservoirs can both add and detract from the aesthetic value of landscapes, depending on their design and construction.
Cultural Acceptability
Generally, impoundments are an acceptable technology. However, because of the land-use changes inherent in dam-building technology, cultural and social problems occur within the communities directly impacted by the construction process
Further Development of the Technology
Future dam construction will be subject to intense environmental scrutiny, focussing not only on direct, in-basin impacts but also hydrological optimalization, including in stream flow regulation. Notwithstanding, the dam construction technology is a well-established technology.
2.Collection And Reuse Of Stormwater
Technical Description
In developing urban areas, stormwater can be gathered in separate stormwater sewers and reused after simple treatment for washing streets, cooling, watering of gardens, and other purposes requiring nonpotable water. In addition to providing this reuse potential, this technology makes possible the treatment of urban runoff before it enters waterbodies. The simplest form of stormwater treatment consists of open or closed sedimentation basins, retention ponds, or storm sewer, in-line separation chambers for capturing oil products. Stormwater management technologies include provision of grit chambers and swirl separators within sewer mains, and skimmers which capture floatable solids and oil products from the water surface of basins. Infiltration ditches also can be used for filtration of oil products.
Operation and Maintenance
Regular inspections during rainy weather should be conducted to minimise the occurrence of blockages within the collection system. If basins are used, moving of the grass within the basins, periodic removal of sediments, and cleaning of the outlet pipe are also required. Litter, soil, and leaf removal is required from in-line separators.
Level of Involvement
This technology could be implemented at the municipal government level.
Costs
Costs will be different according to local conditions, possibilities for stormwater usage, and existing infrastructure. Because dual collection systems are required for stormwater and wastewater conveyance, the costs may be higher than for combined systems (which may require larger diameter pipe networks to convey the higher volumes of wet weather flows).
Effectiveness of the Technology
The efficiency of this technology when combined with simple pond-based treatment facilities is high, with approximately 80% of oil products and suspended solids being removed from the stormwater. Depending on the area drained by the system, a large volume of water can be saved if stormwater is reused for purposes requiring low quality source waters.
Suitability
Reuse of stormwater can be a favourable option for municipalities with scarce water resources and an high demand for low quality, nonpotable water. The desirability of stormwater reuse is strongly dependent on general environmental quality and pollution within the rainwater catchment area, and may vary depending on the intensity and duration of storms and the length of the period between storms. Stormwater quality also varies within individual storms, with water quality at the beginning of a storm pollution being poor (known as the "first flush" effect). Also, the quantity of stormwater is variable, with periodic high flows during storms and low or no flows between storms. Hence, detention ponds, using biological treatment, are often used as such ponds are most flexible with regard to volume. Nevertheless, it is important that such ponds are of adequate volume to detain between a 2 and 100 year recurrence interval design storm, so that the runoff is not discharged into waterbodies without sufficient treatment. Because water quality of the runoff generally improves during the course of a storm, the degree of impairment at the end of the storm is rather low and this water can be reused after simple treatment or discharged into waterbodies without a significant pollution risk. Investigations of the stormwater flows show that long rains of low intensity create greatest pollution loads to surface waters.
Advantages
Using low quality water for nonpotable needs, instead of potable freshwater resources, augments the available supplies of the latter. Providing treatment of stormwater runoff from urban areas also provides an opportunity to upgrade degraded natural waters that have previously received untreated stormwater discharges.
Disadvantages
Because limited treatment methods of purifying stormwater are used, effluents may remain contaminated with persistent pollutants like heavy metals, and, in consequence, should not be used for gardening purposes if the produce is intended for human consumption. Use of contaminated stormwater may lead to contaminant accumulation in the soil.
Cultural Acceptability
This technology is culturally acceptable. Its use is largely outside of the public eye, and, hence, is mainly of concern to administration staff and workers.
Further Development of the Technology
Better schemes of the assessment of environmental impacts connected with stormwater use for various purposes need to be developed. Given that treatment is often needed, improved methods of purifying stormwater, that are inexpensive and simple to install and operate, should be developed.
3.Computer Modelling of the Water Supply System Management
Technical Description
Various computerized management systems have been developed to optimize the operation of water supply systems. For example, the City of Gdynia, Poland, makes use of the OPUS® program for the optimization of its freshwater supply system. Optimization of the water supply system and its components is very important in the planning and management of the system and results in greater conservation and fewer transportation losses of freshwater within the distribution network. A prerequisite for the application of computer-based operations models is a thorough understanding the water supply network and the complete documentation and mapping of each element of the network (including pipe diameter, material, length, year of construction, and friction index). Data on water distribution within the system is also required and can be obtained, indirectly, from marketing bureaus or, directly, from water meter record. Field measurements are also typically needed to verify and calibrate the model.
Extent of Use
Computer-based optimization of water supply networks has been undertaken in only a few urban areas. In Poland, this technology has been implemented in a few cities, including the City of Gdynia, which uses a commercially-available computer program. This program is based upon mathematical graph theory, with the supply points being depicted as nodes within the system connected with arcs. The mathematical modules representing the nodes within the supply system define operational parameters such as distribution areas and water source areas, and length and changes in the diameter or smoothness of the pipe walls. The modules representing the arcs define supply sections, pumps, and valves.
Operation and Maintenance
Skilled engineers and technicians are required for data collection and modelling. Maintenance consists of on-going data collection and entry as water supply networks are upgraded or replaced. Level of Involvement This technology is generally implemented at the municipal level by specialist service firms.
Costs
Depending on the availability of adequate data regarding the distribution system and the level of complexity of the model chosen, the cost of this technology may be relatively low, consisting of the cost of the software and staff time. However, should extensive data collection be required or a computer model need to be developed, costs could be considerable, comprising not only the cost of the computer program, field measurements, data collection, and mathematical modelling.
Effectiveness of the Technology
This technology provides a means to optimize both existing and planned freshwater supply systems. Such optimization, in the longer term, can reduce uncertainties in the estimation of demand and provide information on optimal rerouting of supplies in the event of breakdowns in the supply system. This technology is also useful in designing new systems or additions to existing systems.
Suitability
This technology is especially suitable for use in planning large, complex supply systems in urban areas.
Advantages
This technology reduces the problems associated with ineffective distribution within delivery systems (e.g., by minimizing transit times) through an improved understanding of the supply network. This enhances supply effectiveness, reduces power demands associated with pump operations, and lengthens the working life of the infrastructure and water supply facilities. The models can be used to simulate current and future conditions within a distribution system under various conditions, to plan operation and repair activities, and to assess changes in the system and required improvements due to the reconfiguration or enlargement of the network.
Disadvantages
These models are data intensive, requiring well-documented system information that may not be readily available or correct.
Cultural Acceptability
This technology is largely an hidden technology used by the system engineers. However, provided the level of computerization is adequate for the operation of this type of model, systems modelling is well-accepted.
Further Development of the Technology
Better data collection, organization, and data base creation, as a standard procedure in system design, construction and operation, would enhance the ability of municipalities and water utilities to implement this technology effectively.
4.Lake Rehabilitation
Technical Description
Lakes are important resources not only landscape features, but also as recreational venues for fishing, boating, and swimming, all of which are very popular outdoor activities Lakes also serve life-sustaining functions such as provision of flood protection, drinking and irrigation water, and fish. Lake usage must be balanced between the desires of people to exploit lake-based resources and the capacity of the lake to satisfy these desires. Problems arise as a result of limitations on these uses that can reasonably be prevented or corrected with proper management. Thus, lake and reservoir management is an active process that considers how the various components of a lake ecosystem and its tributary watershed work and fit together, and, through this understanding, identifies the effects of various lake management interventions on these different components, both positive and negative.
Lake management techniques include both watershed-based interventions, such as land use planning and pollution control technologies, and in-lake interventions, such as nutrient inactivation. The combination of measures is site specific, and, typically, a number of complementary measures should be used.
5. Desalination
Evaporation ponds are comparatively low cost method for removing salinity.
Evaporation pondsare most appropriate for smaller volume flows and for regions of relatively high evaporation rates, level topography and low land costs.