Rainwater harvesting
Rainwater is collected from a roof-like surface and redirected to a tank, cistern, deep pit (well, shaft, or borehole), aquifer, or a reservoir with percolation, so that it seeps down and restores the ground water.
[4] Rainwater harvesting is one of the simplest and oldest methods of self-supply of water for households, having been used in South Asia and other countries for many thousands of years.
[5] Installations can be designed for different scales, including households, neighborhoods, and communities, and can also serve institutions such as schools, hospitals, and other public facilities.
[10] Studies by Stout et al. on the feasibility of RWH in India found it most beneficial for small-scale irrigation, which provides income from produce sales, and for groundwater recharge.
Missions to five Caribbean countries have shown that the capture and storage of rainwater runoff for later use is able to significantly reduce the risk of losing some or all of the year's harvest because of soil or water scarcity.
Small farmers, especially those farming on hillsides, could benefit the most from rainwater harvesting because they are able to capture runoff and decrease the effects of soil erosion.
[12] To enhance irrigation in arid environments, ridges of soil are constructed to trap and prevent rainwater from running down hills and slopes.
[13] Water can be collected from roofs, dams and ponds can be constructed to hold large quantities of rainwater so that even on days when little to no rainfall occurs, enough is available to irrigate crops.
Frankfurt Airport has the largest rainwater harvesting system in Germany, saving approximately 1 million cubic meters of water per year.
However, optimized real-time control lets this infrastructure double as a source of rainwater harvesting without compromising the existing detention capacity.
The water percolation in the water-impounded area of the check dams can be enhanced artificially manyfold by loosening the subsoil strata and ANFO explosives as used in open cast mining.
[19][20][21] Exploiting rainwater for value-added products like bottled drinking water makes solar PV power plants profitable even in high rainfall or cloudy areas by generating additional income.
Recently, cost-effective rainwater collection in existing wells has been found highly effective in raising groundwater levels in India.
It provides water when a drought occurs, can help mitigate flooding of low-lying areas, and reduces demand on wells which may enable groundwater levels to be sustained.
Devkota et al,[24][25] developed such a methodology for rainwater harvesting, and found that the building design (e.g., dimensions) and function (e.g., educational, residential, etc.)
Governmental aid and NGOs can assist communities facing poverty by providing the materials and education necessary to develop and maintain RWH setups.
[26] Some studies show that rainwater harvesting is a widely applicable solution for water scarcity and other multiple usages, owing to its cost-effectiveness and eco-friendliness.
[26][27] Constructing new substantial, centralized water supply systems, such as dams, is prone to damage local ecosystems, generates external social costs, and has limited usages, especially in developing countries or impoverished communities.
Several pieces of research have derived and developed different criteria and techniques to select suitable sites for harvesting rainwater.
Some research was identified and selected suitable sites for the potential erection of dams, as well as derived a model builder in ArcMap 10.4.1.
The model combined several parameters, such as slope, runoff potential, land cover/use, stream order, soil quality, and hydrology to determine the suitability of the site for harvesting rainwater.
Rainwater harvested from roofs can contain human, animal and bird feces, mosses and lichens, windblown dust, particulates from urban pollution, pesticides, and inorganic ions from the sea (Ca, Mg, Na, K, Cl, SO4), and dissolved gases (CO2, NOx, SOx).
Prefiltration is a common practice used in the industry to keep the system healthy and ensure that the water entering the tank is free of large sediments.
A concept of rainwater harvesting and cleaning it with solar energy for rural household drinking purposes has been developed by Nimbkar Agricultural Research Institute.
Substantial reform to Canadian law since the mid-2000s has increased the use of this technology in agricultural, industrial, and residential use, but ambiguity remains amongst legislation in many provinces.
[citation needed] The construction and use of cisterns to store rainwater can be traced back to the Neolithic Age, when waterproof lime plaster cisterns were built in the floors of houses in village locations of the Levant, a large area in Southwest Asia, south of the Taurus Mountains, bounded by the Mediterranean Sea in the west, the Arabian Desert in the south, and Mesopotamia in the east.
By the late 4000 BC[clarification needed], cisterns were essential elements of emerging water management techniques used in dry-land farming.
At the site believed by some to be that of the biblical city of Ai (Khirbet et-Tell), a large cistern dating back to around 2500 BC was discovered that had a capacity of nearly 1,700 m3 (60,000 cu ft).
[58] Around 300 BC, farming communities in Balochistan (now located in Pakistan, Afghanistan, and Iran), and Kutch, India, used rainwater harvesting for agriculture and many other uses.
[61] During the later Chola period, the Vīrānam tank was built (1011 to 1037 AD) in the Cuddalore district of Tamil Nadu to store water for drinking and irrigation purposes.
